Noise on top of note

[pops]

Hello, i have recently had two amps that when you play a note especially a low note and let it ring a static starts on top of the note as it is ringing. Amps are fairly quiet, note is solid and it only happens a second or so as it is ringing. It is not noticeable when playing normal, but very apparent if you let a not or chord ring. Thanks for any help.

[Structo]

This usually a sign of parasitic oscillation.
Or cross talk from wires that shouldn't be close to each other.

It is usually caused by (especially in a new build) by poor lead dress.
Particularly in the wiring of the first stages.

This is not discounting the possibility of a poor ground or any other cold soldering joint.

If you built this amp from a proven design, then lead dress is usually the culprit.

Be sure to separate the grid wires and plate wire (unless it is a Dumble ).

Take a chop stick or similar (non conducting) and while the amp is on and connected to a speaker, poke around the wires near V1, V2,

You can usually tell because the sound will change when you poke the right connection.

The best thing to do if you can't figure it out is to post some high resolution pictures of the amp.
Then if anything is obvious to the skilled members here, they will let you know what they have observed.

Welcome to the Amp Garage.

The one and only place, for the best of the best.

[pops]

Thanks Tom. One of the amps is a fender super 6g4 and it has been thru some changes by someone or two, It must be in between the 4 and the 4a as it has circuitry of both, but the faceplate of the 4a. The other is something i thru together and will look at lead dress, it is of no particular schematic.

[martin manning]

FWIW, your original inquiry is not very clear. It sounded like these amps might have been working properly and the noise is a recent problem, but I'm still not sure. Now we know that one is a commercial product with mods, and one is a home-brew, so these are two different situations. Better to ask about one at a time, or at least put them in separate threads. The more specific you are about the details and the questions you ask, the more likely you are to get a response.

[JazzGuitarGimp]

Your post also didn't specify whether or not you're ysing the same guitar and cable with both amps. If this is the case, I'd suggest you try a different guitar / cable before you do anything else.

[pops]

guitar with one amp and mandolin with the other, different cords. Just struck me odd as i haven't experienced it before and then to hear it in two amps in a matter of a week. The 6g4 has a different power tranny and output and ss rectifier. Plate voltage is 505 on the 6L6's. It was biased way hot so put in new power tubes and biased it at 36 ma. A little hot, but in the range and sounded strong. Noise was there before and after, didn't have a lot of time, to look at it, my friend wanted to use it that night.

[Scumback Speakers]

My thoughts to diagnose are as follows...eliminate all of the external easy to swap variables first.

1) Change cabs/speakers. If it still does it then it's not your cab/speakers, unless the one you're using is also bad. Usually that's rare.
2) Change preamp tubes to known good ones, or borrow some from a known good sounding amp to test. Power tubes you said you already did.
3) Change your cables (input and speaker) to known good ones, tested on another amp first.
4) Change guitars to a known good one, just in case you have a loose wire/ground, etc.

If all of this doesn't do it, then you're having fun finding something inside the amp, with tapping, chopsticks and a multimeter.

Good luck!

Jim

[pops]

Just found time to go back in the amp, you nailed it Structo, moved a first preamp wire a tiny bit away grid to plate and no noise. Thanks

[Structo]

That is good news, these types of problems can be hard to track down.

Good job!