KT66 are said to be much better than KT88-6550, a cult following almost, as good as the 300B, but harder to get and more expensive.
Good KT66 are Genelex made in England, either smoked glass or clear. There are new KT66 by Groove tubes, good but no comparison. Almost any good 6L6GC will work on the Quads, but original Quads are hard on tubes.
KT stands for Kinkless Tetrode, I am no expert but having a big coke bottle has something to do with less electron interference, there are a lot of cheap 6L6 branded KT66 due to its high price.
The original amps sound very good, detailed with beautifull highs.
I have not heard the new version so I cant compare.
That said I like my Quads with GE 5871 better...
Go figure!
Good KT66 are Genelex made in England, either smoked glass or clear. There are new KT66 by Groove tubes, good but no comparison. Almost any good 6L6GC will work on the Quads, but original Quads are hard on tubes.
KT stands for Kinkless Tetrode, I am no expert but having a big coke bottle has something to do with less electron interference, there are a lot of cheap 6L6 branded KT66 due to its high price.
The original amps sound very good, detailed with beautifull highs.
I have not heard the new version so I cant compare.
That said I like my Quads with GE 5871 better...
Go figure!