[Karlosak]

Hi,
I'm in the initial process of laying out things for my future project - uncompromising Dynamight

. Everything went fine, before I started thinking about the ground scheme.
I intend to use the standard configuration - PSU box grounded to the AC ground, AMP box grounded to the PSU/signal ground. The amp should be wired in a way to allow running both in balanced/unbalanced mode:

The problem is, two amp ground planes at each side must be connected to single point, pin1 at the input XLR, virtually creating a ground loop. Please see the attached image. It shows only ground wires (signal and power ground), in blue color.

Is this the standard way to wire a Dynamight? I'll do it this way, if no one comes up with some better idea.

I know that it's only a small loop inside a shielded enclosure, however I very well know what a magnetic field can do - just insert a powerful transformer under your RCA interconnects which are wide apart (creating a ground loop). That's one reason I don't like unbalanced interconnects. So please help me to eliminate this problem, thanks.

P.S.: the situation can be further illustrated in dgardner's Dynamight:

 

[Garbz]

The only way to elimiate this problem is to transformer couple the inputs or build two completely mono chassis with no earthing. This normally isn't too much of a problem for a hifi How about only connect one ground tab from the mono RCAs? The virtual loop is gone.

Providing things are laid out properly the "ground loop" (which is common to nearly every piece of equipment) shouldn't be a problem. Shield your cables or use a ferrous metal for your case

My Dynamight actually converts it's single ended signal to balanced not via xformers but via a DRV134. Still has this grounding loop you mentioned though.

It should be worth noting that this insane ammount of flexibility is a source of problems.

 

[Karlosak]

Thanks for a reply Garbz,
I agree that the "problem" I spoke about is a minor issue I shouldn't bother with. I'll try to disconnect one of the input grounds and see (hear) the difference. I'm quite sure there won't be any

.
The aforementioned DRV134 looks like an easy way to include unbalanced->balanced conversion as another input option (next to the standard balanced configuration and unbalanced dual amp). Since I like the idea, I'll try to incorporate it and rise the "complexity meter" one notch higher

.

 

[DigiPete]

Hi Karlosak,

I've got my Dynamite set up as you indicated. The two left amps' signal grounds are grounded to the left psu ground line, and the right amps to the right PSU ground line. I have the PSUs in a seperate enclosure. The amp boards are in thier own case, which I left floating.

No problems with any hum at all

Pete