the best 12v amp design/project

[hannobisschoff@gmail.com]

Hi everyone.

I recently just wanted to build an amp that is powered by a 12v source, since I have a nice big beefy 12v 12amp transformer, and I thought a car amp IC would be perfect.

But easier said than done.
So I came to the forum for help:

The amp should be:
*powered by 12volts
*at least 40watt per channel (I only have 4 ohm speakers)
*at least stereo (more channels are welcome)
*nothing less than class AB

PCB's are REALLY welcome.

This might sound like a tall order, But what's there to lose?

Any ideas/links/former projects?

Thanks.

 

[canadaelk]

You propably should look at D-class power amps. Plenty of them available on ebay and schematics + pcb layouts from the IC mfgs.

I love those solder fumes too, but....don't use your email address this openly in your account unless you want a lot of crapmail or you are really, really lonely! E

 

[hannobisschoff@gmail.com]

Haha. thanks, but that adress is "obsolete"

 

[canadaelk]

Are there any other forums than diyaudio you posted on with the same Q? Don't want to waste my time. E

 

[hannobisschoff@gmail.com]

nope, sorry for wasting your time...

 

[audioguru]

For 40W into 4 ohms the power supply for a bridged amplifier must be about 23V, not 12V.

Your 12V transformer produces a full-wave bridge rectified and filtered 15VDC, not just 12VDC.
Digikey does not have stock on the latest and best car radio amplifier ICs but they have 979 of the older TDA2005. With the 15VDC supply it will have an output of 17W into 4 ohms just before clipping. It is a mono bridged amplifier.

Many class-D amplifiers on e-bay are 40 Whats which is really only 11 Watts. They use an obsolete Tripath IC (they went bankrupt 4 years ago) or a Chinese copy of it.

 

[hannobisschoff@gmail.com]

Thank you very much audioguru.
What is your opinion on an IC like tkis:
TDA7850
https://www.electro-tech-online.com/custompdfs/2012/01/0900766b80a333ea.pdf

 

[hannobisschoff@gmail.com]

Sorry, wrong link

https://www.electro-tech-online.com/custompdfs/2012/01/0900766b80a33a0e.pdf

 

[bountyhunter]

Hi everyone.

I recently just wanted to build an amp that is powered by a 12v source, since I have a nice big beefy 12v 12amp transformer, and I thought a car amp IC would be perfect.

But easier said than done.
So I came to the forum for help:

The amp should be:
*powered by 12volts
*at least 40watt per channel (I only have 4 ohm speakers)
*at least stereo (more channels are welcome)
*nothing less than class AB

PCB's are REALLY welcome.

This might sound like a tall order, But what's there to lose?

Any ideas/links/former projects?

Thanks.

You can buy high power auto audio amp units (with built in switching converters to create higher voltage rails to allow much more power output) for chump change.

 

[audioguru]

What is your opinion on an IC like tkis:
TDA7850

With a 14.4V supply its output per bridged channel is 30 Whats into 4 ohms with a horrible 10% clipping distortion.
With your 15V supply its output per bridged channel is about 22 Watts into 4 ohms just below clipping like most amplifiers.

It has 4 bridged channels so it will be a challenge to cool it.

Edit: I would never buy a "mini" motorcycle amplifier without any detailed spec's. Is 700 Whats actually only 11 Watts?

EDIT again: I don't know why Digikey (North America's largest electronic parts distributor) doesn't have any.

 

[bountyhunter]

I don't know the specs, it was just an example. I know there are a lot of low cost car amps around with good specs and a lot more power because they contain internal switching converters to create higher voltage operating voltages. Like:

https://www.amazon.com/Crunch-Power...1?s=electronics&ie=UTF8&qid=1325824080&sr=1-1

 

[hannobisschoff@gmail.com]

And would the TDA1562 be any good?

 

[hannobisschoff@gmail.com]

What would the current consumption of the TDA7850 be at full power?

 

[Nigel Goodwin]

What would the current consumption of the TDA7850 be at full power?

If you want a 40W amplifier then build one properly, don't bodge it by using the incorrect transformer just because you have one - buy the correct voltage transformer.

You might try googling for 'gain clone' which provide excellent quality low cost designs of similar powers to what you're looking for.

 

[audioguru]

Would the TDA1562 be any good?

I deleted its datasheet from my hard drive last year because America's 2 largest electronic parts distributors Digikey and Newark have not had any for about 4 years. It disappeared when Philips Semi changed their name to NXP Semi like most of their 70 car radio amplifier ICs.
It was an odd amplifier because it had a supply voltage doubler and a switch that selected the normal 13.2V supply or the boosted 26.4V supply. Maybe the switching was audible and sounded bad.

What would the current consumption of the TDA7850 be at full power?

Why don't you look on its datasheet?
With all 4 bridged channels driving 22W into 4 ohms with your 15VDC supply, its heating dissipation is about 13W per channel so its total power per channel is 35W and its total power for all 4 channels is 140W. Then its max current is 140W/15V= 9.3A.

Your 12V/12A transformer will almost be at its max rated power of 144VA.

 

[hannobisschoff@gmail.com]

Does anybody have the schematics or link to a nice STEREO gainclone
(preferably LM3886) project?

 

[audioguru]

There are many gain clone projects on the internet. They are all the same, a copy of the circuit shown on the datasheet.

 

[bountyhunter]

You can build a pretty decent bridge amp using the TDA2003 IC audio amps. Still lots of them around CHEAP. Here's 75 pieces new for $20:
**broken link removed**

Or 10 pieces new for $12:

**broken link removed**

I have a schematic for a DC coupled bridge amp for these designed to run off 12V. I ran it in the back of my Dodge for a lot of years.

 

[Nigel Goodwin]

You can build a pretty decent bridge amp using the TDA2003 IC audio amps. Still lots of them around CHEAP.

But only provides about 14/16W - far too low for his required 40W.

 

[audioguru]

His speaker is rated at 40 Whats (peak or peak-to-peak for only a moment?). Its continuous power rating for a sustained chord might be only 10 Watts or less.

RadioShack sold the Minimus 7 speaker which had a 4" woofer and a dome tweeter in a sealed cast aluminum enclosure.
I bought two and they sounded great. They were rated at 40 Whats each. When a woofer disintegrated I took the speaker apart and it was stamped "Korea nominal 5W, music 10W". The RadioShack replacement woofer was stamped "Japan nominal 5W, music 10W".