Marshall JCM600 Question

[mikjwilli]

While running my JCM600, I max out the Master Volume and control both channel's volumes with each individual volume knob. My clean channel is super quiet. However, the distortion channel is very noisy. In fact, some of my band mates have commented.

Is this normal for this amp? I realize I'm pushing the power amp while maxing out the master. The gain level is probably on 7-8.

I just picked the amp up used and I'm not sure about the condition of the tubes, etc.

Thanks in advance-

[some_dude]

Unplug your guitar lead from your amp and turn it on.

Is it still noisy?

If it is, it's the amp, and it may need to be checked out.

If it isn't, something in your signal chain is causeing the noise.

[Tom M]

Gain + volume = electrical noise. Is your treble/presense high too?

[Simon_F]

I have a JTM600, which is pretty much the same as a JCM600. If you're running with the master volume maxed I'm guessing you have your channel volumes quite low. But on the distortion channel you have the gain up. Inevitably the increased gain will lead to more noise on the distortion channel than on the clean channel. This is normal.

Are you using a multi FX (or any FX for that matter)? Many Multi FX units will add noise to your chain even when no FX are switched in, and this will add a lot of noise to a gained-up distortion channel.

[Jeff_H]

Yup....what they said is spot on. Check to make sure the noise isn't comming from your guitar first. You can also try swapping the pre-amp tube in V1, which is the small tube that is farthest away from the 2 main power tubes. That will tell you if that tube has become microphonic or otherwise bad.

If you're running the Master Volume that high to get extra gain, I've got a suggestion for you. Run your master at about 5, and your channel volumes at about 5 also, adjust them as needed. Take a patch cord (as short as possible, the type you would use to connect 2 pedals) and put the ends in the in/out of the parallel effects loop. This will add extra gain that you can control from the Parallel Effects Loop knob on the front of the amp. Set your main gain slightly lower, and then add gain with the PE Loop knob. Also, turn the presence down a little. The JCM600 is fairly bright to begin with.

[mikjwilli]

Thanks everyone! I'll try everything suggested. Re: FX - I only run chorus and delay thru the loop. O/wise, I do run from my gtr to a crybaby to a Boss tuner and into the amp.