A small help with russian low voltage tube

[croccodillo]

Hello all,

I'm in the process of building a new amplifier.
What I'd like to build now is an hybrid, a tube front-end driving a solid-state class AB output stage.
I already have all the silicon bugs (VAS, driver and output transistors); I have now to choose the tubes for the input stage.
I have simulated the circuit with what I have on hands, 6N6P russian tubes; it simulate very well, but unfortunately the input stage must be powered with a very high voltage (300V), which I'd like to avoid.
I'd like now to find a very cheap, very nice russian tube to place at the input, in manner I can use a very low voltage (not more than 50V) even at the input.
I don't want to use expensive parts, so my idea was to use some russian tube.
I simulate also with a 6AS7 tube in it, but without too much success (maybe 50V@100mA is not a good operating point...).
Any suggestion?
What about 6N27P?

Attached a pdf schematic and the LTspice asc file (rename the .txt file into .asc).

Ciao,
Giovanni

[tvicol]

Use 6DJ8 or ECC88
A very similar approach was presented by me on this forum.
Forumul electronistilor • Vezi subiect - Hibridul meu

Thread http://www.elforum.ro/viewtopic.php?f=28&t=78346

Regards,
Tibi

[tvicol]

And here you have my versions.
The goal was to create a single gain stage amplifier with all vas in input tube stage.
However we have only simulated, but a real test is on the way.

Regards,
Tibi

[MrCurwen]

I hear 6C45P performs very well with low plate voltages.

[ratbagp]

Perhaps you could consider the planar 6S17K-V. I've used them in a competition for a line stage under $100 our local group is running and the more I listen, the more I like them. They do vary so you would probably need to get a few to get the matched pairs but at $2.50 they are inexpensive.

Russian Line Stage

ray

[Mikha]

Hi croccodillo!

I suppose 6N30P will be the best russian solution for your case.
Best regards,
Mike

[woodturner-fran]

You can try the 6n27P - direct substitute for the ECC86.... will work off 24v very well....

[Mikha]

Originally Posted by woodturner-fran

You can try the 6n27P - direct substitute for the ECC86.... will work off 24v very well....

6N27P is not sufficiently linear.

Mike

[Wavebourn]

Originally Posted by ratbagp

Perhaps you could consider the planar 6S17K-V. I've used them in a competition for a line stage under $100 our local group is running and the more I listen, the more I like them. They do vary so you would probably need to get a few to get the matched pairs but at $2.50 they are inexpensive.

Russian Line Stage

6S17K-V is a very nice tube, but I would not use it with 100K pot in the grid: due to high cathode emission and microscopic distances between tiny grid and cathode it's input current is quite high, so a first the pot would scratch, and anode voltage would depend on the volume setting. Also, in LTP filament supply should be very well isolated, since cathode is connected to filament internally.

6N30P here is the winner.

You may try as well 6N16B or 6B28B.

[ratbagp]

Yes, the 6S17K-V anode voltage does vary with the volume setting and the pot does scratch as it is changed. This was just a fun project for under $100 and I wanted to try something different.

ray