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Post by alwaysfreezin on Mar 4, 2008 13:59:41 GMT -7
Hello! I just got an original Rx Head today and I love it!!! I'm running it through one of Z's older 2x10 cabs and it's killer. It does have a slight hum that seems to be coming from the bass, middle, and treble pots. When I turn them all the way down, the hum is gone, but when I turn them up, together or individually, they introduce a hum corresponding with the pot. What I mean is the bass pot introduces a lower frequency hum and the treble pot a higher frequency hum, etc. Not horrible, but definitely there. The volume level does not affect the hum. Any ideas? I'm guessing it's the tubes, but I don't know which ones. Also, the hum is not present when it's on standby. Thank you!
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Post by benttop (Steve) on Mar 4, 2008 14:16:25 GMT -7
I'd be almost willing to bet that it's one of the first tubes in the signal path, most likely the EF86 but maybe one other. Actually I don't even know if that amp has an EF86 now that I think of it, but no matter, check V1 and V2 and replace as appropriate. Those are not real expensive tubes typically...
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Post by alwaysfreezin on Mar 4, 2008 16:52:45 GMT -7
thanks for the advice, I'll check those out!
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sco77
Junior Member
Posts: 66
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Post by sco77 on Mar 4, 2008 17:14:59 GMT -7
V1 should be a 12ax7. If you can get a NOS tube, it will sound better based on my experience. I never noticed any "hum" necessarily, just that the amp is LOUD!!
Scott
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Post by anacephalic on Mar 5, 2008 8:40:22 GMT -7
might want to check your power tubes as well. i had a set that was poorly matched but not horrible and i stuck em in anyway to see how bad they sounded. hum city baby.
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Post by benttop (Steve) on Mar 5, 2008 9:57:55 GMT -7
Power tubes can cause a lot of hum, but if the hum goes away by changing the tone settings, the hum is most likely coming from something in front of the tone stack. Nevertheless, my policy is to try changing every tube in the amp before I consider any other possibility since tubes can do the weirdest stuff!
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Post by alwaysfreezin on Mar 5, 2008 11:56:42 GMT -7
So I replaced all the pre amp tubes (three 12ax7's) but the hum was still there. I also heard a soft crackling noise and the sound that was like a soft wind blowing across a microphone. Could that be the other tubes?
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Post by ruger9 on Mar 5, 2008 14:59:58 GMT -7
I also heard a soft crackling noise and the sound that was like a soft wind blowing across a microphone. Could that be the other tubes? THAT sounds like a power tube to me. Get a new matched quad.
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Post by alwaysfreezin on Mar 5, 2008 15:10:40 GMT -7
Update: I replaced all the tubes and the crackly/wind noises are no more! The hum from the tone pots is still there, so the good doctor recommended I have the grounds on the pots and jack checked out. I think that's all i can do for now I guess. The tone is still there and it's to die for! The worst part of having no patience is wanting the darn thing fixed now!! It's still playable. I'm taking it to a session tomorrow and I'll post how it goes.
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