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

[tomzarbo]

There has been some digging done into one of the non-PE faceplate preamp units used for table radios, boomboxes, and that kind of thing. Here is a thread on that: http://techtalk.parts-express.com/fo...coder-question

And another thread I started regarding the possibility of encouraging PE to design one:
http://techtalk.parts-express.com/fo...14#post1428414

Mike and Neil came up with a few other options for the 'Rotary Knob' lovers among us in that one. I'd still love to see PE design a high-quality preamp/faceplate board that bests what's available out there in the market. I'm sure they would do it if there was a market for it, but since me and a few others like me don't actually constitute a 'market' -- I think it's best to look elsewhere. I always try to purchase from PE when possible, but they can't carry everything...

So here is another option that seems like a decent value that I stumbled upon and ended up ordering...



It is a car radio I found on Aliexpress, but it's better than most of the other ones I've looked at for a few reasons...

Probably the most obvious is that it's not gaudy, it doesn't have weird looking buttons or plastic/chrome embelishments. It looks like it was more of a stock car radio which is something that I like and appreciate... understatedness.

Also, it does have a real remote and a touch-video screen of about 4" diagonal which will play movies and it has a nice FM radio interface as well. Two USB sockets, one for music, the other for charging a phone, plus it's got bluetooth and line-outputs for L and R and even a sub. There isn't much listed as far as it's output capabilities, but even if it's lousy, it can be bypassed. There are options to change the color of the buttons and knob to match the rest of the radio's theme, or it's surroundings I guess. It also has a power antenna turn-on lead which might be able to be connected to a relay that will turn on a seperate amp, that's kind of nice!

It even has fairly decent reviews. But best of all is that big 'ol volume knob right there next to the screen!

I know it's not small, but if I rearrange the format of the radio's I've been designing, it would work fine I think.

I have one coming, and I'll give it the once-over to see how it works and what it's noise issues are. I'm even hopeful that being a car radio that the FM portion actually will pull in a few stations with an added antenna. Could be promising. Oh, and it's $33 shipped! If it's easy enough to dissassemble, I could get into it and see if it could possibly be modified to fit into a more verticle orientation. It even has the 'brushed aluminum' look that I love so much. It looks like some thought was put into making this a pretty decent product... who knows though until I have one in hand.

So, I'll keep you posted on when I get it, how it performs and so on. I'm cautiously optomistic.

TomZ

[tomzarbo]

They also have a smaller one without the video screen, it's similar but has a smaller screen that is the 'green line' type. That one is $20 shipped. They are both single DIN I believe though. You can see the 'cut-out' for the larger screen on this one.

[djg]

Cool. I've experienced corona virus related shipping delays on items from china, FYI. Assuming it's from China.

[Kevin K.]

Wow! Hard to believe they can build something with this many features and sell it for a profit at that price. Does look like a really good fit for your needs. Keep us posted Tom, thanks.

[tomzarbo]

DJG... you know my wife mentioned that. I wondered if I should spray every incoming pkg with Lysol or a flame thrower or something.

Kevin... I know, I don't know how a profit can be made -- or much of one anyway -- from stuff like this at that price including shipping. I'm thinking that quality control on many of these cheaply made electronics items from China is non-existent or shoddy at best. I've had so-so luck with stuff from Aliexpress in the past, but at least I'm usually only out a few bucks when I get it and discover it's junk.

There have been a few jewels in the muck and mire that keeps me hopeful!

Happy Presidents Day everyone!

TomZ

[jhollander]

Tom, looking forward to your review, what's the expected delivery?

[tomzarbo]

Tom, looking forward to your review, what's the expected delivery?

Should be here in less than a month if there are no Coronavirus restrictions.

Just thinking, it may make a decent little mid-fi faceplate/preamp for a larger-amp'd home stereo unit, assuming it's not garbage.

TomZ

[Millstonemike]

... and line-outputs for L and R and even a sub. There isn't much listed as far as it's output capabilities, but even if it's lousy, it can be bypassed. There are options to change the color of the buttons and knob to match the rest of the radio's theme, or it's surroundings I guess. It also has a power antenna turn-on lead which might be able to be connected to a relay that will turn on a seperate amp, that's kind of nice!

TomZ

At 12 V, power out into 4 ohm drivers is about 15 W rms (1/4 of your TPA9274 amps at 24 V). The standard 52 rms for a 4 channel head unit is 13 W rms per channel according to CE measurement defintions. Plan on adding an external amp ... and dealing with ground loop. Unfortunately, the couple hundred ma capacity of the isolated DC-DC converters is likely not enough to power it, even used only as a head unit (but you can measure that). A non-isolated regulator (linear or buck) should handle it no problem. If ground loop is a problem, you could try decoupling caps on both the positive and negative signal sides between the line outs and the external amp.

And don't forget that 12 V delayed relay module if the antenna output is too quick for a simple relay. And add 70 ma or so the the 12 V power source load to keep the relay closed.

I'd be interested in the measured power draw when get it.

[donradick]

Nice find, Tom - and your usual thoroughness in exploring capabilities and possibilities.
Looking forward to assessments of the SQ. The $20 piece would be perfect for boombox for my shop.

[tomzarbo]

At 12 V, power out into 4 ohm drivers is about 15 W rms (1/4 of your TPA9274 amps at 24 V). The standard 52 rms for a 4 channel head unit is 13 W rms per channel according to CE measurement defintions. Plan on adding an external amp ... and dealing with ground loop. Unfortunately, the couple hundred ma capacity of the isolated DC-DC converters is likely not enough to power it, even used only as a head unit (but you can measure that). A non-isolated regulator (linear or buck) should handle it no problem. If ground loop is a problem, you could try decoupling caps on both the positive and negative signal sides between the line outs and the external amp.

And don't forget that 12 V delayed relay module if the antenna output is too quick for a simple relay. And add 70 ma or so the the 12 V power source load to keep the relay closed.

I'd be interested in the measured power draw when get it.

Mike,
thanks for reaffirming my suspicions on the projected wattage output of the unit. I didn't expect much out of it anyway. And truthfully, anything I build with a head unit this big in it will have drivers that will need more than 12 or 15 watts to make it sing.

I was thinking the same thing with using a buck converter to reduce the incoming voltage to 12V as opposed to the isolated converters I've been implementing. I also have a few isolated line out thingy's from the Toni Table Radio build which I didn't end up using if needed.

Regarding the antenna voltage lead... I thought that the antenna output voltage stayed 'on' as long as the radio was on though. So it's a temporary voltage for a few seconds? Well, looks like I have a few more things to learn!

Don, I do seem to be on a never-ending quest to find a diamond-in-the-rough with these preamps. Hopefully this is a decent unit, we'll see when I get it.

I was going to quote your post, but I don't seem to be able to multi-quote anymore? Not sure what I'm doing wrong there.

TomZ

[Millstonemike]

I thought that the antenna output voltage stayed 'on' as long as the radio was on though. So it's a temporary voltage for a few seconds? Well, looks like I have a few more things to learn!
TomZ

Not sure about the antenna voltage timing. I'd bet it's on as long as the unit is on powered - like a turn-on output for a remote amp. What I meant was the delayed relay can buy you extra time for the head unit to settle down before powering the amp. If that's needed.

I'd love to get one of these to tear down - perhaps amputate the power section. Alas, I have a major project going on in my other hobby ....

[tomzarbo]

I got this thing tonight and messed with it just a bit.
I didn't hook up to the speaker outputs yet, just the RCA outputs. No buzz or noise hooked up to a lepai 2020 amp. Looks to draw about .28 amps with the unit "off" with the time displayed on the screen, and about half an amp with the unit on.

I won't say too much until I get to spend a little time putting it through it's paces, but so far, so good; The interface is actually intuitive for one thing.



More in a few days...
TomZ

[Blenton]

Oohhh, jazzy!

I picked up a couple Blaupunkt Toronto media receiver a little while back that have a similar feature set to the less expensive model. BigDWiz of YouTube famedom tested the unit and made them well known. At the time, they were $12. $12!! And they used to be $10!!!! Now they r a whopping $19. But I used one with a meanwell power adapter and and old 2 channel Fosgate amp to power four 6.5” car speakers. For $12 I was blown away!

Interested to to see what u have to say about this one.

[tomzarbo]

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.

* The remote control has the worst plastic smell I've ever inhaled. But, it does have buttons that go 'click,' it uses two AAA batteries, and it feels rather good in the hand, I like it a lot.

* The screen resolution is very good, and the touch screen is adequately responsive to button presses... and most of my devices don't seem to think that I'm a living creature as they often don't register my finger touches as 'presses.'

I'll take a short video of how several of the functions operate if I can to show how it functions.



TomZ

[Millstonemike]

Tom,

Here's a 5V isolated DC-DC converter rated up to 200 ma. ~$2 from Ali-Express.