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Any Direct Drive ESL Amp projects someone could share?
Any Direct Drive ESL Amp projects someone could share?
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Old 27th March 2016, 02:36 PM   #21
Penguin87 is offline Penguin87  United States
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Anyone seen this class-D for ESL design?

High-voltage class-D direct-drive audio amplifier for electrostatic loudspeakers

I can't get into the paper itself, but this might be helpful in ironing out some of the issues.
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Old 27th March 2016, 03:37 PM   #22
alexberg is offline alexberg
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DIRECT-DRIVE DIGITAL AUDIO AMPLIFIER FOR ELECTROSTATIC LOUDSPEAKERS
https://www.linkedin.com/in/john-kota-07156619
quote
Electrostatic loudspeakers (ESLs) are capable of low distortion and have desirably flat frequency response within the audio frequency range. In this paper, a novel approach is proposed for audio amplification using a high-voltage direct-digital solid-state class-D amplifier as a method that replaces impedance matching ESL audio transformers. Optical coupling is used to achieve isolation from the high-voltage side. The proposed stacked MOSFET output stage provides a solution to the voltage swing limitations of the available switching power MOSFETs. An example digital amplifier having 14-bit ADC precision PWM with fc = 50 kHz was implemented at 375 V delivering 7W into Ra =20kΩ. The digital modulator was realized on a Xilinx Virtex4 Sx35-10ff668 at Fs = 100 MHz clock.
end quote
https://www.apexanalog.com/resources/products/pa99u.pdf

Last edited by alexberg; 27th March 2016 at 03:58 PM. Reason: and yet one more
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Old 27th March 2016, 04:29 PM   #23
alexberg is offline alexberg
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What would you expect from student project anyway, no pun intended.
Amp uses four FETs with rather awkward driver topology which includes fiber optics for isolation with small signal BJTs as boosters. No Bandwidth or other audio charts are given. Membrane looks graphite coated: very dark - could be publishing artifacts.
Cheers
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Old 27th March 2016, 06:32 PM   #24
bentoronto is offline bentoronto  Canada
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Any Direct Drive ESL Amp projects someone could share?
Is there a switching frequency for Class D that "computes" for ESLs acting as the clean-up capacitor?

B.
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Old 27th March 2016, 07:06 PM   #25
geraldfryjr is offline geraldfryjr  United States
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I have thought about a HV Class D system every once in a while.
But, Being an analog purist I am not ready to go down that road yet.

Besides such a system gets way more complicated than a simple Class A P-P setup would be and for mediocre performance just doesn't weigh in very well compared to an analog setup.

jer
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Old 28th March 2016, 04:35 AM   #26
alexberg is offline alexberg
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Quote:
Originally Posted by bentoronto View Post
Is there a switching frequency for Class D that "computes" for ESLs acting as the clean-up capacitor?

B.
As said before: there is nothing particular in the amp per se. Q=C*U => 1500*1e-9=1.5 uC => 50k*1.5e-6=75 mA. 75mA*1500V=112.5W of idle dissipation making D-class action rather questionable.
Transition time is around 4 us at +/- 750 V.
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Old 2nd April 2016, 09:18 PM   #27
maudio is offline maudio  Netherlands
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old thread but the contents are still very valid

http://www.diyaudio.com/forums/plana...ve-thread.html
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Old 7th April 2016, 01:48 PM   #28
invisible force is offline invisible force  Germany
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Hello Maudio,
any new insights regarding the transformer working in a nested feedback loop with serial R/L combination inside the outer loop ?
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Old 15th April 2016, 11:28 PM   #29
geraldfryjr is offline geraldfryjr  United States
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I got an email today about some new SIC FET's at Digikey and I really like there specs!!
They have a very low Coss (output capacitnace) in the range of 15pf-30pf !!
These may work very nice for my Desktop models and slightly large Bookshelf type of ESL's.

1200V, 85watt,

http://rohmfs.rohm.com/en/products/d...ct2450ke-e.pdf

SCT2450KEC Rohm Semiconductor | Discrete Semiconductor Products | DigiKey

1700V, 69watt,

http://www.wolfspeed.com/media/downl...2M1000170D.pdf

C2M1000170D Cree Inc. | Discrete Semiconductor Products | DigiKey

1700v, 35watt,

http://rohmfs.rohm.com/en/products/d.../sct2h12nz.pdf

SCT2H12NZGC11 Rohm Semiconductor | Discrete Semiconductor Products | DigiKey

1200v, 108watt,

http://rohmfs.rohm.com/en/products/d...ct2280ke-e.pdf

http://www.digikey.com/product-detai...KEC-ND/4171677


These are about $5 or $6 or so, and are just a few of what is available.
I haven't gone through everything they have yet.
Others are in the $20 to $40 each, but must of those also have a higher Vdds and power dissipation as well.

jer

Last edited by geraldfryjr; 15th April 2016 at 11:41 PM.
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Old 16th April 2016, 04:13 AM   #30
DUG is offline DUG  Canada
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Quote:
Originally Posted by geraldfryjr View Post
I got an email today about some new SIC FET's at Digikey and I really like there specs!!
They have a very low Coss (output capacitnace) in the range of 15pf-30pf !!

...
Crss might be more of an issue.
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