[spritzer]

Normal bias was 200V but was later upped to 230V (around 1977). 
 
Quote:

This is not the input power of the Wee that counts but the input voltage.
Stax headphones operate in voltage, not in amperage. The wattage does not mean anything.
The minimum specifications for the Wee wooaudio are at least 3 Watts on 8 ohms, which corresponds to a minimum input voltage of the Wee of about 5 volts.
V²= PR (P = 3 Watts ; R = 8 Ohms ; PR = 3*8=24 ; V = SQR 24 = 5 Volts)
 
There was therefore the margin with the output 80 volts max of the RKV.

 
All of this is assuming the amp can drive the load of the WEE to max voltage swing which is probably can't.  While you might get some sound out of normal headphone amps it is far from an ideal setup unless you happen to like massive amounts of distortion.  Running anything at max voltage swing is never a good plan. 
 
Quote:

 
Spritzer just reworked a bunch of borked KGSSHV amps and put his faceplate on them.
Guess we'll never know....What say you Spritz?

 
Kevin and I did pay a kings ransom for a bunch of parts and one "completed" amp from Hennyo.  Kevin ended up with the amp to try and get it working and I got the parts.  They did include two chassis but they ended up in the trash as Hennyo had spent hours drilling a bunch of holes into them seemingly just by eye...  The parts made up 6 pcb's and some random scatter of parts but not nearly enough for the full amps.  The PCB's were about 50% populated but bad packaging meant a lot of damage to the sand so I had to strip everything down and desolder every joint.  Now the main problem with all of this was an utter lack of any soldering skill by Hennyo.  Too much solder of unknown quality (as in not 60/40) and probably a rusty nail and a blowtorch to do the soldering.  I had to remove a lot of solder but it would still come back and haunt me. 
 
So I strip down the boards and build them up again properly.  One of the PSU's had a huge explosion thanks to the aforementioned soldering skill so that had to be scrapped entirely and a new one built.  I then got in some new chassis and did indeed have it laser engraved like my other amps since I bloody built these things. 

  I was never going to keep these amps so they are sold to recover the cost of building them.  The main goal was to get the parts out of circulation and into something useable. 
 
Quote:

Is there much difference in sound between the old KGSS and KGSSHV besides being a high voltage version? 

 
There is a difference but it's not too pronounced. 
 
Quote:

Where these made by Stax?
 

 
They were built my Micro Seiki.  The guy who designed them used to work for Stax back in the day. 

 

[Chris J]

 
The knowns here are the voltage, which is 80 volts and impedance 8 Ohms.
80^2 = 6400 (V²= PR). 6400 = PR = P x 8 (Ohms); P = 6400/8 = 800 Watts.
 
IF the calculation and formulas are correct the only way I can see the 80 volts happening with 3 watts power is in a different impedance. In other words those 80 Volts cannot be into 8 ohms with 3 Watts power. The reason I am going through this is that I am very interested to find what's required to drive the Wee/Stax well and what amplifier I need.
 
Also I am quite puzzled why Woo Audio is showing 3 Watts as minimal specs, if this is not very important, and no other criteria. I could actually ask them directly.

 
Never mind.....................I mis-read your post! Oooops!

 

[SBranson]

I saw a few pages ago something about letting the headphones warm up or "charge".

Last night I went into my den and saw the glow of my tubes... Oops I left my SRM007tA on overnight. Well since it was warmed up I sat down to listen to a couple tracks,... WOW!
I had been previously a little underwhelmed by my O2mk1s thinking that I could sense the potential but maybe my source sucked but last night was a revelation.
It was a completely new audio experience. Though the music was familiar pieces, Joni Mitchell's Blue, I felt like I was sitting in the studio. It was an oddly personal and totally engaging experience. I ended up listening for over an hour. Thanks Stax!!

So is this from letting the O2s "charge" or is it just getting the amp more warmed up than usual?

 

[NoPants]

Great work Milo, my hands are just too shaky and the way I eyeball things simply isn't good enough for mechanical accuracy. 
 
Casework will always be my downfall and I am firmly committed to finding ways to weasel out of doing it in the future Granted I haven't explored FPE or camexpert, so I might be cutting myself off short.

 

[eric65]

Quote:

I know what the specs say for the wee, but trust me they are not right.
The input impedance is something like 16 ohms. The output impedance
is something like 100k ohms. Very similar to the stax transformers.
Roughly same voltage gain.

Hello,
 
The Wee input impedance 100K Ohms is false?
 
It would be only 16 Ohms ?
 
How did you get or measure this informations ?
 
Otherwise, can you confirm the amplification ratio of the voltage wee 1:25 (from Arnaud and spritzer) or 1:35 according to my own measurements?
 
Thank you in advance for your clarifications.
 
NB : For details on the calculation of the ratio of amplification 1:35 transfomer of Wee (in french HCFR forum)
http://www.homecinema-fr.com/forum/casques-haute-fidelite/club-des-heureux-proprietaires-de-casques-stax-t29819561-3855.html

 

[eric65]

If the ratio of amplification of the voltage transformers wee is 1:25 and the impedance of the headphone output Wee is 145K ohms (impedance of Stax SR 009), then the input impedance of Wee should be 145000/25x25 = 232 ohms and not 16 ohms ?

 

[kevin gilmore]

you are talking about ac impedance at a particular frequency, and I am talking about the dc resistance of the primary.
 
and this is the problem.
 
the stax headphones are a pure capacitor. they represent a complex load whose impedance is dependent on frequency.
their load translates back to the primary of the transformer at the turns ratio of the transformer.
 
its much more accurate to measure the turns ratio into a known pure resistive load, or measure the inductance of
the primary and the secondary. But something in the range of 1:25 to 1:35 is the right number.
 
at 20hz the reflected input impedance is very high. at 20khz the reflected input impedance is very low. probably less than
10 ohms which is why some of these transformer based units have a resistor in series with the primary. This is because
many power amps really don't like to drive massively reactive loads like this.
 
original decca ribbon tweeters with the low impedance transformers were famous for blowing up power amps.

 

[eric65]

Thank you for that clarification,
 
It joined the measurements taken at the exit of RKV and therefore entry Wee at different frequencies for finding a large increase in amperage and lower voltage, from 5 kHz, which could bring of aténuation RKV combi-Wee in the high frequencies.
 
"  Ok Arnaud
 
Otherwise, you have a clue as to why the amperage increases sharply (with a drop of voltage level) to the sine frequencies  of 5 and 10 kHz compared to the level of amperage and voltage measured at the frequency of 500 Hz sine (see attached figures, published on the previous page).
Measurements made with the Stax SR 009 headphones plugged into the headphone jack of Stax WEE, WEE directly connected to one of the two headphone jacks RKV. WEE input level of 0.20 volts rms at 500 Hz input impedance WEE calculated about 100 K Ohms to the sine frequency of 500 Hz Level potentiometer volume RKV unchanged when these measures to such different frequencies.
 
Sine signal 250 Hz: 2.4 microA / 0.205 V
Sine 500 Hz: 2 microA / 0.203 V (NB: the input of the load R WEE and therefore output RKV estimated at this frequency (500 Hz) to R = U / I = 0.2 V / 0.000002 A = 100 000 Ohms (100 K Ohms)
1 kHz sine signal: 1.7 microA / 0.201 V (Note: sound level estimated listening about a good 80 dB with the SR 009 Stax headphone)
2 KHz sine signal: 2.6 microA / 0.193 V
5 kHz sine signal: 125 microA / 0.160 V
10 KHz sine signal: 163 microA / 0.115 V
 
Eric
 
EDIT: If these numbers are accurate (ie not the result of an artifact of my multimeter for voltage measurements / amps at these high frequencies of 5 and 10 kHz) would mean the RKV / torque WEE 009 + a log10 level loss (0.160/0.200) squared) x 10 (in dB) = 2 dB at 5 KHz with respect to 500 Hz; level drop passing log10 (0.115/0.200) squared) x 10 (in dB ) = 4.8 dB at 10 kHz relative to 500 Hz
To the ear, this could explain the relative softness in acute torque RKV / WEE 009 + if there exists a lower level of 2 dB at 5 kHz and about 5 dB at 10 kHz, which should be well listening to the 009 to mitigate the harshness often found in the upper midrange-treble (5 and 10 KHz)
Attractive hypothesis?   "
 
http://www.homecinema-fr.com/forum/casques-haute-fidelite/club-des-heureux-proprietaires-de-casques-stax-t29819561-3810.html
http://www.homecinema-fr.com/forum/casques-haute-fidelite/club-des-heureux-proprietaires-de-casques-stax-t29819561-3855.html

 

[MacedonianHero]

Quote:

 
What pot did he install?

"Volume control is from my new batch of Alpha pots which were made with even stricter tolerances and the Stax socket is the one from Justin so the insertion force is just perfect (we spent a lot of time to get that just right). "
 
BTW, owning a HeadAmp KGSS, I absolutely love the insertion force on the Stax socket on it. Just feels so damn right
Quote:

Birgir sent me an amp last year, took less than a week door to door. Maybe you'll have the same luck.

 
Good to hear! 

 

[TheAttorney]

Quote:

... Oops I left my SRM007tA on overnight. Well since it was warmed up I sat down to listen to a couple tracks,... WOW!
I had been previously a little underwhelmed by my O2mk1s thinking that I could sense the potential but maybe my source sucked but last night was a revelation.
It was a completely new audio experience...

So is this from letting the O2s "charge" or is it just getting the amp more warmed up than usual?

 
I've posted much the same a while back, not necessarily on this thread. I also left my SRM007t on overnight by accident and heard an improvement in SQ. Not so much a revelation as a nice improvement. This compared to a warmup time of a few hours during an evening.
 
I reckon it's the extended warmup time for the amp that made the difference, not extended charge time of the O2's. Because I repeated the exercise with the O2's disconnected overnight.
Of course, leaving tube amps on all the time may be bad for other reasons...

 

[DefQon]

The same thing can be said for my old SRM1 MK2's, T1S and my current SRM1 MK1 and SRM323S, they sound more enhanced (subtle) if I leave it up for 30minutes to get all the electrons flowing nicely. 

 

[SBranson]

Thanks for the reply.  I haven't had much time to listen lately so sometimes I start listening after the amp's flashing warm up light stops blinking. 

I've had enough tube amps in the past to know that I should turn the amp on and then go do something before sitting down to listen but I couldn't believe how much more subtlety and resolution changed.  I'm excited again.  I guess I'll be treating these with more respect like back in the days when I had the speaker system..
 
I wondered about the "charging the headphones" thing because it's not something I'd ever heard before.

 

[milosz]

 

 
 
They were built my Micro Seiki.  The guy who designed them used to work for Stax back in the day. 

 
Micro Seiki, interesting.  I now remember seeing Micro Seiki electrostatic headphones being sold back then.  Interesting to learn that they were doing some OEM'ing.  Wealth of knowledge here on Head-Fi!

 

[3X0]

Quote:

I've posted much the same a while back, not necessarily on this thread. I also left my SRM007t on overnight by accident and heard an improvement in SQ. Not so much a revelation as a nice improvement. This compared to a warmup time of a few hours during an evening.
 
I reckon it's the extended warmup time for the amp that made the difference, not extended charge time of the O2's. Because I repeated the exercise with the O2's disconnected overnight.
Of course, leaving tube amps on all the time may be bad for other reasons...

IMHO when electrostatics are good (charged up, no problems with either driver, no dust and reasonably driven), nothing is better. Not dynamics, not orthos, nothing.
 
But when electrostatics are bad (dust/buzzing, freshly turned on, not enough power), nothing is worse.
 
I'm sure some will disagree with the second part.

 

[autoteleology]

How does one go about replacing a fuse in a basic Stax amp? I learned that I actually might be able to repair my SRM-Xh.