I recently re-purchased a Direct Stream DAC and Scott has been working with me on this problem, but I wanted to throw it out there and see if anyone else has any bright ideas.
I got a new preamp and the DAC within a few weeks of each other.
Once I started using the DAC, I noticed a hum from the system that does not go away unless:
I pull the RCA cables from the DAC.
I switch off the preamp.
Float the ground on the DAC with a cheater plug. (Floating the ground on the MZ2 makes no difference)
The system is a Linear Tube Audio MZ2 preamp/headphone amp
PS Direct Stream DAC
Berning ZH-270 (with 2 inputs and it’s own volume control)
All plugged into a Synergistic Research power cell 8 power conditioner.
To experiment I borrowed my headphone system components. Chord Qutest DAC & ZMF Pendant headphone amp/preamp.
Everything is single ended RCA cabled.
Here’s how the different combos went.
DSD and LTA MZ2 (as a preamp) I get hum.
DSD and ZMF Pendant (as preamp) no hum.
Chord Qutest and LTA MZ2 no hum.
Chord Qutest and ZMF Pendant no hum.
DSD into the ZH-270 No Hum.
Anyone have any idea where this hum may be coming from? I put new 6SN7 tubes in the MZ2 today and the noise was still there. I don’t currently have an extra pair of 12AT7 tubes to check those.