Hey guys,
Heard a lot of good things about the A90D and wanted to experience it myself so I got it a few days ago from Shenzhen. As I opened it and tried it out I immediately had 2 issues:
1. There is a very noticeable static sound (crackling and popping) on the right side of the headphone/iem that I tried. This sound is persistent regardless of volume, gain, balanced or unbalanced output. It is much more noticeable on my IEM as well and sometime when the popping happen, I was scared that my eardrum might blow up lol. Also, I can confirm that it is not because of my DAC because the static sound is still there even if nothing is connected to the amp, except for the headphone and the power cable. Fyi, Im using a 4.4 balanced for my IEM (Moondrop Variation, stock cable) and the unbalanced for my Hifiman HE1000v1 (also stock cable). I have a couple other headphones and iem to try but at this point I don't think it is my gear issue because I have been using them perfectly fine with other dac/amp.
2. When using the unbalanced output for my headphone, after a few minutes a loud static pop will play and the amp reset to "-5" error. Other people have reported this issue and even Joshua Valour had this issue on his unit. After the first -5, I could reset the amp and test it again, but then the second -5 hit and now I cant reset my amp. I tried turning it off, pulling out the cable, let it rest for several minutes, but when I turned it back on it was still on -5 and I couldn't do anything.
At this point, I am quite certain that my unit had an issue and contacted Shenzhen for an exchange, which they agreed to. But I wanted to post my issue here to ask people who had more experience with the amp about it. Was my unit faulty or did I do something wrong? Also, should I go for exchange or just refund and get another more reliable option?
I only had a few minutes to actually experience the sound before the issue start to pop and I absolutely loved what it can do for my cans so it was such a shame.
I heard JohnYang1997 is an expert on these topics so I would hope to hear from him