OK, a couple of questions.
(1) What is so special as to the AudioValve RKV-II (or lll), amps? I ask in that the "Wee" can apparently be used with 'any' power amp.
(2) In what way is the 'AudioValve Box adapter VERTO' different or superior to the "Wee" when used for Stax headphones?
Many thanks,
John H
Hello John H.
Interesting questions:
Why RKV amplifiers (II and III in OTL mode) are ideal for use with transformer box as WEE or AudioValve VERTO for use with Stax electrostatic headphones?
Because they have no output transformers "Step down" in OTL mode (NB: it is better to avoid the interference of a succession of two transformers: a transformer "Step Down" (voltage reducer) (that of an tubes amplifier "no OTL"for example) followed by a transformer "Step Up" (voltage booster) (that of the WEE box or VERTO box).
Because they are very good (in OTL mode) for operating in voltage (rather than amperage) for high impedance headphones (100-2000 Ohms).
Because they have a very low output resistance (high damping factor).
Because they can get up to 80 to 100 Volts RMS output to a load of 2,000 Ohms (and more again) (NB: the impedance of headphones Stax is very high : 145000 Ohm for a 009 for example)
Because he can operate with a box of transformatreur ratio "step up" weak: only 1: 5.9 for the Jack VERTO input (against 1:50 for the input speaker teminal of the WEE and 1:14 for input speaker terminal "reverse" of the VERTO) which allows to obtain a less distortion of the audio signal between the input and the output of the transformer).
The reverse of the medal of the use of smaller transformers voltage amplification ratio is the need to use an amplifier in input (if possible in OTL mode, without output transformer to avoid sucession (deleterious to the sound quality) of a "step down" followed by a "step up") giving enough volts in output of the amplifier in a high impedance (200-2000 Ohms), at least 30 to 40 volts RMS output, for the input of Jack VERTO and at least 10 to 15 Volts RMS output, for the input speaker terminal "reverse" of the VERTO (either a Hi-Fi amplifier giving at least 10-30 Watt at 8 Ohm (according to the formula: P = U² / R) (P (Watt), U (Volt) and R (Ohm)).
(NB: WEE, with its transformers "no name" of ratio :1:50 is satisfied with a Hi-Fi amplifier outgoing only 3 Watt at 8 Ohm, either 5 Volts RMS for the input speaker terminal of the WEE).
Another factor to consider: the quality of transformers VERTO (custom-made by Pikatron (a German brand of transformers)) inherently is better than the WEE transformers "no name" ; not to mention that the leverage ratio of Voltage, lower, of the VERTOTransformers, provides less distortion of the audio signal (ie less distortion and better response of frequency).
Because they were (RKV-II Amp and VERTO box) tested in direct comparison with the WEE box (+ RKV-II amp) and with the amplifiers Stax SRM 727 and SRM 007t2 (with the Stax SR-009 headphones and also Stax SR-507) and that the best result was obtained listening the combo RKV-II + VERTO (input jack) + SR-009. (link (in french) : http://www.homecinema-fr.com/forum/casques-haute-fidelite/verto-le-boitier-audiovalve-pour-casques-stax-t30052030-105.html)
(NB: for memory, the combo RKV-WEE showed in a comparative amp realised in September 2013 (in blind procedure) in overall viewing, a sound quality similar as the SRM-727 amp and the Electra amp, and greater than that of SRM-007t2 amp) (reference : http://www.head-fi.org/t/681814/amplifiers-shootout-for-stax-009-eddie-current-electra-audiovalve-rkv-wooaudio-wee-stax-srm727-srm007t2 )).
This conclusion focuses on the headphones Stax SR-009 (and probably also the Stax SR-507) due to a remarkable overall synergy.
(listening both very transparent, detailed, natural, non boring and very faithful to the reproduction of timbres (tone) of instruments and voice).
Also, with the RKV amp (+ VERTO) no sound "typical tubes" (hot and colorful); on the contrary, sound extremely neutral, faithful and especially enjoyable to listen to with this combo.
Eric
: http://www.msbtech.com/products/master.php?Page=platinumHome . The general manager (larry gullman) was at the show and very easy / fun to talk to. He seems quite obsessed with the design of his products. The flagship 8 ch. balanced dac foregoes usage of fancy display to minimize noise to the rest of the circuit, using leds instead that are refreshed at the internal clock rate. Anectodical but an example of how far they think about the problem!
