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SpreadSpectrum 6th January 2011 03:14 AM

Anybody use 841s(VT-51)?
I just bought a bunch of 841s and was planning on using them CCS loaded to develop some serious voltage swing. My goal is to get over 200Vrms with low distortion.

I am going to drive them with a source follower at 400V on the plate (800V supply). If the curves in the datasheet are representative they should work well for developing a lot of voltage drive into a high impedance load at low distortion.

I was just curious if anybody has used these and what your opinions are?

Also, I want to make sure that I don't violate the minimum grid bias resistance but can't find that spec. I am planning on using a 15K resistor for the load of the source follower that will drive the 841. Does that sound reasonable?

Vinylsavor 6th January 2011 08:32 AM


This is an interesting tube, I also plan to do something with these some time. I only need to find some good ones. Do you have a source where I could get 4-6 pieces?

I would use them in a DHT phonostage :rolleyes:

Just be aware that they have a very high rp, so they cannot drive a lot. Not really suitable for driving a power tube.

Best regards


SpreadSpectrum 6th January 2011 11:39 PM

I would use them to drive the gate of another source follower so high rp is not a problem. Load would be about 1.5M || 5pF.

Sourcing these is a real problem. I got my hands on 17 of them but I have had to be very patient to do so. They aren't too expensive but the problem is that most of the time you can't find them anywhere.

Vinylsavor 6th January 2011 11:42 PM


If you would be interested to sell a few or to swap maybe with some Lundahl iron, let me know.


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