redgl
Junior Member
Posts: 62
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Post by redgl on Mar 17, 2006 8:20:54 GMT -7
I was playing through my MAZ Sr. last night when I noticed a loud high end hum that occured suddenly when I brought my amp up to a certain level. Everything was very normal until I exceeded 2:00 Master and 1:00 Preamp Volume. Increasing either control above this level started the hum which was very shrill-like but not feedback. It's hard to say how long this may have been a problem because I recently started using a Weber Mini-Mass and first noticed it when I flipped its bypass switch. I disconnected the Mini-Mass and the problem was still there. I haven't played at this high of a volume since I first got the amp and was putting it through the paces. Everything was fine back then.
I have well under 100 hours on the amp, most of which with the Master at 9-10 O'clock. At low levels the amp still sounds as articulate as it ever did (to my ears anyway).
I can still crank the amp as loud as I want with the mini-mass on and there's no problem but as soon as I hit that bypass, look out - squeal city. Should I just go ahead and replace the power tubes?
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Post by John on Mar 17, 2006 10:32:58 GMT -7
First thing I'd do is change out V1 and V2. Before you do this, try gently tapping V1 with your fingernail with the volumes(s) just below the shrill point. (I suppose somebody's going to tell me that's the wrong thing to do...and they may be right!)
sounds like a form of tube rattle. My experience with a higher end hum has come at the expense of preamp tubes rather than power tubes. Sounds like what us old farts call "tube whistle".
Even with most of your playing with a master on 9-10, you're still going to burn through el84 tubes faster than traditional A/B amps. But at 100 hours (or less) I wouldn't be the least bit surprised at burned up el84.
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Post by myles on Mar 17, 2006 11:43:42 GMT -7
First thing I'd do is change out V1 and V2. Before you do this, try gently tapping V1 with your fingernail with the volumes(s) just below the shrill point. (I suppose somebody's going to tell me that's the wrong thing to do...and they may be right!) sounds like a form of tube rattle. My experience with a higher end hum has come at the expense of preamp tubes rather than power tubes. Sounds like what us old farts call "tube whistle". Even with most of your playing with a master on 9-10, you're still going to burn through el84 tubes faster than traditional A/B amps. But at 100 hours (or less) I wouldn't be the least bit surprised at burned up el84. Your idea of V1 / V2 is right on the money. Right off the bat just swap V1 and V2 as it is more likely V1.
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redgl
Junior Member
Posts: 62
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Post by redgl on Mar 17, 2006 12:43:53 GMT -7
Thanks (and karma) to both of you!
I just ordered up some Svetlana 12AX7s as per the Dr's post from some time back. In the meantime I'll switch it out with a reserve I have, for the weekend.
It's probably about time for me to get a new quad of power tubes, too. Any suggestions?
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