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Old 1st October 2008, 09:38 PM   #11
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Why are we interested?
Because we all have similar designs done before you've started yours.
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Old 1st October 2008, 10:14 PM   #12
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Quote:
Originally posted by Wavebourn
Mu, Gm, Rp depend on a plate voltage.
Why don't spend one MOSFET ?
R-C with high time constant on a gate, one gate stopper, one Zener to protect the gate, and one more optional resistor in drain to protect against an overcurrent. A huge ripple reduction for expense of only 3V of a loss.
Gyrator is good.
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Old 1st October 2008, 10:50 PM   #13
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Quote:
Originally posted by kenpeter


Gyrator is good.
Yes, but I meant a source follower.
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Old 2nd October 2008, 05:01 AM   #14
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Quote:
Originally posted by revintage
How come you guys are talking about modulation of a 120Hz signal in a thread I started about an amp for mid that is crossed over 2 octaves higher?

...

PSRR is one characteristic of this design that needs improvement.
Your approach is reduce the ripple, which will work fine.

I guess if you HPF the input at 500 Hz then you don't need to
worry even about modulation with the 120 Hz. Or will the
nonlinearity of the transfer function cause the 120 and >500 Hz
to be partially multiplied, producing sideband frequencies at large
signal amplitudes?

Great idea to use the toroid above 60 Hz. There should be much
less saturation and you can get closer to the core's power rating.

On the original topic, I think it will work as a differential choke
as well as an OPT, within the limits if low frequency saturation.
As such, the DCR may be less of an issue than with an OPT.

Michael
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Old 2nd October 2008, 07:32 AM   #15
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Hi Wavebourn,
Please show us schematics of your previous design for as this must be a help on the way. But you are absolutely on the right track: To reduce ripple from the PSU=fix the problem at the source.


The purpose with this thread was the ESLDD without secondaries and with the toroids CT to ground! Have not seen so much comments or concerns about that except in Michael last thread.

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Old 2nd October 2008, 01:13 PM   #16
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Part of the problem, I have no idea what means ESLDD?
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Old 2nd October 2008, 01:27 PM   #17
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Aha! It is a term used for "Electrostatic Loudspeaker Direct Drive" !

The ML Script has an ESL-panel that is crossed over at 500Hz and has a capacitance of ca 2000p.
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Old 2nd October 2008, 03:28 PM   #18
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Quote:
Originally posted by revintage
Aha! It is a term used for "Electrostatic Loudspeaker Direct Drive" !

The ML Script has an ESL-panel that is crossed over at 500Hz and has a capacitance of ca 2000p.
I finally figured that out, but is wasn't obvious about the 500Hz
unless you know ESLs.

Now the thing I would check with this, is what slew rate your design
can drive into 2nF. It looks like it takes 70mA of peak signal current
to drive the 2nF with a 560V P-P sine wave at 20KHz. This is an
equivalent slew rate of 35V/uS. But I don't know much about ESLs
and what else you need to consider. Is there compensation of the
frequency response or does constant drive voltage over frequency
produce a flat response?

Anatoliy, are you proposing a source follower in the B+ as a
voltage regulator? Should work fine, but I think the voltage
drop would be 3V minimum at the lowest line voltage, increasing
as line voltage is increased. I'll need to try this sometime for B+
regulation.

Michael
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Old 2nd October 2008, 04:16 PM   #19
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Michael,
Hopefully and probably signal levels of that magnitude will never be present at 20k although up to 5k. I do not think there will be a problem. Must try this anyway!

About the SETOR, I will try another cathode arrangement that lowers distortion considerably when simmed.

As I understand it Wavebourns proposal is not so much for regulation as ut for reducing ripple with a MOSFET gyrator.
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Old 2nd October 2008, 04:29 PM   #20
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Quote:
Originally posted by revintage
Hi Wavebourn,
Please show us schematics of your previous design for as this must be a help on the way. But you are absolutely on the right track: To reduce ripple from the PSU=fix the problem at the source.



It was discussed here already on the forum: Alligator project. The main idea is, to use feed-forward only approach on AC, so 2 independent shoulder are counter-modulated, where one is a tube, and another is a modulated SS CCS. Servo makes an average current supplied by CCS equal to the current supplied by a tube, to make a transformer happy.

Quote:
Originally posted by Michael Koster


Anatoliy, are you proposing a source follower in the B+ as a
voltage regulator? Should work fine, but I think the voltage
drop would be 3V minimum at the lowest line voltage, increasing
as line voltage is increased. I'll need to try this sometime for B+
regulation.
Yes, I got rid of ripples such a way of 800V supply in Pyramid-V amplifier after seeing what happens on a power: couple of sidebands, 40 dB down from the fundamental. I did not measure after, but sonically it is more crystal - clean now. The DC voltage drop is about 3V, and nearly independent on current and voltage.
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