#1
Ok, here's the deal, I've got one of the 120 Watt JSX heads, the one with the built in noise gate.

Well, I recently got into a metalcore band, not exactly my chosen style, but I'm having a surprising amount of fun with it. Anyway, the music we're playing demands the highest distortion and volume I can crank out of my amp.

The problem is I'm getting crazy feedback, and it's just been getting worse and worse. I usually have the noise gate cranked at 10, but today I plugged in, and was met with an ungodly, banshee like squeel of feedback. I cranked the volume on my guitar down to nothing, and I was still getting it. So I messed with the noise gate, and realised it was having absolutely no effect. I can't even use the crunch channel anymore without getting this damn feed back, it just won't go away.

A few months ago I had a power surge blow some tubes, and after repairs the tech told me the transistor had been affected and is operating on a slightly wonky frequency. He said it may never really pose a problem, but I'm not sure, could it be that it's finally up and quit on me?

I really don't know what the hell is going on here, any help would be greatly appreciated!
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#2
The volume on your guitar was down, and you STILL got feed back? That sounds like a problem with the amp to me.
Quote by sargasm
There are no genres in metal that end with "core."
#3
Quote by `digitaL.braVo
The volume on your guitar was down, and you STILL got feed back? That sounds like a problem with the amp to me.


or possibly the cable?
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#4
Turn down the gain?


You dont need so much that the amp constantly feedsback
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#5
Quote by Teh GIR
Turn down the gain?


This also is good advice, on my head 75% of gain is is equivalent to 100% gain. Minus all the feed back!
Quote by sargasm
There are no genres in metal that end with "core."
#6
I tried turning down the gain, barely did anything. I had it down next to nothing and was still getting it.

I have yet to check all the cables though, hopefully that's all it is.
My Gear:
2006 PRS SE Singlecut with Dragon pickups
2003 Yamaha acoustic
2001 Squire Strat
28Watt Squire Champ 15
65Watt Peavey Express 112
Digitech RP200 Artist Effects Pedal
Boss Compressor
#7
It could also be a microphonic preamp tube. I had to replace one recently.
#8
A friend's amp has a similar problem some of the time. It's usually a bad cable connection that causes it and by turning the amp off and reconnecting the cable making sure that it connected properly gets rid of it. (He should just get a new cable but he's a cheapo.)

This may not be the same problem on yours however and you have to be more careful powering on an off all the time with a tube amp.
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#9
- Could be a bad preamp tube.
- The onboard noise gate only eliminates hiss, not feedback.
- A Boss NS-2 or ISP Decimator will help. I run one of each with my JSX.
- Turn down the gain and the channel volume.
- Turn up the master volume.
- Don't stand too close to the speakers.
- Try not to have the Treble, Mid and Bass dials set too high. They are active and when set higher than 5 they start to add output to your signal, increasing noise.
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#10
Try the old pencil trick, trun the amp on ethier OD channel then trun the amp down so it no longer feeds back, the lightly tap each preamp tube with a pen or pencil if you hear any of the tapping coming through your amp that tube needs replacing. If thats not the case then mabe you need a pedal noise gate as van Noord sugested, or it could be you are just have it setup and eqed so poorly that it feeds back no matter what. Or it could be an amp issue, since you have already had some work done you might be beter of to get the transitor replaced that the tech said was questionable, try the pencil trick before you take it back in.
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