Crack 1.1 - PC hum

[Neil]

Have had my Crack for about 5 years now. Have used it daily with my HD650's and haven't had any issues, except there has always been a hum from my Scarlett 2i2 USB audio interface. When I unplug the Crack from the 2i2 audio output, the hum is 100% gone, and instead there is a buzzing sound at 65% volume.

However, when PC audio is connected, the hum seems to cancel out the buzzing, but the hum is present at 0% with PC audio and bothersome at 30%. Past 50% is quite distracting when watching films or listening to compositions with notably lovely silence.

I do have an APC UPS powering the PC and all NAS/drives/monitors etc.
When I plug the CRACK power into the UPS power, it is a louder and fuller hum than when I plug the CRACK directly into the wall outlet.

How can I eliminate or greatly reduce the hum?

[Paul Birkeland]

If you can connect a DAC to your PC with an optical cable (and the DAC has its own power source), you will eliminate this source of noise.  Other USB DACs with external power supplies should also provide the same degree of isolation. 

[Neil]

If you can connect a DAC to your PC with an optical cable (and the DAC has its own power source), you will eliminate this source of noise.  Other USB DACs with external power supplies should also provide the same degree of isolation.

Would it be at all helpful if I took apart the Scarlett 2i2 and wired in a solid ground, and grounded the unit to the wall?

Could you link to a couple of ideal DACs for this application? I haven't seen a selfpowered DAC for PC before. I had the DACport which worked great but that was USB with USB power.

[Paul Birkeland]

I don't think there's going to be anything you can do to the Scarlett to break up this noise.  There are tons of DACs with USB jacks that have their own power supplies, just look for the ones that don't look like thumb drives. 

Here's an example of the kind of DAC that should disrupt the noise you're hearing:
https://www.ebay.com/itm/TOPPING-D20-24-96-High-Bit-Multi-function-Decoder-USB-Optical-Coaxial-DAC/173686031213?hash=item28707e836d:g:kYgAAOSwPSxbXuXC:rk:35:pf:0

If your computer has an optical output, then that is also a great choice and it frees up your selection of DAC considerably. 

[Neil]

I don't think there's going to be anything you can do to the Scarlett to break up this noise.  There are tons of DACs with USB jacks that have their own power supplies, just look for the ones that don't look like thumb drives. 

Here's an example of the kind of DAC that should disrupt the noise you're hearing:
***

If your computer has an optical output, then that is also a great choice and it frees up your selection of DAC considerably.

Thank you Paul! This is excellent info. I'll do more research.

*I'm so dumb - I just found out my motherboard has optical out..... is it worth it based on these specs?
Realtek® ALC892 8-Channel High Definition Audio CODEC
- Supports : Jack-detection, Multi-streaming, Front Panel Jack-retasking
Audio Feature :
- Absolute Pitch 192kHz/ 24-bit True BD Lossless Sound
- Blu-ray audio layer Content Protection
- Optical S/PDIF out port(s) at back panel

[fromnowon]

i have the D30 and really like it with my Crack!
no noise at all even with USB.

[Neil]

i have the D30 and really like it with my Crack!
no noise at all even with USB.

Very excellent! Thanks for sharing.

[Paul Birkeland]

The optical out on your machine is a good way to go if you happen to find a DAC in your preferred price range that has toslink but no USB. 

[Neil]

The optical out on your machine is a good way to go if you happen to find a DAC in your preferred price range that has toslink but no USB.

Thank you for that info! I am definitely going to get a proper DAC, either a Topping or a Schiit - but I did discover just how badly I had things set up.

The hum has been reduced by a LOT - now it's only noticeable with the Crack volume up at around 60% and even then it is much much quieter than before.

Stupidly enough, not only was the Crack powered by the same UPS that powered the computer and all other components, but the audio going into the crack was from the headphone jack on my Scarlett 2i4.
So, I've powered the Crack via direct AC wall power now, and from a different breaker than the UPS, and am using the 1 and 2 RCA out ports on the 2i4 to send audio to the Crack. HUGE improvement in listening since the hum is basically gone.

Looking forward to picking up a proper DAC though - probably on MassDrop when a piece of Schiit kit is available

Thanks again for the feedback and help! you guys rock.

[airofu]

I had the same hum issue with my USB DAC getting grounds noise from my PC. I got one of those cheap ebay USB grounding adapters, and it fixed it 100%! Just be aware it dropped my usb speeds down limiting my dac to 96khz, but still decent enough. I'll be looking at a Topping standalone DAC also to hopefully fix up the ground issue later on.