EL34's for a 520V (plate) amp?

[grantford]

Hi guys!
WHat current production tubes can handle higher plate voltages? My shiva is in the 515 to 520 range? I have the reccomended SED winged C's in there now. ANything else available???

Thanks!

[grinder965]

Out of the current production stuff, JJ E34L's are supposed to adequately handle high plate voltages.

[grantford]

Interesting.

ANyone try EH6ca7's or GT el34m's? I have liked the sound of these in the past. Thanks!

[Geetarpicker]

I tried GT EL34Ms in my '68 Superbass 100 which "had" about 490 b+. The tubes would red plate under full load, regardless of how cold you set the bias @ idle. The tubes were fine at idle, but just couldn't hang when you dimed the amp. I then added a small transformer (wired as an autoformer) in the amp to step down the input voltage to about 110v. Now the B+ is about 416, and at that voltage the GT tubes are happy and the amp sounds awesome. I should mention that I first tried the amp stepped down to about 117v with 460 B+ and the GT tubes were still not able to take the B+. Yep now my filaments are a little low @ 5.8v, but many folks say that is probably on the verge of cathode stripping but probably ok.

I was able to run EH6CA7s in the same amp @ full 490 B+ with no problems. However those tubes didn't sound as good to me as the GT EL34Ms, once the voltages are stepped down. I bet they would take 520 B+. And I bet the GTs would last minutes at best @ 520v.

I have a friend that runs JJ EL34s (not sure if they are Ls) in a '67 Superbass with like 560 B+ and now one of his tubes is just now starting to red plate under load. Recently I tried some EL34Ls in a hot running '69 50 watter with a high B+ (470 or 490 can't recall exactly) and they took it.

FYI here is how I reduced the input voltage. Basically a poor man's variac.

http://www.geofex.com/Article_Folders/vintvolt/vintvolt.htm

Hope that helps.

[grantford]

Interesting indeed! I have been running the EH 6CA7's in a marshall with 480v+ for over a year with no probs yet.

[Sparky6string]

I've read about the new Shuguang EL34Bs handling close to 700 volts. Supposedly pretty tough suckers.

[Buckeyedog]

I also think the JJ KT77's can handle the higher voltage. They also sound really good.

[grantford]

I've read about the new Shuguang EL34Bs handling close to 700 volts. Supposedly pretty tough suckers.

holy smokes!