Topping A90 failure issues. Should I try a 3rd A90?

 Very strange.  If there weren’t viable competitors I’d consider trying a third A90, but there certainly are and it seems for whatever reason the Topping’s not working in your system.  If it’s me, at this point I’d shell out an extra $100 and try the Singxer SA-1, which may actually be an even better amp.  Just my $0.02, and best of luck whatever you decide. 

You might try posting a question on ASR. John Yang is the user you would want to contact I believe he works for Topping. I know there are a couple of threads where some problems with the A90 are discussed one thing he mentioned was a bad XLR cable can be a cause. 

@djones51 Thanks very much! 

I have the A90 and it is a workhorse for me. I have been using it recently to break-in new gear. So that means playing it 24 x 7 for a week (no problems). In this scenario I use iPhone ear plugs to output sound. 

When it is not doing break-in work I enjoy the A90 with a Matrix Mini-i 3 Pro DAC using some very old Audience AU24 XLR interconnects. I bought the Mini over the Topping D90 because it was reviewed to be a bit better and also for the incredible ROON streaming options with the Matrix (so no direct computer connection).

I listen to this combo with Meze Empy headphones and it is amazing for the price. This combo comes close to the quality of my Benchmark HPA4 + DAC3B pairing but that combo is much more money.

I know this chain is a bit old, but I think the same thing just started happening with my A90. Static in the right channel from all headphone outs (both balanced outs and single ended out). It seems to be certain frequencies or volume levels that are effected (e.g., I'll head the same "static" noise on each drum hit).

Tried different headphones, different cables, different outputs from the computer (USB and optical to the D90, then XLR to the A90). The RCA outs on the A90 to my speakers do not have the same issue.