@LGD_
Thanks for reminding me about ferrite beads
Have still to find a big ring to attempt looping the DAC cables; I don't expect much as they already have two ferrite beads but you never know.
I'm re-organizing the bookshelf where the Amp and DAC are so I just moved them.
Thankfully, the DAC cables are long enough but I had to replace the cables of the Scarlett with cheaper ones and the measurements of course suffered a big setback.
I have ordered a kit of ferrite beads and started putting them here and there.
Decided to track the changes while applying them on the audio chain cables to see how and when it was improving.
This was the starting situation:
Not terrible but the LF is pretty dirty, dominated by the 50Hz AC pollution and its harmonics, the base of the 1K since is dirty as well and the harmonics are higher than the usual. The SFDR is suffering quite a lot, should be above 120dB.
I already know the probable cause of the AC pollution but I will keep it to track the effect of the ferrite beads.
I will start with USB cables connecting the Scarlett; there are now 2 cheap cables with the HS01 in the middle.
This is adding one bead to the cable from the HS01 to the Scarlett near the HS01, not much different just 1dB in SFDR gained:
This is adding one bead to the cable from the PC to the HS01 near the HS01, much better the SFDR reaches 121.5dB, the LF is much more cleaner and the AC pollution and harmonics are greatly reduced:
This is adding one bead to the cable from the HS01 to the Scarlett near the Scarlett, SFDR jumps to 122,9dB and the LF is much more clean:
This is adding one bead to the cable from the PC to the HS01 near the PC, SFDR goes up to 124dB and there's a lower pollution at 50/100Hz:
This is with the USB power supply connected to the HS01, super high pollution goes back to the Scarlett:
Since a while ago it wasn't like that, I assume this is a signal that my replacement HS01 will die sooner or later.
The measurements dropped like 30dB at some point with the HS01 powered, I decided to leave it unpowered and never plug it again.
Added also the beads to the USB cable providing power to the HS02 and measured it with and without, no change at all.
I decided to leave the HS02 unplugged from external power.
Added also a couple of beads on the PSU cable of the ZD3, near the PSU and the ZD3:
Very small improvement but still some bits.
Basically I have only the AC pollution at 50/100Hz left.
The ZD3 is currently sitting on top of the Yamaha A-S700 Amp together with the Scarlett which is connected to the ZD3 with a Mogami XLR cable with Neutrik Gold connectors.
Quite a decent cable so I wondered if despite the quality it was picking the noise from the Yamaha PSU.
I added a bead to the cable near the Scarlett and the 100Hz went away:
Added another near the ZD3 and the pollution went away:
But this was one lucky measurement, during further repetitions the pollution came back out quite often but greatly attenuated.
Finally I switched off the Amp and got a final measurement, still with a light bump at 50Hz (guess cause the audio cables at some point cross the AC cables):
Definitely worth it to spend some time and money to install the ferrite beads!
Made as well some final comparisons but at 128K FFT since MTA DSD Gen dies generating DSD256 at 256K.
Also measured at DSD512 but could do it only at 64K FFT.
Quite a good measurement after doing a bit of cleaning at PCM 96kHz, nice 125.5dB SFDR:
Even better at DSD128 with 127dB SFDR:
At DSD256 it's slightly worse overall, not sure why it wasn't like that a while ago, but the cleanest HF overall:
At DSD512, same as the Topping D50s, it starts falling down in almost all the metrics but still the HF is very clean:
