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Old 19th March 2009, 12:20 AM   #11
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Quote:
Originally posted by kenpeter
That is absurdly cool!

I'm sure you've shown it before, but I only just now "got" it.
My pleasure!
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Old 19th March 2009, 12:51 AM   #12
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Now if you just flip it upside down and make an anti-triode...

I have no clue if this actually works or not...
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Old 19th March 2009, 02:20 AM   #13
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Quote:
Originally posted by Wavebourn
Here is what works like a charm; actually it is a gyrator. You may use MOSFETs here, or at least one on top to increase voltage divider's resistance and decrease capacitance needed.
It does not provide a constant current on DC. Actually, on DC it provides a constant voltage, but on AC it's dynamic resistance is huge.

I have a hunch that this one escapes the monotonous CCS anode sound. Nice one!
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Old 19th March 2009, 02:22 AM   #14
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Quote:
Originally posted by kenpeter
Now if you just flip it upside down and make an anti-triode...

I have no clue if this actually works or not...
We have to simulate it. Is it possible that C1 must be going to B+ ?
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Old 19th March 2009, 02:28 AM   #15
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Quote:
Originally posted by Wavebourn
It does not provide a constant current on DC. Actually, on DC it provides a constant voltage, but on AC it's dynamic resistance is huge.
Maybe its constant DC current fed from very low impedance that makes tubes hiss on bias points that they were behaving themselves previously loaded with resistors? The most perfect a CCS is, the more the tubes get excited. Especially if its a BJT source.
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Old 19th March 2009, 02:55 AM   #16
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Quote:
Originally posted by salas



I have a hunch that this one escapes the monotonous CCS anode sound. Nice one!
Thanks!
Actually, this one escapes constant flow of anode voltage and it's dependence on tube brand, age, and filament power fluctuations.
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Old 19th March 2009, 03:09 AM   #17
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This gyrator one you posted mimics a large coil. In such a way tubes used to be loaded back in the days they got conceived, whenever enough B+ was not available. Sounds like a more natural way. I will try to simulate one using the P Mosfets and LEDS that are already mounted on my CCS boards. I guess that will be the fastest and most economic way to listen to the gyrator load. I will post my contraption schematic before I will tweak those perfboards. Will you inspect Wavebourn?
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Old 19th March 2009, 03:46 AM   #18
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Hmmm.... I'm afraid you will need too many LEDs. Like a Green Light District (GLD, SY?)
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Old 19th March 2009, 06:19 AM   #19
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Here are SEPP or series push-pull circuits using cascode depletion mode
MOSFETS. The difference between these and CCS is that these will
drive symmetric current, push and pull so to speak, while retaining the
harmonic signature of the triode.

A vanilla CCS will only source up to it's constant current into the load,
where in a practical circuit the anti-triode will source almost 2X the
quiescent current, in exact opposite to the triode's low-current
half-cycle. This is analogous to the choke's energy storage.

It's good to provide some extra quiescent current so the anti-triode
doesn't get starved and clip on the triode's high current half-cycle.
In a line amp this is less of a problem than for a parafeed output stage
or power grid driver. (for a power grid driver I'd arrange it more like
a mu-follower anyway because it has asymmetric drive requirement)

There is a constant voltage variant. It doesn't matter really how you
develop the fixed voltage. It can be used with fixed bias because it
can regulate the plate voltage.

The constant current variant is good for low Rp, high gm tubes in
fixed bias to regulate the op point.

Cheers,

Michael
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Old 19th March 2009, 07:07 AM   #20
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Thanks Michael. That assures that my post#6 can work.
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