Introduction to Power Amplifiers (Diy kit)

ash_dac · 8th June 2006, 09:49 PM

Hi,

http://www.electronic-kits-and-proje.../3000/3048.pdf

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

Hi,

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.

http://sound.westhost.com/project72.htm

/sreten.

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

Hi,

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

Quote:

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...

8th June 2006, 09:49 PM	#1
ash_dac diyAudio Member Join Date: Jan 2005 Location: UK	Introduction to Power Amplifiers (Diy kit) Hi, http://www.electronic-kits-and-proje.../3000/3048.pdf 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 ?

10th June 2006, 12:27 PM	#9
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Self is excellent, but technical. Slone might be an easier start. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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8th June 2006, 09:55 PM	#2
Tim__x diyAudio Member Join Date: Jun 2004 Location: Edmonton area, Alberta	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.

9th June 2006, 08:39 AM	#3
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, 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. http://sound.westhost.com/project72.htm /sreten.

9th June 2006, 04:53 PM	#4
ash_dac diyAudio Member Join Date: Jan 2005 Location: UK	thanks for the advice

9th June 2006, 08:08 PM	#5
Tim__x diyAudio Member Join Date: Jun 2004 Location: Edmonton area, Alberta	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.

9th June 2006, 08:43 PM	#6
teemuk diyAudio Member Join Date: Nov 2004 Location: Suomi, Finland	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.

10th June 2006, 01:36 AM	#7
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Hi ash(aka Peter Crouch???),Gainclone should be a good heardstart.

10th June 2006, 12:22 PM	#8
ash_dac diyAudio Member Join Date: Jan 2005 Location: UK	Hi, 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 ?

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