rolling output tubes

I have a pair of Melody M880 monoblocks in my 2nd system. They use KT88s and have a bias adjustment pot for each KT88. Can I use EL34s or other output tubes instead?

Do output tubes and transformers have to be "matched"? A dealer once told me that transformers designed for KT88s will not achieve EL34's potential. But I thought he tried to sell me another amp. LOL...

This is for my 2nd system and is in a smaller room 12X11. The speakers are 90dB. I want something a bit euphonic from this system but not too much. What other output tubes should I try?

The suggested bias for KT88s is 50mA. But I found it sounded the best between 40-45mA, depending on the tubes used. So if I move to other tubes, what bias level should I start with?

Thanks a lot.
Shuguang KT88-98.What about rolling input/driver tubes? Taking the bias up will sweeten,down more SS-like.Experiment with your biasing first.
Sometimes, sometimes not (bias capability aside.) If you don't have a manual, or you do but that issue isn't THOROUGHLY covered, you MUST contact the manufacturer. Otherwise you're taking (unnecessary) chances ;-)
I have rolled the input and driver tubes already. The stock tubes are probably Shuguang KT88s. I am using cryo'ed Gold Lion KT88s and they do sound better than the stock tubes.

I found that it sounds more SS like if I increase the biases. Is this common? With higher biases, they sound more aggressive, extended, etc....

The manufacturer is not responsive. I had asked a few questions through their importer, but got no answer.
Tried the other directio,lowering.Shuguang makes several kt-88s,thus my sugestion for 88-98s.
I thought your question was about the possibility of substituting EL-34's for the KT-88's.
Yes, my question is about substituting EL34s for KT88s. Thanks.
Vett, the web-site below may be helpful. Also 6 Moons audio reviewer of Melody 880 states that the KT88 M880 is on equal turf for harmonic richness with EL34 amps.
Vett93: YES- Sometimes a manual will include a range, rather than one specific setting for your bias adjustment(ie: Cary SLM-100= 150 to 175 mA). The upper limits of that range will yield a more dynamic presentation, and sometimes sibilance or glare can result also(more Solid State-ish). Of course- the other direction takes one into the "more relaxed presentation" zone. Hopefully: Somewhere in the middle- one will find transparency, with the right tubes/equipment.
the problem isn't the tubes it's the amplifier. melody products are very unromantic. they are typical of the modern tube design, not the classic or vintage tube design. i doubt you will be able to extract much warmth from that amp.