Stax SRM - 727 II

■ New vistas for the non-feedback output stage
The first performance feature required of audio equipment is the capacity to convert air vibrations into sound waves so that the slightest signal can be appropriately heard by the ear. This means that an essential condition of the vibrating medium, i.e. the diaphragm, in the speaker which constitutes the system of conversion from electrical signal to air vibration is that it needs to be as light as possible. Divided vibration, which is unavoidable in the case of point drive, is possible, as is also ultra-miniaturization if total drive is possible. Moreover, if headphones are used, there will be reduction in the mass of air that needs to be driven, creating a more ideal situation. The electrostatic (condenser) type is the system that comes closest to this ideal. STAX refers to speakers of this type as “earspeakers” and has continuously sought for the ideal form. Since a dedicated unit is needed for drive purposes, the development of such units is equivalent to the pursuit of high sound quality in the electrical signal system. The matching drive system and the amplifier system are used for driving electrostatic speakers, and in the case of amplifiers it is possible to build circuits by means of vacuum tubes. In the case of electrical signal systems too, it is generally known that sound quality varies extensively depending on the circuit configuration, parts, etc. Which should be selected? There is also the element of musicality that needs to be taken into consideration when determining the sound that is the be-all and end-all of audio. The new SRM-727II employs semiconductor output drive stage and non-feedback (NON-NFB) output stage for the first time ever in a STAX driver unit. A pure balance DC amplifier configuration is used for the large current emitter follower Class A output stage. A significant increase in dynamic range especially in the upper frequency has been achieved. A high level of sound purity is achieved through the simple two-stage amplification circuit with low-noise FET input stage. This is a brand new driver unit that opens up new vistas for the sense of mass and textural expression supported by a virtually unparalleled degree of resolution, a natural sense of openness, and a powerful power section.
■ Features
●The electrostatic method is a playback method which involves the installation of drive electrodes on either side of a high-polymer film diaphragm with a thickness of only a few microns into each of which a plus signal and a minus signal are fed. This means that XLR connection with a pure balance output CD player makes it possible to listen to the original sound permitted by the balance system without a conversion circuit.
●The output stage has been incorporated by newly developing a non-feedback (NON-NFB) large current emitter follower Class A amplification circuit. This makes it possible to achieve a much more vivid and dynamic sound quality.
●The emitter follower at the output stage makes it possible to achieve lower impedance. A major expansion in dynamic range in the upper frequency has also been achieved.
●DC amplifier configuration without the use of a coupling condenser.
●A high sound quality, low noise FET is used at the input stage with a simple two-stage amplifying circuit. A natural and pure sound quality with high information quantity is realized.
●When connecting your favorite attenuator or pre-amplifier, a direct switch that avoids duplication of the volume unit is included.
●Careful selection of parts with high consideration on sound quality, performance, and the environment.
●In order to avoid magnetic distortion, the chassis is made of aluminum materials, thereby contributing to purity of sound.
●Amplification is set at a low level, thereby facilitating subtle adjustment of volume during XLR input and when using high-output CD players, etc.
●Parallel output terminals (RCA) are included to enable the signal to pass through.
●A new panel face has been designed with rounded corners and a silver brushed finish.
●Earspeakers of PRO bias (5-pin) type can be used.
●Control functions are restricted to the volume, and the input uses a single selecting system between RCA or XLR. This is a drive unit for exclusive use with earspeakers with emphasis placed first and foremost upon purity.
■ Specifications
●Frequency response DC-115 kHz (SR-007 or SR-404, when using one unit)
●Rated input level 200 mV / 100 V Outputs
●Maximum input level 30 V r.m.s. / at Minimum volume
●Amplification 54 dB (x 500)
●Total harmonic distortion 0.01% / 1 KHz, 100 V r.m.s. output SR-007 or SR-404 Signature, when using 1 unit
●Input impedance 50 KΩ / XLR balance 50KΩ×2
●Input terminals RCA×1 or XLR×1 (balanced)
●Maximum output voltage 450 V r.m.s. / 1 KHz
●Standard bias voltage DC 580 V
●Power voltage 120-240V ±10%, 50 to 60 Hz (adjusted for your area)
●Power consumption 55 W
●Temperature range for use Between 0º and 35ºC, max. 90% (no condensation)
●External dimensions 195 (w) x 103 (h) x 420 (d) mm (including VR knob and pin jack (20 + 10)
●Weight 4.7 Kg
●Vacuum tubes 6FQ7/6CG7 type x 4

■ The essence of wide band range.
 
The movement toward wider band ranges in the world of audio is evident. For example, in the appearance of SACD and DVD audio, it is much like the mega-pixel of CCD light-receiving elements in digital cameras. What will CCDs, which have already topped the 10 million mark, carry out? It isn’t simply a question of images not deteriorating as a result of enlargement. The real benefits come from the ability to show every single human eyelash with absolute clarity and from the richness of gradation of shading. Electrostatic earspeaker systems are being reassessed as next-generation audio systems that make it possible to achieve an astonishingly wide range and now, their real value is being recognized. Vacuum tube output stage transformer made possible by use of the electrostatic method, ideal pure balance operation with no need for an inverted circuit, a DC amplified configuration… The new SRM-006tII has evolved into a new territory with wider band range and detailed refinements.
 
■ Features
 
The SRM driver unit shows the true value of electrostatic earspeakers.
Pure balance, DC amplifier configuration.
The key concept is the output stage employing a high sound quality vacuum tube 6FQ7 (6CG7), and further refinements have been introduced into all the individual parts.
A wider range than ever before. There’s no end to technical evolution.


Wide range: In order to make maximum use of the wide-range properties of SACD and DVD audio, the circuit have been constantly been revised, resulting in a wider than ever replay frequency range.
 
Heater power supply: Adopting a rectifier circuits combining low-noise, low-loss Schottky barrier diodes and large electrolytic capacitors. Low-ripple DC power source improves the SN ratio.
 
Output stage: A simple two-stage amplifier configuration using a high-resistance dual three-pole tube 6FQ7 (6CG7) results in straightforward properties that are transparent and clear sound quality.
 
Input: It’s possible to switch between three systems (two RCA input systems and one XLR input system). Pure balance circuit: The electrostatic transducer is driven by electrodes set on both sides of the diaphragm which carry the push-pull signals. This is thus virtually the only replay system that enables the listener to enjoy replay unique to balance transmission without the need to pass through a transformer or an inversion amplifier. The input stage makes use of a hand selected low-noise FET. Unit also employs a total of six acoustic high sound quality relays (three on both sides). Simultaneous switching of the hot side and the cold side of the two-system RCA input means that the input source is isolated of direct current. Almost no interference between different devices.
ipped with parallel output terminals: Input 1 can be directly connected to for example an SACD player for pure quality listening with a shorter signal path, while the output connected to a pre-amplifier or power amplifier with volume control simultaneously.
Use of high sound quality 4-stage volume control: Connection is possible with line level devices such as CD players including XLR.
Front panel: Brushed Aluminum silver finish and designed with rounded panel corners.
 
■ Specifications
●Frequency response DC 80 kHz / +0, -3 dB (in the case of use of one SR-404 unit) 
●Rated input level 200 mV / 100 V Outputs
●Maximum input level 30 V r.m.s. / at Minimum volume
●Amplification 54 dB (x 500)
●Total harmonic distortion distortion: max. 0.02% at 1 kHz 100 V r.m.s. (in the case of use of one SR-404 unit)
●Input impedance 50 KΩ / XLR balance 50KΩ×2
●Number of inputs RCA×2, XLR×1 (balanced)
●Maximum output voltage 300 V r.m.s. / 1 KHz
●Standard bias voltage DC 580 V
●Power voltage 120-240V ±10%, 50 to 60 Hz (adjusted for your area)
●Power consumption 49 W
●Temperature range for use Between 0º and 35ºC, max. 90% (no condensation)
●External dimensions 195 (w) x 103 (h) x 375 (d) mm (including VR knob and pin jack (20 + 10)
●Weight 3.4 Kg
●Vacuum tubes 6FQ7/6CG7 type x 2

Stax SRM - 323 II

The God of beauty lodges in subtle signals.
 
Drawing forth the latent performance of devices to achieve the ultimate in sound quality is one of the pleasures experienced by audiophiles. The attraction of high-end devices in particular perhaps lies in the scale of the expectations that they hold. For example, an important topic is the reproduction of three-dimensional information that recreates the width and height of space. The task is how to recreate in a full and detailed manner the complete tonal expanse and sound that escapes upwards. Because this information is extremely subtle and detailed, there is a need for a particularly light and high-speed diaphragm. A large output amplifier with a large-diameter woofer and a large power section might also be imagined for the reproduction of deep and low sounds. The electrostatic audio pursued by STAX employs an almost ideal method of reproduction involving the total full-range drive by means of static electricity voltage changes using a high-polymer film diaphragm only a few microns thick that realizes the ultimate in lightness. Subtle changes in the music are converted into air vibrations with no loss and no addition of distortion. It takes over the features of a reference monitor device during recording and disc production. Containing a large, high-speed, large-capacity power transformer, it depicts the texture and tone of musical instruments in a powerful manner and has the capacity to recreate passages of low sounds dynamically without falling into heaviness. Through the use of a simple new circuit configuration and high sound quality parts also considerate to the environment, the STAX electrostatic earspeaker drive unit SRM-323II achieves an even more natural spatial reproduction capacity. The sound quality is indisputably at the top end of the scale.
 
■ Features
 
●Significantly strengthened power transformer. An enormous expansion in dynamic range has been achieved by increasing speed and dynamic range.
●An emitter follower is used at the output stage to achieve low impedance. A major expansion of dynamic range in the upper frequency has been achieved.
●A high sound quality, low noise FET is used at the input stage, forming a simple two-stage amplification circuit. A natural, pure sound quality with a large quantity of information has been realized.
●In the case of the electrostatic type, the structure itself is balance operated. A balance circuit is formed up to the moment of conversion into air vibrations. This is the only system that makes it possible to enjoy the sound that characterizes the balance system.
●Solid state DC amplifier configuration not using a coupling condenser.
●Amplification is set at a low level, thereby making it easier to make subtle adjustment in volume when using a high-output CD player, etc.
●Volume is the only control function, and there is no input selector. This is a configuration with the emphasis on purity.
●In order to avoid magnetic distortion, the chassis is made of aluminum, thereby contributing to purity of sound.
●The unit is fitted with parallel out terminals (RCA) that allow the signals to pass through.
●Careful selection of parts with high consideration on sound quality, performance, and the environment.
●Earspeakers of PRO bias (5-pin) type can be used.
●A new panel face has been designed with rounded corners and a silver brushed finish.
 
■ Specifications
●Frequency response: DC- 60 kHz (SR-303, when using one unit)
●Rated input level: 200 mV with 100V output
●Maximum input level 30 V r.m.s. with volume at minimum setting 
●Amplification: 54 dB (x500)
●Total harmonic distortion max. 0.01% (1 kHz / during 100 V r.m.s. output) 
●Input impedance 50 kΩ (RCA) 
●Maximum output voltage: 400 V r.m.s. / 1 kHz 
●Standard bias voltage DC580 V (PRO bias)
●Power voltage AC120V-240V ± 10%, 50 to 60 Hz. (Adjusted for your area)
●Power consumption 29 W
●Temperature range for use Between 0º and 35ºC, max. 90% (no condensation)
●External dimensions 150 (W) × 100 (H) × 360 (D) mm (including knobs and terminals)
●Weight 2.9 Kg