JADIS JA80 with 6550 or KT 88 or KT90 ?


My Jadis JA80 was built in April 1999 and came equiped from the factory with eight 6550 valves.

Before deciding to buy a new set of tubes, I would like to know some opinions about the advantage or inconvenience of using the KT 88 or the KT 90 tubes in my JA80.

Is there any experience of using these tubes (KT 88 or KT 90) in an amplifier designed from the factory to work with 6550 tubes?

Many thanks for your cooperation.
rato456
Bartokfan: As Khrys pointed out above, the JOR's transformers are supposedly optimized for the KT90 tubes, though there still are many who prefer EL34s and KT88s in the amp. KT88s will likely give you a lusher midrange and a more "tubey" sound than the KT90s, which are leaner (Khrys's description as the perfect transistor is the way I felt about the KT90s too). As far as current production recommendations, I don't have any, but check the archives, there are a lot of recommendations on current production KT88s.

I have nearly new pair of JA30’s with KT90's factory fitted. Are any changes or re-calibrations required when changing between KT90’s, KT88’s or 6550’s. Or is it a straight swap?
Bump this one back to the top, looking for an answer to valve inter changeability.
from Jadis via email:
"JA30 is an autobias amplifier, it does not need any adjustment when you change tubes.
Kind regards,
JADIS Service Commercial / Sales Department
Chemin du Pech
11800 VILLEDUBERT. FRANCE
www.jadis-electronics.com
Tel : + (33) 4.68.78.63.30
Fax : + (33) 4.68.78.85.15"
The KT88's just arrived, replaced the KT90's with the Elecrto KT88's and after only 10 minutes of listening, promptly placed them back in their boxes. I'd say the quality lost is near 50%. In fact had the original JOR came with these 88's I'd be one very un-happy camper.
Dumb me, doubting the french.
loss in all three fq's in the 88's.
hopefully my seller will take them back with some discount of course,.if not I;'ll put them up for sale here.
Paul