rack power amp buzz - grounding problem? anyone?

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university81

university81

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so I recently aquired an older 2u rocktron velocity 300,

after replacing the fuses it powers up and sounds fine except for an annoying buzzing sound in the background (kind of like when your guitar is not grounded or your hands aren't touching the guitar with gain). which stays at a constant volume unless i bridge the two channels, in which case it's doubled

is this easily fixed?
or simply a ground loop issue together with the other rack gear hooked up? (in this case an axe fx)

I'll have it checked out by an electrician friend otherwise, figured i'd ask here if there was something i could try on my own first

** update**

it really buzzes in bridged mode, the channels separately seem to be ok, or at least the buzz is hardly audible, will see what can be done, ideas welcome tho

thanks
 
try different outlets in the house, assure its not a local problem with the power source.

check speaker cables, instrument cables - make sure its not a cable grounding out your signal source from being bent.

isolate the power amp from the axe-fx and the rack, power them up separately. this will help isolate any major problems if they exist before ruling a voltage potential across the ground plane heard as ground loop hum.

most likely the rocktron needs a recap and a going through if it is an older unit, especially for safe measure. probably would not hurt to send it to your friend anyway for some regular maintenance if you can.
 
update on this, brought it to work , and tried with a different power cable through a multi socket and... no buzz absolutely nothing , it worked perfectly as it should

after looking at it, it would seem that the power cable i was using at home might not be grounded properly, or maybe the outlets at home aren't .. the unit itself is fine

something i didn't think of at all, but i'll try out some different power cables now as well

the one i was using worked fine with the blackstar ht-5 and everything else...time to try some different cables

thanks for the suggestions glpg
 
Sounds like it could be the cables or even the outlets in your house Paul. I have had some bad buzz/noise problems like that at my place and it's really annoying.
 
well the plot thickens :)

tried it at 16ohms through another cab and the buzz was back...same cables and everything

at 8 ohms through another 4*12 the buzz is hardly noticeable but it is there just very faint

as i got the schematics, a friend who knows what he's doing is going to have a good look through it to see if there's a dodgy connect somewhere, hoping to get it fixed, bought it used and the guy has gone awol since it's been delivered, not very impressed as it was apparantely in perfect working condition...my ass
 
I HATE buzzing! I get a buzz in my setup when SOMETHING in my house goes on, and it stops when SOMETHING goes off!? Refrigerator? Furnace? I can't tell, but it's something!
 
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