We indeed received the unit in early May and our engineers have been doing some tests with the unit. The report just came out and we were about to reach out to you. Attached are some reports done by the engineers regarding noise.
Here is the report from our engineers:
"Progress update for SHD return unit RA#70552:
- Returned unit works normal with expected performance, the measured noise level is quite close to our golden sample.
- After listening check, SHD (with max vol.) is connected to a power amp that max gain is 26.6x, little noise can be heard when ear is touching on tweeter. It became silent just after moving away from it.
- I guess the possible root cause is the loop ground issue and also a large voltage gain 75x on K3 power amp that amplify the noise in audible level.
- If the user wants to get back the SHD, he can try:
1. balanced input power amp
2. K3 as int. amp but fix the vol. control to near minimum (let's say 8 o'clock) as an signal attenuator, SHD set vol. to near maximum and use for vol. control.
3. We can provide an attenuator for RCA port, to decrease the max. signal level from 2V max to 0.44V for K3's bypass. (Not sure it works or not, may affect SNR and THD)"
It appears to us our engineers could not reproduce the exact same symptoms you mentioned in your initial ticket. However they have given some data and suggestions that you might want to take a look at. Please let us know what you think and get back to us once you have made a decision on your unit. Thank you very much again for your patience.