question of soundstage

Maybe try some tube rolling?  When I rolled from OEM tubes on my McIntosh C220 pre to Mullard reissues, my sound stage did widen a bit.

carlsbad2

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.

I guess I should try some different preamp tubes. The speakers that I am using are the Tekton lore reference.

It’s not just Power Tubes.

My 6sl7’s made a big difference. (your A100t uses 1 6sn7 and 4 12AU's)

Originals: Labeled Cayin Brand, unknown maker, sounded great.

blew one (put in wrong socket), I wanted a matched pair of 6sl7’s that had a different appearance so I could not put one in the wrong socket.

Chose 6sl7WGT brownbase, chrome top, military matched pair.($80. each in 2020).

Nooooo. Wrote Brent Jesse, he had me break them in (amp on for 60 hrs, no signal needed), broke in for 3 days, still a no go.

Returned, full refund except shipping cost.

Tried 6sl7gt, General Electric, side getter, cylindrical plates ($40. each in 2020). They sound wonderful, as good as the original Cayin branded ones.

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Power Tubes

My amp came with 6550 Gold Aero, they sounded great. I have a set of 6550 EH Electro Harmonix, matched when new, but used,

I wanted to try new matched KT88’s, went for KT88’s Blue JJ Electronic, I prefer them.