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Post by dlfcci on Apr 15, 2006 12:21:34 GMT -7
Half way thru a gig last night, I started hearing a low volume, high pitched squeal. A first, my sound man thought it was feedback from a mic. I finally discovered that it was coming from my amp. I stopped it by backing off my master a little bit. At the time, I had the master and volume set at about 2:00. Has any one else experienced this? What could cause it?
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robt
Full Member
Posts: 138
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Post by robt on Apr 15, 2006 12:33:53 GMT -7
When this has happened to me, it turned out to be a microphonic power tube--although it was not on a Z but an F. I swapped out the preamp tubes during the show in a frantic effort to fix it because I thought they were the problem. I had put in new power tubes the day before. Well, one of them was bad. I got through the gig by turning down the amp between songs. It was outside and over 100 degrees. Lesson learned: no back up power tubes. With the Maz it's easy to swap power tubes since you don't have to bias. Good luck.
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Post by amakitalo on Apr 15, 2006 12:35:26 GMT -7
Mine does that sometimes if my reverb is too high together with high master volume.
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Post by John on Apr 16, 2006 9:16:09 GMT -7
It's been my experience that a high pitched squeal is a pre-amp tube. Usually V1. However, since MAZ amps burn up el84's at a pretty decent rate, I'd get some new power tubes, because even if it's not the problem, you'll use them sooner or later. Also, being a cathode biased el84, you should ALWAYS have backups around. Put the backups in, see if your problem still exists.
I have not experienced this on my MAZ, but that's only because I keep pretty fresh tubes in it. However, back in my poor days, I had several problems with microphonic preamp tubes over the years. So I've been there.
I'd even try changing around the existing preamp tubes. This option doesn't cost any money. If V1 has gone micro (or reverb driver), by changing them around, chances are you'll put a decent tube in the socket that's been causing the problem. If the squealing stops, question answered.
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Post by Greg G. on Apr 17, 2006 21:30:53 GMT -7
Yeah, I had that happen to me once at a gig with my Trem-O-Verb combo. Made it through the gig and later changed the preamp tubes and all was good again.
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