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Post by Peegoo 🏁 on Aug 5, 2020 22:43:10 GMT -5
That sounds like possibly "shot noise" usually associated with a bad resistor somewhere in the preamp stage.
Sometimes resistors go bad; sometimes they're bad right out of the box. Look here:
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Aug 6, 2020 6:50:38 GMT -5
If the normal channel is ok, then the 1st / easiest thing to try is to swap the tubes in V1 and V2 around.
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Post by larryguitar54 on Aug 6, 2020 18:11:25 GMT -5
It's in both channels. So I"m suspecting a tube that is preamp for both. Otherwise I'm guessing it's in the circuit board. This is my son's amp and it's right out of the box new from GC. I don't know how it sounded at the store but this is what he got when he got home.
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Post by larryguitar54 on Aug 6, 2020 23:53:05 GMT -5
Okay some amp guru explain it to a 6 year old.
I assume, looking at the back of the amp it goes V1, V2 etc from right to left and V1 is preamp for Normal and V2 is preamp for Vibrato?
I read somewhere that if there is static in both channels then the likely culprit is V1 because it is a preamp for both the Normal and Vibrato channel. V2 is, I think, the preamp for just the Vibrato channel.
So that should mean either swap V1 and V2 and see if the Normal channel is quiet and the Vibrato channel is noisy then it should mean that tube is bad. If that doesn't work then try any other 12ax7 in V1 and if quiet then it tells me both of the V! and V2 tubes were bad.
Thoughts?
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Aug 7, 2020 2:10:06 GMT -5
I’m confused - do both channels have the same noise issue? Apart from their power supplies, V1 is independent of V2, no one signal path includes both. If both do the same noise, all I can think of is that the decoupling cap for the HT node that supplies both channels has gone bad in an unusual way. But yes, back to the shop with it  |
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Post by larryguitar54 on Aug 14, 2020 14:34:38 GMT -5
Problem solved. Return and refund.
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