[archi42]

Depends on the USB DAC, and maybe/probably the PC. I don't have/hear interference with my current setup. I did have the issue with another DAC; IIRC I put an RC filter into the USB cable power lines (or did I just add an R into the ground line? Do some research if you plan on trying this).

PCs these days often still have an optical toslink, that can be used to avoid the issue.

[willis936]

I have an ODAC+O2. They're not easy to source for cheap these days. My issue is that the power supply filtering inductor has a cracked iron core (due to me being clumsy). The cheapest solution would be to replace it, but it's not super easy to swap out surface mount components.

I'll just deal with it by keeping the O2 volume low and cranking the volume on a second amp. Long term I'll just buy an element or a schiit.

[archi42]

If you use a second amp, why bother with the O2 at all? Or do you have the integrated ODAC?

I've built the O2 as well, and loved it, since for the first time I could drive the HD650; it even has enough power to properly use them on a flight (don't do it, you'll go deaf). But the form factor just isn't that great for on-the-go. Plus with the batteries installed there is no space for the ODAC, requiring a DAC solution (or a phone with a good DAC).

Give the FiiO btr5 a try instead of spending too much on a schiit, or look for similar devices from other manufacturers. A lot of them can do both USB (96kHz/24bit) and decent (LDAC) bluetooth. I could not tell a difference between a friend's BTR5 (dual ES9219C directly driving the headphones) and my Q5 (dual mono akm4490, ad8620 gain stage with dual op926 buffers when used balanced). Of course my hearing could be too damaged^^'

[willis936]

The ODAC is soldered to the O2. The O2 is in pristine condition (and I did splurge for an OP2227 in the voltage gain stage and WIMA caps). The analog in works on the O2 so I may abandon the ODAC in place.

The Fiio options do look good. My current desktop application has me switching headphone and mic between a work laptop and personal desktop and headphone and speakers often. I use analog switches, but I'm leaning towards a one box solution in the future rather than adding more hardware. So something like a mayflower ARC mk2 perfectly covers all of my demands (including a bass boost option for my open-back headphones). I already use a USB switch with a powered USB hub, so really it would be swapping out 3 boxes and many cables for one box. The schiit hel 2 looks really great but I've read reports of 200 ms latency.