Amp distortion

zeus_threat · 27th July 2006, 04:06 PM

Hi i've been simulating and i have built this amp. Simulation shows distortion and veroboard protoype has problems with inductive loads(x-overs, e.t.c). A 0.5uH helps but does not cure it. Can anyone help?

Thanks

davidallancole · 27th July 2006, 04:27 PM

Where are you putting the inductor? In line with the speaker? What about adding the zobel network from the speaker + to gnd?

CBS240 · 27th July 2006, 04:48 PM

Hi Zeus

Try a forum search on Zobel network. It is discussed extensivly.

http://users.ece.gatech.edu/~mleach/...oads/zobel.pdf

darkfenriz · 27th July 2006, 05:49 PM

I don't know if this is the problem, but R3 is too high. Try around 820ohms.

janneman · 27th July 2006, 06:16 PM

Decrease C4 to 10pF, see if that stops instability.
Sims donot take into account all kinds of parasitic caps and inductance. The map is not the world.

Jan Didden

Nelson Pass · 27th July 2006, 06:40 PM

You are going to need an RC network to ground at the output
(say .1 uF and 5 ohms) no matter what you do.

davidallancole · 27th July 2006, 06:44 PM

I agree with darkfenriz as well. R3 should be lower. Have you put an oscilloscope on the output to see if it is oscillating?

zeus_threat · 27th July 2006, 07:05 PM

Well the inductor in series helped solved mostly but not completely the problem. Shortcircuited in parallel with a 10R resistor is worse. I'll try the 1uF from output to ground. But still my main problem is distortion i am seeing in the simulation. Anyone has any idea where its coming from? Simulation o/p attached for 20Hz and 20KHz signals.

zeus_threat · 27th July 2006, 07:06 PM

Attached is the schematic of the prototype i have built

teemuk · 27th July 2006, 07:11 PM

Looks like clipping into rails... Does that CCS for voltage amplifier stage work properly?

27th July 2006, 04:48 PM	#3
CBS240 diyAudio Member Join Date: Aug 2005 Location: K-town	Hi Zeus Try a forum search on Zobel network. It is discussed extensivly. http://users.ece.gatech.edu/~mleach/...oads/zobel.pdf __________________ All the trouble I've ever been in started out as fun......

27th July 2006, 06:16 PM	#5
janneman diyAudio Member Join Date: May 2002 Location: Where Germany, The Netherlands and Belgium meet Blog Entries: 6	Decrease C4 to 10pF, see if that stops instability. Sims donot take into account all kinds of parasitic caps and inductance. The map is not the world. Jan Didden __________________ /Another new issue: Linear Audio Volume 3!

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27th July 2006, 04:27 PM	#2
davidallancole diyAudio Member Join Date: Nov 2005	Where are you putting the inductor? In line with the speaker? What about adding the zobel network from the speaker + to gnd?

27th July 2006, 05:49 PM	#4
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	I don't know if this is the problem, but R3 is too high. Try around 820ohms.

27th July 2006, 06:40 PM	#6
Nelson Pass The one and only Join Date: Mar 2001	You are going to need an RC network to ground at the output (say .1 uF and 5 ohms) no matter what you do.

27th July 2006, 06:44 PM	#7
davidallancole diyAudio Member Join Date: Nov 2005	I agree with darkfenriz as well. R3 should be lower. Have you put an oscilloscope on the output to see if it is oscillating?

27th July 2006, 07:11 PM	#10
teemuk diyAudio Member Join Date: Nov 2004 Location: Suomi, Finland	Looks like clipping into rails... Does that CCS for voltage amplifier stage work properly?

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