Victorian Boombox Mark IV

[J. Wilhelm]

S,g I haven't had a chance to finish the prototype. But I can finish this weekend. I decided that the most practical way to do it is just to add 4 legs located at about ⅓ distance from each end, as close as possible to the internal baffles, which are hard points with minimal sound vibration; in other words these are standing wave nodes.

To that effect, I went to my local crafts shop and bought a $5 bag with wooden toy wheels, about 1½ inch (3.8cm) diameter and ¾ inch thick. I used these before for my Leviathan computer. The tyre"tread" look very nice, like the legs of 1980s hi-fi components. The wooden wheels aren't glued to the box. Thick rubber washers on each side of the wooden wheel will further isolate vibration, and provide a gripping surface. A pocket screw through the center of the wheel attaches the flexible suspension to the box. The shop had other larger wheels at about 2 inches (5cm) diameter and 1 inch height, which looked **fantastic** but look too big for the total depth of 6 inches of the box. Plus I can't find rubber washers that big. The wooden wheels will be stained and varnished to match the box. I'm undecided if I should use the lighter golden oak stain to make them stand out

I'll be back in a few hours to show progress.

[J. Wilhelm]

A little more progress ove the New Year Weekend:

I worked out this arrangement of rubber washers; basically the wooden wheel is sandwiched between two thick rubber washers, a large one matching the diameter of the wheel, and the other small enough to fit into the wheel well with a nylon washer to hold the head of the screws.

This is where the value of experimenting comes in. In spite of all the washers and wheels being very exact in their dimensions, my wooden speakers may be warped from humidity, stress, etc.  One of the wheels seemed to be too short by almost 2mm. That's a big gap, and I don't think I was that inexact in building the box, so it's got to be due to warping in the box. I tested on different surfaces, a table, the garage floor, etc, to make sure the surface wasn't uneven.

One thinks that a tripod arrangement might take care of the situation, but the geometry of the boombox makes it difficult to implement a tripod. So I worked out a methodology to deal with this on every build: a thin sheet of 2mm neoprene foam, like the one sold for children's projects.  The foam is black, and very squishy. You can cut a washer out of a piece of neoprene with a sharp pair of scissors using the wheel as a stencil. Then you pick the shortest leg and fill the gap with the neoprene, adjusting the screw until there's no gap and all legs are the same height.  On top of that, every leg will have a standard stick-on felt pad.

I opted to apply the lighter color of wood stain. The Golden Oak by Minwax.  The tyre treads created a great effect with the stain

How the boombox looks with legs. Still missing are the felt pads.
These legs or "feet x will be like 4mm taller after I attach the felt pads.
I'll use standard 3M beige or chocolate brown furniture stick-on felt pads

Notice how the speakers cantilever over the legs. The wood is free to vibrates, but the nodes of oscillation are at the baffles and legs, so you minimize sound transmission to the table.  You will still have evanescent waves engaging the table, though, but the overall sound transmission is much lessened this way

[J. Wilhelm]

Progress Report

I've been looking at adding metal grills to the speakers. These could be made from a thin wood frame and gutter aluminum mesh, which I used for making acoustic ramps in the Mk III project.

So I'm taking the first iteration to the next level, but in terms of performance, as opposed to theatrical aesthetics.
The issue at hand is that it's much more difficult tú get cylindrical or spherical containers of any material in the internal right volume range (about 3 liters) that you need to acoustically match these speakers.  So rather than spend my time on fantastical aesthetics, I will seek to target a niche demographic who is interested in oldschool communication and Hi Fi performance. I'm not seeking "Hi-Res" the millennial equivalent of Hi-Fi yet, in particular because this is a retro mid century appliance in more ways than one, but also because I plan to sell different electronics packages for each Mk. IV generation boombox.

There are several alternatives:

1.Public Broadcast of Radio and Television: there's an entire universe of digital and updated information technology outside of paid cable and satellite radio and TV. But I'll also include Internet TV which may cover paid movie and news networks, such as Netflix, turning the boombox into a portable sound bar, but with a built-in TV screen for outdoor applications, and HDMI output for indoor applications (soundbar).

2. Amateur HAM radio. There's a universe of ham radio operators out there I wasn't aware of. GHz range, Microwave, UHF, and even Shortwave (LW MW through Civil Band at 30 MHz). It's wild and I had no idea there had been a resurgence powered by micro computers such as Arduino and Raspberry Pi). Obviously this is a very niche market, but it's ripe for the taking. I don't think I'll pursue this avenue immediately however, because I have a lot to learn about Software Defined Radios which are a new breed of transceivers.

3. Strict Internet Appliance. This is the least attractive to me, on account that your smartphone or tablet already does most of this kind of work. There are Raspberry Pi compatible hardware kits such as Volumio, which turn any stereo device, such as an automobile radio into an attractive desktop Internet Radio. But I fail to see what's so unusual about that, other than explore the so called "Hi-Res" audiophile movent.

I believe I will start by fulfilling the first alternative. It overlaps with my immediate needs, and I've already purchased a 5v powered ATSC HDTV tuner. In addition to a Roku stick I have, I should be well on my way to building a prototype electronics package for option 1 above without much investment on my part (though I also have a surprise beyond that). Roku+ HDTV tuner is a good place to start.



I'll keep talking about this in a few hours in the future (I'm at work)

[J. Wilhelm]

Update

I just received my new HDTV tuner. I'm delighted to say it turned out to be packed with features I didn't expect, and the device is much smaller than expected, which for the purposes of integration to the boombox is the best I could expect.

The tuner includes a DVR (digital video recorder, as well as a so-so media player for music files video and movies if stored on a USB stick, but it supported full 1080p HD video which I connected to a very large computer monitor I have been using as a TV.

It's also got a rather large external 110V AC to 5V DC power transformer which I won't be using on account that i can draw power from the smart lithium battery pack and down convert from about 9V to 5 V DC with a tiny voltage regulator you can extract from any automotive to USB cigarette lighter adapter. That was a trick I learned two years ago during the snow storm that hit Austin. Cigarette lighter to USB voltage adapters have a voltage regulator that can operate with any voltage above 6 Volts, presumably past 13.5 V, a typical maximum for a car battery when it's charging (nominal 12 V).

Since the Roku uses a USB port for power, then it follows I can use the same type of regulator for the Roku.  In fact an HDTV switch, which I will need for the project will also run on 5V. And a 7 inch HDTV monitor will also run on 5V. Lastly, the radio I'm thinking of integrating will likely run on a battery pack. If I can make all devices run on the same battery pack, then there will be 5V regulators feeding each device besides the radio which has it's own regulator. I may need s second battery pack for peripherals, but they'll certainly be charged from the same external power transformer (110 AC to 18 VDC).

So it's looking like the components are coming together all by themselves, which is a good sign in any project.

Photos will be provided in my next post.  But in the meantime I leave you with these two radios I just stumbled upon by chance, and I thought resemble my boombox vaguely in form and function:

Grundig RF 3601 Stereo


SABA Donau

[SeVeNeVeS]

Still watching...........

[J. Wilhelm]

Still watching...........

I will have more photos soon. It's just the busy part of the week at my job.  Expect a breakdown of the HDTV tuner so you can see how small it is and I expect easy to fit into the electronics bay.

I'm missing a 7 inch HDTV monitor and an HDTV switch, but I can test any setup now with my large Dell monitor, which has two HDMI inlets.

The HDTV tuner at hand for local over the air free broadcast (I guess equivalent to Freeview in the UK?). Uses 5 volts from an external mains supply, and consumes about 7.5 Watts of power.
Includes remote with separate volume control, a myriad of features including DVR with HDMI and component sound output. Media reader for movies, photos and music files over USB stick.




The Roku Express 4K+ at hand. 5 volt USB style power supply.
Only has one HDMI video+sound jack, so it requires a "sound extractor module for RCA component sound and digital optical SPDIF output (about $15 on Amazon, also 5 volt USB style supply), but it supports 4K resolution and Hi Res Dolby Surround, and has "voice remote."

Roku scours the Internet available over your house Wi-Fi, and handles subscription for both free and paid TV networks from around the world, over 300 networks. Includes all major news networks (eg BBC CNN, etc) plus paid movie subscription networks such as Netflix, VUDU, HULU plus a considerable number of all free networks such as Pluto and Tubi (movies, reruns news, all advertising supported), YouTube and even government channels such as CSPAN and NASA. It advertises music channels to but I haven't explored that outside of YouTube. Naturally can record programming as well.


The surprise: Radio Tuner, Arduino based radio receiver based on Si-4732 chip for receiving FM Stereo LW, MW, and complete SW (shortwave band). Not at hand yet. Exact model will vary depending on budget and availability, but it's like to be from the Chinese ATS-25X series of portable radios based on Arduino. Features rechargeable battery pack and touchscreen. We'll see what I can do...

[J. Wilhelm]

Sorry, I haven't updated the page for a very long time. A week of COVID will do that to you. And also sorry for pulling a switcheroo. I've decided against using a software defined radio (SDR).

The reviews for most  SDR units are not good. It's still a very new technology that is about a decade, maybe two in use,  mostly used on desktop computers, and small processor versions running open source software for Arduino, Raspberry Pi, didn't mainstream until the start of the Pandemic.

A smorgasbord of different manufacturers in China build the same model, typically based on some amateur open source project, and quality control is next to zero. But the deal breaker is the software which you must manually update using the built-in WiFi, which presents two issues: 1. Using a WiFi connection with software you don't understand written by some obscure party is a security risk to say the least. 2. The software is always the beta version of a final version that's never available. Needless to say, the reviews written by ham operators on basically all open source SDR's are less than stellar.

In contrast, many commercial brands have developed their own digital signal processing radios (DSP), similar to SDRs but based on dedicated purpose-built processor chips developed for well known communications brands, with proprietary firmware, and the reviews on those radios are much better. So that's what I decided to research. The cost is much lower as well, with good DSP "world band radio" units starting as low as $50-100, instead of the typical $100-200 for SDRs only available from obscure vendors and developers.

So this is what I found with excellent reviews from anywhere I looked: The Sihuadon "R-108," a minute radio built in China based on a design by an American company called C. Crane.

The radio is a bit controversial, because Sihuadon, sells the Chinese version of the C. Crane "SkyWave" for about 1/2 the price of the American version. But I have no choice. I can afford $50 for an R-108, but not $100 for the Skywave, and the sound quality of the R-108 is by all accounts head and shoulders above the Skywave, according to ham radio users.

This little monster tunes AM, LW, MW, SW, FM Stereo and VHF aircraft band with both internal and external antenna. It'll tell you the signal to noise ratio of any signal, pulls fancy tricks such as using squelch to tune out interfering radio stations and has direct frequency tuning.  Besides international stations, it can pull more local AM FM stations than any radio I have, and yes, I can confirm the stereo FM sound is very good through a 1/8 inch phono output. Power input is 5V, at less than 10W, and the battery lasts 33 hours. Basically what I wanted. Plus it looks very techy, which is good.

My plan is to integrate it on a front panel, connecting the 5V USB cable to a voltage regulator coming from the Li Ion battery pack. The phone style battery will be the backup battery for the clock, and "emergency use" with the built in speaker when the boombox battery is depleted. It will recharge while the boombox is on, and on "Stand By" mode when it's off. A "Stand By Off" switch will interrupt all power to the radio (and other peripherals) to preserve the Boombox battery pack.

[J. Wilhelm]

So I've been putting the little R-108 through several tests and it looks like the radio is remarkably well suited for use with the boombox. Impedance matching between the radio's headphone output and the amplifier input was a concern of mine, but it turns out the input levels are close to line level (voltage) at about 75% power in the R-108, meaning that it sounds great at 75% volume. At that level,the sound from my smartphone FM radio over Bluetooth is indistinguishable from the line input connected to the radio! That's pretty good. The radio also gives you an estimate for signal to noise ratio for any captured transmission, which is very useful for adjusting the antenna. Reception on the radio is actually the best I've seen on any radio so far. I went from being able to receive about 15 stations on FM band to more than 30 using this radio, apparently these are stations from neighboring cities and towns.

The tests were important, because I'm not planning on using the radio's volume control. Instead the volume knob will be fixed and the amplifier volume knob will control the output to the speakers. You need to find the right sound level. This test is being repeated for the HDTV tuner and the Roku, but I don't expect problems, because these two already have line level outputs (RCA phono jacks).

There are a number of complications that I need to address, though. For one, the electronics in the radio are very densely packed. The mainboard is split in 2 parts with a connection that relies on the good alignment of the two halves of the plastic case. So I'm considering not removing the plastic case at all, and using the radio in "Dock Mode" with power antenna and audio connectors.  (The latter two being 1/8" American/Japanese style phono plugs -very traditional. The radio has a 5V micro USB connection which is just standard for most Android smartphone hardware. In fact, it makes no sense to even remove the backup battery, as it'll be charging when the radio is on.

One downside of this radio is that it's more complicated to operate than a standard radio. When was the last time you needed to choose between 3 tuning modes in a radio? Or use squelch to reduce sensitivity of the radio to tune out unwanted interference from an adjacent radio station? That's why I'm considering an HD radio as well to just offer something more simple and "Hi Fi."

The only thing I really don't like is the type of battery they used, an old Nokia style BL-5C battery, known for being unreliable. Worse, the processor chip used in this radio comes with a known flaw, as it's a first generation device:  The digital chip consumes as much power turned off as it does turned on, which means that it's constantly depleting the battery. That's an unsurmountable problem at this point, which is what led me to keep the BL-5C battery as a backup battery for the radio's clock, in spite the main power source will be the lithium ion battery pack, upsized to use 6 batteries instead of 3 (same voltage as 3 batteries,these are two 9V packs connected in parallel).

That power pack arrangement will give me about 50-60 W of maximum power consumption for whatever I need. I'm assuming a margin of 10 watts for each device: Radio, HDTV and Roku. The amplifier is limited to 30 W. 

There are more challenges regarding the TV screen, which I will address later. It may turn out it's easier to use a full 7 inch Android tablet as a screen, rather than dedicated HDMI capable monitor. I'm hunting for hardware. In a worst case scenario I could use the composite video out from Roku (HDMI to RCA converter) and the composite from the TV tuner to run an old style NTSC standard screen (about 800 x 600 pixels) monitor like those used on automotive applications.

[J. Wilhelm]

Welp. I've taken a plunge. Crossed the Rubicon. I cast the die. There's a high price for following this route (literally), but there's no other way.

7 inch LCD IPS Touchscreen with HDMI input.

I've settled on a type of screen for the boombox. It's been a month long adventure of looking and looking for different options, none of which seemed ideal. But I've learned a bit about HDMI, and LCD, TFT and ISP screen tech.

I started by exploring the idea of using a tablet or phone as a screen. After all, these devices are cheap ($50 USD for a no contract Android device), they have excellent high definition screens (at the cheapest 1600 pixels in the horizontal direction, full HD video is common), they can serve as internet radio and TV with the appropriate apps, and can tune air-broadcast television, with a little help.

One option to use a tablet or smartphone is to buy an external TV tuner USB adapter/dongle with antenna. The other is to buy a similar looking HDMI video capture card USB adapter dongle and use with a camera app.

$10 plus shipping gets you a basic HD resolution HDMI scanner. $20 gives you a 4K resolution scanner.

The latter option was the cheapest to try, so I bought an HDMI capture card for $20 USD and tried it. The image is very sharp, as expected, with a few caveats.

Screenshot of live HDMI video capture from the TV box into my smartphone.

It's got very nice colors and a barely noticeable latency in the image, but you have to put up with an advertisement banner, you need to get the nicest, least intrusive camera app you can find ("USB Camera v. 9.7.9" by Shen Yao, China), your screen needs to have a high resolution, and you set it to the highest resolution possible so that it's a "pixel to pixel" scan, otherwise the latency becomes unbearable. The settings can be confusing too (way too many options). It's expensive (add $20 to the cost of the phone). I don't expect the TV tuning dongle to be any different, as it's also a type of video scanner, except being a little slower than my QFX TV tuner box if my phone needs to run reception too.

Ah, yes! There's one more caveat. HDMI standards also include copyright protection. The Roku device might not want to stream certain paid programming through the HDMI scanner... You just don't know which programs will go through. That depends on your internet TV subscription. Roku just passes the copyright protection along.

So I kept looking for other options.

At some point I got very excited about finding small 5 and 7 inch portable televisions with radio included. It would have been extremely practical to have a radio and TV tuner in one package, because it'd save me a lot of money and time. With an HDMI input on the 7 inch device, I could connect Roku.

You see, small portable television sets are available from China using any global TV standard you specify for about $50-100 USD, depending on where you buy.  That would save me the cost of the radio and eliminate many connections, wires and switches. I would have kept the shortwave radio as an extra option instead for a more expensive model.

Yes, the images on the TV screens are fake. Surprised?

I came so close to purchasing one. The five inch (diagonal) screen devices are too small, and the 7 inch devices are almost too big due to the height of the plastic cases which usually have a panel of buttons in front, but with some imagination could be made to fit. Best of all, the price range is between $50-80 USD. Basically chops the overall radio/TV cost in half.

But what discouraged me were the reviews. Their screen resolution is good, but the most prolific manufacturer (Leadstar) is using the cheapest TFT screens possible, which have a very reduced viewing angle, and very low color and black contrast. Add flimsy case construction and month long shipping times, and it's not a good choice.  If I'm going to charge many hundreds of dollars for one of these machines, it can't perform like a less than $50 cheapo car camera screen.

So I kept looking.

I had already seen the 7 inch Raspberry Pi style HDMI screens, but prior to weighing all my options , I considered them too expensive ($50 to 120), and at 1024 *600 pixels slightly less sharp than a basic smartphone.  Basically it's less than full HD (1200*1024), never mind 4K resolution... about "half K" as one reviewer called it. Compared to the Chinese TVs above it's the same resolution pixel by pixel (1024*600 seems to be standard for most 7 inch screens).

A reviewer's photo of a 10 inch LCD screen with IPS technology

But these screens do exceed the performance of the Chinese TVs due to IPS screen tech, which gives you cell phone quality color and contrast, plus very wide viewing angles. And you have a capacitive touchscreen if you can use it, just like a smartphone.

The board has the ability to connect the touchscreen via USB and the USB plugs themselves double as the power jacks, so the screen runs from 5 V, one of my basic requirements from the peripherals I bought. I can generate 5 volts easily using a car lighter to USB power adapter which contains a voltage regulator. One of the tricks I learned during the last severe Texas Snow Storm (sounds weird doesn't it?)

So this is where I am, and I'll keep you posted as I receive this screen next week. Hopefully I won't be disappointed...

I might look into adding this too:

Cheese... I mean, Cheers!

AYS
Adm. Wilhelm.

[J. Wilhelm]

Guess what arrived yesterday in the mail?  The screen is better than I'd thought. And heavier than I thought.  It's pretty much a plug and play screen, and it turns on just by plugging power in. There's an extra switch to turn off the screen, and four more buttons for displaying a menu with screen settings. The input is exclusively HDMI and it has a pair of diminutive speakers which extract sound from the HDMI plug (barely audible, so won't be much help.  I'll use an HDMI "sound extractor" to get HiFi sound from the Roku. The QFX TV tuner already has RCA sound output jacks.

The package comes with 4 shiny black acrylic plates* that you can stack together like a sandwich to make a plastic frame.  I think that will be useful for the rear of the screen, but perhaps not so much for the front. I'll try to adapt it to a wooden frame.

The resolution is 1024 x 600 pixels, and a respectable 800:1 contrast ratio, and 8 bit color resolution (16.7 million colors). Not quite full HD, but it does have a very sharp screen and over 178 degrees of viewable angle (nearly 180!!), so it's very easy to watch from a side or from above. It has a thick glass screen and the colors are true and deep, but could be a bit deeper, but noting that I haven't horsed around with the contrast, hue and saturation settings (it's all in 50% settings). The pixelation is barely noticeable if you watch 5 inches from the screen, so at a normal viewing distance (say at keast 1 or two feet), pixelation is invisible. It's definitely sharper than 10 inch tablets from say 5 years ago, and way sharper than any portable NTSC screen you ever saw.

There's no question that this was the right choice for the system. The screen is barely small enough to fit in the front panel with a wooden frame. So working with an assembled TV, having to adapt a 12 volt power supply would be unacceptably large and more expensive in the long run.



*Plastic frame included.

Off-Topic: ShowHide

[J. Wilhelm]

Today, I've had a really busy day at the lab. What I set out to learn today was to figure out a way to simplify the audio extraction from the HDTV and Roku devices. It was clear I would use an HDMI interface for the video, but the Roku device lacks an analog sound output that you could feed to the amplifier without a digital to analog converter. That's a non issue for the TV tuner, because it already has a digital to analog sound converter with RCA output jacks.

What I didn't know is that besides the huge number of screen size and resolution permutations, you also have a copyright protection mechanism (HDCP versions 1.x and 2.2, corresponding to HDMI 1.x and 2.2 respectively) screen refresh rates (30 Hz and 60 Hz), and for the HDMI sound channel you have "ARC" a standard to return sound from a television or screen back to an audio/vídeo amplifier so the analog signal can be amplified before sending to speakers.

*Whew* too many permutations, and they all affect and limit what hardware you can use to connect the peripherals, driving the price of the interface hardware sky high. So you'd like to avoid having to add features to what it's supposed to be a simple video switch.

You see, the Roku handles HDMI 2 and the TV tuner HDMI 1. Not a problem you have choices in switches, but you want to drive the price down by not adding too many features like HDCP 2 compatible sound processing - stick to a video switch only, no audio, if possible.

So naturally, I was trying to figure out the simplest method to connect all the devices using HDMI cables only.  O saw three choices after that:

1.If you treat the Roku device differently by adding a sound extractor only for the Roku, you'll find you need a double set of cables and switches, one for sound and one for video. 

2.  The other idea was to use the 7 inch screen's onboard amplifier chip to source the sound. This way, both TV and Roku would have sound be extracted from the screen itself. You'd need a single basic HDMI switch for sound and videos. No sound switch.

3. Otherwise if the sound from the screen was not good, but you wanted to stick with HDMI cables only you'd still need a switch, but with a built-in external digital to analog for sound output, which depending on the format (HDMI 1 + HDCP1, HDMI 2 + HDCP 2, 30Hz or 60Hz, could cost up to $30, because part of the copyright HDCP protection involves sound. You see why this is not attractive. More money and more power consumption to avoid trouble.

I needed to find out how good that onboard sound converter was. So I started by removing the speakers and testing the connectors.

Luckily, I found both speaker jacks had a common ground, meaning I can use a standard 3 pole phono cable to connect to an amp.  I was elated to see the connection worked well enough to be used.  The sound worked well, apart from a slight mysterious lowering in the volume in the signal after a while.

Alas, that was an ominous sign. I encountered a problem about half an hour into testing. I noticed that the video processor chip (Realtek RTD2660H) was running rather hot. Only 4 seconds before you burned your finger on it. I looked at other chips on board. The onboard sound amplifier chip (APA2068) was also running hot.  Most worrisome, one of two onboard voltage regulators (ESP 8266) was running really hot. You couldn't touch it, and it's a very small device!

Also, I noticed that from time to time the screen would turn itself off for a few seconds and start up again. VERY WORRISOME. More testing revealed several triggers:

1. The screen is exquisitely sensitive to power fluctuations. The position of the micro USB power cable needed to be perfectly tight, the choice of USB power transformer mattered a lot (I discovered my smartphone power supply is not providing all of 5V of power at 1.8 Amperes (above screen requirements); the power was not enough for the screen, even if the Roku had it's own power supply!

2. The voltage regulator in question stops overheating when the HDMI isn't connected, naturally, but it overheated more with the Roku connected rather than the TV tuner. That was curious.

3. The sound chip also overheated more with the Roku than the TV.

4. Disconnecting the screen sound jack from the amplifier (boombox) eliminated heating on the sound processor, but doesn't make any difference for the video processor or the voltage regulator. Connecting the speakers starts the heating again. Muting the sound from the screens setup also cuts the heat on the sound processor. This means that heat on the sound processor is normal to that chip. Should be less than 2 watts of dissipation.

I discovered that along with two way communication, the HDTV cables also share power between devices. A peripheral may draw power from a television in your living room!  What I suspect is that the Roku is pulling power from the screen even if fed from it's own power supply, overdriving all the chips on the screen. It looks like the TV tuner doesn't, or it does to a lesser degree.

In the interim, I added impromptu heat sinks to the chips to see if the setup would alleviate the fadeout events.  A small aluminum chip sink for the video processor really helped and a couple of steel bolts for the other two chips seem to absorb the heat well.

The setup helps keep temperature down, and I'm convinced I'll have to use heatsinks anyway, but the sensitivity to the fit in the connections and power supply is still there. You can't even move the screen. Try not to stare at it too long. I noticed that the fadeout events don't happen when connected to the HDTV tuner. This is Roku not playing nice with the screen.

There's an extra power plug for the screen, but I suspect the power supply I'm using is at the edge of being insufficient at this point (two USB transformers, 5V at 1.8 amp for the screen, 2A for the Roku - which should only consume 1A in theory).

It's starting to look like I'll need to buy that expensive HDMI switch with sound extractor (option 2 above), and hope that the switch doesn't draw power from my screen... I'll be more confident about it if the HDMI output from the switch only feeds an image and no sound. At least I won't need a heat sinks for the tiny sound chip on the screen.

[J. Wilhelm]

Lab Day 2

On Monday, I made further progress into the overheating issues:

1. I tackled the problem of power fadeouts on the screen by using a double power supply on the screen (2A) with an extra cable plugged into the touchscreen input. It appears that the flat screen, rated at 0.9 Amps at 5V is using over 1.8 A.  The reason is unknown, but I strongly suspect this is power drawn by the Roku and possibly the TV tuner by way of the HDMI cable.

HDMI has to be one of the more obtuse standards ever devised. I guess HDMI was inspired on the USB standard, but whereas USB is usually unidirectional when it comes to power, HDMI is bidirectional, but has no intelligent way to see a power anomaly between devices (5 volts line), and thus power transfer can happen between devices in any direction.

The way HDMI works is that when a 5V source is detected by a receiver, the receiver initiates a "handshake protocol" which allows the transmitter to request information about the receiver's hardware, like type, resolution, refresh rate and other parameters. It's doubtful you could just sever the 5 volt line and expect that handshake to occur. The most basic Roku model, Roku Express comes with a USB power jack but without a power plug, and advertises that Roku can draw power from the television. That's the smoking gun.  It's likely that my Roku model, Roku Express 4K, uses the power plug to supplement, but not substitute the power drawn from the HDMI cable.The Roku power converter is rated at only 1 A. I don't know how much is consumed beyond that, but it's not unreasonable to assume that anything over 0.9A, the screen's power rating, is Roku mischief. If 2.8 A. wasn't enough (1.8A for screen and 1A for Roku), then combined consumption is about 3A minimum. In my last setup I used 2A for the screen and 1.8 A for the Roku, total 3.8A.

At near 4A. of total power supply, I had no fadeout events. Originally, I expected a combined consumption of less than 2A.

2. The other thought is that power transfer could be triggered when there's a voltage differential between devices. It makes perfect sense. A low voltage on one device could cause it to draw power from another. It's at this point that I need to temper that thought with the fact that the tiny voltage regulator still gets hot with the TV tuner. So I'm not sure that just equalizing the voltage of the video source and the flat screen would eliminate heating, as a good part of the heating may be normal. BUT it's a strong possibility that having all connected devices feed from the same power supply would help in minimizing power transfer between devices.

The design will change now to have a common regulated 5V power supply rail instead of individual regulators as I had stated in previous posts. The power supply should be strong enough to feed 2 amperes per device, I would say. It's not possible to isolate each device completely from the batteries, because of this HDMI power sharing scheme. This situation changes my design by a lot. Stand-by power switches go out the window as well, I'm thinking.

It's an "all or nothing" game at this point, which means I'm going to whittle down a lot of features I wanted to include in this boombox. I may dispense with an HDMI output altogether, for fear that connecting it to an external device like a large screen TV might damage the small screen on the boombox. That was definitely not expected!!

I long for the days when a video signal was just a video signal! Today there's all kinds of baggage allied with the video, like copyright protection HDCP, audio return to amplifier, ARC, power sharing  , and hardware information plus a database on multiple display formats. I won't go into details, but below I show some of the information a transmitting device must have in a database to drive a random screen that comes along its way. The firmware is similar to personal computer video drivers, I'd say.

Video Standards Chart (click spoiler for explanation)

Spoiler: ShowHide

Note often HDMI devices will be called "4K" capable, when in fact that is not a valid flat screen format but a cinematic definition. What we call HD is 720p (1024 columns x 720 horizontal lines arranged in a 16:9 aspect ratio). FHD (1080 x 2048) is actually correctly called 1080p (1920 x 1080, 16:9), and UHD is actually 3840 x 2160, and not what properly is called 4K (4096 x 2160). 

2. In the case of the 7 inch screen I'm using, the format is 1024 x 600 which is actually in between the wide version of the PAL standard, and the XGA personal computer screen standard.  That's basically what the video processor needs to map into "600p" on the screen from the 720p or 1080p signals I'm feeding it from Roku. Colloquially I'd call that "quasi HD."

Hence I realized I have an issue: the video processor is working twice as hard taking a signal from the default 1080p resolution in the Roku, than mapping the 720p signal native to the HDTV tuner. That could explain the difference in heating between the two. That made me feel a bit better, because it meant that if I reduced the resolution on Roku, I could lower the temperature on the video processor.

Indeed, that's exactly what happened. Roku likes to default to the highest screen resolution the screen will accept (1080p), but I have to manually set the resolution to 720p. The video processor now runs at the same temperature for both HDTV and Roku. We have progress.

3. The audio chip is still getting hot, but I noticed that the temperature goes up and down depending on the sound being fed into the amplifiers or headphones. I'm risking a bit by saying that the heating on the sound chip is "normal" but I just don't like how hot it gets.

I have no choice but to device heat sinks for all three chips, in my opinion. I'm very power limited to 25 Watts in this battery setup, so I can't afford to keep piling on devices, electronic switches and so on. One Amp here one Amp there, and suddenly you can't build the boombox at all.

So for the first production model, I've come to the decision to aim for the most frugal arrangement possible and using heat sinks and a common 5V rail for all video devices. This probably means I won't have an auxiliary video input or output to use the boombox as a sound bar, unless I find a way to completely unplug the 7 inch screen, physically with an HDMI plug.

Literally, I need to make a whole screen module "unpluggable" from the boombox via an HDMI plug and hefty "proprietary" DC power plug, so people can't mess with, and burn the poor 7 inch screen. I think that the Roku and TV tuner will be fine connected to a large TV, but you have to isolate the small flat panel completely.

And even then, I'm ambivalent about having power shared between my lithium ion batteries and whichever devices or screen I connect to. HDMI is a curse on portable devices.

Aaaargh!

I may have, however, a clever "sound hub" which has Bluetooth 5.0 receiver and transmitter plus digital optical/coaxial SPDIF input and output, plus analog RCA inputs and outputs. It should allow me to connect to Bluetooth headphones and connect SAFELY to external sound amplifiers and sources with a very high quality digital to analog conversion.  Let's hope i have enough amps left for that.

[J. Wilhelm]

It looks like I may have an inexpensive solution to my power supply issues.  The same supplier who provided the amplifier has started selling small smart voltage regulators with a 3 Amp 30W capacity (10 volt maximum voltage drop). Now the trick will be if I can make the Roku+ flat screen work within those bounds. If you read the specifications, that shouldn't be a problem. But I won't know until I try. In practice, I was using 2.8 Amperes at what I estimate is a 5 Volt drop (the batteries produce about 9-10V).  That means it's time for me to buy the second battery pack as well and try the integrated system. They do warn however that ventilation will be needed close to 30 Watts of power...

[J. Wilhelm]

I've got more progress on the Boombox vis-a-vis the power consumption of the devices. Without actually measuring power loads on the HDTV and Roku peripherals, I've managed to bring down the temperature of the touchscreen chips further down. I think I was right on using a common rail for the power supply of a peripherals and the touchscreen.

I found this double USB power converter at my local supermarket which has one USB slot rated for 1A, and a second slot at 2.5 A.  They're compensated between each other to provide a maximum of 3.5 A, and when connecting both the screen and the Roku I had no issues, but better yet, the temperature of the touchscreen chips, especially the power regulators went down a bit further. The video processor chip also lowered its temperature marginally.  It seems that a common rail power supply is an absolute necessity, thanks to the HDMI cable standard. If I go this route, it should be implemented with the voltage regulator shown in the previous post above and connected to the battery pack.

Also this allows me to set an upper margin for the maximum power available for peripherals in the boombox.  At 5V and 3.5 A, the maximum allowable power consumption would be 17.5 W. This should match the power margin when I'm using the power supply wall converters for the HDTV tuner (1.5A) and the recommended supply for the Tenizio screen (2A).

The setup is disappointingly power hungry, though, for just a TV tuner and Roku. I think the reason is that all 3, the QFX HDTV Tuner and the Roku, as well as the video controller on the Tenizio screen are software defined, that is, based on computer chips processing firmware. In other words, it's like having two out of three Raspberry Pi units running simultaneously at any one time (you can switch between the QFX TV Tuner and Roku, so you're not running all three at the same time).

So it looks like I won't go past 17 ½ Watts, as long as I keep other circuits passive (no preamplifier circuits, digital volume controls, digital sound control devices, etc.  In other words, to stay below 17 W I need to not have additional peripherals attached and rely instead on a strictly passive bass/treble and volume control. Easily doable, but I'm wondering if the boombox is too limited now due to power issues.

You see, 17 W is not a tremendous load, but it can't be ignored either. Because I'm running at only 5 Volts, I need to use relatively large gage cables suitable for 2A loads at least, and also means doubling up on the battery packs (all to be common rail). I can do that with the battery packs, but I'll have to test it for safety.

If I assume that normal personal listening (no breaking any windows here) boombox audio power output is only 10 to 15 W per channel (at 90% efficiency for a class D amplifier) then that translates to about 22 - 33 Watts total power consumption that my boombox is pulling right now, which explains why I need a second battery pack and puts my mind at ease that 17 watts is not too much for the lithium ion battery packs. But I can't go much further than that. Engineers at Parts Express, the outfit that sells the amplifier kits have warned me that because of the use of "smart circuits" in the battery pack, I can only use two packs in parallel before performance drops. At the same time now I'm constrained to a single power source (common rail).

The battery packs themselves run at a potential of between 11 V and 9 V since they're depleted quickly. The "smart" circuits between individual cells manage the power distribution and the battery pack is run directly feeding 11 V to 9V to the amplifier which also has a smart power management circuit. When the voltage drops too low for the amplifier to run, power is shut down to the amplifier.

I have never tested this setup before. I just don't know what to expect as power runs down. This will have to be tested! I could, however, try a completely separate power supply for the peripherals with no smart control from the amplifier, but I also don't know how tolerant the power amplifier is to being fed sound when it's basically turned off. Parts Express do offer an equivalent battery pack that's not meant to work directly with the amplifier. I could buy that battery pack and just connect the power supply jack. In fact, I'm more attracted to the second option.

Because of this situation, I've spent the last 2 weeks pondering whether to switch back to a tablet or Raspberry Pi powered internet appliance approach. Instead of running the equivalent of 2 Raspberry Pis in tandem you reduce yourself to 1 processor and at most an onboard video processor. There's many disadvantages to a computer-based heart for this this system (poor performance of SDR radio tuners, complex software and setup after unboxing, Android or Linux desktop login and human interface issues, Google login, Google Wallet, hackability... ), but there's one powerful advantage: centralized, self sufficient power supply because the screen connects through a USB port that also doubles as the touchscreen port), and very low power consumption overall.

Some really attractive Raspberry Pi alternatives out there at very low prices from
https://libre.computer/
Because of post-Pandemic supply issues, Raspberry Pi is now more expensive and generally unavailable!

Other advantages include: USB communication between HDTV tuner and computer (power flows in one direction only, there's no HDMI cable that could extract power from the Tenizio board), format expandability (TV reception expanded beyond ATSC to DVB for European/Asian market Radio reception at all frequencies and complimented by transmission for Ham radio; Additionally internet appliances like Roku are also available as software... And most importantly, I could potentially add an optical disk drive for $25 to the boombox). A tablet/Pi based "heart" would have a separate power supply from the amplifier altogether, as long as the Tenizio screen is well behaved (5 volt commons rail with the Raspberry Pi ot or tablet). I don't have a number for the power consumption of a Pi with an SDR dongle, though. It's a mystery to me. So I'm further away from implementing a computer based boombox than I'm at developing an "old school" hardware boombox, but I know that I eventually have to go there.


~ ~ ~

As an aside, most SDR radio software out there will only appeal Ham radio users as it's overly complicated, and just requires the user to know all kinds of technical information on radio transmission and reception theory, but I stumbled upon one very easy web-browser based extension that uses the Chrome engine and JavaScript to run one of the oldest and cheapest SDR radio dongles available.  It's called "Radio Receiver" and was written in 2016 by Jacobo Tarrio. It runs a number of SDR radio USB dongles that are based on the "RTL2832U" processor, and receivers based on the chip can be found online for as little as $15. The extension supports FM Stereo, Weather Station and AM bands, and with an external frequency shifter could be used as a shortwave radio as well. I just don't know the quality of reception, though.

The thing I like about this radio software is that it's the ONLY ONE with a "normal person" interface  not designed for extreme Ham radio geeks. And also it's web-browser based, which makes it very easy to access in a desktop. The software falls under the Apache license, so as long as you understand that you'll have to share your improvement over it for free and give attribution to the original developer, you can use it for commercial purposes. The only downside it's that as of last year it's no longer supported by the Chrome store. It's only available through the read only page below or as code from the developers GitHub page.

I've successfully installed the extension in Chromium, the free version of Chrome in Linux, so I'll shop for a dongle online and use on my desktop PC.

Developer's website
https://github.com/google/radioreceiver

Chrome store:
https://chrome.google.com/webstore/detail/radio-receiver/miieomcelenidlleokajkghmifldohpo

[J. Wilhelm]

On the same train of looking for alternatives, I've made a push toward bringing down power consumption a bit further on the peripherals of the amplifier. I've found a second radio tuning module online that includes FM AM and Shortwave, very similar to the Sihuadon radio but at a much lower cost, hopefully lower power consumption and with a much simpler interface with much simpler push button controls.  It's most likely not going to perform as well as the Sihuadon, but at $10 and a small size of 6 by 5cm I couldn't possibly bypass the opportunity to play with it.  It tunes most of Shortwave, and has FM Stereo.

https://www.ebay.com/itm/195138836213

Don't get me wrong, I'm still very positive about using the Sihuadon FM AM SW radio, but I need to keep costs down if I'm not able to implement the fancier features I wanted due to power issues. This radio has very similar features and even shares an aesthetic similarity. It'll be much easier to adapt to a very cramped space. For example, I'm quickly getting discouraged on the HD radio unless it's strictly implemented with a Raspberry Pi or Android device (read above).

HD (officially using the NRSC -5 format in the US), is exclusively licensed by iBiquity, a private company, but there's little to no promotion that I can see in the market, and to most commenting users online, it looks like a dying format or a "dead radio walking" a ghost from Generation X, if you will. HD Radio is very advanced, but it's only available for car radios mostly, like I wrote above. There are no new decoding chips being made for the market since the early 2010s. Any tabletop hardware comes from a few makers and domestic portable receivers are discontinued or available for the auto aftermarket only. iBiquity seems perfectly happy only licensing to auto makers, apparently. At some point iBiquity were purchased by DTS, the surround sound company.

I ignore what the status is for the European equivalent "DAB" aka "Eureka 147." Does anyone here in Brassgoggles know if broadcast digital radio is doing well across the pond? Or has that disappointed in the face of paid satellite radio such as Sirius or XM?

However, according to Wiki there are no plans to either abandon nor have HD Radio take over analogue FM in the US radio at the moment. Even more surprisingly to me HD AM Radio is "a thing," which is part of the same standard for FM (I didn't know) and as late as 2020 the American FCC had issued new rules for AM broadcasting using HD Radio, and there were a handful of AM HD Radio stations operating under license (!?!). So I'm confused whether this is a dying format or just starting to get hold of the market. I think there's a disconnect between the US Government and the public on this issue. Or like HDTV, the government has been lax to promote the technology.

Because of this difficulty in getting hardware, I may just drop any attempt at implementing HD Radio for the first iteration of the boombox. A shame, really. If I do implement it, it'll have to be as an Android or Raspberry application running in a later iteration. I don't think I'm ready to go fully into a computer based boombox yet, though I have a good mind to go there, because I find the current hardware very limiting. I can continue spending small amounts of money to go into a computer boombox, but I think I'm months away from even having a functioning prototype, nevermind the power supply.  In contrast l can assemble my TV, Roku  and radio hardware right now as soon as I assemble a power supply. I just need to lower the cost of parts (hence the radio module above). Hopefully by the end of summer I'll have a finished boombox.

Thinking about a future boombox iteration, I have discovered a very interesting C and Python based script that can use an RTL SDR dongle (see previous post) to tune HD Radio. It easy to compile in Linux. The control of the radio is strictly command line based (you need to run it through a terminal in Linux), and there's no human interface other than that, but it's possible to compile for any platform and it comes with an API, so maybe the resident coding expert, Herr Von Corax, can give me a few pointers? Does Visual Studio work for Linux, or just Windows? It'll take some time for me to develop a graphical user interface (GUI) in Linux for the HD Radio, since I'm not a good coder.

https://github.com/theori-io/nrsc5

[von Corax]

Thinking about a future boombox iteration, I have discovered a very interesting C and Python based script that can use an RTL SDR dongle (see previous post) to tune HD Radio. It easy to compile in Linux. The control of the radio is strictly command line based (you need to run it through a terminal in Linux), and there's no human interface other than that, but it's possible to compile for any platform and it comes with an API, so maybe the resident coding expert, Herr Von Corax, can give me a few pointers? Does Visual Studio work for Linux, or just Windows? It'll take some time for me to develop a graphical user interface (GUI) in Linux for the HD Radio, since I'm not a good coder.

https://github.com/theori-io/nrsc5

As far as I know, Visual Studio is Windows-only. There is Visual Studio Code for Linux, but despite having used it for several months I'm unsure how "visual" it really is. On the other hand, there are a number of GUI libraries for Python, and if it has an API you can probably get it to talk to just about anything.

[J. Wilhelm]

Thinking about a future boombox iteration, I have discovered a very interesting C and Python based script that can use an RTL SDR dongle (see previous post) to tune HD Radio. It easy to compile in Linux. The control of the radio is strictly command line based (you need to run it through a terminal in Linux), and there's no human interface other than that, but it's possible to compile for any platform and it comes with an API, so maybe the resident coding expert, Herr Von Corax, can give me a few pointers? Does Visual Studio work for Linux, or just Windows? It'll take some time for me to develop a graphical user interface (GUI) in Linux for the HD Radio, since I'm not a good coder.

https://github.com/theori-io/nrsc5

As far as I know, Visual Studio is Windows-only. There is Visual Studio Code for Linux, but despite having used it for several months I'm unsure how "visual" it really is. On the other hand, there are a number of GUI libraries for Python, and if it has an API you can probably get it to talk to just about anything.

That's what I thought. I've already started looking at Python libraries online. There was a recently published article listing all the repositories. Thanks for the advice!

One way or another this issue has a solution, but I'm inclined to say that if I turn to a computer based electronics bay, then it's likely I'll have one or two SDR receivers for radio and television, depending on where I ship the boombox. Television regional standards vary a lot nowadays, and ATSC is no longer shared with Japan, the way it was with NTSC.

I can't tell you the specifics yet, but I've noticed that SDRs circuits used for Ham radio tend to be the same as European DVB-T television receivers, whereas receivers capable of decoding ATSC HDTV are different, probably due to decoding or encryption issues related to NTSC. So I'll still need two receiver USB sticks and two separate scripts as well.  I may, however, switch power between the two USB devices (radio and TV) to save energy. The European version of the boombox would only need one receiver stick. 

I haven't found a universal multimedia receiver outside of internet radio (eg Volumio), which would already have ready made packages for broadcast TV or radio, because as far as I can see most multimedia environments don't include over the air transmission! We're all about Internet today. The Ham Radio crowd and the Internet Radio crowd are two different species of DIY animals, apparently, which means there's no universal package i can use as a GUI for the screen.  I'll need to hone my coding skills.

[J. Wilhelm]

So, again, I'm going in a new direction. I've decided to ditch Roku, or at least sideline it as an optional purchase, in favour of an Android TV stick.  The reason is that while Roku does have a limited selection of Internet Radio apps, it has no way to get a media app such as VLC or connect to a hard drive or an optical disk. Acquiring that function requires a fourth hardware platform like Raspberry Pi with Linux or Android and that's far too redundant, not to mention expensive (The other three hardware platforms would be Broadcast HDTV tuner, Broadcast Radio tuner and Roku)

The King is dead. Long live the King!

Now I've thought about ditching everything and just installing a tablet with full Android, as Android TV doesn't have native touchscreen support. I may still do that, but the problem besides the obvious complexity of having a full tablet OS, is that most tablets aren't upgradeable, they change size every time a new model comes out, and they're on average no longer available for a price tag of $50. After the Pandemic it's more like $75 for a bargain basement deal like an RCA tablet.

I've bought an Android TV stick for about $35 at Wal-Mart.
I'll be experimenting with a DVD burner and VLC hopefully.

But Android "sticks," on the other hand, are cheap (about $30), have good updated hardware, also connect to an HDMI port. Unlike Roku, they also have at least 1 USB port free, sometimes memory expansion slots, and more importantly they're compatible with some DVD optical drives and burners. To top it off they're easily replaceable. Sell your customer a new stick when the old one becomes obsolete or damaged and send it by mail! So by adopting an Android stick, I can now expand Internet Radio capability, add storage, hopefully run VLC to play and record media for said storage, and include a slim laptop style DVD burner as an anachronism that I think will be appreciated by my intended clientele. Internet Radio and TV, storage and optical drive will all be handled by Android.

The Broadcast HDTV and radio will eventually be folded into the Android device as the software becomes more mature, or I'm able to write code for an off the shelf Software Defined Radio stick. Right now the technology doesn't look mature enough in the commercial or consumer electronics sense of the word in spite of being available for two decades at least - it's only suitable for ham radio,  experimenters, and the military in my opinion. Perhaps early 2000s HDTV Windows-based units, eg Happauge-brand, are easier to run by the public. About 20 years ago I remember having separate NTSC TV and FM Radio (PCI?) cards in my Win XP PC - both worked "so-so").

UPDATE: June 25

Got the alternative radio over the mail. AM FM SW.  Looked good on paper.  But it's more like a paper weight. It's defective; none of the keys work. Shame it's got a nice amber display, but it's just a nice blinking clock at this point. Even if I got a replacement, this one took 3 weeks to get here. It's not worth the time, especially if defective units are coming in among healthy units. This means my only option for a radio is the Sihuadon radio, which is very good, but forces me to spend $50 and the radio takes more space in the electronics bay. This will affect the final configuration of the boombox. May force me to make a special moving mechanism for the 7 inch screen.

Second Update! June 25.

I made the little radio work! It turns out that connecting 5V to the USB port alone doesn't work without a connection to the battery.  The computer triggers an error protection mode. This isn't the case for the Sihuadon R-108 which can work from USB power alone without a battery.

I've put the radio through a few tests, and some of the results were predictable. The sound on the little radio module is very good, very clean, but it just doesn't measure up to the sound of the Sihuadon.  There's not much bass, basically at least while connected to headphones. I will need to test with a very high impedance connection (line in for the amplifier) to discount the possibility that the 150 or so Ohm load of the headphones is not having any effect, but because the output jack is already designed for a headphone, the situation doesn't look promising.

The sensitivity in the FM band is good, but the sensitivity in shortwave is near zero. I expect you absolutely need a quarter wavelength antenna to make it work. That's not the case with the Sihuadon which can catch strong SW bands with less than a 35 cm long antenna. The shortwave tuning is horrid, however. It's got no "fast mode" tuning to traverse the 25 Mhz spread of the Shortwave band, which makes looking for a known station extremely tedious. I don't think SW is very useful in this radio. Otherwise, it's a neat little module, perhaps useful for another project.

[J. Wilhelm]

The New King and Queen?

A quick update on the project. As I'm in a state of emergency trying to keep myself from becoming homeless and jobless, I've had to dial back on the rate of progress on this machine.  I do have, however an awful lot of findings and conclusions, and I've arrived at some important decisions regarding the type of derivative products I'll be able to offer (assuming I survive this summer).

I've reached the conclusion that Android TV is far superior to Roku in many ways, from a peripheral-compatibility perspective, but also from a legal perspective. As Roku only works with a handful of Roku approved devices, if I were to use Roku inside the boombox, I'd open myself to leaving the customer without a warranty or support from Roku. So legally, I can't sell Roku as part of the boombox, unless I sell Roku as a plug-in, separately from the boombox - which I may do for a derivative product in the low end of the range (read on).

Which by the way, I may have to do very very soon, owing to the fact that I'm very close to losing my income and I may have to develop a quick inexpensive product to offer online NOW.  No pressure...!

The idea is to gather locally sourced materials like a wooden decorative box and cheap Bluetooth speakers and combine with a battery and 7 inch screen plus a Roku to make a "tabletop internet radio and TV." Keep costs minimal and manufacture lightning-fast.  Maybe I could start selling some volume that way with the Roku being sold in it's own box.

The other conclusion I reached is that it'll be not impossible - but incredibly difficult to continue with Android TV/Android Phone/Linux using ARM processor based hardware if I want to offer optical disk support. It's no better for Linux. After all, both operating systems are related, and actually Linux will have a harder time adapting, I'm afraid.

After much reading and experimentation, I've learned that most Linux distributions tend to be only partially compatible with ARM main boards owing to the fact that Chinese made "PC compatible boards" are based on a chip form factor known as "System on a Chip (SoC)," meaning most of the main board, save for RAM and storage is built into a single chip which needs firmware to make run the circuits around the ARM-based CPU.

In plain English this means you have to adapt firmware to the Linux kernel to make the Linux work, and there are hundreds of different SoC chips, each of which needs a different adaptation of Linux to make it work. Android, which ironically is a type of Linux has a bit more compatibility with ARM devices. So this is a developer paradise but a customer's nightmare.

But all things being equal, there's a handful of ARM based SoCs that took well to Linux. Just not all of them, and I don't have the time to wait to see if someone has a perfect match for my hardware.

So if Android is a type of Linux, why not just insist on adapting Android to play optical media instead? Well, besides me not being a code developer, Android no longer supports optical drives since around Android 6 or so. Worse, Google is forcing all releases of media software providers (eg Video LAN/ VLC) to no longer provide optical and DVD decryption support either, since about 2020 (Android 8?). In other words, Papa Google just doesn't want you using optical disks, period. A lot of smart TV owners have been complaining over the last two years that their USB DVD players no longer work. Most people don't know why.

I did manage to buy and operate a USB DVD player (pictured above), but it needs to disguise the data stream as FAT 32 formatted data (pretend it's a flash disk). Only a very few devices, mostly from LG and Hitachi can do that. The LG drive I have can play CDs and data DVD +- RW disks, that is, something like.mp4 formatted movies, but not commercially encrypted movie DVDs or Blu Ray discs. You have to "rip" the disk in your computer first and transform encrypted VIDEO_TS/AUDIO_TS files into .mp4 or whichever else format you want with the help from decryption codecs (eg Video LAN's libdvdcs).

Nevertheless, Android TV is still the cheapest and easiest way to make a home theater boombox. A TV Android stick is worth about ½ the price of an Android tablet at around $35. I believe this would be the "midrange" of my line: Boombox with Android TV and ARM based hardware, but no support for optical drives or touchscreen. If you want touchscreen it's got to be an Android tablet or phone, not an Android stick. And the Android tablet is a good option actually. Broadcast Radio and Broadcast TV are entirely optional, as well as a stand alone DVD/Blue Ray player. Very cheap to add a read-only DVD player. Problem is, most tabletop units are too big for my boombox. I'm going to be exploring a Tablet-based system probably after I replace my current job this August. As soon as I get a new job I'll jump to that, because I've spent the last significant amount of money, about $110 (read next paragraph below) to finish the Mk IV Boombox.

So what's left beyond that? A PC compatible stick with Intel Celeron or Intel SoC (eg Apollo Lake), or AMD Excavator SoC. That raises the price from $40 to $160 or even $260 for the computer stick, depending which one you get (Lenovo, ASUS, Azulle, as Intel no longer sells their "Intel Compute" line of Celeron based PC sticks shown above).

The operating system for the top line boombox would either be Windows 10 Pro, or Linux Ubuntu 22.04 full desktop edition. Then optical discs with decryption will be available (not Blu Ray, though). At that point the boombox would become a full HTPC (Home Theatre Personal Computer). That would be the top of the line, suitable for this expensive wooden box I've built as shown. Both Ubuntu and Windows support touchscreen relatively easily.

So there you have three different lines of product, based on hardware and software capabilities. I do expect the lowest line to outsell the other two, for obvious reasons. So it's not like I've eliminated Roku, but rather I have to offer it in a different form, sold separately and for relatively inexpensive "tabletop radios"

[J. Wilhelm]

Mid August Update on the Project.

I'm in the process of interviewing potential employers this week, so I'm only giving you a partial quick update today. There's one more to follow in the next two weeks. But a lot of things have happened since my last update. The project is still in full swing and will not stop.

First, the most important development:

Windows 10 Pro is chosen for Mark IV

T'was an extremely lucky occurrence that when I purchased a used Azulle 3 PC Stick for $50, it was loaded with Windows 10 Pro, and it basically worked "right out of the box" without needing to find any drivers. The seller actually sent me a late model PC, with a 64 GB memory chip and a 4GB RAM chip, which is higher than baseline 3 models. Basically it works like an updated Azulle 4, which is the current model, except for the actual CPU processor type.

The Azulle 3 is powered by an Intel Atom quad core processor (I incorrectly posted "Celeron" in the pictures below because I was expecting that before they sent it). The touchscreen was installed automatically without having to prompt Windows to find a driver. Windows did the same thing for the optical drive, running the LG USB DVD+-RW as Windows has always done since the 1990s and 2000s. Better yet, it did the same for a 2000s Era external USB sound card I had lying around, a "Creative MP3+" sound card I've had since about 2003, which almost brought tears to my eyes.

Errata: Intel Atom, not Celeron CPU

It. Just. Works. Plug and Play. No questions asked. That's s winner to me.  Late generation Windows OSs have"Desktop Mode" and "Tablet Mode," the later of which has automatic touchscreen support and onscreen keyboard. I don't have to look any further. Linux would do everything too, but it'd be more complicated to set up.

The sound card provides separate headphones output with it's own volume control, it provides analog line level input, and analog lines level output for the amplifier. It has digital SPDIF line level input and output (oh that beautiful red LED light), and a microphone analog input.  Windows 10 can't load the old Windows XP Era Creative software, and you can't download it from the Creative website, so I'll have to look at a solution to replace the sound card if I want "Hi-Def" sound and digital sound control and sound effects.

The MP3+ card doesn't exist any longer, except as a used item on eBay, so it'll be replaced with an equivalent generic Chinese card for the production model anyway. Most cheap external USB cards look very similar to the Creative MP3+, so it's a matter of shopping around.  Actual Creative sound cards are very expensive and weird looking now, so I'll have to think about it.

Naturally, the Azulle 3's Bluetooth (v. 4.5 in this case) connects with anything Bluetooth without trouble. The sound of the Creative card and the Azulle Bluetooth connection are nearly indistinguishable when played through the amplifier. The sound card liberates the Bluetooth connection for another audio device, like headphones, or Bluetooth speakers. Bluetooth simultaneously handles a secondary input device as a keyboard, mouse, or remote control with keyboard.

The only problem with upgrading to Windows, is of course the cost, but it's also the size of the computer stick (read below). $250 when new, and $50 as a used, a previous generation PC is not a trivial expense. It forces you to "go all the way" with the features on board the boombox.

At roughly the size of a large candy or wafer bar, it requires more space and needs to dissipate heat. Remarkable it doesn't tax the power supply of the LCD screen. The reason is that Windows natively provides the same resolution that the 7 inch screen uses. This is the coolest temperature I've measured on the video processor and the voltage regulators on the LCD screen.

Changing the battery setup was easier than I thought, but I haven't installed the voltage regulators to provide 5 Volts (two of them for a total of 10 Amps) and I found there's not enough space inside the central compartment to accommodate all the electronics. So I'll be borrowing an idea from the Mk. I Boombox to accommodate the computer, radio and television circuits plus the sound card. There's also a bad issue emerging with the American HDTV ATSC Standard I'll discuss later - ATSC 1.0 is being discontinued for v. 3.0. Consumers as well as manufacturers are unprepared for the change (I smell $100 government issued vouchers to force the public to switch to the new standard. Your tax dollars at work).

I'll talk about this on my next update, but I can say this new arrangement will also fulfill the requirement for a modular electronics bay that will differ from one model to the next, so I can offer several models with different capabilities at different price levels.  Most likely I will have a line with Android TV as I detailed above ("medium range" price level).

Finally, this arrangement will probably add greatly to the "wow factor" which could justify the price tag on this machine.  I'm aiming for a mid-century/ Art Deco type of aesthetic for this device, and when you see it's final form, you'll find that the Boombox project makes a "full circle" (or should I say "Loop de Loop"?), but more in Dieselpunk mode with a touch of Cyberpunk. "Cyberpunk Noir," I'd call it.

It ain't the thing if it ain't got the swing.

Cheers!

[SeVeNeVeS]

All getting complicated. I love it!

Do carry on with the updates good sir.

Is all that lot being crammed into the existing case?

(best of luck with the job search btw)

[J. Wilhelm]

All getting complicated. I love it!

Do carry on with the updates good sir.

Is all that lot being crammed into the existing case?

(best of luck with the job search btw)

All will go in except for the big keyboard, naturally. But I will need an external wooden module as shown with a flip-up lid.  You've all seen that solution before in the Mk.I for an iPod dock. Obviously it'll be stained and varnished to match. I'll do my best to make it Art Deco with a specific theme.

The screen will flip open. Behind the screen will be the PC, exposed to the air to radiate heat behind an Art Deco themed grille. I take inspiration from a dashboard Windows PC I made for my Mustang circa 2004 (I'm only talking about the aluminum-"stone" flying wing over a lacquered wood panel). The illuminated blue button was the on switch, flanked by two LEDs for power and hard drive activity on a mini ITX board with Windows 95.

The radio will be in a panel under the lid/screen, where the iPod dock is located in the Mk.I, if you flip open the lid. The optical drive will be under the whole module, illuminated from a negative angle notch (if you squint you can see a curious notch under the wooden box. Just above the optical drive, you have an angled surface facing down where the sound card inputs/outputs are placed similar to the Mk I. Or, if not possible, then the inlets will be on the side of the module. The TV card (without the plastic case may fit hidden inside the module and in front of the amplifier.

(Thank you. I have a firm offer from a not-so-exciting job, ie, the same type of job I was doing, I'm waiting for one job  at a big box hardware shop (very convenient), and I was rejected at a pet supermarket type business, oh well)

[J. Wilhelm]

I have not many pictures today, but I wanted to make a quick update as I might be able to post about materials selection for the front face of the boombox and the grills in front of the speakers.

I've found a set of suitable materials to use and a way to attach them.  Basically, I need a way to keep the stick PC open to the air,q and hide it at the same time. I had previously decided that I needed to place the computer in the back of the touchscreen itself, so when you flip the screen open the PC is radiating heat above and toward the back of the boombox. That also means that there's no stress on the HDMI cable between screen and PC, otherwise those connections aren't very sturdy and it causes the screen to black out momentarily when there's any motion of the HDMI plugs. I may use a ribbon cable, but for serviceability, I prefer commercial HDMI plugs on the ribbon instead of ribbon slot connectors.

The way to hide the PC is to have the "Flying Wing" symbol (above) double as a heat sink and radiator. I intended to use aluminium bars (3/8 inch diameter) to make the "Flying Wing" as shown, abut I realized I'd need heat conductive putty to attached to a foot plate that I could in turn attach to the PC stick. Thermal epoxy is expensive and not the best, material, thermally speaking. Instead, I found copper pipes in that same diameter. Copper is very expensive, will tarnish and it's softer than aluminum rods, but the copper can be soldered easily to most metals, so it'd be relatively easy to assemble a heat sink/ radiator, not to mention heat conduction would be better across a soldered joint.

So, how to hold the pipes in parallel?  I would not use epoxy putty in between rods or pipes, because it'd interfere with the heat transfer. This is meant to be a radiator. Instead, I found fluted wood moulding, about 3 inches wide that can be sliced thin and used to hold the tubes to the wooden surface of the boombox, very much like frets on a guitar neck are underneath the strings. The wooden "frets" will hold the pipes straight.

As an additional benefit the "fret and string" method will help me design Art Deco grills for the speakers, if I replace the copper pipes for wooden dowel of the same diameter.

I'll post pictures in the next few days.

[J. Wilhelm]

So I have a set of pictures to explain what I'll be doing this weekend until presumably Tuesday. There are three things that will be finished simultaneously.

1. Expanded electronics bay with computer, screen, radio, and if possible the air-broadcast television tuner.

2. Grills over the speakers.

3. Radiator and heat sink for the Azulle computer stick

The reason these three are simultaneously assembled is that the materials used have double duty and physically overlap over each item listed above.

If I'm successful the Mk. IV Boombox will end up having an Art Deco look finished in two-tone wood stain with spar varnish and copper.  Something like this crude drawing below. The copper pipes will be a Flying Wing motif and a functional heat radiator (orange stripes in drawing). The speaker grills will mirror the Flying Wing motif.

A crude sketch, I admit.

When the Mk. IV Boombox is fully assembled, I expect it will have an uncanny resemblance to the Mk. I Victorian Boombox, except that it'll be Art Deco/ Dieselpunk, instead of Steampunk.  I love it when things go full circle.

Below is a hobby or craft wooden box from the local hobby shop, something always readily available. I sawed off the bottom of the box at a 20° angle (approx - the angle is set arbitrarily), and then reinforced the corners of the box with ½ inch square dowels. The box is somewhat light and flimsy, made from something like Bass Wood, which is stronger than Balsa Wood, but still very light. The open grain might give me an issue when staining and trying to varnish the wood. I'll just have to deal with that.

I replaced the flimsy brass hinges with two springed cabinet door hinges so as to allow the lid of the box to support the weight of the screen and computer stick. The bottom of the box was attached to the boombox body, by way of four large wood screws.  The "chin" of the wooden box has a sufficient angle to allow a person to reach and insert an optical disk into the drive which is just the right size to be fitted under the bottom of the boombox between the four legs. I'll try to add illumination for good effect and night time use of the boombox. There's a good chance than any volume control I add as well as the tuning knob of the radio will have to be fit on the side of this craft box (fairly unusual location, as space will be very tight even with this added electronics bay).

However, I don't like the look of the lid, it looks too blocky and thick.  So I'll employ a trick used for early tablets and smartphones, namely hiding the thickness of the lid by having a "curved" profile that yields thinner edges. So I propose an "Art Deco cross section," made from a ½ inch x 6 inch wood plank and moulding. The computer will be embedded inside the wood plank's thickness with both sides of the PC exposed to the air (the thickness of the PC stick is exactly ½ inch).

I intend to take advantage of the fluted moulding shown, and use ⅜ inch diameter copper pipes and similar poplar round dowels. The dowels will become the grills of the speakers, and the copper pipes will form the heat sink and radiator of the computer stick. The pipes will be soldered to a large steel washer which will be then attached to the hottest part of the PC stick (where the CPU is located) by way of a thermal pad. I'm not sure o could use thermal paste, because the PC stick is corrugated (intentionally to increase the surface area for radiating heat). The main ½ inch plank will be screwed to the cabinet hinges, since that's the strongest part of the assembly.

The touchscreen will be installed on the surface of the opposite side of the pine wood, and I have not decided exactly how that will be finished, but rest assured I'll be getting creative with lots of wood moulding. There will be precious little room on that side of the plank, owing to the fact you have various cables, at least an HDMI cable and three mini USB cables connecting all the devices together. More USB cables will connect the expanded bay to the main amplifier and power supply in the main body of the boombox.

Cheers!

J. Wilhelm
𝕬𝔡𝔪𝔦𝔯𝔞𝔩 𝔲𝔫𝔡 𝕷𝔲𝔣𝔱𝔰𝔠𝔥𝔦𝔣𝔣𝔢𝔫𝔤𝔢𝔩

[SeVeNeVeS]

You been busy. Still watching you know.

And congrats on the new job.