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Old 6th March 2006, 10:38 PM   #1
kekso22 is offline kekso22  Germany
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Default replace C-multiplier in ZEN9?

hi,

replacing the capacitance multiplier of ZEN9 with a L-C-L filter (like in SE triode amps) maybe can further improve it.
It prevents current from the audio path flowing into the power supply cap and modulating with the high load currents from the rectifiers.
Especially the Aleph current source is critical here, because it draws not a constant current from the supply.
The following schematic is an electronic L-C-L filter. The Fet acts as an gyrator (L), has low impedance at 0Hz and becomes high impedance in the audio band. It has a start ramp of some seconds and also some regulation. I have used this circuit with great success in my SE triode designs.

Please tell me what you think.

Regards
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Old 6th March 2006, 10:44 PM   #2
kekso22 is offline kekso22  Germany
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Sorry,
of course C-L-C not L-C-L !!!
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Old 7th March 2006, 01:53 PM   #3
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Very intersting . . .
High impedance by bootstrapping, isnt it?

Regards
jh
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Old 7th March 2006, 04:46 PM   #4
kekso22 is offline kekso22  Germany
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Yes, it's bootstrapping or gyrator (the C is transformed to L).

Spice shows:
5 Ohm @ 1Hz
42 Ohm @ 10Hz
418 Ohm @ 100Hz
3.4 kOhm @ 1kHz
1.7 kOhm @ 10kHz

Regards
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Old 8th March 2006, 03:49 AM   #5
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Understood, and thanks for the confirmation . .

Regards
jh
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Old 8th March 2006, 07:59 AM   #6
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Kekso22

By the way . .
As I understand . .
C3 covers the Aleph ac fluctuation . .
while MOSFET keeps the voltage regulation . .
Really interesting . .

When I set 0% Aleph ac current gain with my F1, my ear touch-distance away from the speaker does not detect any noise. But, If I increase the ac current rate above 0%, the noise starts to come out of the speaker at the same rate of ac current gain . . still not loud, tho . .

Your proposal will cure this noise concern . . ?

Regards
jh
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Old 8th March 2006, 06:19 PM   #7
kekso22 is offline kekso22  Germany
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Hello jh

maybe it will improve the noise level.

I think there might be another problem when using only one cap.
This cap after the rectifiers is heavily stressed by the high current pulses (10..20A) from the PS.
If the Audio current (around 2A with ALEPH) is also flowing thru this cap, then this audio current is modulated with
100/ 120Hz resulting in increased THD.
I will try this circuit for my ZEN#9 (if I get JFETs !!? )

Regards
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