HELP!!! My amp is messed up!!!

jbright44

Member
Messages
1,034
I have a mesa boogie nomad 100 head. On channels 1 and 2 everything is fine, no matter the gain, no matter the volume, but on channel three, if I get it turned up past a certain volume (using the master, the ouput or the gain control) it starts whistling this really loud, really shrill whistle. It only does it on channel 3 and I've even tried standing in different locations and as far away from the amp as possible to rule out feedback and it still does it. It stops doing it when I play the guitar then starts back again when I stop. I've got the amp set to 60 watts its got a brand new matched quad of JJ 6L6 power tubes and 5 brand new JJ ECC 84's and my rig is as currently as follows:


Guitar -> New Korg DTR 1000 -> amp -> cab. I'm controlling the channel switching with and Axcess Electronics CFX4 and a Behringer FCB1010. There is nothing in the effects loop.

Please help me figure out what this could be. I'm at a loss.

EDIT
Ok, scratch that. With enough volume, it does it on channels 1 and 2 as well, but they are more like rediculous levels of volume than I will not be using at this point (output on 3:00 master on 3:00). The thing is, the 3rd channel does it at a volume level that I consider relatively low (gain at 11:00, master at 9:00, output at about 10:00). Could it be speakers? It is a small room (10 ft/10 ft'), could it be feedback? I'm really worried here. Please someone help.

EDIT II
I'm using a Gibson Les Paul Standard w/ Burstbucker Pro pickups.
 

TechpriesT

Member
Messages
273
check your cables, buy george L's for the most noiseless.
Put copper shielding foil on the inside of your electronics cavity on the guitar and under the pickups. While your at it try a noise suppressor on your amp.
The only way something is wrong with your amp as i see it, is if you turn down the volume on the guitar and it still makes the whistle.
 

John Phillips

Member
Messages
13,040
Does it stop if you roll the guitar's volume down?

If yes, it's the pickups.

If no, it's probably a microphonic preamp tube (just because they're new doesn't mean it can't be), or - very unlikely, but just possible - something to do with the Korg.
 

jbright44

Member
Messages
1,034
Originally posted by John Phillips
Does it stop if you roll the guitar's volume down?

If yes, it's the pickups.

Yes it does. So it's the pickups. Well, I like these pickups. What can I do to stop it?
 

John Phillips

Member
Messages
13,040
You could have them wax potted.

They may not sound exactly the same though. You really have to choose - if you like the tone of unpotted pickups, you're just going to have to accept not using as much gain and/or volume in a small space... :(
 

John Phillips

Member
Messages
13,040
If you can get further away from the amp, in a place where there aren't so many reflections off the walls, you'll stand a better chance of controlling it.

10'x10' is a pretty small room for playing loud guitar in...

I like slightly microphonic pickups, BTW. I occasionally have trouble in our usual practice room, which is about 10'x20' - some days are louder than others :). Backing off the tone knob a bit helps, usually.

I never have any problems on stage, even though I'm actually louder there. One thing to avoid if at all possible is guitar in the stage monitors though.
 




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