Gold Lion or Shangwaung Treasure KT-88's are both excellent
I have a Cary SLI-80F1 integrated with Genelex KT-88's and like them very much. As for the 6922 varients I use Amperex 7308's from Upscale Audio and again really like these tubes. I know you said no NOS tubes but these were a vast improvement over the EH 6922 tubes. For current production tubes you may want to try the Genelex here as well but they are kind of costly IMO and I have never tried them so I can't comment on how they sound in my amp. Otherwise for reasonably priced current production tubes I have had good luck with the EH tubes.
From what I can see, there should be oodles of room to physical fit KT-120's. Not sure if the bias range or power supply can support this tube though. Anyone know for sure as I have also heard good things about this tube, but have not investigated it as I did not think it was compatible. Anyone know for sure?
I don't know if this list has changed but here are the ARC amps that Hifigeek1 mentioned in a different Tung Sol KT-120 thread.
The following is a list of ARC amps that are authorized to use the KT-120:
VS55, VSi55, VS60, VSi60, VS110, VS115, REF110, VM220.
I hope people find this useful as there seems to be a lot of confusion about it.
My dealer Lyric told me the opposite. The VT100 MKII was on the list of approved amps for the KT120 upgrade. I was called specifically by the rep and given this info because I had enquired previously about using the KT120s.
Did you get the list from ARC or is your comment based on second hand info?
Awesome. Well they don't keep me in the loop. So the issue isn't whether the amp can handle the increased heater current because it can, the issue is the fact that the tubes are mounted horizontally. Because the KT-120 is longer and heavier, there is a risk of tube sockets loosening up to the point where the tube looses contact with the socket and the tube arcs. That is basically the issue. That is why ARC does not support the use of KT-120's in that amp. BTW it does sound very good with KT-120's.
Well I'm not a fan of KT-88's in any ARC amp. I would make sure the output tube sockets were nice and tight and go with the KT-120's. Just so you know you can't just put any 6922's in that amp. I get them from ARC and it requires a 1-2 hour set up procedure so that distortion is low and the DC balance is correct.
Go with the KT120s you wont regret it. They will make a substantial improvement in your VT100MKII.
There are no issues re loose sockets, etc, as Hifigeek suggested.
I may not be a service rep, but I am very cautious and made sure that I investigated negative possibilities before making the change to the KT120s.
Thanks to all for your assistance on this. I plan on keeping the EH 6922 signal tubes, I just got through re-biasing them at about their midlife (using the A. Collins method). And my current output tubes seem to fit very snug, so I think a couple of quads of KT120's are on now on the menu. Will let everyone know how it goes. Cheers!
The REF3 and PH8 both use a 6550C for power supply regulation.
Are you suggesting that based on these data points, Sinaker01 should use the 6550C instead of the KT120 as power tubes? Perhaps you havent noticed, but ARC has replaced the 6550C power tubes with KT120s in all of its current amplifiers.
Ok, so, just finished installing and biasing (adjusted to the same 130 mV the amp recommends)a matched octect of Tung-Sol KT120's. Less than an hour playing time skipping through a bunch of artists I am familiar with(now Keith Jarrett playing J.S. Bach) and the verdict is positive so far. Can't speak to whether it can play louder than the EH6550's but they sound very good-perhaps a touch more effortless and glassy than the Electro Harmonix tubes but that could be just fresher tubes, hard to say. Mind you, the 6550 were only put in last Fall, so they were probably just at their "half life" based on my listening habits. Will keep the group informed as they break in, but good news is nothing went bang and they are dead quiet as well.
So the verdict after decent breakin time- they're pretty good. Not what I would call a flat out night and day difference but a bit more "drive" and a little less glare in the upper ranges especially when the volume is turned up. All in all I'm pleased for the $450 spent, but I will give full props to the EH6550 tubes - they were a good value. Assuming I can get 2 years out of the KT120 set, I am happy with the change over. BTW, one big physical difference is the heft and weight of the 120 vs the 6550. These things feel like they're built to last. Cheers!
Just a footnote comment about the KT-120s. I had about 3000 hours on my KT-120s and thought it might be a good idea to retube my amp. I bought a complete set of tubes from Upscale Audio and dropped them in. The price is about half what ARC would charge. Kevin Deal burns in his tubes for 72 hours before matching and then checks three electronic attribtes: bias, G2 and transconductance. After about 20 hours of break-in, it's quite obvious that the amp sounds better. FWIW.
Btw, one of the matched sets did not take a bias adjustment. I put an old tube back in and everything was ok. Called Kevin. He immediately shipped out a replacement matched tube. Everything is now good to go!!
Is the ARC VS 115 wired in triode?? Regardless, thanks for the advice anyway. The 6H30 audio tubes were pushing between 4 and 5K hours too. So I retubed the whole VS 115 batch.
As an aside, I just ordered a retube set FROM ARC for my ARC Ref 5. There's probably over 3K hours on the 6550 C and 4 to 5K hours on the 6H30s.
Not sure what I did makes sense, i.e., buying VS 115 tubes from Upscale Audio and Ref 5 tubes from ARC. The thought process is that "ARC grade" matching might be more critical in the line stage than the amp. That's probably not a valid assumption, but it's a done deal. In any case, as stated, the KT-120s bias just fine and the amp sounds great, so I'll just have to "suffer" [sic] with the Upscale Audio tubes in the amp -- NOT.
Triode-wired tubes give a more refined sound. Richer in inner detail as many would call it. I would describe the sound as more linear, the microdynamics of low level passages are better preserved so you wont spent time hunting for the right listening volume.
In pentode or likely Ultra linear in the VS115 config, you get better bang for the buck esp in the dept of bass dynamics. if you like gut punching bass, keep it as it is. If you love violins, female vocals, and choral music, AND your speakers are 89dB/W/m or better, go triode.
Triode-wired tetrode or pentode tubes can last longer assuming same B+ and bias in both modes.
Many amps can be rewired to run the power tubes in triode mode. Pull the screen grid input resistor and connect the screen grid to the plate via a 100Ohm flameproof resistor. But it really depends on whether the biasing circuit has enough range to get the tubes biased to the 55-65mA per spec after triode conversion.