RUSSIAN SUBMINIATURE TUBES

Sometimes I am wrong … I would had never thought, that there would be some kind of Audio-tube in the world, I did not know and which is absolutely worth to be known.

Yes – I was wrong and I fell in love with them ... from Russia with love!

By occasion, I found – for myself – a completely new area of tubes: The Russian subminiatures.

What I am writing about are very small items of tubes, with wiring leads instead of socket type, military grade and versatile for the handling. Some years ago, these types were let out to public use by the Russian authorities, while they were former mainly used for military and aerospace applications.

When all the world forgot about tubes during the late sixties, Russian engineers developed these items, so they reveal the latest news in tube tech.

There are many several types of triodes and pentodes, but like in our other Audio applications, we could stay to some few types with which we may cover mostly all Audio applications.

However – what are the dominant benefits of these tubes:

They almost show no microphonic behavior

They are small and light-weighted

They are intended for soldering into a PCB

They may be easily compared to other socket-type tubes

They are military grade – most of them...

They may be operated with good results at low supply voltage levels

They are rugged, durable and long-life

They are cheap (!!!)

Any more questions?

Fine – then let us talk about the specimen, I found to be best for Audio usage.

Triodes

6N17B-V

This is a double triode with high µ (mu) of about 75 and a transconductance of about 3,3ma/V. It may be used in all applications needing high amplification factors with not so big driving capabilities. It is likely comparable to a 12AX7 but will work with a supply voltage of +100VDC up. I tried it in a RIAA preamp and in several guitar preamp applications with good results. Since microphonic behavior is at very low level, it is capable of very high-gain situations!

6N16B-V

This is the mule of this class while it is one of the best sounding tubes in the world! This double triode shows a µ of about 25 and a transconductance of about 5mA/V. It is best used for amplification stages where not so big amplification factors are needed but high driving capabilities. It is also at its best, when used as a cathode follower. It may be compared to a 12AT7 or a 6SN7 and it will work also with a supply voltage of +100VDC up. I tried it in a line preamp, a headphone amp, as output stage in my CD player and in several guitar applications with good results.

6N16B-VR

This is the same tube as 6N16B but it has altered connection and a shield between the two triode systems. It should be used, when crosstalk between channels may be given or if another form of coupling between the two halves should be avoided.

6S31B-V

This is a superior single triode for any application, where high transconductance is the demand. It shows low mu of about 17 but 18 mA/V! It is also recommended, if lower plate voltages are used (<100VDC). It will work as a power triode, if the maximum plate current of 60mADC is sufficient. Max. power dissipation is 2,5 W.

I used it widely for shunt regulator applications and as a cathode follower to drive low impedance loads directly, e.g. in the 600 ohms headphone amp.
Maybe the best triode in the world for building of a low impedance SRPP stage!

Pentode

6P30B or  6P30B-R

This is a pentode with medium transconductance (4,5mA/V) and relatively low Ugk of app. -14V. It may be used for small output stages, single-ended as well as push-pull. It shows a very beautiful sound when overdriven, comparable to an EL84. This coloration can be controlled easily by altering the g2 voltage -> with lower values it will tend more to 6V6 direction. I like the ultra linear wiring, but that depends on personal taste.

For Jazz guitar use, my favorite application is a push-pull output stage in ultra linear connection of about 2W. It performs like a big power amp in sound, breathing and compressing when driven hard, sweet melting voice when kept clean, well and all with such a tiny wattage! You might play Metal in your living room …

For Audio use I prefer the triode connection and a single-ended-A wiring. This will give only little power, but it shows such a sweet sound ...