bad 'grind' undertone from my amp

[skuller]

recently ive noticed an annoying buzz, of sorts, coming from somewhere in my rig.

to give perspective: Mesa DR 3Channel > 4 ohm out > Mesa Road King Cab.

I noticed this sound the first time I ran the cab in 4 ohm. There is some sort of strange buzz, lingering beneath the tone I like from the amp. Hopefully this makes sense, but the amp sounds good, bar this obnoxious grinding sound (not a good grind) that seems to ride below the amp.

With my FX loop on, its not quite as noticeable (10 band EQ, decimator), but it is still there. I took some clips last night with a 57, and I can post it if I remember to bring it home (my studio has no internet access), but its really starting to bug me.

Any ideas as to what this could be? It doesn't sound like a blown speaker, as it's not popping. I've tried several instruments through the rig. Epiphone LP w/ stock pups, LTD F250 w/ EMG HZ4, LTD EC400 w/ EMG 81/85, Ibanez S7 w/ stock pups, and Epiphone LP w/ EMG 81/85. Not quite as noticeable w/ the actives, but still present.

I think it may be the tubes needing replacement, but then again I'm not sure. I have the amp running in silicon diode mode. Orange channel on 'vintage', and red channel on 'modern'. The sound isn't very noticeable at all on the green channel.

Thoughts?

 

[Matt Crooks]

Sounds like a grounding problem (particularily since it's less obvious with the actives). Try using the amp in another part of the house. Also try using a different guitar cable.

Also, is the RK cab 4 ohm? I thought it was 8ohm for all 4 speakers, but I don't have one...

 

[kaomao]

maybe it's something like this. Who assembled the cab lef it inside, it was near the magnet of the cone and it was producing a buzz.
I found it on my cheap harley benton cab, as soon as I remove it, it sounded good.

 

[skuller]

Matt Crooks-
That sounds like an annoying, but completely plausible situation. I have only been running it out of one power supply. I will try that later this evening after work. Thanks for the suggestion.

The RK cab has 2 sets of 8 ohm in (one for each pair for 12's), and one 4 ohm in thats used to run all 4 12's.


kaomao-
Ill open it up tonight to check it out. Sounds like another annoying, but plausible scenario.:zombie:

Thanks for the comments. Feel free to post more if other ideas come up, as again, I don't have net access at my studio.