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Old 12th May 2009, 06:58 AM   #51
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Hi Phillipe,

Your stator has a lot more open area than mine. Do you think that more open area is better?
Have you tried using it with a direct driven headphone amp?

Wachara C.
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Old 12th May 2009, 08:32 AM   #52
Phil47 is offline Phil47  France
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Hello Wachara,

A lot of questions !

A greater open area gives a better frequency response (at my mind !), but performance depends on a lot of factors.

I also made several direct drive amplifiers with 6CG7/6FQ7 or EL34 output tubes and other ES headphones but unfortunately L'Audiophile magazine disappeared in 1995.

I used 3,5 µm thickness "Terphane" for the active and the passive diaphragms. Terphane is DuPont de Nemours's Mylar made under license by Rhone-Poulenc. My Terphane is a D type especially designed to make Mylar condensers. The passive, not stretched, diaphragm protects the active diaphragm from ear moisture. I used this technique from Stax.

I made a special machine for stretching and sticking the active diaphragm on its support. The machine uses pliers, pulleys, lead weights and strings. The diaphragm is stretched with precision to compensate electrostatic forces on the diaphragm then frequency response and efficiency are the same for all diaphragms. Silkscreen printing technique is used to apply epoxy glue on the diaphragm frame (support de diaphragme) and the other parts.

Philippe
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Old 12th May 2009, 09:41 AM   #53
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Hi Phillipe,

Thank you very much for your kind replies. I'm sure many of us here will benefit from your techniques.

About the amp you built, would you be so kind to share with us? I made mine from the design from www.tubecad.com . I make a complete diagram as follow:


Click the image to open in full size.

I strongly recommend those who want to build an ES headphone also build a set of direct-drive amp. It sounds so much better as compare to using transformer.

Wachara C.
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Old 12th May 2009, 10:37 AM   #54
Phil47 is offline Phil47  France
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Sorry, I have some problems with attached files !

I think your amplifier design is good. Schmitt type phase splitter with high value common cathode resistor and negative supply gives signals of equal amplitudes.

For "L'audiophile" magazine I used the "A circuit", slightly modified, from Stax. I think this is the first direct-drive amplifier for electrostatic headphones (end of the 60's !). It's appears in the Funya site : http://wiki.livedoor.jp/funya2420/d/6FQ7

Philippe
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Old 12th May 2009, 11:50 AM   #55
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Thanks Phillipe for the circuits. They look interesting.

Wachara C.
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Old 12th May 2009, 12:55 PM   #56
Phil47 is offline Phil47  France
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Post "edit" function doesn't work read "B circuit" instead of "A circuit" for Stax ES amplifier.

The Stax "A circuit" :

Click the image to open in full size.

The Stax "B circuit" :

Click the image to open in full size.

I used this "B circuit" in my article "Un amplificateur pour casque électrostatique" in L'Audiophile ; May 1990 :

Click the image to open in full size.

Philippe
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Old 12th May 2009, 01:01 PM   #57
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Thanks for sharing Phillipe. Your amp looks really nice.

Wachara C.
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Old 12th May 2009, 01:07 PM   #58
Phil47 is offline Phil47  France
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Thank you, Wachara !

Home-made machine used to stretch the diaphragm :

Click the image to open in full size.

Philippe
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Old 12th May 2009, 01:16 PM   #59
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Wow, Phillipe! That's what I want to see most. Thanks for sharing.

Wachara C.
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Old 12th May 2009, 01:37 PM   #60
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Here is another picture of my amp.

Click the image to open in full size.
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