Regarding the public posting of schematics:   http://www.diyaudio.com/forums/headphone-systems/229934-version-o2-desktop-amp-oda-11.html#post3506094   Quote:jcx   http://www.head-fi.org/t/611348/help-needed-to-upgrade-the-capacitor-in-otl-tube-amp/15#post_8417041   Quote:jcx  ...

I remember starting that thread years ago (under a different user name). After my first haphazard test build, I eventually worked out the noise/hum problems by rebuilding it with a better power supply. The amplifier worked well afterwards. The output impedance of this amp is relatively high...

Regarding the recent SRM-252 replacement wall-wart discussion, here's a relevant link: http://tangentsoft.net/audio/wall-ps.html  

Quote:   Quote:   I wouldn't. Kevin Gilmore specifically recommended against using an unregulated supply in this post. http://www.head-fi.org/t/223263/the-stax-thread-new/22995#post_9532128 In all likelihood, the original unregulated 12V wall-wart was designed so that the...

Here's a possible solution for the SRM-252 power supply. This isn't really a recommendation as I haven't tried this one myself, just a suggestion. It could potentially be a piece of junk. http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_162996_-1 12VDC at 500mA with a...

Quote:   As far as I know, the Elpac WM series wall-wart that originally came with the Gilmore Lite is also linear regulated, but I understand what you're getting at. The audiophile in me would also immediately go for a linear supply over a switching one, if given the choice. My point...

The Stax SRM-252 and Koss E/90 have switching power supplies within close proximity to the amplifier circuit. They both work just fine.  

Thanks for looking it over. Most of the part values were chosen somewhat arbitrarily. Any improvements that you think are worthwhile, feel free to add.   On a side note, this schematic of the SRM-001 by kevin gilmore might be of interest.   http://gilmore.chem.northwestern.edu/stxp.gif

Quote:   It's just a derivation of an amp from tubecad. The load resistor value could be adjusted.   http://www.tubecad.com/november99/page9.html

A hand made triode. Video is at the bottom of the page.   http://paillard.claude.free.fr/  

Quote:   I can think of a few reasons. The old buffers are relatively basic implementations using few transistors and hence vaguely understandable to someone (like myself) with limited electronics knowledge. They all have a high quiescent current so they are more likely to operate in...

People fixate on price too often, and incorrectly assume that performance is directly related. I could easily live with the "mid-fi" AKG K702 or Stax SR-202 as an end-game rig.

I'm also interested, but quietly lurking as the discussion is largely over my head.

Quote:   Is it a CCFL inverter for LCD backlighting? I've wondered about the viability of using them for the output stage of a DIY electrostatic headphone amp. I'm not sure what the typical switching frequency is for those. IIRC, the output waveform is far from resembling a sinewave. I...

I thought this might be of interest. I also have images of the box that I can post if desired.      

Nevermind.

Quote:   http://www.tubecad.com/november99/page3.html According to the article, the impedance of a capacitive load decreases as frequency rises, and subsequently, more output current is needed. As far as how much music actually contains 20kHz content, I couldn't say. It looks like...

I'm curious where the idea that the regular Stax amps are insufficient to drive the O2 originates from. Are there any objective measurements around to verify this? SR-007mk2: Impedance : 170k (at f = 10 KHz) Capacitance : 94pF (including cable) Sensitivity : 100dB / 100V r.m.s. at f = 1...

  Err, nevermind. (Overly negative impression of EAH-830 removed...)

Quote: Actually, it was two pairs of Lambda Pros, one normal bias, and the SRM-1/MK2 for $700.   http://www.ebay.com/itm/Complete-Stax-Headphone-System-Lambda-Pro-Non-Pro-Stax-SRM-1-MK2-Amp-/140674771604   Two of the pairs are being sold here. It looks like he may have replaced...

I should have mentioned that it was a higher resolution image. I enlarged it to twice the original size to better see details.   Another clue pointing towards the K250 having passive diaphragms at some point in the past is within the service document itself. Part number 11 - "diaphragm...

I bought my first pair of Realistic Pro 50's off of ebay back in 2006 for $25. At the time, it was a complete unknown. I don't think it had ever been mentioned on Head-Fi. I only picked them up due to the physical resemblance to the older AKG headphones. After receiving them, seeing the "Made in...

Quote:   You seem to be relatively unfazed by this acquisition. Mr. Gilmore as well. Perhaps there's more to this news than meets the eye. In your opinion, would it be wise to buy whatever Stax equipment we want as soon as possible, or wait it out and hope for the best?

It was a recent ebay auction with a misspelled title. Presumably the reason that it slipped under the radar.