Low E string harsh

[Colas LeGrippa]

Hi, on a small high gain amp of my own, everything's fine but an issue with oscillation I think. When hitting the low E string rapidly,  I get a weird buzzy sound. The amp is very well filtered and I went through all soldered joints.
I don t have the schem cause I didn t draw it.
It is a SE amp , one plate driven power tube, 4 gain of stage. So, 2 X 12ax7 plus the power tube. SS rectifier, no tone stack (as usual in my builds ).
Lead dress seems ok to me.
What would be the cure ? (bad answer: remove gain.).


Thanks

[jim]

I suppose you have tried another guitar through the amp?  Sometimes the problem can simply be a loose speaker or chassis screw rattling around. Hard to say what could be
going on based on your post.  Jim

[shooter]

I get a weird buzzy sound.

had that on an SE, mine was guitar, fat E string.  not a guitar guy so it took me a minute 

other things;
powering gain stages, good practice, no more than 2 per PS tap
if "V1A" is un-bypassed, or too much cap on cathode
coupling caps not well suited to bass freqs

time for my nap 

[Colas LeGrippa]

To get rid of oscillation generally speaking can I put a low cap 50pF or so accross a plate resistor of a given stage ? On a pp a snubber cap accross powerbtubes plates will do the job

[shooter]

plate resistor of a given stage ?

yup, has some effect on tone

[Colas LeGrippa]

I know, that s my problem....oscillation with good tone or no oscillation with poor one...
Lowering the pre volume pot does the.job.
So I ll live with it. Thanks.
( I was hoping that there was a magic trick unknown from me   )

[shaun]

I rebuilt a GA-5 a bunch of different ways, trying to get rid of what I assumed was some sort of distortion in the bass end of the spectrum - drove myself crazy. Then I switched from my modded tele to a strat, and that did the trick.

I had put an oil and paper cap in the tele along with hi-output pups a few years earlier, so I now wonder what I did to the guitar that it distorts the low end. Never heard until now, I guess.

[Colas LeGrippa]

Found the issue finally.
I had moved the two 100uF in series to make room for the tone pot I would have liked to install. That has been the beginning of issues that I solved by swapping the filters caps by a cap can that I  installed outside the chassis. I guess the proximity of the 100uF caps with othet components was causing the motorboating sound over the guitar. Now the inside of the chassis  is cleaner, my guitar tone is cleaner and my mind is cleaner too.


I swapped the 20 uF.of the 2 preamp tubes by 47uF ones. Uselessly. I swapped them back for 20uF...I thought that was a cap issue, anyway I worked all day on that . I swapped the 5881 for a gold lion 6550 NOS from the 60's that I got for free. Now this amp got a killer tone.


Btw, how can I post a sound clip in this forum ?


Colas