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Old 31st May 2009, 04:14 PM   #1
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Default Firstwatt F1 to drive Stax

Hey, I'm currently in the process of building a Firstwatt F1 and came across this post: http://www.diyaudio.com/forums/showt...t-133128.html. The thread died out fast however its an idea I hope to pursue. Is it possible to drive electrostatic headphones out of an F1 (or other NP designs)? Has anyone had success doing it? Also does anyone know the procedure for wiring a Stax style electrostatic input? If you have any ideas, thoughts or experiences regarding my conundrum please share them. Thank you.


Mile
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Old 31st May 2009, 05:13 PM   #2
DougL is offline DougL  United States
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Here are several designs for driving Stax Headphones.

Here is a class A design by Kevin Gilmore A Current-Domain Electrostatic Amplifier for Stax Omega II Headphones

Here is a Tube design that has details for wiring the DIN plugs:
All-Triode Direct-Drive Amps for Electrostatic and Electret Headphones

And this hybrid design: Blue Hawaii Hybrid Electrostatic Amplifier for Stax Omega II Headphones

The load is a 100 pF capacitor, and a 200v pp minimum output is required.

Doug
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Old 3rd June 2009, 09:22 PM   #3
DougL is offline DougL  United States
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Nelson,

How would you design for a 400Vpp swing with a load of up to 150 pF?

I was looking, and a Zen V7 style inductively loaded output stage with a 300V or higher power supply might be feasible. Perhaps Cascode A La Zen V8 to lower the distortion. A tube push pull output transformer might have enough primary inductance for the application.

Av is about 100, so 2 stages are minimum.

While you cab get 300V out of a 18V transformer, its not going to be pretty.

Doug
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Old 3rd June 2009, 10:53 PM   #4
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Quote:
Originally posted by DougL
How would you design for a 400Vpp swing with a load of up to 150 pF?
We used to have a nice headphone amp for the Stax built out of
tubes by Bruce Moore laying around here (the amp, not Bruce).
I don't know where it went, but he probably built more than one.

I have some nice 1000 volt Jfets, so I would probably use those in
a circuit with balanced output and no feedback.

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Old 3rd June 2009, 11:00 PM   #5
DougL is offline DougL  United States
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1000 Volt Jfets would be the ticket.



Doug
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