Connecting external dac to ultra

[robtw62]

I've got a Fiio K11 R2R and have been using the USB connection for a while now

My setup:
Tidal -> Wiim Ultra -> Fiio K11 R2R (NOS) -> Yamaha cx-1000 preamp -> 2 x NAD 218 THX amps (mono mode) -> Yamaha ns-1000m

Today I noticed a buzz coming from both woofers when using the Fiio.

I switched to using the Wiim internal DAC and the buzz was more obtrusive - now at midrange frequency. I eventually tried removing the USB connection from the Wiim and the buzz disappeared.

I then connected Wiim to Fiio using S/PDIF cable and the buzz then also disappeared when using the Fiio.

I had learnt to live with the very low level pops between songs when using the USB connection to the Fiio.

I set the sample rate switch latency to 100ms for the S/PDIF connection (something I had read on this forum) and I no longer get the pops between songs either.

I'm sticking with using the S/PDIF connection. The sound quality to me is as good - but I may be biased - as that buzzing was really annoying even if only just audible.

 

[Vignus]

I've got a Fiio K11 R2R and have been using the USB connection for a while now

My setup:
Tidal -> Wiim Ultra -> Fiio K11 R2R (NOS) -> Yamaha cx-1000 preamp -> 2 x NAD 218 THX amps (mono mode) -> Yamaha ns-1000m

Today I noticed a buzz coming from both woofers when using the Fiio.

I switched to using the Wiim internal DAC and the buzz was more obtrusive - now at midrange frequency. I eventually tried removing the USB connection from the Wiim and the buzz disappeared.

I then connected Wiim to Fiio using S/PDIF cable and the buzz then also disappeared when using the Fiio.

I had learnt to live with the very low level pops between songs when using the USB connection to the Fiio.

I set the sample rate switch latency to 100ms for the S/PDIF connection (something I had read on this forum) and I no longer get the pops between songs either.

I'm sticking with using the S/PDIF connection. The sound quality to me is as good - but I may be biased - as that buzzing was really annoying even if only just audible.

Same DAC and same issues. I also switched to optical cable and clicks and buzzes are gone. I find that the sound was slightly fuller with USB (no, I don't measure) but the difference is so small that I don't care. I wonder if the issue has anything to do with the USB cable but I'm not willing to buy a second one.

 

[Deleted member 20976]

Ground loops and other ways of injecting hum on interconnected devices can often be difficult to diagnose. I feel your pain

 

[robtw62]

I'm back using a USB connection to connect my Wiim Ultra to my Fiio K11 R2R.

I found the solution to the buzz I was experiencing using USB as set out in this post of mine in response to the suggestion of using a USB isolator in that thread:

R

Post in thread 'Enhancing USB Audio: My Experience with ADUM3160 USB Isolator on WiiM Ultra'

Jun 23, 2025

I can confirm this suggestion works. Based on this thread I bought https://www.amazon.com.au/DSD-TECH-SH-G01B-Isolator-High-Speed/dp/B0CBJYGBL3 for $34.99 and am back using USB to connect the Wiim Ultra to Fiio K11 R2R.

Before doing this I had changed to using S/PDIF due to the buzz I was experiencing from the USB connection.

The USB connection now has a lower noise floor than the S/PDIF connection had.

I can also confirm that my highest resolution songs are still playing at their correct bit-rate too.

• robtw62

• 

 

[gazza1101]

I'm back using a USB connection to connect my Wiim Ultra to my Fiio K11 R2R.

I found the solution to the buzz I was experiencing using USB as set out in this post of mine in response to the suggestion of using a USB isolator in that thread:

R

Post in thread 'Enhancing USB Audio: My Experience with ADUM3160 USB Isolator on WiiM Ultra'

Jun 23, 2025

I can confirm this suggestion works. Based on this thread I bought https://www.amazon.com.au/DSD-TECH-SH-G01B-Isolator-High-Speed/dp/B0CBJYGBL3 for $34.99 and am back using USB to connect the Wiim Ultra to Fiio K11 R2R.

Before doing this I had changed to using S/PDIF due to the buzz I was experiencing from the USB connection.

The USB connection now has a lower noise floor than the S/PDIF connection had.

I can also confirm that my highest resolution songs are still playing at their correct bit-rate too.

• robtw62

• 

Do you prefer the sound with the Fiio K11 R2R?

 

[robtw62]

I still prefer the external DAC NOS mode as per my previous post(s) earlier in this thread:

R

Post in thread 'Connecting external dac to ultra'

May 28, 2025

Until quite recently I agreed with you. But listening to very loud music exacerbates problems.

I was using the default wiim ultra filter: Linear Phase Fast Roll-off Filter type.

I found the song All By Myself by Celine Dion (1996) was harsh in the treble at very loud volumes.

So I tried all of the wiim ultra filters in the order that I'd prefer next best looking at their frequency curves. Every one sounded better each time.

The last one I tried, the one I least wanted to sound best knowing the frequency curves, was Corrected Minimum Phase Fast Roll-Off Filter.

So I used that filter...

• robtw62

• 

I can only consciously determine the better DAC at extremely high volumes. But at normal listening volumes I'm finding listening to music to be less fatiguing with the DAC NOS mode - maybe this is subliminal as I can't (easily) distinguish the difference between the 2 DACs' at normal listening volumes.

I'm now finding the noise floor for for both USB and S/PDIF connections to external DAC to be equally quiet since using the USB isolator, so I'll need to find the time to determine if either is actually better than the other.