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  3. 1351603120

KT120 in Audio Research Pre-amp?

I recently exchanged my totally worn out 6550C's for KT120 tubes from Tung Sol in my VT200 MkII. It required a small modification, I'll spare you the details, but it was a succesful operation, quite happy with the sound of the KT120's.
I have some spare KT120's and I was wondering.... is there any danger in replacing the Svetlana 6550C of my Audio Research Reference 3 for a KT120 tube? Since it is a risk-free replacement for most ARC-poweramps, I was wondering if this would be the same risk-free replacement for their pre-amps like a Ref3.
128x128midcall
13 responses Add your response
lloydelee21
1,202 posts
 
Email ARC...should be a quick answer. The KT120 can draw slightly more current (i thought)...so just need to be careful.
roscoeiii's avatar
roscoeiii
1,155 posts
 
Yes, contact ARC.

Why ask here when you can talk with the company that built the amp?
spinaker01
491 posts
 
Talk to Calvin at ARC but I believe I heard that this is one place the 6550 should remain in place and NOT use a KT120. (Love them in the VT100 amp though!)
midcall's avatar
midcall OP
2 posts
 
Manufacturers normally prefer to be on the safe side and and are concerned less about what actually sounds best. That's why I ask the question here, hoping to get a more objective opinion. I will ask it ARC as well of course, but wanted to drop the question here first.
hifigeek1
770 posts
 
Do NOT use a KT-120 in the power supply of an ARC preamp. Use the 6550 only!
lloydelee21
1,202 posts
 
Manufacturers have long-term reputations to protect if they are reputable manufacturers. But if there is no safety risk to the unit, they usually tell you to go ahead an experiment...in the case where a manufacturers says dont do it...that they did not design the unit to increase the draw necessary to drive the KT120 (which draws i thought higher current slightly than 6550)...i would take that advice and not risk it.
microstrip
180 posts
 
No. In NO case the 6550 should be replaced by other type of tube in the ARC power supplies. Even the new REF250 still has the 6550 in this position.
lloydelee21
1,202 posts
 
Microstrip! Barely recognize you over here, relative to WBF! ;) May PM you over there for some advice...
hifigeek1
770 posts
 
I am a warranty repair station for ARC. KT120 in the regulator is no bueno...
midcall's avatar
midcall OP
2 posts
 
Okay, very clear. No KT120 in my Ref3 for sure. Thnx guys.
hansk46's avatar
hansk46
122 posts
 
so , no problem what I did two years ago , replaced the original 6550 tube by a NOS Tungsol black gitter , replaced in the REF 3 , and the CD7 .
regards Hans ( the Netherlands )
djcxxx
105 posts
 
So how exactly did you get the KT120 into the VT200MkII? I was told by ARC it was not possible.
borham
2 posts
 
Midcall and other forum colleagues:

Sorry not being able to help with KT120 in Ref3.

However I wonder how could you replace 6550 by Kt120 ( and perhaps nowadys by Kt150) in you Vt200?

Which mods have you done? Were they safe? And sound wise, did it improved?

Thank you very much for your help
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