[blubliss]

+ a billion

 

[mulveling]

I used to own an RKV Mk II and it was a really nice sounding amp, but it wasn't reference quality even with an HD650 (e.g. a Headamp Gilmore Reference or GS-X Mk 2 will beat it no problem). So the idea of it competing with the Gilmore electrostat designs on the MUCH MORE RESOLVING SR-009, with a freaking transformer box sandwiched in the middle no less, sounds very very funny to me.

 

[eric65]

  I used to own an RKV Mk II and it was a really nice sounding amp, but it wasn't reference quality even with an HD650 (e.g. a Headamp Gilmore Reference or GS-X Mk 2 will beat it no problem). So the idea of it competing with the Gilmore electrostat designs on the MUCH MORE RESOLVING SR-009, with a freaking transformer box sandwiched in the middle no less, sounds very very funny to me.

 
The have you tried? (the Verto box + RKV-II amp + Stax SR-009)
 
Personally, I would have the chance to do so within 15 days.
 
We'll talk about when you'll have the same experience as mine.
 
Kind regards.

 

[davidsh]

Will probably have plenty of headroom, though..

 

[eric65]

   
And me, I would wait only 15 days to get the all-new AudioValve Verto box http://www.head-fi.org/t/727630/audiovalve-rkv-ii-otl-amp-2014-version-audiovalve-box-adapter-verto-for-stax-headphone-and-for-low-impedance-orthodynamic-eletrodynamic-headphone#post_10756994 , which coupled to the AudioValve RKV-II (OTL) amplifier and the headphones Stax SR-009 (that I already own), that would do better than all the amplifiers Stax currently in production (including SRM 727 and SRM 007t2) if one believes the first trials and listens in France. 
http://www.homecinema-fr.com/forum/casques-haute-fidelite/verto-le-boitier-audiovalve-pour-casques-stax-t30052030.html
I would affirm you soon.
 

 
Quote:

  I used to own an RKV Mk II and it was a really nice sounding amp, but it wasn't reference quality even with an HD650 (e.g. a Headamp Gilmore Reference or GS-X Mk 2 will beat it no problem). So the idea of it competing with the Gilmore electrostat designs on the MUCH MORE RESOLVING SR-009, with a freaking transformer box sandwiched in the middle no less, sounds very very funny to me.

 
You have misread my previous post.
 
In this post, I did not put in competition the new combo AudioValve RKV-Verto with the productions (of quality) of electrostatic amplifiers made by Gilmore, but only with amps Stax currently in production (SRM 252 to the SRM 007t2) which according to firsts listening carried out in France, and no offense to all those who have not yet listened to, would be, in terms of the sound quality, below the combo in question.
 
My only reference at the Gilmore productions, concerning the command time significantly shorter for AudioValve productions (a few weeks instead of several months).
But the industrial means, perhaps, are not the same?

 

[eric65]

Otherwise, what you have not understood, is the mode of operation of the tubes of the amplifier RKV II (or III in OTL mode).
 
To continue the example from the HD 650, the load seen by the amplifier is equal to 300 Ohm (that's the impedance of the headphones HD 650).
 
With electrostatic headphones Stax SR-009 (very high impedance: 145000 Ohm) with multiplier voltage transformer (with very low ratio only 1:5) (low distortion), the impedance seen by the amplifier RKV will be included in a range (wide) ranging from 2000 to 6000 Ohm (depending on frequency). 

However, you should know that that PCL805 tubes of RKV excellent for use mainly in tension (voltage), with an optimal charge of approximately 4000 Ohm (the one originally scheduled to operate these tubes in the cathode-ray TV).
 
To summarize, we can say that the RKV-II (or III in OTL mode) will be better with headphones Stax SR-009 (via the Verto box and  its transformers of low ratio amplification of voltage : only 1:5) rather than with the HD 650 headphone (regardless of the quality of the headphones) simply, for a matter of impedance matching.
 
(NB : If you fear not to translate the french language in english, I give you a far more details link on this issue of adaptation of impedance of the tubes of the RKV : http://www.homecinema-fr.com/forum/post178200031.html#p178200031 ) 

 

[kevin gilmore]

so I did a careful and complete synthesis of the RKVII driving a lundahl LL9202
transformer wired as 6.625:1 which is as close as I can get to the 5:1 with
the best spice models for the tubes and full specifications from lundahl.
This is what I got
 
http://gilmore.chem.northwestern.edu/rkv.jpg
 
top box green is frequency response, red is phase
 
bottom box red is input square wave 1khz, green is output
 
so if your hearing extends to only about 6khz you are going to be fine.
 
The build time and price of a BHSE is irrevelant.
A great many have built their own BH. A few have even built something similar to the BHSE.
A fair number have built megatrons (about 8) and T2's (more than 40).
 
All of which will seriously exceed the performance of  a poorly designed high impedance futterman design driving
what is likely to be a very poorly made cheap transformer in a box designed with multiple
windings to drive all sorts of stuff.

 

[MacedonianHero]

I second that. I didn't know which Stax amp to buy and Birgir told me to get a 717, which is still very good and running fine. The modded 727 is the same as a 717 soundwise.

It makes me wonder why Stax do things like this in the first place. I know plenty of Stax owners who bought a Stax amp with the phones, and got fed up with the amp.

You know, if you wanted to go another step, you could get a DIY KGSShv or buy a Woo or BHSE if you like tubes. The jump from the 717/727 is not subtle.

Doesn't the 727II have more power/voltage than the 717 too? Agreed that the unmodded SRM727II isn't anything to write home about.

 

[eric65]

  so I did a careful and complete synthesis of the RKVII driving a lundahl LL9202
transformer wired as 6.625:1 which is as close as I can get to the 5:1 with
the best spice models for the tubes and full specifications from lundahl.
This is what I got
 
http://gilmore.chem.northwestern.edu/rkv.jpg
 
top box green is frequency response, red is phase
 
bottom box red is input square wave 1khz, green is output
 
so if your hearing extends to only about 6khz you are going to be fine.
 
The build time and price of a BHSE is irrevelant.
A great many have built their own BH. A few have even built something similar to the BHSE.
A fair number have built megatrons (about 8) and T2's (more than 40).
 
All of which will seriously exceed the performance of  a poorly designed high impedance futterman design driving
what is likely to be a very poorly made cheap transformer in a box designed with multiple
windings to drive all sorts of stuff.

 
Hello Kevin,
 
Thank you for your very interesting theoretical study of the RKV-II amp, and its frequency response (with a Stax electrostatic headphones), using a 1:6 ratio transformers (if I understand correctly).
 
There is just a small problem concerning this study; I can't yet speak of listening (already made by Pierre Paya) of the RKV-Verto combo (with its transformers 1:5), that I will soon receive, but the combo RKV-Wee (with its 1:50 transformers); much worse in theory than transformers 1:5 of the Verto; and well, I don't have the impression of having heard a loss of 16 dB at 10 KHz with this combo when listening to a sinus signal at 10 KHz (from a CD test), nor even in our comparison of amps (we were 4 testers) directed in September 2013 where the RKV-Wee gave rather good results compared with Stax SRM 727 and especially the Stax SRM 007t2.
 
Mystery! (between theory and practice) 

 
 
PS: my hearing is correct (aged 48) up to 12.5 KHz.
 
PS bis: I don't doubt the quality of your products.
 
Well cordially
 
Eric
 
 
Edit : Here my measurement readings (to the microphone in free field) of the RKV II-Wee combo (with Wee transformers 1:50) with the Stax SR-009 headphones at different frequencies (500 Hz; 1 kHz; 2 kHz; 5 kHz and 10 KHz) for a 0.20 Volt RMS signal at 1 KHz (frequency control) (Wee input = RKV output) with the same position of the potentiometer of RKV for measurements:
 
(Stax SR 009 : signal 500 Hz  = 75,2 dB SPL (free field))

 
(Stax SR 009 : signal à 1 KHz (frequency control)) (Wee input = 0.20 Volts rms) = 72,5 dB SPL (free field))

 
(Stax SR 009 : signal 2 KHz  = 74,4 dB SPL (free field))

 
(Stax SR 009 : signal 5 KHz = 72,4 dB SPL (free field))

 
(Stax SR 009 : signal 10 KHz = 78,7 dB SPL free field))

 
Conclusion : Not significant roll-of at 10 KHz (relative to the frequency control 1 KHz) with the combo RKV-Wee + Stax 009.
 
 
Also: other data interesting to read (comparative amp and headphones: steps to the microphone)
 
A: comparison of headphones 009 / 007 mk2 on the combo RKV-Wee (NB: same position of the potentiometer on the RKV: input 0.20 Volts rms at 1 kHz = 73 dBA SPL on the 009)
(averaged for 009 on RKV - WEE) free-field measurements :
 
500 Hz : 73,2 dBA / 70,8 dBA
1 KHz : 73,0 dBA / 71,0 dBA
2 KHz : 75,0 dBA / 69,5 dBA
5 KHz : 71,5 dBA / 70,2 dBA
10 KHz : 76,5 dBA / 73,0 dBA
12.5 KHz : 62,0 dBA / 64,5 dBA
 
B: comparison of  009 headphones with amps RKV-WEE / SRM 727 / SRM 007t2 (NB: level benchmark standard for amplifiers: 73 dBA SPL at 1 kHz with the 009)
free-field measurements :
 
500 Hz : 73,2 dBA / 73,0 dBA / 73,3 dBA
1 KHz : 73,0 dBA / 73,0 dBA / 73,0 dBA
2 KHz : 75,0 dBA / 75,0 dBA / 75,5 dBA
5 KHz : 71,5 dBA / 67,7 dBA / 68,2 dBA
10 KHz : 76,5 dBA / 69,9 dBA / 71,0 dBA
12.5 KHz : 62,0 dBA / 56,0 dBA / 61,0 dBA
 
Conclusion : significant roll-of at 12.5 KHz (relative to the frequency control 1 KHz) with the three amplifiers RKV-WEE / SRM 727 / SRM 007t2 + Stax 009.

 

[chengka7]

Damn, so wanna find someone to build me a dynahi or BHSE, but Corey is not taking order this year, and still have difficulties finding a skilled builder....

 

[David1961]

Because Julian is better at describing SQ than I am, my findings are only going to be short from hearing Julian's KGSSHV and my BHSE.
Using his and my 009's with the source being my k-01, I found the KGSSHV had a stronger bass which listening to Rammstien sounded very impressive, however from the BHSE everything sounded so life like ( well as close to life like I've heard from a headphone combo )
So from the two amps I preferred the BHSE but I was still very impressed with the KGSSHV, so much so I'll definitely be getting one when I've the spare money.
I was also very impressed with the build quality and looks of Julian's KGSSHV, I would've preferred it with a silver faceplate and everything else matt black, but I can ask for that when I'm ready to get one.

With the BHSE we only used the PH tubes but because Julian's KGSSHV only has XLR sockets, we were only able to use my silver XLR's with his amp and my copper RCA's with my BHSE.
When I use my BHSE I mostly use my silver cable XLR interconnects ( that's only since I started using the PH tubes ) because I find they give me more detail and transparency, so whether using the silver XLR's with KGSSHV and copper RCA's with the BHSE brought the amps closer together, I can't say, but Julian did try my BHSE with both interconnects and he said he couldn't hear any difference.
All in all though Julian's KGSSHV ( IMO ) is a very impressive amp, and for what it cost him is worth every penny or dime.

 

[James-uk]

What would you guys recommend for a budget 'starter ' stax rig?

 

[davidsh]

What would you guys recommend for a budget 'starter ' stax rig?

207 and srm323. I have no first hand experience with Said equipment, though

 

[milosz]

  so I did a careful and complete synthesis of the RKVII driving a lundahl LL9202
transformer wired as 6.625:1 which is as close as I can get to the 5:1 with
the best spice models for the tubes and full specifications from lundahl.
This is what I got
 
http://gilmore.chem.northwestern.edu/rkv.jpg
 
top box green is frequency response, red is phase
 
bottom box red is input square wave 1khz, green is output
 
so if your hearing extends to only about 6khz you are going to be fine.
 
The build time and price of a BHSE is irrevelant.
A great many have built their own BH. A few have even built something similar to the BHSE.
A fair number have built megatrons (about 8) and T2's (more than 40).
 
All of which will seriously exceed the performance of  a poorly designed high impedance futterman design driving
what is likely to be a very poorly made cheap transformer in a box designed with multiple
windings to drive all sorts of stuff.

40 DIY T2's?  Wow.  And mine's still not done!  
 
You know, I'm tired of waiting for it to finish building itself- maybe I should intervene.

 

[milosz]

What would you guys recommend for a budget 'starter ' stax rig?

Hahaha  Koss ESP-950's.   Best electrostatic sound you can get for ~$750  all in.  (ESP-950's include an amp.)
 
Not Stax, though- excellent sound, but different from Stax.
 
Stax on a budget, I'd look for a used T1 with a pair of Lambdas of some kind.  Some folks like the old low-bias Lambdas, others like the high-bias Lambda Pro's. I have a pair of Lambda Signatures which I got with a T1 for about $800. Love them.  (I also love my ESP-950's.)
 
Lambda Signatures have the famous "Stax Etch"  hyper-detail artifact in their sound, which I happen to like.  The (non-'Signature') Lambda Pro 'phones that I've heard are closer to neutral.  So, an SRM-T1 and a pair of Lambda Pro's or Lambda Signatures depending on your 'detail' (i.e., modest treble coloration) preference.  That would be my suggestion.