Alternative to Faceplate/Preamp unit for Table Radios...

[Dukk]

Very nice. I was cruising Ali a couple weeks back for something just like this. I found a few but single DIN touch screen headunits are harder to find.

RE: Antenna turn on. This *might* only activate when Radio is selected. Traditionally, car radios that have both an amplifier turn on lead (on continuously when head unit is on) and an antenna lead will turn the antenna lead off when listening to alternate sources to put the power antenna (remember those?) away.

The built in amplifier section shouldn't have any parasitic draw, but who knows. The draw when off is to support the clock and most likely radio presets and any DSP settings as they are usually volatile memory.

[tomzarbo]

I kind of thought that 280 milliamps was sort of a lot for it being on 'standby' mode, but since it's a car radio and they're not at all trying to save every milliamp of draw, 280 milliamps isn't all that much I guess. Still, I was expecting less than that. It does have the screen on all the time when off to display the time/clock.

Mike, thanks for the link for the convertor. Pretty cheap, and I don't mind waiting a few weeks for this stuff.
I'm not clear on what it would be used for in this case though?

Dukk, I didn't think of the antenna lead switching off when changing sources other than the FM radio. I'll test that out to see.

It does have settings that need to be remembered such as all the FM presets, the color of the LED glow on the face, and other stuff I guess.

I'll try to run through every option when I get a few good hours this week or weekend.

It's funny, I search for something at Aliexpress and it seems unless I get the wording just right, I can't find what I'm looking for. Other things... there are so many hits that come in... they have dozens and dozens of car stereos in the double DIN size, some of them look similar, maybe just different faces to basically the same guts. But you're right, not many of the smaller ones, fewer with touch screens.

TomZ

[Dukk]

I have yet to ever buy from Ali as I find it frustrating to navigate and when I do find something I need a minimum order of eleven million of them

Some units have display settings that can turn it off when powered down.

[tomzarbo]

So I messed with this a little bit more today. I took a video of it on my phone. It can do more that what I showed, but at least you can get a feel for how it operates.

Link: https://www.youtube.com/watch?v=W5hF...ature=youtu.be

One thing I forgot to do is to press the volume knob, that gives you up/down for bass, treble, balance, fader, brightness, contrast, saturation, hue, beep on/off, and maybe a few other things.

I don't mess with phone dialing features on phones, so I'm not sure what any of that stuff does -- make/receive calls through it? -- but it looks to work like a phone once connected through Bluetooth. It can obviously play Bluetooth through the phone as well as good old music.

The FM radio pulls stations in just fine. It's not amazing I guess, but it works. Once a station was dialed in, it seemed stable with no static. I noticed also that rather than just 98.1 it can do 98.15... not sure if it's really dialing in the station with more accuracy or it's just a gimmick.

The units built-in amp will power a set of speakers (at least one pair of 4 ohm Neo Nano's) to fairly loud levels without sounding bad. I even hooked one side to an 8" subwoofer that is my footrest and it had no issues with that. I only had it hooked directly to the speakers for 8-9 minutes, but it didn't get hot on the back, mid 90 degree F but I wasn't cranking it super loud either. I suspect with low to medium volumes with two speakers connected, it would be okay. Sound quality seemed fine.

There was a slight on/off click when powered with the built-in amp. The click is louder when connected to an amp through the RCA jacks. I think the quality is better with RCA outputs, though.

The antenna power line is active as soon as the radio is turned on, no matter what mode it's in; so using it to power a relay or delay turn-on for an amp should be okay I would think depending on how much amperage it can deliver.

The included instruction booklet is nearly useless except for the wiring diagram, which is also on the back of the unit. The instructions are for a different unit... actually several different units, but not this one exactly. Doesn't matter, it's self-explanatory pretty much.

I'm not really super-adept at fiddling with this stuff, but I just wanted to give a basic idea of how the screen works and what a few of the features were. I probably should have gone over it several times, then made the video, but...

Bottom line is, it works fairly well, not as clunky in operation as I thought it would be. The video screen is attractive, the graphics are not blocky or jaggey, it looks like it belongs in a modern car actually.

It will make a real nice table radio or boombox head unit. With one of the adjustable on/off relays that Mike was referring to connected to the power antenna lead, it could potentially be amp-quiet when turned on/off as well if using with an external amp.

I'm leaving some stuff out I'm sure, if you have a question about something I didn't get to, let me know.

TomZ

[tomzarbo]

Here is another much shorter video for a super-quick look at the unit up close: https://www.youtube.com/watch?v=gKt8l2BlDsg

TomZ

[Millstonemike]

I have yet to ever buy from Ali as I find it frustrating to navigate and when I do find something I need a minimum order of eleven million of them

Some units have display settings that can turn it off when powered down.

Not Alibaba, Aliexpress ...

[Dukk]

^ Thank you for the redirection. I will have to check it out - frankly I have been dissatisfied with any 'Ali..' website but maybe I have always viewed only Alibaba

Any EQ function on that piece Tom?

[Millstonemike]

I can say a couple of things now...

* It's almost weightless, very light.

* It doesn't look like the 'Wattage' speaker output circuit can be removed from the equation; or I should say it's not on it's own 'Amp-Only' board... The board in the back looks to have more than just 'output generating doo-dads' on it, but I'm not 100% sure about that.

* I'm not sure how much amperage would be saved by removing the output stage from the equation. The amp chip is screwed to the back aluminum 'heat sink'... could the leads to that chip just be clipped, saving those milliamps? After about 20 minutes of messing with it, it didn't get even warm, so leaving it as-is wouldn't be a problem I'd think.

....
TomZ

All good info. I agree, removing the "amp" from the circuit might not save much. But, perhaps, just enough. IIRC, you mentioned 280 ma draw sans speakers. The amp chip might draw 50 to 150 ma idling. Removing that draw gets you in the vicinity of 200 ma (just cut the power pin). That's why I posted the 200 ma DC-DC isolated converter. I think isolation may be needed if you add your own amp to the mix. And you can't isolate the main amp. It requires too much power.

Can you post a high-res pic of the chips , lettering. I'm pretty sure the white Linear IC is the power amp.


On another note, look at the mechanical construction. When embedded in a custom build, I think you can lose the back and side panels (I love how the back panel is formed like a giant heat sink - maaaketing). Then you can mount the "amp" board close to the main board and save a ton of space.

[tomzarbo]

Dukk,
I think it's just Bass and Tremble, and various combinations of those for the Rock, Jazz, Pop, etc. presets on the EQ. They're not all bad sounding though.
There is also a 'Bass Boost' or I think they call it 'Loudness' button as well.

Mike,
So cutting the power line to the amp chip will be enough to kill the extra draw?... I'll take some higher resolution pictures tonight of the innards so we can see what types of chips are used. It looked to me that there was more circuitry than just the normal 'amplifier' stuff on the back, but if we could figure out which lines are the DC V + and -, the antenna, RCA output lines, I guess it could be bypassed. We'd have to see if the front board works on 12V or 5V, I'm guessing it is reduced to 5V for that one.

Man, that would make a really thin piece of kit there without that stuff on there. I'm thinking a continuity check on the ribbon cable unplugged from the front board would give me what I need to do that.

I'll hopefully check this out in a few days. It's interesting! It has promise I think.

Ahh, back to work!

TomZ

[Millstonemike]

Dukk,
I think it's just Bass and Tremble, and various combinations of those for the Rock, Jazz, Pop, etc. presets on the EQ. They're not all bad sounding though.
There is also a 'Bass Boost' or I think they call it 'Loudness' button as well.

Mike,
So cutting the power line to the amp chip will be enough to kill the extra draw?... I'll take some higher resolution pictures tonight of the innards so we can see what types of chips are used. It looked to me that there was more circuitry than just the normal 'amplifier' stuff on the back, but if we could figure out which lines are the DC V + and -, the antenna, RCA output lines, I guess it could be bypassed. We'd have to see if the front board works on 12V or 5V, I'm guessing it is reduced to 5V for that one.

Man, that would make a really thin piece of kit there without that stuff on there. I'm thinking a continuity check on the ribbon cable unplugged from the front board would give me what I need to do that.

I'll hopefully check this out in a few days. It's interesting! It has promise I think.

Ahh, back to work!

TomZ

Like I mentioned. The white linear IC backed up against the back plate is likely the power amp. You could cut the V+ on the leg holding it to the PCB. That would insure the remaining circuitry was still powered.

Lots of power amp chips using this format are in consumer electronics. It's likely a class A/B amplifier. Not as efficient as Class D. But maybe not much different when idling. Then again it's using older solid state design. A similar, currently available, quad amp chip for car radios from ST has a typical idle current of 190 ma (range from 120 ms to 350 ma) If we can't get the chip's datasheet, you could always measure the pins.

Oh. Good point, the DC-DC converter is 5 V. You likely need 12 V. Not to worry, There are isolated converters that will do 24 V DC to 12 V DC @ 500 ma. They just cost more (~$15).

But it "Kills two birds with one stone". You can power the main amp with 24 V DC and convert that 24 V down to an isolated 12 V DC for the face plate.

You could do a 4 woofer, two tweeter rendition and use the the units existing amp. If you use 4 ohm woofers, you'll get a decent spl out of the stock units quad output at 12 V.

Decisions decisions ...

[tomzarbo]

I took some higher resolution pics this afternoon...

These are from the rear board.


More...

[tomzarbo]

These are from the rear board as well:


A few more...

[tomzarbo]

These are from the front board:


That should be the important ones I hope.

[tomzarbo]

Sorry some of these pics are still a little fuzzy, I took a boatload of pics and these were the best believe it or not.

The ribbon that connects the front and rear boards have very close wires which I doubt I would be able to test out without shorting. It may be possible though because where it attaches to the front board they alternate top and bottom with their attachments, so there is essentially double spacing there. That may be more than my fat, feeble fingers can handle, though.

From the first pic in post #27 it looks like there is a voltage regulator(s) ? on the rear board that I'm guessing brings the 12v down to 5v to send to the front board? I really shouldn't say because I'm just guessing, but that is what they do so... There are two of them, only one has markings. There are some other chips on that rear board as well, maybe it's all basically amp-related? I think there is probably something on that rear board that triggers the 12v for the power antenna lead though, but there again, I'm guessing.

Seems like just cutting the pertinent line to the amp chip would be the easiest and cleanest way to reduce milliamp draw like Mike said.

Actually, without some kind of way to attach the rear terminus of the ribbon cable to something that could easily be soldered to for antenna, RCA output, power in, etc. I think I'd have a hard time messing with this to get to the individual cables on that ribbon; and again, that would eliminate the 12v antenna power lead which I think is mandatory... see below.

*** One more thing, I messed with this a bit more today, there is definitely a click/thump coming out of the RCA jacks when the unit is turned on/off. I think it would bother me a bit to hear that each time it's cycled. I didn't notice it being so loud previously, probably because I had the external amps volume lower, but it's actually loud enough to be kind of annoying.

Upon power-up, there is a fairly big 'click' almost immediately.
There is an approximately 2 second delay on power-down then you hear the click; that one is milder.

Possibly a time-delay relay device like Mike suggested previously would be able to take care of that being an issue though.

More to think about...

TomZ

[neildavis]

You should be able to turn off the power amp by grounding pin 4 of the chip (Standby). In standby mode, the chip draws very little current. But check to make sure pin 4 isn't tied to 12V. The data sheet shows that this pin is usually tied high with a 10K or so resistor and a 1uF to ground, which gives a "virtually pop-free" turn-on (or so they say...).

The Bluetooth is provided by a different chip than that other decoder board. The chip is made by Buildwin, part of the AppoTech Group, and it is probably a CW6690G with a custom part number for that code. It is probably decent enough quality, even though it is intended for the low/moderate priced market. That chip shows up in several makes of Bluetooth speakers and the only "reviews" I found are favorable.

This decoder/preamp would be better if that TM2313 chip was on the main board rather than the amp board. It's a preamp chip with analog switches, tone and volume controls with decent specs, but putting it on the same board as the power amp means you can't get rid of the amp. Not a huge deal, but it it means you can't just unplug that amp board to make the assembly smaller and lighter..