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Please Help With Ground Loop!!!
Old 23rd September 2010
  #1
Gear Head
 
TYSE LEE's Avatar
 

Please Help With Ground Loop!!!

Hi there,

Our new Studio B consists of a very simple layout and signal flow incl. ISA220, Eureka, Fender Rack Tuner, and digi pre's.

I have just bought a Radial BigShot ABY so we are able to go:
Input - Guitar
Tuner Out - Tuner
Out A - Eureka Pre (DI)
Out B - To head/amp

Using Out A alone has some hum but then as you add the Tuner and Out B the issue gets much worse (while still only listening to Out A).

Advice?
Old 23rd September 2010
  #2
Gear Head
 
TYSE LEE's Avatar
 

Please Help With Ground Loop!!!

Bump
Old 23rd September 2010
  #3
Gear Head
 
TYSE LEE's Avatar
 

Please Help With Ground Loop!!!

Bump?
Old 24th September 2010
  #4
Registered User
From what i can tell about the Bigshot ABY, only output B has the isolation transformer. In theory, that should eliminate any ground loop between two different amps.

My guess is that the rackmount tuner is a chief suspect. This is AC powered? So basically if there is any potential difference between the ground that the tuner is plugged into, and the amp that is connected to Output A - you will have a ground loop. In theory Output B should be isolated.

Does flicking the ground lift switch make any difference?

I would try temporarily replacing the rackmount tuner with a battery tuner, to see if the problem goes away. If it does - I would get a cheap isolation transformer just for the tuner. Quality for the tuner signal won't matter at all.

I find Radial stuff to be generally very good. In a perfect world, every output would be transformer isolated, but that would bump up the cost.

It's possible that this isn't ground loop hum. Maybe you have a noisy environment that isn't conducive to long unbalanced cables. It seems to me that the ABY box is really intended as a stage box, where the cables are relatively short. For studio use, if you are running long cables between rooms, I would recommend using balanced cables - I just can't get along with the noise that unbalanced cables pickup.

There are plenty of options to consider - Radial certain have some solutions to this sort of problem.

Personally, I'm a fan of passive Reamp boxes, for solving all sorts of problems. If you go direct from your guitar to a DI/preamp, you can send the balanced line level a long distance, and then use a Reamp box sitting on top of your amp to drop it down to instrument level. That keeps your unbalanced cables as short as possible. Being passive, you get complete transformer isolation.
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