This looks like the ideal driver tube:
http://frank.pocnet.net/sheets/093/6/6S4A.pdf
I'm thinking 6922 > 6S4A > 300B
http://frank.pocnet.net/sheets/093/6/6S4A.pdf
I'm thinking 6922 > 6S4A > 300B
6s4a is my all time favorite driver tube for electrostatic
headphones. As a 300b driver it should work well, but the
extra voltage it is capable of is very much wasted on a 300B.
2 sections of 6sn7 in parallel has more drive capability and the
300B really wants that when you go into positive grid drive
current.
headphones. As a 300b driver it should work well, but the
extra voltage it is capable of is very much wasted on a 300B.
2 sections of 6sn7 in parallel has more drive capability and the
300B really wants that when you go into positive grid drive
current.
Has anyone got the tools to simulate this circuit before I build it?
Any of the experts out there have a simulation tool that can handle this circuit.
I would like to assemble this weekend if it looks feasable.
The current sources will be a Supertex Enhancent mode FET.
Power Supply and a 1 minute delay circuit for the B+ are complete and tested, I will draw them out over the next few days.
Any of the experts out there have a simulation tool that can handle this circuit.
I would like to assemble this weekend if it looks feasable.
The current sources will be a Supertex Enhancent mode FET.
Power Supply and a 1 minute delay circuit for the B+ are complete and tested, I will draw them out over the next few days.
Here is the circuit after some minor tweeks
All filiments are DC.
1 minute timer for B+
Constant Current Source found at
http://home.zonnet.nl/horneman/mosfet.htm
All filiments are DC.
1 minute timer for B+
Constant Current Source found at
http://home.zonnet.nl/horneman/mosfet.htm
Attachments
6S4 is a good looking triode, but is designed for 150V operation, and a limit of 160V.
Meanwhile the 300B is normally biassed at -60 to -80V, and to allow some margin, the driver must be able to swing +/- 100V. With anode voltage = 150V idle, 6S4 can manage the negative swing, but going +ve, the curves become obviously nonlinear above 200V or so, even if CCS loading is used.
Only high quality option is to try a series cascode, which is what the tube was designed for. IME, an NPN transistor in the upstairs position is best here.
Meanwhile the 300B is normally biassed at -60 to -80V, and to allow some margin, the driver must be able to swing +/- 100V. With anode voltage = 150V idle, 6S4 can manage the negative swing, but going +ve, the curves become obviously nonlinear above 200V or so, even if CCS loading is used.
Only high quality option is to try a series cascode, which is what the tube was designed for. IME, an NPN transistor in the upstairs position is best here.
Tung Sol datasheet for 6S4 says 500V max. GE datasheet for 6S4A says 550V max. The 6S4 is a terrific driver tube and can even make a pretty decent output tube. You'll be interested to see its use in the upcoming 4th edition of "Valve Amplifiers."
"Linearity looks really good"
Umm, did you look at the 3rd page of the datasheet? The Mu curves are horrendous. Not even constant Mu at constant current. Should work OK for P-P, but SE looks like a disaster. As suggested earlier, it looks just like a bigger version of a 6C4.
http://frank.pocnet.net/sheets/093/6/6S4A.pdf
http://frank.pocnet.net/sheets/093/6/6C4.pdf
Umm, did you look at the 3rd page of the datasheet? The Mu curves are horrendous. Not even constant Mu at constant current. Should work OK for P-P, but SE looks like a disaster. As suggested earlier, it looks just like a bigger version of a 6C4.
http://frank.pocnet.net/sheets/093/6/6S4A.pdf
http://frank.pocnet.net/sheets/093/6/6C4.pdf
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