#1
So I'm getting high frequency feedback from my Fender Twin (90's small knob version), specifically when I turn my Reverb up around 6, or if I turn on my Phaser, certain combos of my reverb pedal and two delays.

I've had this thing for 7 years, and I haven't changed tubes or anything like that. Not much of a handyman by any stretch of the world, but I'm willing to get my hands dirty.
#2
If the problem is a tube they are very easy to change. If they've been in there awhile, be patient pulling the tube out but there's no need to get your hands dirty.
Fender Mustang/Derfenstein DST> Boss Power Wah> Pedal Monsters Klone> Bogner Uberschall> Walrus Audio Janus> Randall RM20> Line 6 M9> Randall RM20
#4
I just sold a 90s Twin today.
When the reverb is engaged, it's always had a little hiss, like the overdrive was on.
From what I read and read and read, this is a very common problem for the 90s Twins.

But if it's actually a high feedback and not hiss, then the reverb tube is my number 1 guess.
Do the eraser trick on the tube to see if it's bad.
Awesome!
#5
Buy a new preamp tube and try it in every position until the problem goes away. And no, biasing is not the issue and it only applies to power tubes. It is possible that it's a microphonic power tube but unlikely.
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#6
Quote by sheaaa
I just sold a 90s Twin today.
When the reverb is engaged, it's always had a little hiss, like the overdrive was on.
From what I read and read and read, this is a very common problem for the 90s Twins.

But if it's actually a high feedback and not hiss, then the reverb tube is my number 1 guess.
Do the eraser trick on the tube to see if it's bad.


What is the Eraser Trick?