You should not speculate and write negatively if you do not know about Cayins.
My Cayin A88T was deigned in Germany, built in China: hand built, point to point. Beautiful workmanship inside and out.
This extremely positive review is why I bought my Cayin A88T which sounds terrific.
https://6moons.com/audioreviews/cayin/a88t.html
excerpt
"The Cayin 88T is the first integrated amp I’ve ever had in my system that sounds so good, I have absolutely no desire to go back to the big mono block amps and the preamp. In fact, in many ways, the Cayin sounds better!"
"No, I didn’t decide to start this review with my summation. That wasn’t me talking. That’s a famous American manufacturer speaking".
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The more powerful A100T is also a terrific tube amp, 8 power tubes, individual bias pots and meter. Subsequent mark 2 and 3; and other models like the A100T have external bias adjusters and meters
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What tubes are in an amp is part of the different sound between amps.
Mine came with 6550 power tubes, I changed to KT88’s. It sounded great with the 6550’s, I prefer the KT88’s.
Bias: when switching tubes, I had the bias adjusted by Steve at VAS who used to be the distributor of Cayin USA. (my mark 1 has needed 16 ohm taps, bias is internal, no meter)
I blew a 6sn7 (put in 6sl7 socket), bought a matched pair, they sounded awful. Brent Jesse let me return/try a different brand, they sound as hood as the originals.
Thus, I would wonder what tubes are in OP’s very high quality Cayin.