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-   -   SUSY for electrostatic headphone amp (http://www.diyaudio.com/forums/headphone-systems/19830-susy-electrostatic-headphone-amp.html)

Prune 5th September 2003 07:29 AM

SUSY for electrostatic headphone amp
 
I need to build a great amp for my Stax electrostatic headphones. There are a number of DIY designs, several of them by Kevin Gilmore. I want to ask you guys how one of them can be modified to be a super-symmetric circuit.

The amp is the Blue Hawaii and besides Gilmore it was also built by zzz at head-fi.org and there's some discussion there; both think the sound is better than the commercial Stax amps.
The first two stages are the ones from this one at Headwize:
http://headwize2.powerpill.org/proje...lmore2_prj.htm
They connect to http://gilmore.chem.northwestern.edu/kgt2.jpg
with example power supply http://gilmore.chem.northwestern.edu/kgt2ps.jpg
(sorry the thing is in parts, I didn't draw these)
It's described here
http://www4.head-fi.org/forums/showt...threadid=17717

Sooo,
can this be modified to make it a SUSY amp???

Petter 5th September 2003 09:46 AM

http://groups.msn.com/StaxOTLDCcoupl...thfibrillation

Go to the link: Documents, or Dokumenter to get the word file - I am not able to upload it to this group since it is about 300KB.

You might find the thought process interesting.

Petter

Prune 5th September 2003 11:12 AM

MSN is giving me trouble. Could you please email the document to me? Also if you can't post it directly, I can upload it to where people can access it by http.
address: bdt AT shaw DOT ca

jackinnj 5th September 2003 12:03 PM

Re: SUSY for electrostatic headphone amp
 
Quote:

Originally posted by Prune
http://gilmore.chem.northwestern.edu/kgt2ps.jpg

Talk about carrying coal to Newcastle ! -- somehow I miss the point of using two half-wave bridges for two regulators -- if you have a center tapped transformer you can use a full wave bridge and pull the ground return from the CT.

Prune 5th September 2003 01:56 PM

Here's Petter's writeup in a zipped Word file:
http://www.cs.ubc.ca/~trifonov/doc.zip

Petter 5th September 2003 07:10 PM

Slightly off topic as this is not Susy

Goal: DC coupled tubed 2 stage Stax amp.

Note use of folded cascode to really drive the voltages down seriously in order to enable DC coupling.

Note use of current sources to set up correct voltage levels and simultaneously bias tubes correctly

Current sources can be anything you want - for the most part they would be implemented as semiconductor devices.

Note optional feedback - not intended to be used by me due to anticipated reactive load.

Note use of large degeneration resistors in second stage in order to get low output impedance even with these small tubes (6S4 after our friend Gilmore)

Petter

Petter 5th September 2003 07:14 PM

2 Attachment(s)
And the file ....

Prune 28th September 2003 03:20 PM

OK, I'll try again...

This is the original schematic.

This is my attempt at modification. Does this make a SUSY circuit? (Or would it even work, or blow up or something?)

I moved feedback from the sources to the gates, crossing it (actually the cross is at the top of the first stage), and added the 5 ohm resistor between the sources (I'm just guessing at the values here). Input resistors are for protection, since output has 800 V swing.

kevin gilmore 29th September 2003 11:59 PM

will work except for the fact that the input impedance
is now 1k which may be hard on a number of preamps
especially tube units and the gain is now only 200
which means you need at least 4 volts of drive voltage.
Better to make the 1k resistor 200 ohms, and plan on
having a preamp that can drive this. Also low impedance
step attenuators are hard to find.

quote
Talk about carrying coal to Newcastle ! -- somehow I miss the point of using two half-wave bridges for two regulators -- if you have a center tapped transformer you can use a full wave bridge and pull the ground return from the CT.

Not when you want to use the much more available n channel
fets for the regulated power supplys... Two seperate
regulated 400 volt supplies tied together at the output to
generate +/-400 volts. Can't do this with a center tap.

Prune 30th September 2003 01:25 AM

Kevin: Can't gain be increased by lowering the feedback, or would it be too low if reduced from what it currently is?
So there's no way to set up a higher input impedance in this configuration?

To the supersymmetry guys: my original question is still unanswered -- does this make a SUSY circuit or am I missing something?


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