Earth Problem

[paul_5]

Hi All, I'm currently running a separate pre and power amp and am experiencing some earth noise. Is there anything to be gained from unwiring the earth on one of the mains plugs and using a suitable piece of insulated wire between the two earth points (little screws) on the backs of the amps?

any advice would be appreciated.

[Monckyman]

Could you provide more info?
Is it a lack of earth type low freq buzz or an earth loop type low freq hum?
It would be good to see pics of the back of your units, or a wiring diagram.
Please don`t remove the earth from anything just yet, it`s pretty dangerous.
MM

[icastle]

To echo MonckyMan, don't start disconnecting the earth cables in the mains plugs.

I'd be more inclined to try linking the two units together at their grounding points as a starting off point if you believe you have an earth hum.
Also make sure that both units are powered from the same mains socket.

[paul_5]

Cheers for that guys - I'm not touching anything yet. Upon further inspection I'm still getting some signal through even with the master volume on the Pre down fully, which to me says the fault might be with the pot (assuming it's working as a simple voltage divider). Hopefully thats it, as it's [i]much[/i] easier to fix.

[xgsjx]

Have you tried just the power amp on it's own (no pre plugged in)?

[paul_5]

Yup, dead quiet. The problem is at the Pre end somewhere. It's all coming from the same ring in the building (4 way extension for both ams and the pedal board) so I reckon I should have a pretty quiet setup.

[BOD2]

Don't ever remove the earth connection from a mains plug - that's an accident waiting to happen.

How are you connecting the pre and power amp together ? With a mono jack lead, or an XLR lead ? If it's XLR then you could try disconnecting the earth from one of the XLR connectors to break the earth connection in the lead. If it's a mono jack lead then you can't do this.

[paul_5]

Thanks BOD2, I'm using unbalanced 1/4" leads (the SVP Pre outputs are unbalanced). I've spoken to the guys at Panic Music in Cambridgeshire (UK's only authorised Ampeg repair shop) and they seem to think that the problem is down to inductance between the two transformers as they currently sit on top of each other in a big rack unit. They recommended that I place the power amp 2 feet away from the pre and see what happens. I might look at some sort of shielding, now, where did I put those spare "Batfink" wings?