[JayDM]

I recently picked up a Questyle CMA15 to replace my previous stack and make some room for an E-stat system, and I’ve been having very strange issues with noise. First off it’s not really a hum or a hiss but more of a high pitched, electronic whine, like some sort of sci-fi SFX.

I did not notice it through the CMA15 at first, rather I heard it through my WA-6 tube amp while using the CMA15 as a DAC, where it was audible at high, but listenable volumes. Afterward I cranked the CMA15 up way past listenable volume and heard the same noise coming through, softer than on the tubes, but very clearly there.

At first I assumed it was a USB problem. As soon as the USB cable even touched the USB ports on my PC I would get noise through the tube amp, even when it was switched off. Remove the USB cable and the noise went away. Attempted changing USB cables, switching to USB C, using different ports, adding an iFi iSilencer 3.0. No change, still the same noise, perceptible at the same volumes on both devices.

Problem at the very least diagnosed, right?

No. At least I don’t think so.

This has been annoying the hell out of me all day and I’m pulling my hair out figuring out fixes that don’t require adding more large gear to take up space(defeating the purpose of buying the Questyle in the first place). However on a whim I unplugged the WA-6 from the CMA15.

Problem solved…

As soon as I unplugged both RCA cables connecting the units the CMA15 becomes whisper quiet.

What?

So I start trying different RCA cables. No change.

At this point I’m highly unclear as to what is going on. My previous DAC, a Holo Spring 3 KTE was dead silent via USB with a GSX Mini and the WA-6 was also silent. Now the CMA 15 is completely silent via USB when not connected to the WA-6, but as soon as I connect to the tube amp I get the strange noise through both units while the WA-6 only seems to cause the problem/noise when the CMA15 is connected to my PC via USB.

So:

PC>USB>CMA15 as DAC & AMP= Fine

PC>USB>CMA15 as DAC & AMP>WA-6= Noise out of both units

PC>USB>CMA15 as DAC>WA-6 as AMP= Noise out of WA-6

Power to both units>No USB>CMA15>WA-6= No noise, however also no music since I’m not connected to my PC.

I mean yes, I can solve the problem leaving the WA-6 out of my chain, however I really like the thing and it’s one of the few tube amps(perhaps the only SET tube amp) I have space for. So I would like to avoid getting rid of it.

Anyone who can shed some light on what is going on here and possible solutions, I would really appreciate it.

 

[Monsterzero]

https://www.head-fi.org/threads/adv...eceiver-recommendations.969832/#post-17743135

 

[Poganin]

I had the same issue when I added a tube amp in my chain which was PC > USB > Aune S6 (DAC) > Feliks Audio Echo (AMP). In my case it was also the USB connection from PC that was causing the hum and some high-pitched noise whenever I moved or clicked my wireless mouse. I got rid of it by making sure that both S6 and Echo were plugged into the same power strip, which was different from the one that my PC was plugged into. Both power strips were also plugged into two different wall outlets, but I don't know how much that was a factor.