Buzzing amp.

[gregga41]

Hi guys,
as usual, when i have a problem, guitar or amp-wise, i turn to you all.
I recently bought a near-new Fender Hot Rod Deville 4 X 10.
I'm new to tube amps, as this is the first i've owned.
The problem is a massive Buzzing when connected to my guitar.
I can still play, as the volume of the music, overrides the buzz.
It's when i stop playing that the overwhelming buzz takes over.
When i disconnect my 330 from the amp lead, there is no buzz.
I've tried a different guitar,(Epi casino), the buzz is still there.
Anyone had this proble? Is it the amp, the lead or the guitar?
How do i tell?
I'm thinking should the amp be serviced?
Really, i don't have a clue!
HELP!

[kiramdear]

Are you set up near any fluorescent lights or appliances, things like that?

[doctorwho]

Could be a ground loop from something not being grounded right. Hard to diagnose from afar.

One easy thing to check: make sure that you are using a shielded instrument cable between the guitar and the amp. If the cable is an unshielded speaker cable (sometimes they look the same on the outside!) that will be the cause of the problem (picking up RF interference).

[doctorwho]

Greg, any luck yet?

BTW, the reason I mentioned the cable is that I was using a cable at the last mini-con that is "bad" in that it was producing a high-pitch "hiss" (which, I must confess, I did not notice - and I thought I had good hearing!).

[soundmasterg]

If the amp is quiet with no instrument plugged into it, then it is most likely a problem with your instruments, or the cord that you are using to plug them into the amp. Also as mentioned, flourescant lights, dimmer switches on lights, etc., can cause hum and/or buzz problems. Do you have any guitars with humbuckers on them to try as a test? They should be much quieter than the single coil pickups in most situations. Make sure the cord you are using to plug in is an instrument cable and not a speaker cable as the speaker cables ones are not shielded. With nothing plugged into to the input of the amp, if you turn the volume up to half way or so, is the amp buzzing a lot or is it somewhat quiet still?

Greg

[gregga41]

Greg, any luck yet?

BTW, the reason I mentioned the cable is that I was using a cable at the last mini-con that is "bad" in that it was producing a high-pitch "hiss" (which, I must confess, I did not notice - and I thought I had good hearing!).

Thanks for all the input guys.
It seems to be a mixture of all things mentioned here. The studio we use for rehearsal doesn't seem to be wired all that well, as we sometimes get the vocals from another band coming through our amps. Last week in the studio, i set the amp up differently, ie: angled it upwards, purchased a few new leads, and the buzz seems to have faded immensely. Our lead guitarist plugged his brand new strat in, and it buzzed worse than my 330.
I also noticed that when our vocalist adjusted the levels for his microphone at the mixer, the buzzing increased. It's pretty much sorted now, but i have to remember to switch my Boss SD-1 off after using it.

[gibsonlp]

Sounds like a bad grounding to me.