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-   -   F3X (https://www.diyaudio.com/forums/pass-labs/363516-f3x.html)

woofertester 24th November 2020 09:22 PM

F3X
 
Has the notion of an F3X ever been discussed? I searched and did not find anything. The application would be direct drive of electrostatic headphones or even full-size ESL panels.

Zen Mod 24th November 2020 09:36 PM

have none of these, so - it didn't crossed my mind

woofertester 24th November 2020 10:38 PM

Quote:

Originally Posted by Zen Mod (https://www.diyaudio.com/forums/pass-labs/363516-f3x-post6424575.html#post6424575)
have none of these, so - it didn't crossed my mind

The first electrostatic speaker I listened to was at a co-worker's house. It was Acoustat model X which had a direct drive tube amplifier. The sound was very different from any other speaker and in a good way. The speakers are push-pull and the THD is on the order of 10X lower than voice coil magnet speakers.

That led me to build a pair of Roger Sanders DIY ESLs in the 1980s. They were driven using a pair of UTC tube transformers that I still have. I always wanted to listen to ELSs with a direct drive amp.

Now I have Stax Lambda and Stax Gamma ESL headphones with a Stax SRM-313 direct drive amp. It uses Toshiba JFET inputs a-la Pass but all the rest is garden variety BJTs which I would like to transform into SIT driven output stage a-la Pass F3.

The DC rails on the Stsx amp are + / - 300V and the bias on the diaphragms is something like 240V.

I think an F3 based design can be DC coupled for this application.

Zen Mod 24th November 2020 10:46 PM

it looks easy on paper (hell of a cascoding, plus converting a core to LTP, should solve most of puzzle) but certainly needing decent polishing time

so, lemme pass that one, no need to be wise-a$$ if I'm not planning to invest bench time

zchopper 25th November 2020 12:16 AM

umm . . .
 
1 Attachment(s)
Quote:

Originally Posted by Tea-Bag (https://www.diyaudio.com/forums/pass-labs/133433-choky-susy-f3-lu1014s-post1662435.html#post1662435)
For those who have been hording LU's or waiting for a balanced F3 amp, ZM proposed the following.
:D

That was followed by what I am convinced is easily the single greatest perpetration of diyaudio in history.

donut-a-la-overkill

Called the Choky Susy F3 or Donut a'la Overkill

There is a pic in one of the threads where they were pouring the case at the foundry. Epic. Attached is one pic I keep and look at when I need inspiration.

Zen Mod 25th November 2020 10:03 AM

yup Kwayzee Danske MetalKid - Magura

later resorted to games making money

schematic was result of his insisting on concept and me making patches

these days I'll do it differently, most likely

Gyuri 25th November 2020 11:12 AM

It isn't X-ed, only bridged:

So, this is my Quad ZV9!

Once upon a time, I have listened it with Focal Jmlab Vega speakers, sound was comparable to a factory Pass XA30.5.
Of course that was better.
But I was not ashamed of my amp.

woofertester 25th November 2020 01:38 PM

Quote:

Originally Posted by Gyuri (https://www.diyaudio.com/forums/pass-labs/363516-f3x-post6425127.html#post6425127)
It isn't X-ed, only bridged:

So, this is my Quad ZV9!

Once upon a time, I have listened it with Focal Jmlab Vega speakers, sound was comparable to a factory Pass XA30.5.
Of course that was better.
But I was not ashamed of my amp.

Congrats on a very nice amplifier build.


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