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November 28, 2020, 11:25:54 AM

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Author Topic: High-voltage transconductance circuit United States Patent 7551025  (Read 4281 times)

rodriki1

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Hi guys,

what do you think about this recent patent on pentode replacement????
do you think this could really show the behavior of pentode after phase splitter...
the author claims it can do even the grid conduction effect or compression..

unfortunatelly those patents are always surrounded by mistery. i say tha it is
because they never are together with some real sample.

thanks in advance.

teemuk

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Is the inventor the same person as Mitch Margolis of Manley Labs fame? Would be quite interesting shift from $$$$ high-end tube audio HiFi products indeed.

J M Fahey

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It's interesting, should build one to hear it, probably it will sound very good.
In fact, both FETs and MosFets behave like "perfect pentodes", with "horizontal" current lines, depending only on gate voltage but not on drain voltage at all (beyond the initial ~1Volt "turn on" or "saturation" area)
This inventor tweaks that curve enough as to mimic a 6V6 curve, and also mimics bias-shifting, grid-rectification, etc.
A very "Pritchardish" school of thought, nothing against that.
The acid test will be, of course, building a Champ with it and comparing it to the real thing.
I find the Fig 5  example not so interesting. I see local feedback taken from an extra OT winding, Mackintosh style, maybe good for Hi Fi amps, not so much gor guitar ones.
Fig 6 gets back on the "good" track.
All above opinion based on a very brief Patent reading, maybe tomorrow I see that under a different light.
What slightly annoys me is the unnecessary inclusion of the Power Supply (here called Power Conditioning) and Fan (cooling) circuits within the Patent body.
They sure don't influence sound!!!
Well, maybe a special power supply provides "sag", but since he does not mention it specifically ........

rodriki1

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Is the inventor the same person as Mitch Margolis of Manley Labs fame? Would be quite interesting shift from $$$$ high-end tube audio HiFi products indeed.

thanks for answers. it sounds you are right. the same guy...
i still have been dreaming about some one like andrew barta able
able to show us creative alternatives for tubes...

Jack1962

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Well if memory serves me , there have been high voltage FET's for a number of years that you can use in the place of a preamp tube , however it would be very interesting to test one that could be used in place of a power tube indeed.

                                                   Rock On

J M Fahey

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Hi Jack.
In fact you*can*use a high voltage Mosfet to replace a power tube, there are a couple 800V and 1KV types, what you can't do is build a metallic tube, EL34 size, put a Mosfet there , make it dissipate , say, 30W and not burn it.
You just have too much thermal resistance.
Now if you mount it to some kind of heat sink, it's possible.

Jack1962

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How ya doing J M ?
Yes you probably could , and perhaps get tone that is very cllose to that of a tube , which brings up another thought , with a MOSFET it the power section , you no longer need the output transformer lol lol loll