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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

Showing 13 responses by hifigeek1

hifigeek1
770 posts
 
I can tell you, they're still susceptible. If your amp was wired in triode, you might be able to get away with it.
hifigeek1
770 posts
 
It's bound to happen at some point.
hifigeek1
770 posts
 
Bifwynne, I have to find my thread or the list of ARC products that can use it. I think there is an issue with space in the VT100 series. The KT-120 is too tall I believe.....
hifigeek1
770 posts
 
Thank you Jedi. May the force be with you always!
hifigeek1
770 posts
 
The filament supply was not designed for the extra current needed to run the KT-120. The above list is from Audio Research and represents what they have tested and are comfortable with running KT-120's in. Caveat Emptor.
hifigeek1
770 posts
 
I received the list from ARC as I am a warranty repair station for them. I suggest you contact ARC and speak to Kalvin. I suppose it's possible they updated the list. But that's news to me.
hifigeek1
770 posts
 
I believe there have been a few issues with the 6550EH's and ARC gear. They are currently using the Sovtek 6550WE. I would continue to use the 6922EH as that is the tube that product was voiced with.
hifigeek1
770 posts
 
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.
hifigeek1
770 posts
 
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.
hifigeek1
770 posts
 
BTW Never use a KT-120 for the regulator pass element in any ARC product. It's a definite no no.
hifigeek1
770 posts
 
Wow 3000 hrs. is well passed the recommended ARC replacement time. I would say you got lucky..
hifigeek1
770 posts
 
Next time let me know BEFORE you buy your tubes. I can help.
hifigeek1
770 posts
 
You also lose about 30% of your total power output. Clipping is much softer.
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