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Old 7th March 2009, 08:30 AM   #1
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Default About a very very simple class D PA amp

Hello

Here is a very very simple class D PA amp.

For sure this amp would have a high distortion. This is my first class D amp, but it is only for 100 to 300 w for PA only.

Is there any errors in this schematic, and is there any suggestions of simples modifications to made it a bit better ?

For Q3 I would use MJ2955 or for higher power MJ15004

How about a power mosfet for Q3 ?

Thank you

Bye

Gaetan

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Old 9th March 2009, 07:32 AM   #2
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Hello

Nobody reply... wow the circuit are soooo bad ?

I found another one who seem better, it is a low power class D amp.

So, how about this one ?

Thank

Bye

Gaetan

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Old 9th March 2009, 11:28 AM   #3
Pafi is offline Pafi  Hungary
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None of them have any practical value. These are only veeeery old, very amateur experiments. Forget them!
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Old 9th March 2009, 10:33 PM   #4
fredos is offline fredos  Canada
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Right! Specialy with all transistor C-E error in second schematics!
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Old 10th March 2009, 12:21 PM   #5
Cheops is offline Cheops  Estonia
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http://static1.album.ee/files/77/381...77381_j4rB.jpg

Simple, cheap and working not very bad, considering the quality of TL494 "built in" comparators. Try DBL494, its a little bit better one(datasheet).
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Old 10th March 2009, 04:15 PM   #6
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Quote:
Originally posted by Cheops
http://static1.album.ee/files/77/381...77381_j4rB.jpg

Simple, cheap and working not very bad, considering the quality of TL494 "built in" comparators. Try DBL494, its a little bit better one(datasheet).

Hello

Is there a web page giving more infos about that circuit ?

Why 60 v for the mosfet and 30 v for the speaker ?

Thank

Bye

Gaetan
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Old 10th March 2009, 07:30 PM   #7
Pafi is offline Pafi  Hungary
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Quote:
Originally posted by Cheops
http://static1.album.ee/files/77/381...77381_j4rB.jpg

Simple, cheap and...

Unfortunately it contains some errors. U1 Pin 15 and 16 swapped, left side of R3 should be connected to U1 Pin14.

Output DC level should be adjusted very precisely, carefully, without load.
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Old 10th March 2009, 10:34 PM   #8
Eva is offline Eva  Spain
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There are much better ways to do a class D amplifier without much more parts or expending much more money.

Also, this output stage with bipolar transistors is not likely to produce much more than +/-1A reliably and is not efficient due to the voltage drop on the 1K resistors, it's designed the wrong way.

Do some research...
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Old 13th March 2009, 02:21 PM   #9
Cheops is offline Cheops  Estonia
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Quote:
Originally posted by Pafi



Unfortunately it contains some errors. U1 Pin 15 and 16 swapped, left side of R3 should be connected to U1 Pin14.

Output DC level should be adjusted very precisely, carefully, without load.
Sorry about those mistakes; too quickly drawn image(original on paper ).

The +30V is actually PSU-s ground(not the amplifiers). Measuring the circuit is a lot easier this way.
Some pics: http://static1.album.ee/album/262631/50086439

Btw this version is the first one(perfoboard), just for practice, and uses ferrite in its output filter. First three os-pictures show heavy ringing, which was eliminated by ceramic caps in power rails(C10, C11, etc; other 3 os-pics).The second version uses double sided PCB and ferrite is changed to iron-powder one(T106-2).Cam is broken and I cant make more pics...
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