Hi
I have been using the coaxial RCA SPDIF input and the USB input for quite a few years now.
I have a digital cable from a CD transport going into an iFi SPDIF iPurifier into the RCA SPDIF input. The iPurifier is powered by a ultra capacitor power supply.
I have a USB cable from a streamer going into a USB regenerator (I shall not mention the brand as I have had issues with the manufacturer over service and other products purchased) and another USB cable going from the regenerator to the USB input. The USB regenerator is also powered by another ultra capacitor power supply, identical to the one powering the iPurifier.
Both power bricks (they are switching power supplies) powering the ultra capacitor power supplies are plugged into a power strip from the mains wall outlet. My preamp, the streamer and CD transport are also plugged into that power strip.
Lately I have discovered that when I have the streamer playing and then proceed to turn the CD transport on, the sound on my system mutes. It is neither the preamp nor power amp as when I reset both the DS and the streamer (power recycle), everything returns to normal. I am guessing it is something happening between the DS’ digital inputs and its analog output into the preamp.
The only thing I have changed recently is the digital SPDIF RCA cable from the CD transport. It is now an Aural Symphonics Echelon Digital which has some built in grounding. Earlier models which I used had a separate ground wire meant to be attached to chassis ground for effect. I do not recall this happening before on these earlier models, nor on a Cardas Clear Digital SPDIF which I also used.
Would anyone hazard a guess as to what is happening and how I can “fix” it? I am guessing it may be a grounding issue.
The other question I have is with regards to galvanic isolation of the USB regenerator. It has a switch whereby galvanic isolation is activated (default) or defeated. I had never given it much thought and always just left it with galvanic isolation on. However, when I encountered this issue with the inputs, I tried defeating the galvanic isolation. I found I preferred the sound without galvanic isolation. There seemed to be more gain - my preamp volume had to go a few clicks lower. There was also more bloom and ambient detail which was pleasing to the ear. It was as if the galvanic isolation scrubbed it too clean and sterile. Highs were less strident. Bass however was less tight. It was overall a fuller sound - on recordings which were already full and warm sounding, it could be a wee too much of a good thing. The strange thing is it not only exhibited these traits on the streamer which fed the USB regenerator but also the CD source as well. Lest you think me mad, I have gone back and forth a few times and it is definitely what I found. Is there a logical or technical explanation?
It has been puzzling.
Thanks