Distortion? or Clipping?

blap0220 · 16th July 2007, 04:42 AM

Hello Everyone!

I have a problem with my ESP P3A amp. It works beautifully up to a certain high volume level. When I turn the volume loud (not really loud), on certain songs where there's strong bass, I hear a slight fuzz *tststs* sound. This only happens on one of the two channels. I'm using the same components on both channels. Another thing is, when I turn the good channel off, the channel that fuzzes does not fuzz anymore. Does this point to a problem in the power supply? I don't think it's clipping because one channel does not ever exhibit this problem. Any suggestions would be appreciated?

Thanks

darkfenriz · 16th July 2007, 04:46 AM

sounds like something with grounding topology. Try experimenting with it and avoid any forms of loops.

jnb · 16th July 2007, 04:59 AM

Could it possibly be that one of your transistors has gone into secondary breakdown and needs replacement?

blap0220 · 16th July 2007, 05:17 AM

Secondary breakdown? I've replaced the power transistors already when trying to fix this issue. So are the driver or first stage BJT's susceptible to secondary breakdown as well?

I'm using 10,000uF on the rails. I was thinking about dropping this to 4,700uF to see if it would help. Does it make sense to try this?

Thanks

Jan Dupont · 16th July 2007, 06:15 AM

Lovering the rail cap value vill not help you in this matter....

If the buzz is in the range of 60 to 120 Hz I will support darkfenriz in the ground loop problem.....

Otherwise I would check all solderings one time more

jnb · 16th July 2007, 08:05 AM

It is conceivable. BTW, I've encountered this fuzz problem with op-amps. The fuzz seemed level dependent and was a little more like modulated white noise than hum.

AndrewT · 16th July 2007, 09:00 AM

Hi,
could this be instability in one channel causing oscillation?

blap0220 · 16th July 2007, 07:31 PM

I'm pretty sure it's not a ground loop hum. It's a white noise sound like jnb describes. I am more inclined to think it is a transistor, but wonder why it only occurs when both channels are playing. The noise does not occur if only the one channel is playing. Could it still be the transistor?

Thanks

anatech · 16th July 2007, 07:57 PM

Hi blap0220,

Quote:

I am more inclined to think it is a transistor,

From ...

Quote:

Could it possibly be that one of your transistors has gone into secondary breakdown and needs replacement?

No.
Once a transistor has gone into secondary breakdown, it has become a piece of wire that only looks like a transistor. Your problem is not a transistor.

I would support some of the other posters here like darkfenriz who is on the right track with ........

Quote:

sounds like something with grounding topology. Try experimenting with it and avoid any forms of loops.

ACD with ...

Quote:

Otherwise I would check all solderings one time more

AndrewT with ...

Quote:

could this be instability in one channel causing oscillation?

who I completely agree with. The instability could be caused by a number of things, so recheck all you work and solder joints carefully.

All these members are pointing along the same path, even though it may not appear that way.

-Chris

blap0220 · 17th July 2007, 04:56 AM

Well. I'm reluctant to believe it's a solder issue because I've touched every joint over. Doubt it's because of ground loop, because there is no hum. And the other channel works just fine. My wiring is pretty good as far as the layout. I am most interested in JNB's suggestion because he says that he has encountered this buzz before. Can a transistor be someone degraded but still functional?
THanks

16th July 2007, 04:42 AM	#1
blap0220 diyAudio Member Join Date: May 2007	Distortion? or Clipping? Hello Everyone! I have a problem with my ESP P3A amp. It works beautifully up to a certain high volume level. When I turn the volume loud (not really loud), on certain songs where there's strong bass, I hear a slight fuzz tststs sound. This only happens on one of the two channels. I'm using the same components on both channels. Another thing is, when I turn the good channel off, the channel that fuzzes does not fuzz anymore. Does this point to a problem in the power supply? I don't think it's clipping because one channel does not ever exhibit this problem. Any suggestions would be appreciated? Thanks

16th July 2007, 06:15 AM	#5
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	Lovering the rail cap value vill not help you in this matter.... If the buzz is in the range of 60 to 120 Hz I will support darkfenriz in the ground loop problem..... Otherwise I would check all solderings one time more __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com

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16th July 2007, 04:46 AM	#2
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	sounds like something with grounding topology. Try experimenting with it and avoid any forms of loops.

16th July 2007, 04:59 AM	#3
jnb diyAudio Member Join Date: Dec 2006	Could it possibly be that one of your transistors has gone into secondary breakdown and needs replacement?

16th July 2007, 05:17 AM	#4
blap0220 diyAudio Member Join Date: May 2007	Secondary breakdown? I've replaced the power transistors already when trying to fix this issue. So are the driver or first stage BJT's susceptible to secondary breakdown as well? I'm using 10,000uF on the rails. I was thinking about dropping this to 4,700uF to see if it would help. Does it make sense to try this? Thanks

16th July 2007, 08:05 AM	#6
jnb diyAudio Member Join Date: Dec 2006	It is conceivable. BTW, I've encountered this fuzz problem with op-amps. The fuzz seemed level dependent and was a little more like modulated white noise than hum.

16th July 2007, 09:00 AM	#7
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, could this be instability in one channel causing oscillation?

16th July 2007, 07:31 PM	#8
blap0220 diyAudio Member Join Date: May 2007	I'm pretty sure it's not a ground loop hum. It's a white noise sound like jnb describes. I am more inclined to think it is a transistor, but wonder why it only occurs when both channels are playing. The noise does not occur if only the one channel is playing. Could it still be the transistor? Thanks

17th July 2007, 04:56 AM	#10
blap0220 diyAudio Member Join Date: May 2007	Well. I'm reluctant to believe it's a solder issue because I've touched every joint over. Doubt it's because of ground loop, because there is no hum. And the other channel works just fine. My wiring is pretty good as far as the layout. I am most interested in JNB's suggestion because he says that he has encountered this buzz before. Can a transistor be someone degraded but still functional? THanks