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Post by scottunzicker on Sept 16, 2022 7:50:53 GMT -7
Howdy, all! Short story long, I get a gentle onset and gradual increase of a high-pitched thweeeeeeeeee sound on the Z-Lux when I'm running in 40 watt mode. Settings: pre-volume nearly maxed out at 5 o'clock, treble around 10 o'clock, mid nearly off at 7 o'clock, and the bass anywhere between 9-10 o'clock. The only thing that makes it stop is rolling the Master volume all the way off. I then have to bring it back up and find out how far I can push it, which is usually around 9 o'clock or so. Cutting the Reverb doesn't do it, and neither does rolling off the pre-volume. Oh, also, I'm running just a tiny amount of boost/bypass. Of course, I'm guessing tubes, but I've tapped them all and nothing seems particularly microphonic, and I JUST replaced the 5881s with a brand new matched quad (paid more than DOUBLE what I did two-ish years ago).
Any advice or suggestions welcomed.
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Post by headshrinker (Marc) on Sept 16, 2022 8:01:32 GMT -7
If it doesn't do it in the half power mode, I'd guess a power tube. If you still have the old ones, put them back in and see if it does it. If not, it's a power tube. Mark where you take the ones in there are before you remove them. I believe in half power the tubes that are "not used" are the outside ones, though it could be inside. Try swapping insides to out sides. and then see if it does it in half power. If it does it limits the problem to two tubes instead of four. Swapping them around may solve the problem, if it's just a positional thing.
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Post by scottunzicker on Sept 16, 2022 8:06:20 GMT -7
If it doesn't do it in the half power mode, I'd guess a power tube. If you still have the old ones, put them back in and see if it does it. If not, it's a power tube. Mark where you take the ones in there are before you remove them. I believe in half power the tubes that are "not used" are the outside ones, though it could be inside. Try swapping insides to out sides. and then see if it does it in half power. If it does it limits the problem to two tubes instead of four. Swapping them around may solve the problem, if it's just a positional thing. Yeah, I'm hoping that's it. If it is the power tubes, that chaps my butt a little bit, as they're less than a month old.
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Post by premiumplus (Dave) on Sept 16, 2022 8:51:55 GMT -7
I think the tubes that are cut in half power mode are offset. Not pairs like every other half power scheme that I've seen. Swapping positions may help, like Marc says. The output tubes are V6-V9, so it would be (V6, V8) or (V7, V9) pairs that are cut. If memory serves it's (V7, V9). I remember because I went round and round with microphonic JJ tubes a few years ago and went to 5881s. I ended up going back to 6V6s when JJ got their act back together.
At any rate, I agree with Marc. If it's only happening in half power mode it's likely an output tube.
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Post by nmz on Sept 16, 2022 10:01:17 GMT -7
Thinking power tubes
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Post by daddyelmis (Greg) on Sept 16, 2022 10:55:20 GMT -7
I think Doc confirmed his half power design keeps power on all tubes at some level, rather than cutting all power to a pair, and that’s one way that the amp keeps its tone at half power.
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Post by scottunzicker on Oct 3, 2022 6:25:29 GMT -7
Well, new tubes didn't solve the problem (at least I have two good sets now?). I have discovered that whatever power tube (I use 5881s and have swapped various ones in that position) lives in V10 seems to be really sensitive to the tap test, being much noisier than the rest. Can a socket make things go haywire like that?
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Post by premiumplus (Dave) on Oct 3, 2022 7:51:02 GMT -7
The tube socket might need retensioning, or the 'shark' tube retainer may be loose. Check to make sure the socket mounting screws are tight. Having one socket behave like that is a new one on me.
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Post by scottunzicker on Oct 10, 2022 7:20:05 GMT -7
Short story long, V1 and V2 were JUST microphonic enough to set a chain reaction going at high volumes to produce the sound. I ordered a nice, NOS JAN GE 5751 for V1 and already had a JJ ECC83 lying around for V2, swapped them in, and all seems well. Hope everyone has a good week. I'm taking the Z-Lux to play the Chevy Main Stage at the State Fair here in Texas tomorrow (Tuesday 10/11) with the Rob Roy Parnell band. Cheers!
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