TC RH450 Strange hum

[ingenius]

Guys,
have just submitted this to TC Support its really strange but i thought somebody here might be able to throw a little light onto it

"Can you help me with a really strange fault with my RH450.My 2 passive basses, a 2005 Rickenbacker 4003 and a 1997 De - Armond Starfire both hum when plugged into the head. This hum goes away when you either A. Turn both pick up volumes up to near max, or B. The hum nearly disappears if you touch the strings or bridge. I have changed the instrument cable and this has no effect. So i cannot play on different pick - ups as when i turn one down the hum appears.
I also have 2 active basses, A MM stingray 2008 and a 2009 Sandberg California JJ4 which do not suffer at all. The Sandberg has 2 pick ups which i can choose from...the stingray is a single H."
thanks in advance
Keith Murray

[Ou7shined]

Given the above, it doesn't sound like the amps fault. Sounds more like your passives need shielding (assuming they have no earthing issues).

Edited April 5, 2011 by Ou7shined

[icastle]

[quote name='Ou7shined' post='1188715' date='Apr 5 2011, 10:19 AM']Given the above, it doesn't sound like the amps fault. Sounds more like your passives need shielding (assuming they have no earthing issues).[/quote]

+1
The amp just amplifies whatever it sees applied to it's input socket, it doesn't differentiate between active\passive basses.
Given that the hum almost disappears when you touch the bass metalwork, I'd say there's a poor earth connection somewhere.

[ingenius]

[quote name='icastle' post='1188780' date='Apr 5 2011, 11:26 AM']+1
The amp just amplifies whatever it sees applied to it's input socket, it doesn't differentiate between active\passive basses.
Given that the hum almost disappears when you touch the bass metalwork, I'd say there's a poor earth connection somewhere.[/quote]

MMM yep that is what i thought.. but why doesnt it happen on the Active basses...could this just be a coincidence that both passives are faulty ??
regards
Keith

[icastle]

[quote name='ingenius' post='1188791' date='Apr 5 2011, 11:33 AM']MMM yep that is what i thought.. but why doesnt it happen on the Active basses...could this just be a coincidence that both passives are faulty ??
regards
Keith[/quote]

It could be, but that's quite a coincidence.
The two passive basses are significantly older than the two active ones.
Although the baseline technology remains pretty similar, the materials and construction\assembly methods used have generally improved somewhat.

I'd be tempted to take a peek inside on of the active basses and compare that to the guts of one of the passive basses.
I bet the active basses are nicely shielded inside and have nice shiney solder connections while the passive ones are just electronics in an unshielded wood cavity with a few dull joints.

You don't by any chance have (or have access to) another amp to check that the problem stays with the guitars?

[ingenius]

[quote name='icastle' post='1188819' date='Apr 5 2011, 11:51 AM']It could be, but that's quite a coincidence.
The two passive basses are significantly older than the two active ones.
Although the baseline technology remains pretty similar, the materials and construction\assembly methods used have generally improved somewhat.

I'd be tempted to take a peek inside on of the active basses and compare that to the guts of one of the passive basses.
I bet the active basses are nicely shielded inside and have nice shiney solder connections while the passive ones are just electronics in an unshielded wood cavity with a few dull joints.

You don't by any chance have (or have access to) another amp to check that the problem stays with the guitars?[/quote]

Thats my next line of inquiry.. i need to find an amp to borrow just to exclude that.. also will change the power lead ( kettle type) to the amp just in case the earth has gone faulty
thanks for the reply and thoughts
regards
Keith M

[angosmyth]

Hi. I have the same problem and it's driving me insane. The amp never made that noise before but now it started. I have tried my basses in other bass amps and there is no issue. Did you get your amp sorted?

[HowieBass]

If it's just started happening and you haven't had the grounding fault with those basses previously (and that could be what the hum is by the sounds of it) then I'd suspect a fault with the earth to the amp - try a different power lead or have a look in the mains plug itself (if it's the type you can open up rather than the moulded on variety) to see if the earth has come adrift. You could also try the amp plugged into a different mains socket just to eliminate that too.