Adrian89

Hello guys, my main head is a JCM 900 SLX and when I push a fairy amount of gain, it sounds with a lot of HMMMMMMMMMMMM. I dont know if the amp got that sound because of the gain or it maybe has any issue....

__________________
TH3 G3Ar
- JCM 900 SL-X and SV MKII 100HD with LIne 6 sv412
-Bunch of pedals ( WD,BM,NR-2...)
-Ibanez Universe uv777pbk,Rg 2550&321mh
-http://backtorlyeh.bandcamp.com/

MrFlibble

When you turn gain up everything is compressed and amplified. That means not just your guitar's signal but also any 50 cycle hum, noise, interference and whatever else.

You can either turn your gain down or you can use a noise gate/suppressor; putting one light noise gate before the amp and a heavier noise gate in the amp's effects loop is the best way to reduce excess noise without ruining your guitar's signal and amp's tone too much.

__________________
Yes, I know everything. No, I can't play worth a damn.
A child is trafficked and sold for sex slavery every 30 seconds. Support Love146.

Adrian89

Can also be the electrical installation of our rehearsal room? The amp sounds as good as always but that noise...

__________________
TH3 G3Ar
- JCM 900 SL-X and SV MKII 100HD with LIne 6 sv412
-Bunch of pedals ( WD,BM,NR-2...)
-Ibanez Universe uv777pbk,Rg 2550&321mh
-http://backtorlyeh.bandcamp.com/

tukk04

It could very well be dodgy electrical; like MrFlibble said a noise gate could help, but if you suspect electrical because the amp is quiet at home, a power conditioner could help. Even just a $39 (US that is) monster rack conditioner.

__________________

Adrian89

IT was from a day to another, It started to make this NSSSSSSS sound when on high gain settings, doesnt sound when playing and we have even recorded and its not present but...Sounds like a ****ing fridge

__________________
TH3 G3Ar
- JCM 900 SL-X and SV MKII 100HD with LIne 6 sv412
-Bunch of pedals ( WD,BM,NR-2...)
-Ibanez Universe uv777pbk,Rg 2550&321mh
-http://backtorlyeh.bandcamp.com/

zl1288

Sounds like a preamp tube is going bad to me, if you have any spares try to swap them out and see if that helps