F3X

[woofertester]

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]

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

 

[woofertester]

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]

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]

umm . . .

For those who have been hording LU's or waiting for a balanced F3 amp, ZM proposed the following.

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]

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]

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]

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.