Hi Guys,
Going to try this again. Here is a spec sheet for a KT90 (Electro Harmonix). Assuming I'd be game to fork out for these...can someone please confirm KT90s are actually rated for a HIGHER plate voltage than 6CA7's? It says 850V (EH) compared to 800V for 6CA7 (JJ). But is it really that simple? Am I to conclude that KT90's are even beefier than 6CA7's and should do just as well or better in holding up to the MM demanding electrics? I know nothing about tube limiting values or how pentodes, electrodes etc work. I've attached the 6CA7 spec sheet also. I'm as much an electrics guy as Mike Tyson is a florist so any help appreciated. It pays to ask.
Anyone tried these in their MM or heard on anyone who has?
Back in the day my buddy's Twin used to run with tubes so hot they glowed light orange and kicked off serious heat. You could feel it a few feet away! I've got my 6CA7's biased to 23 currently and had no problems. Would I be able to bias the KT90 a bit higher, say 27 or 30 due to the fact it's rated a bit higher?
Thanks,
Ted
PS - not really Ted Nugent
| Attachment | Size |
|---|---|
 6ca7.pdf | 497.92 KB |
| kt90eh.pdf | 1.29 MB |
Answering my own question. . .
Hello Musicmen,
Just finishing this off for someone in the future who might want to put KT90's in their late 70's Musicman (with the phase inverter). Works great! No mods needed. Just bias. The sound is excellent to my ears. Still Musicman but at 'clearer' or 'cleaner' sound than I've gotten with EL34's or 6CA7's. The EL34's always sounded a bit spikey/harsh past a certain point and I was forever having to adjust this or that setting to try to get the shrill out. 6CA7's fixed this mostly, but the tone is a bit different. I like it, and have a pair in one of my MM. The other MM has KT90's where they will live happily ever after. The bass is more pronounced than the 6CA7's - but crisp, not wooly or underfined. The high end has no shrillness at all until 7 on the Treble knob. Granted your mileage may vary according to speaker. It's an interesting sound. Chimey and clear. But the tubes ain't cheap! I've got EH. Just do a search to find how much they'll set you back. After you've put away the vomit bag, remember that theoretically they might last a long time as the plate voltage is rated even higher than EL34's as the doc in the above thread demonstrates.