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Old 19th March 2006, 10:06 PM   #1
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Default Nelson's "modulated supply" patent.

Hallo Mr. Pass and PassDIYers.
I have a question: what is the current source for?
Does it have something to do with maximum Vgs of 20V ?
Could it be replaced with a resistor?

regards
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Old 19th March 2006, 11:09 PM   #2
joensd is offline joensd  Germany
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If you want to get real medieval you could use a resistor.
IŽd say the Zen amp is as simple as you want to go.
The first article from the zen series will give you the answer you need, plus much more.
Zen amp article & others
You should find the answer by page 2 already.
(if I understood your question)
These articles are a joy to read and will enlighten you
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Old 20th March 2006, 01:25 AM   #3
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Quote:
Originally posted by joensd

...
if I understood your question
...
I'm highly affraid you didn't.
Probably I wasn't clear enough- my qeustion is about attached schematic (23 source).
My first guess is that current source is not needed in class A operation of output devices, but may be useful at class B, because it will define Vgs of 'supply' mosfets.
Moreover current source seems to complicated (Yes, Nelson) here because it works with pretty constant voltage (2*reference_voltage(27,29)-2*Vgs drop), so why not a resistor?
I'm not sure, therefore I ask, maybe guru itself of one of his followers have built (or deeply analysed) it and will answer.

regards
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Old 20th March 2006, 02:22 AM   #4
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Hi, Darkfenriz

Quote:
, maybe guru itself of one of his followers
Lord of The Rings?

Quote:
why not a resistor?
You mean CS/33? I think it cannot be replaced with a resistor. 33 is for forcing current, big current (7A, example) pumping current flowing from 23 to 21. For mosfets 11+13, this current will flow from 21 to 23, making it a circling around 33 and 11+13. 33 is one key of this patent.
If other amp is biased by 50mA, 100mA or 2A, with this patent you could bias 7A at final transistors

Quote:
what is the current source for?
Let's imagine you wanted to build classA power amp, but you have rail voltage of +/-100V. It is not wise practically. With this patent, the rail could be +/-100V, but heavy bias (7A) only flowing through point 21-23 (if V27+29 is only 14V, that means this 7A current only flowing through 7V of 11+13 = 49W dissipation).

Mosfets 11 and 13 is maintained heavy biased (7A), which is very good for linearity, but they only dissipate low heat (49W), and the supply can be as high as +/-100V.

Anyone knows what comes from PassLabs that uses this patent?
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Old 20th March 2006, 05:07 PM   #5
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Thanks David
it makes sense, I didn't realize the current arrow is 'up'.
However the voltage drop on current source is 'down', so practical realization won't be so simple.
regards
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Old 20th March 2006, 07:54 PM   #6
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It's a riff on the Sano (et al) Class A circuit, but I have reversed
the relations between current and voltage.

The purpose of this topology is to run higher current through
a cascoded gain device than is going through the output circuit.
We feed the gain device more current through an isolated current
source, and the additional current is used to improve the linearity
of the gain device. Because the gain device and the current
source are all running at low DC voltages, the additional
dissipation is small.

The improvement is not trivial, as the linearity of the device
improves dramatically with higher bias for FET type devices.

I haven't released a commercial product with this, but I do have
one sitting in a First Watt chassis.

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Old 20th March 2006, 08:27 PM   #7
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I don't mean to thread jack, and I also don't mean for Mr. Pass to reveal too much about his patent (I know it's proprietary)

==> How would you make a floating current source like the one dedscribed, supplying current "against the grain" so to speak?
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Old 20th March 2006, 09:26 PM   #8
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The patent is a public document (#5,343,166). You can create
the floating current source with a separate isolated supply
(a separate transformer or transformer secondary would do it).
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Old 21st March 2006, 02:03 AM   #9
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Quote:
I haven't released a commercial product with this, but I do have one sitting in a First Watt chassis.
Mr. Pass, I got a feeling that this patent and how the LU1014 should be used is matched (but I dont know how to draw sch of them both).

Is it possible to use this patent with LU1014?

5,343,166+LU1014 = Awesome amp+higher watt

Hi, Darkfenriz,

One Japanese exotic amp designer (S. Kamijo) uses this principle.
http://www.diyaudio.com/forums/showt...698#post335698
The 7A Tanggo transformer is part #33, 7A is circling around 2SK1380
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Old 21st March 2006, 08:03 PM   #10
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Quote:
Originally posted by lumanauw
Is it possible to use this patent with LU1014?
Like peanut butter and chocolate.




(peanut butter and chocolate is a popular american sweet)
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