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Amplifiers shootout for Stax 009 (Eddie Current Electra, AudioValve RKV + WooAudio Wee, Stax SRM727 / SRM007t2)
Feb 23, 2014 at 10:37 PM Post #61 of 98
Cat6man: congrats, color me envious :wink:
 
Feb 24, 2014 at 3:41 AM Post #62 of 98
cat6man said:
   
Eric,
 
I'm listening right now to 009 + BHSE + D1 Dual and if anything can get better than this, I think my head would explode.
 
My big issue now, evaluating the TotalDAC, is the the digital volume control has to be set at -30dB or lower feeding my VTL amps to Nola speakers.
The digital attenuation kills the magic.  I tried comparing 0dB attenuation in DAC + BHSE vs. -28dB attenuation in DAC and more gain in BHSE and it was no contest.  The BHSE attenuator is much superior to digital volume control at those levels.
 
I'm trying to find a way to keep Vincent's DAC but I don't use a pre-amp (or want one) and the digital volume control is a roadblock for me.
 
Marty
 
p.s. If the T2-like is really noticeably better than the BHSE, I don't want to hear it!  These *&! head-fi meets have already cost me much more than I ever anticipated 
smily_headphones1.gif
 
Click to expand...

 
Cat6man,
 
Congratulations on your very good audio system (Japanese estat, American amp, French dac).
What wonderful production of High-end Hi-Fi material !
 
Listening, yesterday evening,  the 009 + RKV amp (without Wee 1:50 voltage  transformers) + Dac Audiomat Maestro Reference (*) + Audiomat D1 Drive is not bad either and if anything can get better than this, I might lose a very good bottle of Bordeaux...​ 
smily_headphones1.gif

 
 

(*)[size=11.818181991577148px] [/size]French dac (Audiomat), also : http://www.mutine.com/Fiches/Mutine_Fiche_Audiomat_Maestro_Reference_En.pdf
as Totaldac D1 Dual : http://www.totaldac.com/REFERENCE-D1-eng.htm
.
 
Jul 6, 2014 at 11:11 AM Post #64 of 98
Interesting read =)
I know I was switching between 3 stax amps in a not so scientific pattern (SRM1MK2, 727 and 424 was it?)
I could barely hear a difference in general between amps that ranged $500 from each other.
Then I tried my friend's custom amp and it improved tenfold compared to the tiny bit of little improvement the 727 was able to bring over the others.
 
Jul 21, 2014 at 1:23 AM Post #70 of 98
Hello
 
Here is the latest information (with specifications in English) produced by Mr. BECKER (rkv father) of AudioValve Germany on its box adapter VERTO (necessary to operate Stax Headphone with the RKV (OTL) amp, but also with orthodynamic and electrodynamic low impedance headphone, with the highest quality of sound reproduction that is).
 
" Description (VERTO)

The passive box can be used together with AudioValve RKV II and RKV III tube based headphone amplifiers. There was a simple idea behind the VERTO. Why not use the transformer in step up mode to produce the high voltage for the STAX electrostatic headphones? The RKV models use one transformer per channel (impedancer) to drive low impedance headphones (< 100 Ohm). In the RKV III the transformers are mounted inside the case, for the RKV II the impedancer can be bought as a separate box. RKV II and III are regarded to belong to the best sounding headphone amps regardless of price, see many reviews all over the world.

For a game changing product a simple idea is not enough, you have to find also a proper implementation. There are already promising approaches in the market combining transformers with headphone amps to drive STAX headphones. But RKV and VERTO are now exploiting the full potential of that approach. Inductance and capacitance of the transformer can harm the sound. The Pikatron output transformers we use have only very little stray inductances and capacitances. To avoid distortion we use only a low step up ratio of 1 to 5. But key is the fact that the output impedances of RKV II and III are extremely low, too low to cause any negative effect on the sound.

The VERTO supports the current STAX PRO plug with 580 V DC bias as well as the former bias of 300 V used by older STAX headphones. The higher PRO bias uses a 5 Pin connector, the 300 V DC bias can be identified by a 6 Pin headphone plug at the end of the headphone cable. So the VERTO is suitable for all STAX models.

The VERTO has is connected to the headphone amp with a phone cable and standard plug coming with the VERTO. There is nothing to buy for you in addition to the VERTO. Also the VERTO does not require a separate supply voltage. This ensures that there is no interference and hum caused by main connection. The RKV III has to be switched to the OTL mode when driving the VERTO.
To increase the versatility we implemented a switch for 8 ohm as well as 32 ohm. So you can connect high efficient loudspeakers as well as headphones with low impedance. Feel free to drive mobile headphones designed for Apple devices as well as low impedance high end planars like Audeze or Abyss. Check to drive your high efficient loudspeaker with your tube and transformer based RKV and VERTO chain!
Since the connection of the VERTO to the headphone amp is implemented via a standard phone plug you can use it also with other headphone amps instead of the RKV II and III. You will achieve very good results in the case you use a headphone amp with low output impedance and a high output voltage. We doubt that you will get to the same ultimate sonic quality as with the RKV models. The RKV II and III are able to deliver 100 volts peak-peak drive.

We use only high quality components in the box. The Picatron transformers are built based on our specifications. For wiring the main audio connections to the sockets of the headphones and the STAX female socket cable we use a well-known German high end audio cable manufacturer by the name of HB cable design from Cologne. The core of the cable is made of silver-plated oxygen-free copper conductors stranded several times.
Specification:
- Compatible with all STAX electrostatic headphones (580 V DC PRO bias 5 Pin connector as well as 6 Pin 300 V DC bias)
- Suitable for low and middle impedance dynamic or planar headphones as well as ultra high efficient loudspeakers
- 3 switchable modes for STAX electrostatic mode, 8 ohm and 32 ohm
- One Teflon female jacket for STAX PRO bias 5 Pin and 6 Pin headphones
- Two Combi jackets phone plug and XLR for dynamic and planar headphones
- Loudspeaker terminals to connect spades or bananas
- 60 cm cable with phone plug fixed to the case for connection to the headphone amp (like Audio Valve RKV II and III as well as other headphone amps with low output impedance and high output voltage)
- No separate supply voltage needed, static high voltage is generated by the signal
- One high quality Pikatron output galvanic coupled transformer for each channel
- Internal bias voltage for STAX 300 + 580 VDC (LED controlled)
- Internal HB cable design with a cross section of 0.72 sq. mm, embedded in a PTFE Teflon insulation air. The conclusion is a 5 mm diameter strong silicon of insulation, the high-voltage signal line outwards reliable and well insulated
- The device provides both the required for the operation of the headphone-static voltage of 300 / 580 VDC, and up to 550 Vrms signal voltage
- Bandwidth up to nearly 100 KHz - ( 470 pf load )
- Dimensions: w * h * d ( cm ) - 110 * 105 * 165
- weight: 2 kg
Options:

- Silver case (black on request)
- Chrome mode switch (golden on request)
- Cable with phone plug 60cm length (different length on request)
- Price: 690,- EUR including VAT "
 

 
Aug 29, 2014 at 1:27 AM Post #72 of 98
Oct 12, 2014 at 5:27 PM Post #73 of 98
I have arrived late to the party but a few comments about the original post, most important first:
1. Excellent test
2. I agree with Arnaud's comment questioning why each tester called "out-loud" their preferred (A/?) amp for each criterion. Solomon Asch (1936) established strong conformity and convergence effects between testers when this is done. This is a well-replicated and reliable effect and routinely used in design of conformity-based studies
3. It is indeed a pity the reference amp was heard three times more than the other 3. One can imagine the brain adopting its 'sound' as 'the standard' and other perhaps meaningful but subtle differences not being noticed. They fall below the JND - just noticeable difference - threshold where on a more level playing field they might have been noticed. However, this is speculation. I have no idea whether the effect would be enough to matter
4. "...the differences...are not statistically significant" - really? What was the statistical test used, and with what assumptions? But maybe the test is stated and I missed it in my quick read through...
5. Again, excellent test!
 
Oct 20, 2014 at 4:05 AM Post #74 of 98
argo duck said:
I have arrived late to the party but a few comments about the original post, most important first:
1. Excellent test
2. I agree with Arnaud's comment questioning why each tester called "out-loud" their preferred (A/?) amp for each criterion. Solomon Asch (1936) established strong conformity and convergence effects between testers when this is done. This is a well-replicated and reliable effect and routinely used in design of conformity-based studies
3. It is indeed a pity the reference amp was heard three times more than the other 3. One can imagine the brain adopting its 'sound' as 'the standard' and other perhaps meaningful but subtle differences not being noticed. They fall below the JND - just noticeable difference - threshold where on a more level playing field they might have been noticed. However, this is speculation. I have no idea whether the effect would be enough to matter
4. "...the differences...are not statistically significant" - really? What was the statistical test used, and with what assumptions? But maybe the test is stated and I missed it in my quick read through...
5. Again, excellent test!
Click to expand...

 
Thank you. 
 
Indeed, this procedure (in blind) can still be improved: for example, for the two (blind) testers, give their answers in writing (not in orally)
 
Too bad that the procedure is too complicated (and tedious) to make, to retry (again) by integrating, this time, in addition,  the latest amplifier: the  combo RKV-VERTO. 
Surprises again ? (such the feeling of combo RKV-VERTO is so good compared to the 727 amp, but in free listening (not blind)), but it remains the domain of the hypothesis ...
 
(NB: I think the test, if he was again performed (hypothesis) and managed, is powerful enough to show significant differences, such as that found between the combo RKV-WEE versus SRM 007t2 in direct comparison in this blind procedure).
 
 
Amplifiers shootout for stax-009 : eddie current electra - audiovalve rkv/wooaudiowee - stax srm 727 - Stax srm 007t2
 
Direct comparison (in blind test) (detailed results on page 1) :
(NB : indécis = undecided)
(NB: bis : 60 votes for each direct comparison) 

 
(Note: for a sample of n = 60 votes, the difference of vote between an amp A and B must be at least 2 sqr (n) to be significant, it's correspond a difference of at least 15 votes in (the round value of 2 x sqr (60)) on a sample of 60 votes) 
 
(Note bis: the difference of vote between the RKV / wee and the Electra is 17-21 = 4 votes (out of 60 votes including  22 undecided): therefore not significant). 
 
(Note third: the difference of vote between the RKV / wee and the SRM-727 is 24-18 = 6 votes (out of 60 votes including  18 undecided): therefore not significant). 
 
(Note fourth: the difference of vote between the RKV / wee and the SRM-007t is 48-6 = 42 votes (out of 60 votes, including 6 undecided): therefore significant).
 
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