Best way (grounding scheme) to put a tube stage between interface preamp (THAT1510) and converter?

[777funk]

I currently have an M-Audio Profire 610 in which I have patched a basic 12AX7 gain stage between the THAT1510 mic pre and the converter. I like the sound. But... I have a dedicated power supply for the 12AX7 (12V adapter with a DC/DC converter for the HT). This was necessary because it seemed to have power supply noise (high frequency) with a shared power supply.

Is there a way to just use the 12VDC already internal to the M-Audio without ground noise? What about using the phantom power for the tube's HT? It seems like a tube sounds better over 100VDC. Maybe there's a good way to turn 48V into 2x48?

 

[scott2000]

Is there a way to just use the 12VDC already internal to the M-Audio without ground noise? What about using the phantom power for the tube's HT? It seems like a tube sounds better over 100VDC. Maybe there's a good way to turn 48V into 2x48?

Sounds to me like you are already happy with the sound you're getting from the workaround you have cobbled together?
Are you trying to make a prettier workaround? Seems still a Goldberg of sorts.... nothing against that at all ..

 

[ccaudle]

Is there a way to just use the 12VDC already internal to the M-Audio w

Assuming that the power supply has enough excess power capability to run a tube stage, it should be possible. A tube needs about 150mA for the heater running on 12V.
Does the ProFire have +12 and -12 supplies, or just +12? If it has bipolar supplies you may need to make sure that adding extra current draw to just the positive doesn't start saturating the transformer.

What current did you bias the tube to, and what voltage are you current using for the HT? Maybe you just needed a lower noise DC-DC converter.
Is the step-up currently inside the chassis, or outside?

 

[777funk]

Sounds to me like you are already happy with the sound you're getting from the workaround you have cobbled together?
Are you trying to make a prettier workaround? Seems still a Goldberg of sorts.... nothing against that at all ..

That's exactly it. It's kind of a mess right now. I have jacks drilled into the side of the case and a bunch of cables running to an Altoids tin (double decker with the DC/DC in the bottom Altoids tin and 12AX7 in the top one) and back to the M Audio interface. It'd be awesome to have the sound I'm getting, but cleaned up and inside of the M-Audio.