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In Reply to: Citation II's with KT90's posted by Apogee on July 29, 2006 at 12:04:06:
I forgot to ask if anyone is successfully running the KT90 type III's in Citation II's without any problems?Thanks!
Steve
Follow Ups:
Steve
Looking at your asylum name I take it own apogee speakers? Very nice speakers and I almost bought some divas but instead I bought the martin logan monolith 2s to replace the acoustat 3s which I still have..
Anyway I run a lot tubes in my citation 2 including 6L6gcs at times with reduced bias but I can honestly say the shuguang KT88SD which is marketed by penta labs is my personal favorite of the kt88s and they perform very close to my nos GEC/Genelex KT88s and the EH KT88s are very good to once broken in.If your running a mschane modded citation 2 on your Apogees,its a combo thats going to be very picky what you throw at it much like the Logans but it will be a sound thats unsurpassed by almost anything.
Steve,It is not a problem with the type III per se. Pre-NATO campaign type IIIs are fine, if you can find them then use 'em! However the current production KT-90 tube has misaligned screens causing significant screen overheating which causes the red on the plate. I've personally seen screens so badly misaligned that the tube glowed like a regular 25 watt light bulb when B+ was applied. It was all the white hot screen wires all glowing!
Many of the KT-90s being produced now show red on the plates at 30 watts dissipation, that's 60% of normal spec. To turn down the bias in a Cit II that far to limit dissipation would completely change the character of the amp. The KT-90 and the amp work best when the bias is at least 75 ma. 75 ma. with 460 volts on the plate would mean dissipation of about 35 watts. That's not safe with many of the current KT-90s.
Misaligned screens also mean higher distortion and accelerated wear to certain areas of the cathode. So the curent tube will likely have a shorter lifespan.
Please take Eli's advice and stay away from them - you're asking for trouble if you don't.
Jim,
Whaddaya think about this? Just ran across it surfing...http://www.vasaudio.com/product_citation.htm
I *like* the loudness button!
Well, it might be a good amp, but as ARC said - different tubes, different circuit, different rectification, less power, etc... you can slap the name on anything I guess. Although, I wonder if the H-K people will take exception to the name?Anytime they want to have a shootout with a McShane/REAL Citation II I'll be happy to oblige them.
I think if they take you up on this "Anytime they want to have a shootout with a McShane/REAL Citation II I'll be happy to oblige them." They'll discover they're actually twins sons of different mothers!You're a class act Jim, keep up the good work....
Thetubeguy1954
I wonder in what way they consider these totally generic Chinese Vas Deferens monoblocs to be "direct descendants" of the Citation II. Using EL34s, much different input circuit, lower power output , tube rectifier, etc etc. I have a 2002 Chevy Malibu that is a direct descendant of the waykool 1960s Chevelle Malibu... in that it has wheels and tires, and an engine! I guess they are descendents of the Cit II in that they will amplify an audio signal... other than that the are strict middle-of-road average Chinese amps.
Figured I'd better repost it down here so the thread made sense...Thank you for the info thus far.
One more question, I've been reading about the Chinese GEKT88's as being very, very good although hard to source.
I have had the pleasure of running the Chinese brown based KT66's and they were nothing short of awesome. I also noticed Jim has them on his site...
What about running the GEC copies in the Citation? Has anyone tried them first hand? Opinions?
Jim, I'm a past customer and still have 4 matched sextets of GE 6550A's in reserve that I bought for another amp but I'd rather not use them in these amps... (To everyone else, no they're not for sale)
Thanks,
Steve
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