Our SPS preamplifier is the best basic preamplifier we know how to make and where only a single tape recorder is used will handle virtually all of the requirements of an audiophile working with carefully chosen records and tapes -the former played on a normal output level phono cartridge.

Where a low output level moving coil cartridge is used, our DW 535 pre-preamplifier is ideal, preserving the very low distortion characteristics of the moving coil cartridges. While expensive, it does the job without compromise in circuitry which could lower the price but which would be easily audible as lowered definition or a muddy mid range.

As an alternate, and where two tape machines are used, our SPL preamplifier uses a circuit derived from the basic circuit of the SPS, but which requires considerably more circuit board room to ensure proper stability margains at ultrasonic frequencies. It has the DW 535 pre-preamplifier built in, and has a separate low power stereo power amplifier which permits it to drive even electrostatic earphones.

For frequency response corrections on material of musical merit but less than ideal recorded characteristics, our SG Graphic Equalizer is the Black Box of choice, permitting exacting frequency compensation with the ability to filter out scratch or rumble.

The second missing item is the Power Amplifier. In the past we have built power amplifiers to order, but have felt that it must be possible to build a unit having total reliability with exceptional performance. We have never made any secret of the fact that as yet we have not found such a unit on the market. We do think, after several false starts that we at least have the circuit and the mechanical packaging system - but the most we will say is that it's in the works.

This brings us to our speakers - which started us in business. It is not generally realized that the very first full range electrostatic speakers manufactured in North America in 1958 were designed by personnel now with this company. However our designs diverged from the mainstream in 1965 so that our full range units are unique in that they have no crossover networks from below 30 Hz to above 15+ kHz - about nine octaves. Thus, with all cells carrying the entire range there is Total Coherence of sound without phase distortion to modify wavefronts, and to introduce coloration.

In spite of this, Patented operating principles allow our 3rd Generation Speakers to operate at concert-hall levels at reasonable efficiencies. This is expensive, but we have tried to keep the designs as simple as possible, paying a premium to obtain components which behave as close to the ideal as possible. In this respect we feel that we have solved problems both psycoacoustic and electroacoustic that our competitors don't even realize that they are going to have to solve.
 
 
 
 

One is a distinctive black-cloth belted design, capped top and bottom with rosewood and having a sunken black band bisecting the cabinet around the sides and across the top. Internally, the driver cells are hermetically sealed into a welded steel frame with mylar front and rear diaphragms.

The other is derived from the enclosure used for our Mark 2 and 2A units. This uses a 1/8" thick aluminium extrusion as the case. It is inert gas welded into an exceptionally rigid frame, and lined with mastic bonded dampening material. The frame is pebble finished in black anodizing having a muted sheen which does not fingermark. This style of cabinet permits units to be stacked in multiple for sound reinforcement or other professional use. It is admittedly too modern for some environments, but totally functional.
 

We don't attempt to design our equipment for everyone. If you have a feeling that part of the prestige of owning a stereo system comes from the complexity of the control panel, then you probably wouldn't be happy with our equipment. But if you're choosing components for what they don't do to excellent sound source material, then our equipment is matchless.
 

Noted for exceptionally low distortion and ultra high definition, a state-of-the art device employing discreet semiconductor augmented integrated circuitry.

 

Inputs: Low level magnetic, Load Impedance approx. 8.2 ohms; 47 ohms or 100 ohms.
Outputs: Z-out ranges from 200 ohms to 5 kOhm depending upon setting of internal level adjustments.
Input Sensitivity: 50 uV for 2.5 mV out, 200 uV for 10 mV out.
Input overload: 200 mV
Distortion: Under 0.002% at Rated output 20-20,000 Hz.
Frequency Response: ± .1 db 30 hZ to 130 kHz, ± 1.5 dB 9 Hz to 500 kHz.
Square Wave Performance: Rise time under 600 nanoseconds. Settling time under 400 nanoseconds for 1% error band.
Overshoot: None
Dimensions: Main Case: 2" x`10" x 7"
Transformer case: 3 "  x 2 1/2" x 2 1/2".  Weight: 31/2 lbs.
 

Inputs: Low Level Magnetic 1,2; Normal Magnetic 1,2; Tuner, Aux. 1, Aux. 2, Tape 1, Tape 2.
Input Sensitivity: Low Mag. 30 uV for 1.5 v out, Normal Mag. 1.5 mV for 1.5v out, High Level &Tape, 400 mV for 1.5vout.
Phono Overload: Low Mag. 2.5 mV to 100 mV (depending on internal gain set), Normal Mag. 130 mV.
Maximum output: 25 volts peak to peak.
Distortion: Harmonic, well under 0.002% 20 to 10 kHz @ 1.5 v out
Intermodulation, well under.002% @ 1.5 v out. 
Signal to noise ratio:
Low Mag. better than 70 dB referenced to 10 mV at output of Pre-preamp, RIAA weighting. 
Normal  Mag. better than 80 dB referenced to 10 mV at input.
Frequency Response: High Level, ± 1.6 dB 1 Hz to 0,7 mHz.
Low Level Input Impedance 8.2 ohms or 47 ohms.
RIAA Equalization Accuracy: ± 0.15 dB 40 Hz to 20 kHz.
Square Wave Performance: Rise time: High Level In: Under 950 nanoseconds, Norm Phono Input: Under 1100 nanoseconds, Low Level Phono In: Under 1600 nanoseconds
Settling time: High Level In: Under 900 nanoseconds.
Normal Phono Input: Under 1300 nanoseconds.
Low Level Phono Input: Under 1500 nanoseconds, 1/2% error band.
Overshoot: None

Dimensions: Panel 13"x6 1/2", Case 11" x 5 1/2" x 10", Trans- former case 4" x 6" x 6". Total weight under 18 lbs.
 

Connections: Preamplifier input and output; Tape 1 in, Tape 2 in, Aux 1 in, Aux 2 in, Tape and Aux. inputs brought out on top of unit using RCA-type Jacks, and on front panel using earphone type jacks. Tape 1 out, Tape 2 out, Aux. 1 out, Aux. 2 out. Tape and Aux outputs brought out on top of unit using RCA-type jacks, and on front of unit
using Earphone type jacks.
Operating Level: 1.5 Volts RMS in/out all controls flat.
Maximum Output Level: 15 volts p. p.
Distortion: Harmonic, under 0.007%.
Intermodulation under 0.01%.
Signal to noise Ratio: Better than 90 db at 1.5 volts.
Frequency Response: (all controls flat) ± 1.5 db 10 Hz to 700 kHz.
Square Wave Performance: Rise Time under 1200 nanoseconds (all controls flat). 
Settling Time under 1200 nanoseconds for 1% error band. 
Overshoot: Under 2% at 20 kHz. 
Controls: 8 Pairs of center detent slide controls (left 
right channels brought out side by side) controlling boost and cut (up to 12 db cut or boost) at center frequencies of of 45 hZ 100 Hz, 225 Hz, 500 Hz, 1150 Hz, 2500 Hz, 6000 Hz & 13,500 Hz.

 Dimensions: Panel 13" x 6 l/2", Case 11" x 5 1/2" x 10". Wt.12lbs.
 

It is difficult to express the performance of these speakers in specifications, much of the psycoacoustic art used in their design is apparent only upon listening, and no definitive parameters as yet exist in this area of perception. As an example, the large radiating area used results in a very low sound gradient in the listening field of the speaker, that is there is only a very small level change from the area right in front of the speaker, to the area at the rear of the average an actual listening room. This approximates the gradient field in an actual concert land this absence of "acoustic glare" results in an apparent ability of the listener's hearing to increase the apparent ability of the listener's hearing to increase its discrimination between subtle tonal differences, and do this without listening fatigue. The resultant sound has an effortlessness which is lost where the sound is projected from 10" diameter holes as in most speakers. (or 14", or 8" as you will have it). The combination of a crossover free 9 octave region, the very wide frequency response, and the excellent high frequency dispersion result in a sound that is closer to the source in fidelity than ever before achieved.
Operating Level: Average levels of 100 dB can be realized in the listening field with amplifier powers of 250 watts/channel (at 4 ohms). The speakers are of 
capable of producing peak levels of 115 db when driven from stable amplifiers. We suggest the use
an amplifier with sufficient power that it does not enter the clipping region of protection, as the excellent transient response of the speakers will make this all too obvious. Thus a 200 watt per channel amplifier wil be sufficient for most rooms, unless very high sound-pressure-levels are necessary.

Input Imperence: The input impedance (contraryto general belief) is quite smooth from 600 Hz through 14kHz being 2.7 ohms ± 0.2 ohms.This median level will rise to approx. 3.8 ohms after 4 months of operation. The anomalies in the impedence response is a 70% rise at 16 kHz (the upper crossover point to the ultrasonic units), a rising characteristic above 25 kHz (approx. 17 ohms at 100 kHz) and a smooth rise below 600 Hz which peaks at about 22 to 40 ohms depending upon room loading at 110 Hz. At low frequencies the impedence does not drop below 8 ohms (even at DC).

Frequency Response: With the necessary qualification that frequency response below 100 Hz will be dependent on its smoothness on room characteristics and speaker placement, it is generally possible to obtain a response lying within ± 4 dB from 30 Hz to 18 kHz. The high frequency response smoothness will be somewhat dependent upon the number and level of room reflections.

Distortion: Generally under .1%, there is a rise above 10 kHz to .3% at 16 kHz, and a rise below 55 Hz to about 2% at 37 Hz, at a level of 85 dB 1 meter on axis. We have found that the most prominent distortion characteristic noticed will be the transient intermodulation distortion characteristics of the power amplifier used. Having tested a number of commercially available power amplifiers we have found that there is far less ringing at square wave inputs (from 5 kHz to 20 kHz) than would be inferred from the trade literature and power amplifier reviews.

Size: Aluminum  1 meter x 1 meter x 24cm.
                           39 3/8” x 39 3/8” x 9 1/2” 
                           Approx. 64 lbs/speaker
 
Size: Wood Trimmed Steel 1.05 meters x 0.98 meter x 24 cm
                               41” x 39” x 91/2”
                               Approx. 104 lbs/speaker

ST-300 A 10 1/2” H x 19” W x 11” D same
                   26 cm x 49 cm x 27 cm same
 

The ST-300 A unit comes complete with 25 foot cables for each speaker and weights 105 lbs.