I just finished upgrading the stock 5532 OP amps that were in the front sockets of the aiyima t7 tube. And wow what a change. I used the op 1656 on adapters and I was very afraid it would not fit because as you can see the separate PCB shelf in the design creates a very close tolerance between op amps and seperate tube board . They do make contact but it is already 99% inserted.
The sound change is immediate and I am going to upgrade my suca audio pre amp the same way . I might get the same model but I’ve also heard good things about the muse op amps But it seems complicated since those are single channel and not dual like the 1656? Anyways I found myself turning the volume about 10% more than usual The sound is more airy and clarity throughout has increased I would say about a 10% improvement in total sound. After I upgrade the power supply I think this would rival most preamps under $500. And it certainly rivals my bellari maybe not in warmth But fidelity and musicality are even better. and that’s 300$ so maybe the schiit Freya would be a nice comparison no matter how ridiculous that may sound.