Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: munkeyboy on February 04, 2021, 02:52:18 pm
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I know I must be missing something very basic.
In the past few amps I've been building, I keep getting static/fizz/buzz kind of sound at breakup. I've been thru different cables (speaker and instrument), different speakers/guitars, re-flowed solder joints, checked bias, swapped known good tubes, clean/re-tension tube sockets, etc.. On my last SE build, I've tested three different OT: 2 old vintage and one brand new. In fact, I've gone thru 3 different circuits with that as well. All components are new, besides tubes, sockets and iron (except the new OT I tried). This sounds like it could be blocking distortion, but I have tried grid stoppers, conjunctive filters, lower coupling caps, lower bypass caps, shielded cables, etc.
Older builds don't seem to have this issue. I have a particularly high gain orange tiny terror 6v6 build that doesn't have any static/fizz. Uses the same cab and cables as other tests.
I'm not looking for a walkthrough assistance on this latest amp. I will post separately for that. However, since this is an issue I seem to face often, I would love to capture different personal experiences with this phenomenon and what was used to correct it. Especially if they were abnormal cases. Oddly, it is difficult finding sound examples of blocking distortion or oscillation.
Also looking for a good tutorial for the simple man on using a scope to find issues. I have a digital scope and a cheap wave generator. I have tried using this in the past without much luck.
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static/fizz/buzz kind of sound at breakup.
simple things;
those terms typically point to bad solder, sloppy socket, arcing between pins
using a scope to find issues.
set the sig-gen up with the scope;
clean sinewave, 800hz-1000hz, amplitude ~~~ 100mVac
once you're confident that's what the sig is and the scope verifies, record image;
plug the signal where the guitar plugs in, set all knobs to 5 (verb trem OFF)
put scope on speaker wires, record image
the 2 images should look about the same (might have to adjust vol/gain if there's clipping)
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static/fizz/buzz kind of sound at breakup.
simple things;
those terms typically point to bad solder, sloppy socket, arcing between pins
using a scope to find issues.
set the sig-gen up with the scope;
clean sinewave, 800hz-1000hz, amplitude ~~~ 100mVac
once you're confident that's what the sig is and the scope verifies, record image;
plug the signal where the guitar plugs in, set all knobs to 5 (verb trem OFF)
put scope on speaker wires, record image
the 2 images should look about the same (might have to adjust vol/gain if there's clipping)
Thanks. Is there bad solder vendors/wire that can cause issues. Granted, I'm using thin solder wire right now cause that's what I had on hand from pcb stuff. It is quite frustrating to work with and will be ordering new thicker wire.
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Bad solder connection(s) to chassis?
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what he said^
I use 22ga, which is small, if you're using 30ga, you might have problems
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Yes, i'm using 0.1mm (not sure what that equals in gauge.. 38ga?). Just ordered kester 44 .062