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ash_dac 8th June 2006 09:49 PM

Introduction to Power Amplifiers (Diy kit)


Is the green LED used in the bias for temperature compensation ?

The power output is a bit low but I may try the kit as it could be modified for higher power (I only need 10W).

Any thoughts ?

Tim__x 8th June 2006 09:55 PM

This doesn't look like a great amp to me. No collector load for Q1, poor temp comp. (Vbe multiplier would be better), no turnoff resistors for the drivers, poor low-frequency response (100ufs is to small). If you want more power, I'd pick a different design.

Clever bootstrapping, but that's about all I can say.

sreten 9th June 2006 08:39 AM


Yes the green led is used for biasing, but temperature compensation is minimal.

I agree with TX's comments, you may learn something by building it
but an IC based solution for example will have far better performance.
The design IMO is not suitable to be scaled up to 10W.


ash_dac 9th June 2006 04:53 PM

thanks for the advice

Tim__x 9th June 2006 08:08 PM

There are a lot of other good kits out there, and a few good boards (like the ones at Rod Elliott's Elliott Sound Productions).

Almost any amp can be scaled down more easily than up. ESP's Project 3A can be scaled down with only a change to supply voltage (15v+15v would be good), R8 (10k), R9/10 (1.5k) and C5 (220uf). Even that much is probably unneccasary.

teemuk 9th June 2006 08:43 PM

Every circuit can be scaled up or down and optimized but you have to know how to do it first. I have to admit that I liked the tutorial and I wish I would have seen it two or three years ago when I was still struggling to learn how simple power amplifiers work. It gives some food for thought and a nice alternative for building just chip amp kits. IMO it may be a very effective way to start learning about discrete amplifier circuits. Maybe the circuit does not impress with superb sound quality but I think the original idea was to keep it as simple as possible, otherwise it might scare away the people who know fairly little about PA circuits. I think, the design is fairly good for something with 1/2 to 2 watt power rating and serves the purpose of the kit well.

Leolabs 10th June 2006 01:36 AM

Hi ash(aka Peter Crouch???),Gainclone should be a good heardstart.:)

ash_dac 10th June 2006 12:22 PM


I have purchased Audio IC Op-Amp Applications by Walt Jung for a good price.

I'm hoping this book will provide a good background reading for gainclones, preamps, IV convertors for current DAC's.

For Power amplifier design I was thinking about one of Doug Self's book.

Any thoughts ?

pinkmouse 10th June 2006 12:27 PM

Self is excellent, but technical. Slone might be an easier start.

mikeks 10th June 2006 03:10 PM


Originally posted by pinkmouse
Self is excellent, but technical. Slone might be an easier start.

On the contrary, Self's book is concise and to the point...

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