So I bought a Crack Amp Kit, which is a Tube based Headphone Amplifier. I have built it, all the resistance and voltage checks are good, but when I plug in a DAC to the Crack Amp, I have buzzing in my ear, which doesn't affect the quality of the music itself, just the buzz is present.
So the Gear I have is:
Odac (USB Based DAC)
O2 Amp (AC Powered)
Crack Amp (Ac Powered 3 Pin)
Schiit BiFrost DAC (AC Powered 3 Pin)
T1 Beyerdynamic Headphones, HD650 Headphones, HE400 Headphones - Noise is present in all of them.
Troubleshooting has led me to the following list of things:
1) Amp with nothing connected - No unusual noise
2) ODAC connected to Crack, but no USB Connected - No unusual noise
3) ODAC connected to USB on Desktop Computer, connected to Crack - Noisy
4) Bifrost connected to USB on Desktop, Connected to Crack - Noisy
5) ODAC/BiFrost Connected to Laptop via USB - No Noise
6) ODAC to Headphones directly, connected to PC or Laptop via USB - no Noise
7) BiFrost Connected via Optical SPDIF to Crack - Slight noise - Not as bad as via USB
8) ODAC connected to PC via USB then Connected to O2 AMP - No Noise
9) ODAC Connected to Laptop via USB then Connected to O2 Amp - No Noise
10) Noise from 3 doesn't seem to change as I adjust the volume knob on the crack
11) Noise from 3 doesn't seem to change if I remove one of the RCA's or the other, or if I swap them around
12) Noise from 3 not affected by type of music playing, or sample rate etc.
13) Noise from 3 can be drowned out if the volume is loud enough (Music
14) The Music coming from the crack in 3 sounds Excellent, just the buzz in the background
15) Noise from 3 moves from right hand to left hand depending on how far the headphone is inserted into the jack.
16) BiFrost connected via Toslink - Noise.
17) I have removed all peripherals from my PC except power, and the cable connecting me to the DAC - Noise.
I am at my wits end, the buzzing isn't something I can live with.
I am told it's likely a grounding issue, probably a ground loop, but that if this is the case then Toslink connection between my PC and BiFrost shouldn't have a problem, which it does.
What can I do to further troubleshoot the problem ?