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Which tubes to roll

I just picked up a Cary CAD 120S. I wasn't planning on rolling tubes so soon but one output tube was missing so I've started looking into it.

Right now it has KT88EHs as the power output tubes. I was thinking about trying some different ones, say, the SEDs but I was wondering - which tube have more of an effect on the output: the the input 6NS7s or the KT88s?

I noticed on Ebay they have a matched octet of winged-c SEDs for $400 that are supposed to be the original Svetlanas.
wireless200
swampwalker's avatar
swampwalker
5,138 posts
 
no idea who is selling them, but in general, e-bay is a crap shoot for tubes.
tpsonic
1,092 posts
 
If replacing the KT-88s,I would suggest the Gold Lion or Shuguang KT88-98.I have never cared for russian tubes.
You might consult Vintage Tube Services/Andy Bauman on the input tubes-very knowledgeable.
hotsauce
108 posts
 
On every tube amp I've ever had the input tubes made more difference in tone than the power tubes.

If that amp is tube rectified you can also roll that for different presentation. A rectifier thats higher voltage will bias the amp towards a more agressive sound, lower voltage more relaxed.

You can run 6550C's, 6L6, or EL34 as power tubes instead of KT88's in that amp.

After you change tubes you should let them warm up, and reset the bias(140ma) as per the manual. When I swap tubes I first set the bias low with the old tubes, swap tubes, then once warm bring the bias up to spec. The eliminates the chance of being over bias on different type tubes.

John C.
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