PreAmp hiss....gate or revalve?

[Twigman]

My HA3500 has quite a hiss from the tube side of the pre....my tech at work has ordered a couple of new 12AX7s to try to see if one of them can quieten it down but I was wondering if sticking a noise gate on the effects loop of the amp might be the answer?
The effects loop is post the pre-amp, isn't it? (not so sure about this)
Anyone tried this to eliminate tube hiss?
What drawbacks might there be?

[Ziphoblat]

The effects loop is after the pre-amp on every amp I've ever encountered. I'd imagine replacing the pre-amp valves is the first port of call. I had a problem with my Genz Benz Shuttle 6.0 hissing a lot (along with a master volume that didn't do anything) which ended up being a loose jumper cable. You could reduce how noticeable the noise is and make it less irritating by gating it out, but it's still going to reappear each time you hit a note, you'll get a much purer signal by eliminating it at the source.

[4 Strings]

There's only one valve, they're not expensive and the worst that can happen is that you've bought a spare valve. If your tech reckons that's the problem give it a try, if it's not he'll have to try something else.

If the effects loop is after the preamp then this is the best place for your gate isn't it, so it can gate out noise made be the preamp. It could have no effect on it if before.

However, I honestly don't think there's much point filtering out faults, where would it stop with a dying amp and a rack full of effects?

They are good amps, worth getting it fixed, if you can't they aren't expensive on the 2nd hand market, get another. (I've got an ad for an HA5000 on here somewhere!) Probably cost as much as a noise gate.