[gepardcv]

On an unrelated note: does anyone know if the 507 pads are compatible with 207 and 307? The pads all look the same size, but for some reason Yama's site says the pads are compatible with the 407s and 507s, no mention of the 207 or 307.

 

[Michgelsen]

Yes they are compatible.

 

[remilio]

Is there anywhere in the net a video tutorial which shows how to disassembly the top part of Lambda's arc? I mean this thing - https://www.staxusa.com/parts/head-band/stax-signature-headband.html

 

[Jonathan66100]

Hi all : ) 
 
I'm not even sure that the Stax amps, with XLR inputs are really Full Symmetric. 
 
Kevin Gilmore seems to confirm that the kgss, kgsshv, kgbh, T2 and all other Stax amps are not entirely symmetrical. 
http://www.head-case.org/forums/topic/8327-im-on-a-roll-the-kgsshv/page-14#entry387893
 
"kgss, kgsshv, kgbh, T2 and Every Other Stax amp are balanced and-have differential inputs, goal 
are not symmetric and definitely not complementary Either. One of the results is That power supply 
noise and drift are now a Significant outcome. "
 
Or even impossible, for electrostatic amps to be fully symmetric. 
http://www.head-case.org/forums/topic/8327-im-on-a-roll-the-kgsshv/page-14#entry387740

"Fully differential amps fully complementary symmetry are the best. Unfortunately not 
be in electrostatic amps UNLESS you want to do serious transistor stacking. "
 
Spritzer says that all Stax amps after MK2 SRM1 are fully symmetric (Fully Balanced) provided they have XLR inputs. 
http://www.head-fi.org/t/223263/the-stax-thread-new/17445#post_8175985

"SRM-1 Mk2 Is Where things get tricky since There Are So Many variations of it. The first ones Were Some weird Mk1 / Mk2 fully DC coupled hybrid though later purpose units are much more similar to the current crop of Stax amps like the 313 . Now the amps are fully balanced from input to output only though MOST-have RCA inputs. "
 
And resellers of stax says the amp is balanced with her XLR input, but they no talk about full balanced or symmetrical.
 
Symmetrical and balanced is the same thing ?
 
Thank you.

 

[Michgelsen]

From my limited understanding, symmetrical and balanced are often used as synonyms, but a distinction can be made in amps.
 
In any case, Stax headphones are always driven balanced, that is from both sides of the membrane, thus by both a + and - signal at the same time from different sides, and thus need four-channel amps for stereo audio. If you look at internal photos of electrostatic amps, you often see four-channel pots being used (or 2×2), meaning that the amps are four-channel throughout. Apparently, if I understand the posts you quoted correctly, the four channels of the amp do not have to be or cannot always be exact copies of each other, which is what would make a fully symmetrical amp. I have never seen an electrostatic amp that operates as two-channels, but is splitted to four only at the output.
 
Please correct me if I'm wrong; I know nothing of amplifier design.

 

[Jonathan66100]

Thank you for taking the time to answer me Michgelsen ! 
They it is played to nearly full symmetric.
 
KG also speaks of power supply noise and drift.
It's complicated : D

 

[FrankCooter]

   I have never seen an electrostatic amp that operates as two-channels, but is splitted to four only at the output.
 
Please correct me if I'm wrong; I know nothing of amplifier design.

 
No commercial designs that I'm aware of, but occasionally done in the DIY world. The signal is run single-ended all the way until the last stage, where it is split into a balanced output via a phase-splitting transformer.
 
Like all other amp topologies, a series of trade offs is involved. The big negative is the transformer, which if done right, is heavy, bulky, expensive, and no matter how good, will not have the technical measurements of a balanced direct-coupled design.
 
The biggest advantages are the elimination of the neg. HV rail,which allows much greater flexibility in power supply design. the ability to use unusual tubes such as DHT's in the output, and simpler overall circuitry that produces an inherently balanced output that is not subject to drift or variation.

 

[eric65]

   
No commercial designs that I'm aware of, but occasionally done in the DIY world. The signal is run single-ended all the way until the last stage, where it is split into a balanced output via a phase-splitting transformer.
 
Like all other amp topologies, a series of trade offs is involved. The big negative is the transformer, which if done right, is heavy, bulky, expensive, and no matter how good, will not have the technical measurements of a balanced direct-coupled design.
 
The biggest advantages are the elimination of the neg. HV rail,which allows much greater flexibility in power supply design. the ability to use unusual tubes such as DHT's in the output, and simpler overall circuitry that produces an inherently balanced output that is not subject to drift or variation.

 
See also : http://www.head-fi.org/t/727055/diy-tube-amp-for-electrostats-transformer-coupling-vs-dc-coupling#post_10730457
 
 
Hello FranckCooter, 
 
Your publications (rare) are highly appreciated for their quality and pedagogy. 
 
You explain unprejudiced the advantages and disadvantages of electrostatic headphone amplifiers using transformers step up behind a tube amplifier operating in OTL mode. 
 
If I understand correctly, the theoretical performance of such an amplifier (with transformers step up) will always priori inferior to those of direct-coupled amplifiers do not use output transformers. I want to believe. 
 
However, and this may seem paradoxical, hearing performance may be different due to the inherent imperfections of transformers that can sometimes make it more enjoyable to hear  (by coloration ?) with electrostatic headphones (overall synergy?) at least on some music sound with the SR-009 Stax headphone. 
 
This is what we discovered by chance in a comparative test (with a rigorous protocol) using two headphone Stax SR-009 (two testers in blind, six audio criteria and five musical choice (60 votes for each A / B amp comparison)) with 3 amplifiers direct drive (Stax SRM-727, Stax SRM-007t and Eddie Current Electra) compared to a tube amplifier OTL (Audiovalve RKV-II) coupled to the transformer box WooAudio WEE (via an adapter) (see the results of this study the following links : http://www.head-fi.org/t/681814/amplifiers-shootout-for-stax-009-eddie-current-electra-audiovalve-rkv-wooaudio-wee-stax-srm727-srm007t2/60#post_10976349 ; and : http://www.head-fi.org/t/681814/amplifiers-shootout-for-stax-009-eddie-current-electra-audiovalve-rkv-wooaudio-wee-stax-srm727-srm007t2 (page 1))
 
This study seems to have inspired Mr. Becker Helmut, the German manufacturer of tube amplifiers (AudioValve brand), who produced, in June 2014, a step up voltage transformer box optimized for operation with own headphone amplifier OTL of the mark (RKV -II) : code name : "Verto".
(NB: the ratio step-up voltage amplification of the Verto box is lower than the Wee : ratio 1: 5.9 (against 1:50 for the Wee) 
(NB bis: the RKV can get 80-100 Volt RMS (AC) out of an load estimated at 2000 Ohm ; the transformer box Audiovalve (named from the Latin name "Verto") are Pikatrons transformers, manufactured specifically to specifications, according to the manufacturer). 
 
Listening results (subjective) of combo OTL RKV-II amp + Verto transformer box, look very promising, especially for listening through headphones Stax SR-009. 
http://www.open-end-music.de/vb3/showthread.php?p=166271#post166271 (german) and http://www.homecinema-fr.com/forum/post178235362.html#p178235362 and http://www.homecinema-fr.com/forum/post178238699.html#p178238699 (french)
Dynamics does not seem constrained; no known treble attenuation (at least up to 10 KHz) for listening to a normal level of 75-80 dB, with peaks of 95-100 dB level. 
Timbre (tone) seem very natural, both sweet, precise and just tone. 
 
Recently, I learned that Mr. Becker would get an integrated solution of its Verto transformer box with their OTL amp (RKV-II) : all elements (OTL tube amp + transformers) are integrated in a single box : tube amplifier OTL (+ step-up transformers (1: 5 or 1: 6 ?), probably the same as those of the Verto?) who should be appointed from the Latin name (or Italian?) "Luminare"). 
(last known link of the AudioValve "Luminare" amp : http://www.attsaar.de/Rechts/KHV-Audiovalve.html (german))
 
All this to say, it's with some enthusiasm, your ideas and concept of combining an integrated amplifier tube amplifier + transformers step up voltage) seem took days, not in a DIY form, but a commercial form, which will be available to lovers Stax headphones in the same manner as the direct current amplifiers driving already sold. 
 
I found your interesting idea ; our tests with transformers box (Wee and Verto) showed the feasibility and the reality of such concept audio.

Finally, Mr. Becker obviously interested in the application of this concept now seems to bring out the DIY to apply industrially (commercial design).
 
I just wanted to keep you informed of all these the latest developments (June and October 2014) you might be interested, in the small world of electrostatic headphones. 
 
Yours.
 
Eric

 

[kevin gilmore]

actually there is an unbalanced commercial design that drives the loudspeaker single sided with
one of the stators at ground, and the bias voltage fluctuating with the music.
 
Beveridge.  They were very impressive speakers in their day. Probably still are if there are any
left that still work.

 

[Jonathan66100]

Hi Eric, FrankCooter and Kevin : ) 
Thank for your reply FrankCooter and Kevin : )
If I understand correctly, the fact that the stax amps are not completely symmetrical, they have nevertheless of big advantage not be.

 

[eric65]

  actually there is an unbalanced commercial design that drives the loudspeaker single sided with
one of the stators at ground, and the bias voltage fluctuating with the music.
 

 
Nothing heard nefarious about sound quality.
 
The bias is regulated and stored by buffer capacitors; It remains stored for tens of minutes, even in the absence of music input signal.
 
And the "Luminare"? (amplifier built-in)  http://www.attsaar.de/Rechts/KHV-Audiovalve.html
 
 
 
Hi, Jonathan
 
There are advantages and disadvantages for each technology (amps with direct drive or with step up transformers)
 
Eric

 

[NoPants]

I think any impressions involving the RKV Mk3 should be discredited on account of how hideous it is

 

[preproman]

  Forgive me. Can anyone provide a thorough comparison of the T2, BHSE and KGSSHV. Using either/both 009/mk1. 

Also add The KGST to that as well.

 

[eric65]

  I think any impressions involving the RKV Mk3 should be discredited on account of how hideous it is

 
As is probably the case of the headphones JPS Abyss...
And yet, the two coupled have a sound particularly good together ...
 
 
NB: RKV-II amp is not so ugly that it (you can choose the color silver for the feets)
 

 

 

[kevin gilmore]

a fully symmetric,complementary and differential electrostatic amp is possible.
you need a pile of 2sa1968's and a pile of 2sc4686a's. You have to limit
the power supplies to +/-450V.  and you need a fancy floating output stage
control circuit to exactly control the output stage bias.  Think something
along the lines of the computer that controls the Ragnarok.
 
you will blow up lots of parts before you get the bias control exactly right.
Maybe when Jason has nothing else to do for a few weeks.
 
Don't forget the "Carbon"    (kgst with silicon carbide fets as the output stage)
 
and "NanoTube"   (Silicon Carbide Circlotron)
 
I have at least one each of diyt2,kgsshv,kgst,kgss,bh,bhse,ges,es1,megatron and probably a few more
that I forgot.
 
its really hard to figure out which amp/headphone to listen to every day.