Tonefiend Forum

Hello Tonefiend...ers?
I've run into a problem.
My setup consists of an old Hofner 4578, with original mics (yet not original wiring), and a Fender Prinecton 112+.
The amp started to make noise recently, even at 0 volume. That is problematic.
Yet, what's more problematic is this: when playing an E on the 14th fret of the 2nd string, or on the 9th fret of the 3rd string, the note starts getting sustained a tad too much. After a few seconds, it's become a roaring, high pitched buzz, and the string itself starts to vibrate on its own out of feedback. This also happens with the open A string as well; after a while of leaving it alone it gives the same high pitched E.
It's quite unbearable, and completely breaks a solo if you happen to play those frets.
What I realized was that by setting the pickup volume to a rather low number (under 5) this doesn't happen as much. So I'm guessing there's something wrong with the pickups?
Has something similar happened to anyone?
Thanks in advance

This sounds like acoustic feedback (where the amp drives the string), and not magnetic feedback (where the amp drives the pickup). The biggest reason I think that is because the string is vibrating, and it's at certain notes (E&A).

My guess is that for some reason, there is now more gain at that high E frequency. The frequency of E3 (E one octave above the 1st string E) is 164.81Hz. If you are hearing harmonics of this frequency the feedback could be at any integral multiple of that frequency.

My first piece of advice is to fix your amp. This may fix the problem by itself.

If that doesn't work, you may try physically moving the guitar and amp - this would change the acoustic path for feedback.

That's very useful info, thank you all.
By mics, I meant pickups, sorry! And no way I'm replacing them, they make the guitar get a certain tone I wouldn't like to get rid of.
Fixing the amp is my main priority now, but I really do need to consider the cost. The amp cost me around 400 dollars (2000 argentinian pesos, but things are much more expensive here). If it's a simple fix, then it shouldn't be that much of a pain.
I did actually move the amp around quite a bit the last few weeks, but it wouldn't stop happening. Turning my back to the amp also didn't help, nor pointing the axe in any direction for that matter.
A friend told me that maybe it's the acoustics of the room that make that specific frequency ring as it does. I find it feasible, but not much I can do about that.
I do confess though, I kind of like the unlimited sustain (sometimes). Damping it just a bit and toying with the volume pot for a while... it can be fun. But I feel this pro doesn't outweight the cons.
Thank you so much for your advice. I'll see what I can do!

sounds to me like a bad solder joint inside the amp, probably the input jack. when you hit the resonant frequency of the cold solder, it starts oscillating.
if you're handy and know how to take stuff apart, try cleaning and tightening all the jacks and pots on the amp, and if you open it up, make sure all your grounds are good.

usually when i see this kinda problem cross my workbench, it's a cold joint on the ground of the input jack.