Rack Mount DAC issue

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Hi all,

Firstly, apologies if this is the wrong area.

I have a studio where I have a built desk rack with the following equipment:

- 1RU 1794A DAC (runs off a two pin external AC power pack)
- 3RU EQ (three pin IEC)
- 2RU Tube Compressor (three pin IEC)
- 1RU VCA Compressor (three pin IEC)

All connected to a common ground in the rack rail.

I have this minor issue where if I have the DAC on initially, then power on the EQ (which sits above the DAC), the DAC's sync light will flash and if anything is being played back will then turn to what sounds like a weird sample rate (distorted and weird pitch).

To overcome this, I power on the other devices first before the DAC but could anyone explain why this is happening? It only seems to be affected with the EQ, the two compressors don't have the same affect.

Should I isolate the DAC from the rack rail ground?

Thanks in advance!
 
Hi marce, it's actually equipment I've built myself (except the DAC is a Ross Martin) based on existing designs. Unfortunately I don't know enough to troubleshoot this issue.

I was thinking to just isolate the DAC from the rack with plastic washers but any other suggestions welcome. What did you want to know about the equipment?
 
Fingers crossed, though its not an unusual problem, especially with DIY stuff, you never think snub on off switches until they cause problems. Also in commercial stuff, that's why most PCs have soft start, to avoid rabid on and off switching and mains arcing.
 
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