6N1P Data sheet differences

[mashaffer]

For a SE 6BQ5 amp project I have percolating I had intended to use 12A_7 series tubes for the VAS due to availability but I am beginning to think the 6N1P would be a better choice. I will be using simple cap coupled topology and UL output sans loop FB most likely with LED bias.

One of the things I like about it is that the natural bias points around 1.7-2V land right in the 7-10mA range that a red LED would like. I have two data sheets on hand and the curves and maximum ratings are quite different. One sheet is a Svetlana sheet and the other from an unknown Russian source and has both Russian and english text.

The Russian sheet (yes I know that Svetlana is Russian also but I mean the one with Russian text) says Va max is 300V while Svetlana says 250V. Also the curves are quite different with a 2V 8mA bias point being at a plate voltage of 180 on the Svetlana curves and 140 on the Russian sheet's curves.

So the question is for the Sovtek tubes that I have on hand is either of these sheets correct for these tubes? If not is there a correct data sheet for this tube available for download?

Also how are the microphonics with the Sovtek tubes? They will be in close proximity to a sub but the coupling caps will be chosen to roll off below 80Hz in this application.

[Wavebourn]

Don't worry Mike: anyway spread of parameters of Russian tubes is wider than barn gates. However, tubes with stamped rhombus or a star on them match closer to specs because they were tested by Defense Ministry QA.

[mashaffer]

Do you think I should stick to 250V B+ for safety sake?

[Wavebourn]

I think you should stick to cathode bias resistor to minimize impact of spread of parameters.

[mashaffer]

Hmm... I can see the logic in that. Of course then some of the rationale of using the 6N1P in the first place disappears but it is still more linear with higher gain than a 12AU7 and better current capability than the 12AX7. 12AY7 is a very nice preamp but not as common as the other 12 series tubes so the "find it on any street corner" appeal of the 12 series doesn't really fit that one.

No decision is ever cut and dried is it?

[Wavebourn]

6Н1П (6N1P) are nice tubes, I use them. Speaking on max ratings, I would stick with stricter ones, for longer tube life. Also, sometimes manufacturers of Russian tubes specify max voltage for hot tub and for cold one. Cold rating is higher. That means, while tubes are cold and don't draw current voltages may be higher.
However, all that ratings matter mostly when you have a warranty and can claim a defective tube that did not survive specs. Otherwise, it is up to you to decide: George (tubelab.com) usually tests his tubes for real specs instead of factory guaranteed ones.

[Ian444]

Originally Posted by mashaffer

Do you think I should stick to 250V B+ for safety sake?

The specs are for voltage from anode to cathode, for example, with a B+ of around 350V and an anode load of 150K you end up with around 135V across the tube.

[Arnulf]

Originally Posted by mashaffer

Do you think I should stick to 250V B+ for safety sake?

Where our "ratings are for transistors" forumite ?

[TheGimp]

The 250V is during operation. The anode resistor will drop some voltage. There will be a brief period during turn on when the voltage will exceed that value, however some tube data sheets list this as a seperate parameter.

I would keep the anode DC operating voltage below 250V and not be concerned.

[mashaffer]

Of course. I keep forgetting that the spec is for Quiescent voltage not the maximum swing of the AC waveform.