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Old 12th July 2007, 11:36 PM   #11
EUVL is offline EUVL  Europe
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I knew I shouldn't have posted schematics until they are tidied up.

The output series resistors were there because I did not have my CAD with me (with which I schematics was drawn) to remove them, as is the case with one or two other minor features which shouldn't have been there. It was posted as a general idea of how such a circuit might work. That is why I attached no component names & values.

There are four resistors connected to ground -- a pair for the balanced input, and a pair for the balanced output.

And of course designed as a follower, it has (near) unity gain and no feedback, like the F4. When used as a power amp, I should probably use at least 3 pairs of devices in parallel to get decent power output.

I don't think I have missed anything this time, but do feel free to point out any mistakes.


Patrick

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Old 12th July 2007, 11:48 PM   #12
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Given that solid state people are allergic to multiple power supplies, the Circlotron topology doesn't find many admirers other than in its native tube versions. I find ways to toss in extra rails here and there, but even the most basic version of a Circlotron requires two independent power supplies.
I've got eight or ten versions of the New-Tron, but they're pretty much on hold at the moment. I'm short on time and there aren't enough people interested to keep things moving.
A quasi-complementary circuit is more likely to catch peoples' interest--at least here.

Grey
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Old 13th July 2007, 02:30 AM   #13
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Joe and Patrick, Yes, sorry, I don't even remember seeing those output Rs... I was refering to the pair closest to Gnd in the latest schez...

Grey, go for it! I'm interested Would not the Circlotron be considered a Quasi Comp circuit??? Maybe Laterally rather than Vertically or ???
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Old 13th July 2007, 04:03 AM   #14
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The Circlotron is...a Circlotron. The two power supplies make it unique. Another difference between it and a quasi-complementary amplifier is that both sides receive the full voltage swing; they're both followers. In a quasi-complementary output the upper half of the circuit receives the full voltage swing. It's a follower. The bottom half, however, is not a follower. It's a grounded cathode/Source/emitter and as such supplies its own amplification. It only needs sufficient signal to match the upper half, but that's a much smaller signal.
Yes, there are numerous examples of quasi-complementary circuits out there that apply the same magnitude signal to the upper and lower portions of the output. I will simply suggest that the designers of such circuits...well, they didn't think it through. That is--no doubt--a contributing factor to the somewhat uneven reputation that quasi-complementary amplifiers have endured over the years.
As for the various power JFET circuits I've got...all I can say is that I've been trying to get a PC board done for the last ten weeks or so. Yet it remains stubbornly trapped in my computer. I've yet to figure out a way to get any electronics done at work and my home time is horrendously over-committed. I'm still clearing the bricks and rubble from when the DOT wrecked my mailbox, along with a thousand other things. Spiders and wood crickets have invaded my lab space. It's pretty sad, actually.
Look to Nelson. He'll have something long before I will.
For that matter, I expect my usual analogy between my progress and glaciers will need updating. I see the glacier has sprinted ahead.
Perhaps I should look to plate tectonics for comparisons.

Grey
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Old 13th July 2007, 01:10 PM   #15
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I have to admit that I do not understand why the 2 floating PSUs are such a big deal.

In any direct coupled amplifier, one needs a positive rail PSU and a negative rail PSU. So as in a circlotron you still need 2 transformer secondaries, at least 2 banks of caps, and 2x whatever regulator (series, shunt, CRCRC, CLCLC, ....) youz might choose to use. The onlything you don't have for the power stage of the circlotron is a common ground. And the only thing extra for a circlotron is 4 rectifier diodes.

OK you need a separate +/- PSU for the frontend if you want more gain than unity, but many people use separate PSUs for frontend (at higher voltages) anyway.


Patrick
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Old 15th July 2007, 12:53 PM   #16
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Euvl, one of the concerns about the two floating power supplies
is that a stereo amp will need a total of 4 floating supplies.
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Old 15th July 2007, 01:17 PM   #17
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I don't think many people here building Pass Amps use single transformer for stereo, when you would need up to 2kVA for 1 channel only.

And even then, you can get a transformer done with 4 secondaries at nominal extra charge. And you would want to do that anyhow even for fixed rail amps for better left/right separation.

Perhaps when Nelson would publish a circlotron one day, then everyone would rush into it.




Patrick
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Old 15th July 2007, 01:30 PM   #18
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Quote:
Originally posted by EUVL
...Perhaps when Nelson would publish a circlotron one day, then everyone would rush into it.


Yes, I would think your right about that
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Old 15th July 2007, 01:55 PM   #19
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Old 15th July 2007, 02:57 PM   #20
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The problem with two power supplies isn't financial or logistical. It's conceptual. It's not what they're accustomed to.
"Where's the ground?"
"There isn't one."
"Well, then how do you hook them together if there's no ground to reference them to?"
"In series--circuit/power supply/circuit/power supply."
"But how do you know which one is the positive rail and which one is the negative rail?"
"There isn't a positive and negative."
This is inevitably followed by a perplexed frown and the sound of the door closing behind the departing DIYer.
Then add the fact that for all that people will put up with ninety-nine stages in their electronics, they want their power supplies as simple as possible. Like the chassis, the power supply is one of those things that represents an unwelcome intrusion of reality when the DIYer is in a mad rush to get the circuit done.
"Look, Ma! I built myself an Aleph!"
"That's nice, dear...now where's the chassis and power supply?"
"But they're not the Aleph part, Ma. It's the Aleph part that cool and different." Followed by the reverent whisper, "And it's patented!"
"And how far will that circuit get you without the power supply? Now go back to your room and build a power supply."
"Aw, Ma...do I have to?"
"Go. Now."
And so the power supply is accorded second-class citizen status. Only grudgingly is time devoted to it.
And the Circlotron needs two power supplies? Huh! Junior runs as fast as he can in any other direction.
Dear Gussie! What do you mean you want a third power supply for the front end?
Get out of here!

Grey
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