AudioValve RKV-II (OTL amp) (2014 version) + AudioValve Box adapter "VERTO" for Stax Headphone (and for low impedance orthodynamic/eletrodynamic headphone)
A very promising concept to listen to the best electrostatics headphones, and also orthodynamics and electrodynamics headphones of market.
The first listen appear to be very promising, at least above the Stax SRM 727 amp and the combo RKV + WooAudio Wee box (which already equalled the Stax SRM-727 amp and even the Eddie Current Electra amp during our comparative of amplifiers made in September 2013 http://www.head-fi.org/t/681814/amplifiers-shootout-for-stax-009-eddie-current-electra-audiovalve-rkv-wooaudio-wee-stax-srm727-srm007t2)
More transparency than the Woo-Wee Energizer.
Better sound than the SRM 727 (with Stax SR-009 headphone)
A very reasonable cost (690 EUR for the passive AudioValve VERTO box, since that is his name)
And also the opportunity to listen to the best headphones (ortho or dynamic) of the market, even low impedance (via the integrated impedancer, defeatable)
Last specifications (by Helmut BECKER- rkv father on head-fi)
" 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 "
Link to the constructor :http://www.audiovalve.info/rkv/audiovalve%20rkv%20mark2.php
and some of the comments made on the HCFR french forum (Stax thread)
http://www.homecinema-fr.com/forum/post178189300.html#p178189300
http://www.homecinema-fr.com/forum/post178189569.html#p178189569
http://www.homecinema-fr.com/forum/post178189887.html#p178189887
A very promising concept to listen to the best electrostatics headphones, and also orthodynamics and electrodynamics headphones of market.
The first listen appear to be very promising, at least above the Stax SRM 727 amp and the combo RKV + WooAudio Wee box (which already equalled the Stax SRM-727 amp and even the Eddie Current Electra amp during our comparative of amplifiers made in September 2013 http://www.head-fi.org/t/681814/amplifiers-shootout-for-stax-009-eddie-current-electra-audiovalve-rkv-wooaudio-wee-stax-srm727-srm007t2)
More transparency than the Woo-Wee Energizer.
Better sound than the SRM 727 (with Stax SR-009 headphone)
A very reasonable cost (690 EUR for the passive AudioValve VERTO box, since that is his name)
And also the opportunity to listen to the best headphones (ortho or dynamic) of the market, even low impedance (via the integrated impedancer, defeatable)
Last specifications (by Helmut BECKER- rkv father on head-fi)
" 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 "
Link to the constructor :http://www.audiovalve.info/rkv/audiovalve%20rkv%20mark2.php
and some of the comments made on the HCFR french forum (Stax thread)
http://www.homecinema-fr.com/forum/post178189300.html#p178189300
http://www.homecinema-fr.com/forum/post178189569.html#p178189569
http://www.homecinema-fr.com/forum/post178189887.html#p178189887
![size]](http://files.head-fi.org/images/smilies/smily_headphones1.gif[size=13px][/size])
