Russian / Soviet Tubes

[TheGimp]

Over in the Trainwreck Discussion..Z-Wreck thread:

http://ampgarage.com/forum/viewtopic.ph ... 0&start=60

there was a diversion to a discussion on Soviet Tubes (6N2P) vs 12AX7 (pages 4 and 5) that seems to be taking on a life of it’s own so I’m starting this to avoid hijacking the thread as it looks like the discussion may grow legs.

Mark posted a nice chart of 12A_7 vs 6N2P heater wiring near the bottom of page 5 (also 6N1P but not 6N3P).

That got me thinking that it should be possible to use a double pole double throw switch to configure the heater supply and switch tubes.

Having the switch in the wrong position would result in no heater voltage to the 6N2P if configured for 12AX7. Likewise if configured for a 6N2P there would be 6.3V across the 12AX7 heaters, which wouldn't be an issue.

Pin 9 would have to be switched along with either pin 4 or pin 5. In 12AX7 mode pin nine would connect to the switched 6.3V and 4/5 would be shorted together. In 6N2P mode pin 9 would be shield to ground and 4/5 would each be to one side of 6.3V.

Switch current capacity would only be 1.5A for three tubes, and would really not be an issue as one would not change switch settings with power applied. Micro switches are available with a 6A rating so no issue there.

[mbeldyga]

[img:640:480]http://www.mif.pg.gda.pl/homepages/tom/ ... erw_sw.gif[/img]

source: http://www.mif.pg.gda.pl/homepages/tom/ ... rwisowy%22

[Bruciep07]

What a great idea, easy way to hear tonal differences from 6N2P's to 12AX7's... This may be the basis for me to do a 2 bottle rocket...

[TheGimp]

Exactly, except no need for a center 'Off' position.

Right for 12A_7, left for 6N1P, 6N2P, 6N6P, 6N23P, 6N30P but not 3P.

6N6P/6N30P would make a good PI, and could even drive quads of KT88 and possibly KT120s.

[TheGimp]

Does anyone have a recomendation for how to test for noise (hiss) in tubes?

I found a lot of variation in the 6N2Ps I have (Voshod mfg). I used the output of the amp (trainwreck Liverpool derived with three 6N2P and two 6N6P for output) and measured rms signal with gain on full and a 8 ohm resistive load on the output. I used an oscilloscope at 250uS/div and 20mV/div (iirc) and had a relative measure.

I'd like to come up with a better (more uniform) way of measuring the tubes for selection/elimination.

[Structo]

Here is a good data sheet for the 6N2P.
In English too!

http://www.mif.pg.gda.pl/homepages/fran ... 6N2PEV.pdf

[M Fowler]

6N2P guide from other thread.

[TheGimp]

Ah ha... I saw that and thought I posted in the wrong thread.


More good links for Soviet tube specs:

http://www.radiolamp.su/list.php?a=6

http://klausmobile.narod.ru/td/list_e.htm

http://www.mif.pg.gda.pl/homepages/frank/

[M Fowler]

I received my 6N2P EB but I am sure I asked for EV?

[VacuumVoodoo]

Cyrillic "B" is latin "V"

[M Fowler]

Aleksander,

Thanks for the help with that

Mark

[Ian444]

Russian - English
H = N
П = P
C = S
B = V

Therefore 6H2П-EB (Russian) = 6N2P-EV (English)

I hope the 6N2P's sound OK as I bought some a couple of months ago to try in a guitar amp not yet built.
I have had a lot of joy with 6N1P's in hifi, its difficult to make them sound bad (= very versatile), and they sound great. They work well where you might use a 12AT7, only better IMO.
There are also Russian 6P14P-EV, basically a drop-in replacement for EL84, and 6P6S, same again for 6V6.

I have a hifi amp with a switch on the front panel to swap between 6V and 12V heaters on the preamp tubes, although I didn't enjoy wiring up the heaters all that much it was so well worth it! If you are inclined to go that way, I recommend it.

Here is an interesting thread on 6N2P, not the 6N2P-EV, but it may help grounding pin 9, who knows...

[Markusv]

Just bought 2 quads of 6P14P
They are really nice. Seem to have added a bit of clean headroom over the el84 jj's I had in my liverpool.
They seem to not get "crushed" so quickly and the distortion is more open

If that makes sense FWIW...

Cost me $35 shipped for the 8 tubes

[David Root]

Pardon my ignorance but could someone tell me what are the approximate equivalents for the 12A*7 series, the 6CG7/6FQ7 and the 12BH7? And what is different, if anything?

And tonal differences too, I realize that may be a stretch.

[TheGimp]

Probably the best way to approach the Soviet Tubes is the reverse, give the soviet designation and closest western equivalent.

6N1P - Many claim 6DJ8 but it does not really match closely. Probably ECC81 is closest or 6N7.

6N2P - 12AX7 but 6V filament only

6N3P - 2C51

6N6P - maybe 6FQ7, 6CG7 or 6GU7

6N23P - 6DJ8


Of these twin triodes, most of my experience is with the 6N1P(-EV).

I've done some measurements of distortion vs bias / Vka, and found that biased with a cheap red led (not my idea) and current source(again not my idea) for the anode load it can be tweaked to give very low distortion with a B+ of 250V and Vka set to about 115V. I built three stereo amps, with two using this configuration and all three sound great.

The 6N3P actually had lower distortion when biased with an IR LED (1.1V) and constant current source for the anode load. However the 6N3P has a weird heater pin-out (pins 1 and 9, with pin 5 shield) and I prefer the standard 4,5 connections for tube interchangeability.

6N6P has a big plate and low output impedance that would make it a great phase splitter for driving tubes with a greater drive requirement (like KT88s).

I've been collecting parts to build a stereo 6P3S output amp with 6N6P PI and 6N1P input stages.