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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
Out of interest, why not a PNP Darlington? (obviously the others and the capacitors etc would have to be changed too)

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Wed Aug 02, 2017 7:42 am
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
Sangoma wrote:
Out of interest, why not a PNP Darlington? (obviously the others and the capacitors etc would have to be changed too)



Just using what I have and I just don't think it would be necessary for what I'm playing with at the moment. I have a BD675 from the first amp, but I'll need two for this. The only other Darlingtons I have are TIP137s and as they use body diodes... probably will end in tears :)

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Thu Aug 03, 2017 6:58 am
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 Sick of over priced extention speakers from the big three. 
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Post Re: Sick of over priced extention speakers from the big thre
Time for an update:

Ok.. totally abandoned the class A design. Too power hungry.... problems with parasitic oscillations... impossible to control bias properly... it was a mess.

I've gone for class B, but with careful consideration of biasing to minimise crossover distortion.

Designed this amp from the ground up. I've simulated it in LTSpice, and it looks good. THD of 0.04 at 6 watts into 8 Ohms. Total power RMS should be around 7 watts.

Built on breadboard. Works well!

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Designed a new board for it.

Because the design reminds me of the old amps you used to get in 70s audio equipment, TVs, Radios etc, I thought I'd give it an appropriate name :)

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I need to change the driver transistors named on the board. They are now BD139/BD140s.

The design is working really well. Doing around 7 watts RMS with 24v feeding it.

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I love it when you design something from the ground up and it works. Great feeling.

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Fri Aug 11, 2017 11:10 pm
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