View Full Version : EL86, low voltage star?


mashaffer
05-16-2009, 08:37 PM
I understand that the EL86 has approximately the same plate dissipation as the EL84 but is optimized for lower voltage and higher current (eg. transformerless designs). Since AES has them for under $4 I got to thinking that a handful of those might make for a nice little amp using some low voltage transformers I have on hand that are not very useful for anything else.

I have several 50 to 60 volt trannies that even with a double only get up around 120 to 150V. If I can find a nice low rp preamp tube maybe a nice little amp could be designed. What do you think?

mike

jaymanaa
05-16-2009, 09:22 PM
killer tube IMHO, sort of under appreciated or over shadowed sort of the like the small but mighty 6AQ5

BTW, they will take a lot more voltage than the RCA man. says. I think it was Lafayette gear that ran them pretty hard and got a killer tone from them.

dmax99
05-16-2009, 09:53 PM
Talk to Kegger, he uses them for his amp builds.

steerpike2
05-17-2009, 02:10 PM
They also have very good heater-to-cathode insulation.
I have a Philips amp that use 4 of them, they sound very nice.

Kegger
05-17-2009, 10:37 PM
I built a push pull triode amp with them, 250v and 50ma per tube, quite nice!

Also triode strapped they have a gain an plate resistance simular to the 12B4
I plan to build a preamp using them. :)

mashaffer
05-18-2009, 05:19 PM
I built a push pull triode amp with them, 250v and 50ma per tube, quite nice!

Also triode strapped they have a gain an plate resistance simular to the 12B4
I plan to build a preamp using them. :)

Intriguing. Have you ever tried them at lower voltages like say 120-150V? Do you think they would work well with B+ in that range and say fixed bias. Interesting thought about the preamp project. What is the Rp in triode mode?

mike

kvflyer
05-18-2009, 06:01 PM
NOS price at Radio Daze is just $4.00 each. Not a lot of quid...

mashaffer
05-18-2009, 07:06 PM
NOS price at Radio Daze is just $4.00 each. Not a lot of quid...

Yep, and especially tempting if they can be used for preamp and power service. Although I have some doubts that they would have enough gain (at least in triode mode) for use as a VAS in a power amp. Maybe a nice combo splitter/driver...

mike

Kegger
05-18-2009, 08:25 PM
They should make a sweet preamp when strapped triode!

Roughly 7.5mu and RP of 1k, they prefer low voltage, say 150v and high current at say
25ma at least or higher, if running them as the outputs 150v and 70ma with a 2.5k load
in SE or 5K in push pull is really where you could run them, I used an el84 8.5K push pull
output with the higher voltage and lower current in the triode wired push pull amp.

I've ran them as drivers at 150v and 25ma, they are quite a versatile tube....:thmbsp:

GordonW
05-19-2009, 10:02 AM
PPP Circlotron with about a 500-600 ohm CT primary? That could be a 240:24VCT or 240VCT:30VCT transformer as an OPT. Around 135V-150V on the B+, or so...

Or, three-by-three per channel (six tubes per channel) PPP Circlotron, with a 240VCT:36VCT (full secondary winding would work with 8-16 ohm loads, half secondary with 3-7 ohm loads) transformer... could get close to 40 watts per channel, in theory, in pentode mode. Maybe 25w/ch in triode mode?

Could be a cheap bench project! You could probably use an isolation transformer as a power transformer...

Regards,
Gordon.