This is what it says in Jadis' website:
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2- POWER PENTODES
KT90 : With its plate and screen dissipation of 60W, the KT90 is the most reliable tube that we know of. This is why our JA 800 amplifier uses this tube exclusively. The KT90 will also be supplied as the standard choice in the new JADIS range (JA 50, JA 100, JA 250)
6550C : The most widely used power tube. We use Russian tubes produced in St. Petersburg .
6CA7 With a sweeter sound than the KT90 or the 6550, this tube can be used on a large variety of amplifiers.
KT88 : This is the reference tube for audiophiles. We use tubes specialy built for us
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http://www.jadis-electronics.com/pages_eng/info/tubes.htm
_________________________________________
2- POWER PENTODES
KT90 : With its plate and screen dissipation of 60W, the KT90 is the most reliable tube that we know of. This is why our JA 800 amplifier uses this tube exclusively. The KT90 will also be supplied as the standard choice in the new JADIS range (JA 50, JA 100, JA 250)
6550C : The most widely used power tube. We use Russian tubes produced in St. Petersburg .
6CA7 With a sweeter sound than the KT90 or the 6550, this tube can be used on a large variety of amplifiers.
KT88 : This is the reference tube for audiophiles. We use tubes specialy built for us
_____________________________________
http://www.jadis-electronics.com/pages_eng/info/tubes.htm