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Old 17th February 2012, 12:12 AM   #1
JZatopa is offline JZatopa  United States
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Default picasso class A amp - mods and tips

So i just picked up a picasso class A amp for a pretty good price. I am running it bridged on a pair of DE500 + image dynamic horn bodies. I had the set the gains differently on each side for some reason but now that they are equal both channels sound the same. I do however have a hiss, I am not sure it's the amp or a problem elsewhere that has been magnified by the new amp. Is this an issue with these amps?

So what mods have people come up with to improve the sound of this amp? I am running it on 8ohm compression horns and I am considering upping the bias so I can make sure the amps are staying in class A. For an amp that is supposed to be class A it did not get warm in the hour I have used it so far.
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Old 17th February 2012, 12:19 AM   #2
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This amp cannot be made to operate full class A. Anything over a few watts will cause it to go to class AB operation.
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Old 17th February 2012, 12:58 AM   #3
JZatopa is offline JZatopa  United States
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I only new a few watts, my horns are 107db/w/m. Actually I'm not that worried about it leaving class A. I am worried that these amps are supposed to run hot and this one is not. There is a chance that it has been opened up or repaired before. Is there a guide for checking the bias?

What else can be done to improve the sound of these amps besides cap upgrade and opamp upgrades. I would not be surprised to find that opamps have come a long way since these amps were made.
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Old 17th February 2012, 01:30 AM   #4
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I don't know what the factory specs for bias are for this amp.

I don't help with mods unless they are needed to make the amp reliable.
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Old 17th February 2012, 02:38 AM   #5
JZatopa is offline JZatopa  United States
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Should I be concerned about the difference in gains for each bridged channels. I balanced them but shouldn't they be pretty close already?
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Old 17th February 2012, 04:21 AM   #6
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"This amp cannot be made to operate full class A. Anything over a few watts will cause it to go to class AB operation"

how will i be able to keep it below a few watts? i want it to stay in all time class A how can i do this?
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Old 17th February 2012, 07:16 AM   #7
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Only play it at low volume.

You cannot distinguish between a well designed class B amp and a class A amp. Class AB is the best compromise.
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