EL 509 / 6KG6 output tubes w/plate cap top

[hilldweller]

I know there are some very knowledgeable out there and I always appreciate your advice.
Has anyone out there have any experience with the EL 509 / EL 519 N.O.S. Beam power tubes ? I see that they can output 1 amp of current and may be ideal for a high power amplifier.
I was considering building a 120 watt or more amp with these,

http://www.thetubestore.com/Tubes/6K-Ty ... L509-EL519 ]

http://www.ok1rr.com/tubes/EL509.pdf

[Geek]

Ummmm, not outside of power supply pass tubes or RF linear amps

A known caveat with these is they like to oscillate. Take all precautions including anode snubbers.

Cheers!

[kheper]

Looks like a tube that the guy from tubelabs would like, a TV sweep tube. The main limitation is the max 300V on the screens. UL mode is out, so you'll have to run in pentode mode: a little more power than UL mode but more distortion and non-linearity.

The only schematics I've found are kinda exotic. Screen drive for 9-10W in SE.



https://www.tube-town.net/info/sed-tech ... eNo33.html

[Geek]

Looks like a tube that the guy from tubelabs would like, a TV sweep tube.

There we go! Shoot George an email

[hilldweller]

Looks like a tube that the guy from tubelabs would like, a TV sweep tube. The main limitation is the max 300V on the screens. UL mode is out, so you'll have to run in pentode mode: a little more power than UL mode but more distortion and non-linearity.

The only schematics I've found are kinda exotic. Screen drive for 9-10W in SE.



https://www.tube-town.net/info/sed-tech ... eNo33.html

I was thinking something like this,

[Photo removed]

[kheper]

Pretty nice screen regulator, voltage doubler and individual output tube bias supply. Watch out for 700Vdc. That could really bite you.

[hilldweller]

Yea, .7 kv would be hard to recover from if at all!

[Geek]

ARGH! The way that zener is used

[Impmon]

ARGH! The way that zener is used

"Transcendent Sound, Inc": 'nuff said.

It does have one nice feature: the buffered voltage gain stage up front. It doesn't say what V1 is, but given a -0.9V Vgk, I'd guess 6AV6 or 6SF5 or something in that family: lots of Av, but not much current sourcing and therefore, they like a Hi-Z, Lo-C load -- like a cathode follower.

The screen reg is OK, but I'd prefer not dropping 550V across the series pass device. Better to use an "economy" power supply, or separate the screen supply from the plate supply completely. It needs a better voltage reference than that. Zeners are noisy, and relying on series current only could cause a drop-out, and the screen voltage loses its regulation. For screen supplies of ~150V, I use VR-75's as voltage references.

[kheper]

To avoid dropping the B+ for the screens, the screen voltage could be extracted from the doubler at the juncture where the first two electro-caps meet. It should be ~350Vdc. If possible, I'd go with a separate, well-filtered screen supply, but it looks like the designer was intending to create a "compact" 150W amp.

[Shannon Parks]

Bruce asked that the schematic come down. Here's a link to the PDF edition of Audio Reality:
http://www.transcendentsound.com/Transc ... ality.html

Shannon

[hilldweller]

Bruce asked that the schematic come down. Here's a link to the PDF edition of Audio Reality:
http://www.transcendentsound.com/Transc ... ality.html

Shannon

Ooops, I didn't know you knew Bruce Rozenblit.
I thought that because the book was no longer in print and the circuit had no patent, I thought I could post this. Sorry for being ignorant!

[Geek]

Patent and copyright are two different things.

Copyright is life of author + 50 years. Though I heard there was a battle to extend that to 75 years or something

Cheers!

[Shannon Parks]

Ooops, I didn't know you knew Bruce Rozenblit.
I thought that because the book was no longer in print and the circuit had no patent, I thought I could post this. Sorry for being ignorant!

It was an honest mistake any of us could make, Hilldweller. I don't personally know Bruce, but I dropped him an email just to CMA. The DMCA scares me after I lost internet for a week two years ago. Wifey wasn't happy.



Shannon

[jonnyeye]

Traynor made 300W from a quad of 6KG6s in their YBA3a bass/guitar amp back in the 70's. 560V on the plate, 140V screen supply from a separate winding; the schematic doesn't give the output transformer impedance (but in class B, 535V into 1K9 gives you 300W so that's a good place to start).

That all said I wouldn't want to build an amp with 6KG6/EL509s today, because they are popular tubes (especially among the OTL and RF linear crowds) and not in production in the original top-cap version (Ei used to make them, and Winged C had tooling for the Soviet equivalent, but neither are making tubes right now). Even the 6P45S (Soviet version) is getting harder to find - in ten years you might not be able to get any version for reasonable prices. JJ makes the octal EL509-S which is usable but intended for OTL service; at 600V B+ or less you are likely fine, and they are likely to still be making them for a while.