Parasitic oscillation?

[corduroyew]

One of my customers replaced their fender vintage noisless single coils with a set of my pickups and I just got this message from them.

On my guitar, when the amp is cranked, I get this weird tremolo effect when I dig into the strings. It's rather annoying, and almost makes the guitar sound out of tune. I'm thinking it may have to do with how much feedback the guitar is getting, so I'm going to shield it soon to see if that helps. What do you think may be causing this predicament?

I'm pretty sure he is using an epi VJ that he modified for more gain. I was thinking this sounded like it could be Parasitic oscillation from the amp. The Epi VJ is not known for having this type of problem but it could be the mods he has done to it. His old pickups didn't give him this trouble but they were noisless singles which have horrible high end anyway. The pickups he got from me were formvar so they have lots of high end. I've emailed him some questions to help further trouble shoot this issue but I was wondering if any of you have any ideas about what might cause something like this.

[EtLa]

it sounds like stratitis, the single coil pickup is set to close to the strings.

[corduroyew]

That was my 1st thought too but I wanted to give him the benifit of the doubt because he does know how to properly set up a guitar. I guess I didn't want to insult him by bringing that up 1st thing but I guess even people that know what they are doing can overlook little things.

[jack briggs]

it sounds like stratitis, the single coil pickup is set to close to the strings.

+1. Wolf tones (not Wolfetones!)

[EtLa]

I guess I didn't want to insult him by bringing that up 1st thing but

sorry I didn't mean it too

[corduroyew]

sorry I didn't mean it too

LOL... I meant to his face. People get upset when you state the obvious. You know what I mean? Even though 9 times out of 10 it is the obvious solution that fixes the problem. I just worry too much about upsetting people.

It probably is just wolf tones from the pickups being too close.

[Possum]

funny....

damn this is such a good example of how stupid some guitar players can be
Tell him he needs to change all the tone caps in his amp, that'll keep him busy for hours. Parasitic oscillation in an amp is real noticeable it usually starts to build then sounds like its going to blow your amp or your amp just cuts out.
This is a really good example of why NOT to fully charge your strat magnets also