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Old 5th January 2012, 11:40 PM   #1
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Default the best 12v amp design/project

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.
Note: I am a beginner (did about 2 amps before) :-)
This might sound like a tall order, But what's there to lose?

Any ideas/links/former projects?

Thanks.
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Old 5th January 2012, 11:51 PM   #2
Pano is offline Pano  United States
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You'll only get about 18 watts RMS out of a real 12V amp powering 4 ohm speakers. You might hit 40W peak, if the supply is a bit hot - like 13 volts or more. However, you could see 16-17 volts with that big transformer after it's rectified and filtered. That would get you closer to your power goal.
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Old 5th January 2012, 11:54 PM   #3
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Would the filter caps have any influence on the voltage after it's filtered?
But how do those Car amp ic's get watts far larger than 18w out of 12 volts?
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Old 6th January 2012, 12:08 AM   #4
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They don't, unless they convert the 12V to 24V or higher or employ a BTL scheme. E

Last edited by mickeymoose; 6th January 2012 at 12:12 AM.
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Old 6th January 2012, 12:17 AM   #5
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Hi
There are probably only these two methods which are useful to extract more power from a 12V system.

1. Build a design using an output transformer with suitable taps. The output transformer can step up the output voltage.
But this would need expensive transformers. It used to be commonplace for old (1950's germanium transistor) amps because there were no high voltage power transistors.

2. BUild a ferrite core converter to generat +/-35V from your 12V supply. This is actually likely to be cheaper than using an output transformer design; and will let you use pretty standard amplifiers of your choice.
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Old 6th January 2012, 12:30 AM   #6
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So would the cheapest (and easiest) not be to use a car amp IC which steps up the voltage internally?
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Old 6th January 2012, 01:01 AM   #7
wahab is offline wahab  Algeria
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The cheapest and most efficient would be to buy one of those
Pioneer 12V car amps for a few dozen bucks.

Some have amazing perfs , better than the majority of DIY amps promoted
in audio forums.
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File Type: jpg PIONEER GM2200 2.jpg (668.9 KB, 510 views)
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Old 6th January 2012, 01:20 AM   #8
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Default maybe this can help you

I have not only designed a similar amplifier: a dual Op Amp driving a pair of Push-Pull MosFets, output transformer coupled, but I did it around 1996, commercially producing and selling them in somewhat great numbers (around 100 units).
And even so, I do not claim having had the idea "out of the blue".
I was somewhat inspired by Music Man guitar amps, which uniquely cathode drive 2 or 4 output tubes, with two very high beta power transistors, which in due time are driven by a couple Op Amps.
I thought that a MosFet was, in a way , "the tube and the high beta bipolar all-in-one" equivalent.
Breadboarding proved the validity of the concept.
No Simulation Software way back then, at least none available for me in Argentina.
Some pictures:

1998 Bass Player, happy with his "unplugged" 60W street amp:

Click the image to open in full size.

2000 Classic Double Bass player , also with 60W Battery Amp.

Click the image to open in full size.

This is the PCB (2002 upgraded version)

Click the image to open in full size.

This is the Top Overlay (Parts Layout)

http://img851.imageshack.us/img851/3...pwroverlay.png

It includes a 555 power oscillator inverter to get the -12V rail (actually 10/11V) for the Op Amp, which is a classic TL072.
The amp includes NFB from the speaker terminals, to provide *some* dmping and lower distortion to a bearable level.
Not Hi Fi by any means, but provided *LOUD* 60W RMS without "exotic" (way back then) converters,
Still a lot of them working , generally at Tourist spots, where AC power is unavailable or impractical (Public Squares, Beaches, Subway Stations, etc.)
jm2c
warm regards
andrew lebon
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Old 6th January 2012, 01:24 AM   #9
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Quote:
Originally Posted by andrewlebon View Post
I have not only designed a similar amplifier: a dual Op Amp driving a pair of Push-Pull MosFets, output transformer coupled, but I did it around 1996, commercially producing and selling them in somewhat great numbers (around 100 units).
And even so, I do not claim having had the idea "out of the blue".
I was somewhat inspired by Music Man guitar amps, which uniquely cathode drive 2 or 4 output tubes, with two very high beta power transistors, which in due time are driven by a couple Op Amps.
I thought that a MosFet was, in a way , "the tube and the high beta bipolar all-in-one" equivalent.
Breadboarding proved the validity of the concept.
No Simulation Software way back then, at least none available for me in Argentina.
Some pictures:

1998 Bass Player, happy with his "unplugged" 60W street amp:

Click the image to open in full size.

2000 Classic Double Bass player , also with 60W Battery Amp.

Click the image to open in full size.

This is the PCB (2002 upgraded version)

Click the image to open in full size.

This is the Top Overlay (Parts Layout)

http://img851.imageshack.us/img851/3...pwroverlay.png

It includes a 555 power oscillator inverter to get the -12V rail (actually 10/11V) for the Op Amp, which is a classic TL072.
The amp includes NFB from the speaker terminals, to provide *some* dmping and lower distortion to a bearable level.
Not Hi Fi by any means, but provided *LOUD* 60W RMS without "exotic" (way back then) converters,
Still a lot of them working , generally at Tourist spots, where AC power is unavailable or impractical (Public Squares, Beaches, Subway Stations, etc.)
jm2c
warm regards
andrew lebon
Very nice, especially the 555 power inverter.

I have yet another question, which would be better:

Two TDA1560 circuits,
or one TDA7850?
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Old 6th January 2012, 01:29 AM   #10
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Default pcb

hi this pcb and component layout is from diy audio its not my design and i have not tested it
warm regards
andrew lebon try ic UPC1230 GOOD SOUND AND SMALL PCB
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File Type: png faheymospwrbottomlayer.png (11.3 KB, 490 views)
File Type: png faheymospwroverlay.png (10.3 KB, 473 views)
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