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Old 27th February 2006, 04:46 PM   #21
beppe61 is offline beppe61  Italy
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Quote:
Originally posted by richie00boy
1) If you look at my website you can easily adapt the op-amp supply or the high voltage supply to your needs
2) A 50V supply is not needed at all, 18V would be sufficient, but some component values would have to be scaled down.
3) The high voltage supply would fit in with your philosophy of minimal parts and has no loop feedback.
Dear Mr. Richie00boy,
1) Thank you sincerely for your valuable suggestion.
I will study your circuit in depth.
2) I must be completely honest: I do not even know how to start for scaling down components values.
I will stick with the 50V supply also because I want to set-up a good PS around that value to be used with other prototypes I have in mind and at hand (a Bride of Zen in my closet waiting for a better power supply).
3) Well to call it "philosophy" could sound presumptuos.
It is just that it intrigues me to see what can be obtained, in terms of sound, from very basic topologies.
On the basis of what I heard from a BOZ (1 mosfet line stage) and a 2 bjt preamp I am quite optimist.
It has become a sort of obsession maybe, but that is.
Also considering that many respectable audio designers have abandoned complex topologies in favour of simpler ones maybe doing a lot of efforts to optimize them.

Thank you again.
Regards,

beppe
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Old 27th February 2006, 08:42 PM   #22
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I suggest you look at my high voltage differential supply then. Use the top half of the circuit only and make the following changes:

R1 220R 4W for 100R 2W
D1 BZX79C18 for a 51V type BZX79C51
R3 15k for 1.8k
R5 3.3k for 20k
Omit the LED and it's resistor

The input voltage of 60V is not critical, a 45V transformer (giving 62V when rectified) would be OK.
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Old 27th February 2006, 11:00 PM   #23
noname is offline noname  Russian Federation
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a very simple modification of Darlington with only one rsistor,
reduce THD 100-200 times -
from 0.2% to 0.001% measured.
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Old 27th February 2006, 11:14 PM   #24
x-pro is offline x-pro  United Kingdom
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Quote:
Originally posted by noname
a very simple modification of Darlington with only one rsistor,
reduce THD 100-200 times -
from 0.2% to 0.001% measured.
It would be proper to note that this circuit was published in Russian magazine "Radio" (12-2005) by M. Kulish. Here is the first page of that article (djvu) :

x-pro
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Old 27th February 2006, 11:24 PM   #25
noname is offline noname  Russian Federation
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Yes, thanks a lot that you place a copy of origin of this circuit.
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Old 27th February 2006, 11:36 PM   #26
lineup is offline lineup  Sweden
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Quote:
Originally posted by noname
a very simple modification of Darlington with only one rsistor,
reduce THD 100-200 times -
from 0.2% to 0.001% measured.
A big problem with that circuit
is that if you use one single darlington transistor, like BC372 in first simple example,
this circuit will be impossible.

You have to use 2 transistors, in a darlington arrangement.


There is a difference using one darlington transistor
instead of 2 transistors in darlington.
In first case you have not many choices to modify or add resistors.

This is one major reason, why one darlington
is ALMOST NEVER USED in high quality audio circuits.
Including power output stages.
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Old 27th February 2006, 11:43 PM   #27
x-pro is offline x-pro  United Kingdom
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Here is a bit more about that circuit:

I've simulated the simplest circuit from that article in LTSpice. Here it is:

It is not a darlington as such, rather a two-transistor error-correcting circuit with a very good performance. In the next message I will attach the result of the simulation - FFT from "output 1" and "output 2" for 2 V p-p input/output.

x-pro
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Old 27th February 2006, 11:45 PM   #28
x-pro is offline x-pro  United Kingdom
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And this is the FFT graphs:
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Old 28th February 2006, 12:04 AM   #29
lineup is offline lineup  Sweden
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Quote:
Originally posted by x-pro
Here is a bit more about that circuit:

I've simulated the simplest circuit from that article in LTSpice. Here it is:

It is not a darlington as such, rather a two-transistor error-correcting circuit with a very good performance. In the next message I will attach the result of the simulation - FFT from "output 1" and "output 2" for 2 V p-p input/output.
Quote:
Originally posted by x-pro
And this is the FFT graphs:
Is a dramatic improvement, taking output from point 2.

And the simulated response of output 2, is at real Hifi level low distortion.
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Old 28th February 2006, 02:07 AM   #30
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Hi, Xpro,

Do you have a version of non-djvu for your post#24 attachment? My computer cannot view .djvu
Quote:
It is not a darlington as such, rather a two-transistor error-correcting circuit with a very good performance.
I'm always interested in anything that contain words "Error Correction"
Do you have idea how to implement this for push-pull / output stage?
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