Hi, I just found on a french forum a message highlighting a Q&A exchange between Harman and a customer About the poor performances of the AV40:
Q:here are reviews out in the internet that the AV40 (and all the newArcam AVR's) measured poorly in SINAD- and Jitter tests. Are you awareof this?
A: We have seen the review and notified the reviewer as to exactly what errors they made. One such mistake was that they introduced a ground loop while measuring which considerably raised the noise floor, which is a rookie mistake. They also set the bit measurement to 16 bits rather than 24 bits which gave an incorrect result. Unfortunately, inexperienced reviewers like this cause a lot of damage, but do not own up to their mistakes. We urge customers not to believe everything they read online.
Amirn, can you please comment on the above?
Sigh.
Yes, I have their response. I have been holding my response to them confidential as professional courtesy until they get back to me. I am saddened to see them run with their opinion without closing the loop with me.
For now, their assertion as quoted is wrong. There is no ground loop or we would see mains and harmonics in the FFT response:
The noise is broadband and covers all of the spectrum, not just at 60 Hz and multiples as we would see in ground loops. Here is a quick example of mains leakage:
Their testing involve using a portable class 2 HDMI signal generator. Since they don't see the noise issue there, they automatically jumped to the conclusion that there must be ground loops in my testing. I have explained to them that they need to use a standard consumer video source, not a an HDMI signal generator that is likely to produce much cleaner signal. And that there is no evidence of ground loops per above explanation. I have heard no answer from them.
This is on top of the fact that I am using balanced XLR for my testing. So there better not be ground loop anyway.
Communication with them on these issues is difficult because they are using an older Audio Precision analyzer so have no ability to replicate my tests directly. And I am going through an indirect channel to do that instead of speaking on the phone which I have offered to do multiple times.
I have re-tested the unit across the board in response to their feedback and found a couple of things that improves its measured performance. I will be posting those corrections. The overall picture doesn't change much though.