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Old 31st October 2008, 12:31 PM   #1
spirus is offline spirus  Greece
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Join Date: Jun 2005
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Exclamation Ever heard sth like this?

I just had the following peavey classic amp brought for making a loud sound just like microphonics!
I thought it was some tube going out...
Tested with an ES335 close to the cab and while the normal channel didn't do anything when i switched to the lead channel I had it screaming and playing...
i changed the second tube which is engaged in the lead channel only and...
I switched to a telecaster thought it might be the hollow body resonating due to its proximity...
The microphonics seemed to vanish but while driving the lead channel full cw and reverb full cw there it is!
I thought due to its open pickups etc etc
I tried a gibson standard covered pickup poles and playing away from the cab...
And imagine that when playing through the normal input I have the sound even playing less volumewise...
When trying the bright input I have nothing volumewise even in high volumes!
The difference between the two inputs is just a resistor and a capacitor!!!
Might it be the carbon resistor had gone bad?
Anyone encountered a problem like this before?
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Old 5th November 2008, 08:14 AM   #2
spirus is offline spirus  Greece
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Default I c...

no one?
so I'm encountering a unique problem, ha?
better look at it moer caerful from the begining...
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Old 8th November 2008, 03:41 AM   #3
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Those amps have a pretty high gain channel and if you're standing right in front of the speaker using a stock Gibson Humbucker or a Fender single coil it probably will be microphonic with nothing out of the ordinary in amp or guitar.

With this said I've seen a cable, a jack or a bad pot make a bad microphonic sound before, a squeal at high volumes. Our guitarist Robby had such a problem at the last gig so on the first break I tightened the contacts on the jack in his guitar, problem solved. He doesn't use a really high gain amp but he does use a lot of volume while playing lead.
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Old 15th November 2008, 08:18 AM   #4
spirus is offline spirus  Greece
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Default thanx but....

thank you dave for the info but unfortunately...
I unscrewed all the pcbs(a real pain in the ***!!!) I ersoldered I changed the tubes but I still have the same problem!
do you think I should replace the resistor in the normal channel?
it seems quite strange to me but...
any more ideas?
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Old 15th November 2008, 08:27 AM   #5
spirus is offline spirus  Greece
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Default the shemo!

just in case...
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File Type: gif peaveyclassic212poweramp_800x600.gif (37.8 KB, 130 views)
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Old 15th November 2008, 08:31 AM   #6
spirus is offline spirus  Greece
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Default the schemo!

just in case...
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File Type: gif peaveyclassic212preamp_800x600.gif (46.8 KB, 113 views)
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Old 15th November 2008, 08:33 AM   #7
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What happens if you put a Boss pedal (no true bypass) inbetween you guitar and amp... is it gone?

I am thinking guitar cable inductance//capacitoance resonance..usually a non-true-bypass pedal solves it..
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Old 15th November 2008, 10:37 AM   #8
spirus is offline spirus  Greece
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Default well...

to tell you the truth I haven't tried something like that...

but...

why was that non existent before???
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