Single Stator Electrostatic Headphone - issues? - Page 4 - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th October 2012, 01:18 PM   #31
diyAudio Member
 
Join Date: Oct 2007
Location: Aarhus, Denmark
Hi both,

- again thank you for your replies. I'll be getting back to the membrane coating shortly, however, right now have a slight challenge finding - hopefully good-sounding - low signal transistors that can be used for a higher-than-expected-voltage electrostatic headphone amplifier. Can I ask you if you both use tube amplifiers?

@Wachara: Can I ask you what you use for membrane coating now?

@Gerald: I've taken a look at the Licron MSDS sheet and it is classified as a safety class 4-1 product here in Denmark. Which is a quite safety requiring material (when disposed of it should e.g. also be marked as containing potentially carcinogenic substances). So, if possible, I'd like to find a less "active" material to cover my membranes, although I might get back to it if I can't find such a material. But thanks for suggesting ;-)

Greetings,

Jesper
__________________
... Being mindful about sustainability also in my audio endeavors matters to me ... paying CO2 - and a quite fair pollution compensation helps create a good listening "energy" ...
  Reply With Quote
Old 24th October 2012, 04:17 PM   #32
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
At the moment I use transformers for my ESL's.

I will be exploring some some direct drive methods in the future.

I have built a FET type amp for around 200v using stacked up IRF510's and single FET's such as the IRF740 and IRF840's.

It worked but I did not test it on an ESL yet as this was two years before I had gotten one back running again.
So I don't have a complete design but I did post a schematic of what I was working with in another thread.

These might help to give you some idea's,

All Discrete Class-A Headphone Amp

Looking for HV fets for direct drive

jer
  Reply With Quote
Old 27th October 2012, 05:16 AM   #33
diyAudio Member
 
chinsettawong's Avatar
 
Join Date: Jun 2006
I now use this:

Click the image to open in full size.

Click the image to open in full size.

The gel is much better than the spray.

It has been working very well for my headphones.

About the amp, I use tube amp.

Wachara C.
  Reply With Quote
Old 29th October 2012, 08:33 AM   #34
diyAudio Member
 
Join Date: Oct 2007
Location: Aarhus, Denmark


Wachara your images made me smile :-) I guess DIY audio allows for much creativity in finding solutions to things ... And if I remember correctly you live in Thailand where humidities can be quite high so if this works in Thailand I guess it may also work in most other places ... (I hope)

However, when looking at the images I cannot see which company makes this? Might I ask you to just briefly post about who makes it?

@geraldfryjr: Hey Gerald. Thanks again for posting and linking. However, for now I'm not too keen on using either ICs or FETs in the signalpath and unless I missed something in the threads you link to they use either one or a mix of both (right?).

What just spurs my interest, though, is that the electronics design looks like the one I saw when I looked into plasma headphones. Hmmm... ??? I would like to link to this headphone site but google chrome gives me a warning when trying to go to the link so maybe not a good idea (malware). But if you're interested (and maybe have a good anti-virus program) then a google search on "Plasmasonic" should bring up a site. It's the second link on my computer (the "membres" link).

I'll be looking further into finding HV low power bipolar transistors that could be suitable for a superb ESL headamp.

Greetings for you both from an autumn clad Denmark,

Jesper
__________________
... Being mindful about sustainability also in my audio endeavors matters to me ... paying CO2 - and a quite fair pollution compensation helps create a good listening "energy" ...
  Reply With Quote
Old 29th October 2012, 04:16 PM   #35
diyAudio Member
 
chinsettawong's Avatar
 
Join Date: Jun 2006
Hi Jesper,

The link to the maker and product is here: SEMO PRODUCTION LTD.

I've been using it for over a year and so far so good. However, I think other product brands with similar function will work as well.

Wachara C.
  Reply With Quote
Old 29th October 2012, 09:05 PM   #36
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Another thread has been started on the topology here,

8 Watt Hifi with few parts

I like it because of its simplicity and has been the easiest way I have found so far to control a much much higher voltage with a smaller one.

You can also use some H.V. BJT's as well.
Horiz. output transistors such as the 2SC1308 and others are a good example,However they cost much much more than some of the FET's I have used and availiblility is getting some what limited due to the diminishing CRT industry.

2SC1308 pdf, 2SC1308 description, 2SC1308 datasheets, 2SC1308 view ::: ALLDATASHEET :::

If you don't like using opamps the output stages are similar to Nelson Pass's class A amps such as the Alphe series or Zen amps, even his new amp camp program could possibly be scaled up for high voltages as well.

I like using on opamp because the negative feed back reduces the THD quite a lot and it is nearly self biasing once the output current is set through output device.

I did design a full blown Class AB type traditional amp for a +- 500v bipolar supply and it is much more involved and not cheap to build.
It used four 400v TO-3 type BJT's in the output stage.
And was to be used in a BTL configuration so that I could get a +-1000v swing across the stators.
I think I even did a version for a +-775 volt supply as well for 3KV p-p.

So far I have only done it in Circuitmaker (spice) simulator and was before I fully understood how it works so it needs some slight tweaking.

But basically I took a common power amp circuit and cascaded all of the transistors so that they wouldn't breakdown from being over voltaged.

I have seen the "Plasmasonic" stuff and it is very interesting and I may get into messing with it sometime,But it is not very efficient,However I would like to build an apparatus though.

The links are in one of these threads.

http://www.diyaudio.com/forums/searc...archid=5189442

If you still have difficult finding it I can re-compile the links for you.

jer

Last edited by geraldfryjr; 29th October 2012 at 09:12 PM.
  Reply With Quote
Old 31st October 2012, 10:58 AM   #37
diyAudio Member
 
Join Date: Oct 2007
Location: Aarhus, Denmark
Hi both,

@Wachara: Thanks - I'll see if this product or something similar is available near Denmark.

@gerald: Hey ... thanks again for posting - just FYI I've attached a copy of the LTSpice schematic I'll be using for my headphone amp. Values & transistors are not correct and R8 - R10 will not be there. The 2SC1308 seems to be quite high voltage but if you look at the datasheet it's the CBO value that is high and not the CEO which is what I seek.

Anyway, I wouldn't use a 5-7A transistor for a sensitive signal like this .. a TO92/TO220 based transistor is more likely to be my choice and then about 0.1 A max current. I believe they may sound better.

Regarding the Plasmasonic I was earlier interested in this myself but not anymore - I'm not too keen on the high voltages nor the ozone emitted.

Best regards,

Jesper
Attached Files
File Type: pdf HPamp.pdf (11.5 KB, 22 views)
__________________
... Being mindful about sustainability also in my audio endeavors matters to me ... paying CO2 - and a quite fair pollution compensation helps create a good listening "energy" ...
  Reply With Quote
Old 31st October 2012, 03:02 PM   #38
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Yes the CBO is like 1500v or something but the Ceo is like 400v or so.
Data sheets vary I think I have seen it listed as high as 600v or 700v but I think 400v is safe.

The main issue with those devices is that they have a very low HFE so you would need a good driving stage to use them,There are better ones as I had just used it for an example.

In your simulation make sure that you measure the voltage across the C and E so that it doesn't exceed the devices ratings.
I have found this to happen in the simulations even though there was no error.

You might want to take a look at the ZTX series of transistors from Zetex, they can be commonly found and have a very high CEO some as high as 650v I think.
But typically of 450v to 550v and have both PNP and NPN compliments as well as very linear with Pd's as high was about 2 watts.

I used those in my cascaded power amp design that I only simulated.

jer

Last edited by geraldfryjr; 31st October 2012 at 03:06 PM.
  Reply With Quote
Old 2nd November 2012, 01:55 AM   #39
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Prehaps something like this could be scaled for higher voltages using the Zetex high voltage BJT's,

http://waltjung.org/PDFs/WTnT_Op_Amp_Audio_2.pdf

Cheers !!

jer
  Reply With Quote
Old 6th December 2012, 12:40 AM   #40
Struth is offline Struth  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: books at londonpower.com
Hi Guys

The Stax driver uses +/-200V and a symmetric circuit. One can easily make each stator driver with complimentary diff-amps of MPSA42/92 at the input, and a push-pull VAS stage of IRFBE30/MTP3P50 mosfets - six devices for each stator. This should be driven by a low-level circuit that can provide balanced signals from a single-ended source.

Note that the mosfets in the above example are overkill as far as power capability goes, but both are rated for 500V or more and they have similar gm. One could easily swap cascoded MPSA42/92 output stages and have an all-BJT circuit.

Some of the historic ESL head phone builds suggest that each stator looks like 100pF. You could do a simplistic calculation to see what 100pF looks like at, say, 40kHz - 40k-ohm here. At lower frequencies the instantaneous impedance is higher, so even an unbuffered VAS can drive this pretty easily. Power to the load is essentially zero and the peak current is typically less than one milliamp.

If you wanted to go for something simpler, the CFP circuit in the above sim can be flipped upside down, so the output device is an NPN or N-ch mosfet. The input can be a singleton or a diff-amp. In either case, the input devices can be quite low voltage - even the 2N3906 from the sim - as only the N device sees the load voltage. DC feedback can be used back to the input to stabilise the idle point, with an AC path to set the higher signal gain required. With an 800V mosfet like the IRFBE30, you can operate the amp from the bias supply and have lots of signal swing.

The simple circuit needs to be doubled to drive both stators, and again a balanced drive circuit is required.

One can take these ideas sideways and incorporate common-mode current sources and have gain and SE-to-balanced drive all in one stage. The ESL Headphone Driver note in our new book coming out in Jan (DSN-1) shows how, along with many tube circuit options.

Note that if you are heading towards a tube driver solution, the voltage ratings of the tubes are conservatively misleading. There is an assumption that the tube may be used in a transformer loaded circuit, and thus the flyback voltage must be accommodated in the rating. So, a 12A_7 is rated for a lowly 300V, where its actual open-circuit voltage rating is 540V. Similarly, a 6L6 may be rated at 360V to 500V depending on the version, but the actual arc-over point is more than twice this value. Running with a resistive load from much higher supply voltages than listed is safe with most tubes.

Have fun
Kevin O'Connor
__________________
London Power / Power Press Publishing
www.londonpower.com

Last edited by Struth; 6th December 2012 at 12:43 AM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Single stator electrostatic headphone. gentlevoice Headphone Systems 16 2nd February 2010 11:33 AM
Single stator design yrmeli Planars & Exotics 6 11th November 2005 07:42 AM
single stator esl. tade Planars & Exotics 2 4th July 2005 05:00 PM
Electrostatic stator design martinv Planars & Exotics 16 6th September 2003 06:46 PM
DIY Electrostatic Stator insulation schpeltor Planars & Exotics 7 13th February 2002 07:11 PM


New To Site? Need Help?

All times are GMT. The time now is 02:57 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2