If you have a tube circuit, it can probably be adapted. Here is an article on how triode tubes can be replaced directly by high voltage MOSFETs.
MOSFET Follies - letting the Solid State Demon into your tube amp
MOSFET Follies - letting the Solid State Demon into your tube amp
It's no secret that I like MOSFET voltage followers. As a "concertina", AKA split load, phase splitter is a tweaked voltage follower, a MOSFET doing that job rates to be quite satisfactory. Look here, where Jeff Yourison is working (with a little help from yours truly) on a PP 6Y6 amp that employs a MOSFET "concertina" phase splitter.
While FET current amplifiers are highly satisfactory, I'm very dubious about FETs as voltage amplifiers. The cross coupled phase splitter is a somewhat complex bit of circuitry. Voltage amplification is occurring, along with the generation of the 180o out of phase signals. I can see depletion mode (for self biasing ease) MOSFETs source followers at the I/P of the transformerless version, but linear triodes being employed in the voltage gain positions. Perhaps the DN2540N3-G would be suitable in the voltage follower "slots".
While FET current amplifiers are highly satisfactory, I'm very dubious about FETs as voltage amplifiers. The cross coupled phase splitter is a somewhat complex bit of circuitry. Voltage amplification is occurring, along with the generation of the 180o out of phase signals. I can see depletion mode (for self biasing ease) MOSFETs source followers at the I/P of the transformerless version, but linear triodes being employed in the voltage gain positions. Perhaps the DN2540N3-G would be suitable in the voltage follower "slots".
Here is am improved version of the Van Scoyoc cross-coupled splitter published in 1957:
http://www.next-tube.com/articles/cci/cci_EN.pdf
I ran it through LTspice, and it works perfectly. The only thing is, I don't get the bit about "cathode voltage of power tubes must be increased by 20 volts." My limited knowledge of tubes does not help, especially since the simulation works without this. Why is that necessary? To improve the voltage swing range? In practice, would this be implemented with voltage divider resistors off B+?
http://www.next-tube.com/articles/cci/cci_EN.pdf
I ran it through LTspice, and it works perfectly. The only thing is, I don't get the bit about "cathode voltage of power tubes must be increased by 20 volts." My limited knowledge of tubes does not help, especially since the simulation works without this. Why is that necessary? To improve the voltage swing range? In practice, would this be implemented with voltage divider resistors off B+?
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The only thing is, I don't get the bit about "cathode voltage of power tubes must be increased by 20 volts."
The phase splitter's O/P cathode followers and the O/P tubes' control grids that are DC coupled to them "sit" at +20 VDC. Correct operation of a tube, with few exceptions, requires the control grid be negative with respect to the cathode. Implicit in the remark is a cathode (self) biased set up. Since the control grids of the O/P tube pair are at +20 V., instead of 0 V., the cathode has to be raised above ground 20 extra volts to achieve the desired operating point.
If the cap. coupled O/P cathode followers are replaced by DC coupled ZVN0545A source followers, cap. coupling to the O/P tubes' grids can be employed and any valid biasing method will work.
'The last circuit is a LTP, to me one of the best ways to make a phase splitter. I would make it with two lsk170's or something like that, then cascode it with transistors that can withstand the high(ish) voltage.
Or maybe looking to Calvin's fine buffer-thread make it with a CFP pair as input + a shielding cascode. Then you can run the output tubes without any coupling caps.
Or maybe looking to Calvin's fine buffer-thread make it with a CFP pair as input + a shielding cascode. Then you can run the output tubes without any coupling caps.
I can read Dutch and Flemish, but my French is non-existent. It's a shame because it seems like the site contains a lot of useful information.
I eventually managed to figure out that one needs to click on "Schéma de l’amplificateur" to see the schematic of the amplifier. Here are the actual links.
http://www.novotone.be/_site/projets/Projet35/Fig02.pdf
http://www.novotone.be/_site/projets/Projet37/Fig02.pdf
Correct operation of a tube, with few exceptions, requires the control grid be negative with respect to the cathode.
Thanks for that. The light suddenly came on and it nearly blinded me. I should read on tubes some more.
Thanks for the input so far,
Great ideas and circuits.
I was wondering how easy/hard it would be to implement, (reduce space) with some of the more complex splitters. Nice to see other examples.
Theoretically I guess you could build a whole tube circuit with FETS I wonder if anyone ever has and what it sounded like (Off topic) FET with OP Tx.
Back to phase splitters the small 6V6 is interesting.
Regards
M. Gregg
Great ideas and circuits.
I was wondering how easy/hard it would be to implement, (reduce space) with some of the more complex splitters. Nice to see other examples.
Theoretically I guess you could build a whole tube circuit with FETS I wonder if anyone ever has and what it sounded like (Off topic) FET with OP Tx.
Back to phase splitters the small 6V6 is interesting.
Regards
M. Gregg
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Those days i have presented a new type of phase splitter. There are also version specified for tube circuits.
Have a look at this thread:
http://www.diyaudio.com/forums/solid-state/238405-fully-differential-phase-inverter.html
Francesco
Have a look at this thread:
http://www.diyaudio.com/forums/solid-state/238405-fully-differential-phase-inverter.html
Francesco
I can read Dutch and Flemish, but my French is non-existent.
try with google translator
Here are the actual links.
wow, a wimpy BS107
btw, would a simple SS 'phase splitter' handle multiple parallel output tubes better than if a tube
wow, a wimpy BS107
btw, would a simple SS 'phase splitter' handle multiple parallel output tubes better than if a tube
The Velleman K4000 comes to mind with a 12AX7 in concertina driving 4 EL34 per channel. You may have a point!
Regards
M. Gregg
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