Does it go into protection mode with both input and output disconnected?
I haven't tried that but I will. Thanks for suggesting it.
It seems you have been able to isolate the amp to one unit. I am assuming you've used it on the left and right channels of the DAC? That would eliminate a DAC issue.
Thanks, I'll try that as well I will report it here.
By protection, do you mean during program material or only on powering on and off?
I mean that it doesn't produce any sound. The blue light is on but the amps doesnt do anything. If I switch the Balance/Unbalance switch I hear a little "electric" clicl coming from it but nothing else.
Once is back to work, everything is fine, for days, until I have to shut them down again.
I do wonder why you aren't using XLR cables.
Because I read in this forum that few users that A/B XLR vs RCA with STA9 amps found the RCA connection better sounding. Since I didn't have XLR interconnect to start with I "trusted" them and always used in unbalanced mode.
I've also read that from a theoretical point of view an XLR connection can potentially reduce de dynamic of the signal by about 10DB due to the fact that it's physically impossible to make the 2 XLR signal paths identical. So when you add the 2 signals to remove the noise you also remove part of the signal.
Plus my RCA interconnect are 20cm long. I didn't feel I was exposing them to too much interference.
Anyhow this is my "reasoning" behind my choice. But I'm open to suggestion and hear different opinions