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What tubes for sibilant SET Triode amp

I have recently bought a Cayin/Spark 9021DEX amplifier. This is a zero feedback SET design in which I currently use the original Chinese made 211 output tube a 6SN7 GTB by Sylvania as a driver tube and a late Siemens ECC88 at the input. The bias on the output tube checks fine the sound is great with a minimal tendency to sibilance. As I am going to buy a set of back-up tubes anyway - which tubes to buy to get rid of the tendency to sibilance? Opinions seem to vary considerably! Any suggestions??

Preamp is a MacIntosh C220, Speakers are Gallo Ref 3.1 and Analog Front End is a VPI Superscout with a Shelter 90X.
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sogood51
2,157 posts
 
I replaced my ecc88's with Amperex tubes soon after I bought my preamp. I didn't like the Siemens tubes at all.

Dave
4est
507 posts
 
I agree with Dave. Many (maybe most) ecc88/6dj8/6922 are microphonic even when they test well.
atmasphere's avatar
atmasphere
11,843 posts
 
So your amps make about 12-15 watts- that means the Gallos have to be about 102 db to really take advantage of the amplifier's capabilities, and I don't think they are anywhere near that! So my guess is you are pushing the amp too hard to let it show off what it can do. Instead, you're getting a lot of distortion out of it (sibilance). I think you will find that if you go with a more efficient speaker things will change a lot. SETs in general are not known for sibilance!
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