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Retubing an ARC VT100 mkll

Thinking of tube rolling my VT100 mkll. Currently using EH for both the 6922 input and 6550 output tubes. Less than 800 hours on the entire set, so its not that I need an entire retube, just looking to improve the sound if possible. What would give the biggest improvement, changing out the input or output tubes to KT88/90? Bear in mind I would need a closely matched OCTECT of either so bizarre/rare vintage tubes are out of the question. Thinking of Gold Lions or similar, any thoughts from the scholars?
spinaker01
gmorris
351 posts
 
Spinaker01:
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.
spinaker01 OP
491 posts
 
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!
oregonpapa's avatar
oregonpapa
4,867 posts
 
Call ARC and buy a set of their new 6550s. I replaced the power tubes in my REF-PH8 and my REF-3 with these tubes. At first listen, there was a blacker background with much better definition and separation. Once broken in ... amazing.
johnsonwu
469 posts
 
OregonPapa, you mean you can hear a big difference after you replace that regulator pass element 6550 in the PH8 and Ref 3 Preamp? How old was the 6550 that was replaced?
gmorris
351 posts
 
Oregonpapa:
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 haven’t noticed, but ARC has replaced the 6550C power tubes with KT120s in all of its current amplifiers.
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