Spectral DMA-90 Pair - Experience the Spectral Magic

Quick photos to give a general impression - better photos will be posted shortly.

A pair of Spectral's renowned compact amplifiers that have all the virtues the Spectral is known for at an affordable price. Spectral has increased prices for new models dramatically in last 5 years so quality used amplifiers are the best way to "join the club".

These were my introduction to Spectral and since then I've move up the line making these extras and in need of a good home.

Superb build quality using top class parts. Some minor signs of wear - only one noticeable blem on the faceplate of SN 801592, inevitable nicks on the speaker binding posts and RCA input jacks, and wear on the lettering by the binding posts as shown in the photos.

This pair has been used for Mono operation but can be changed to stereo with a simple switch for on the rear panel. Both have the low noise transistor update from the factory at a cost of $500 each. New boxes for each amp at the time of servicing.

Serial Numbers 801572 and 801592 that were originally sold as a mono pair by Goodwins.

Buyer responsible for shipping and transaction fees. NOTE - the shipping will be for 2 boxes. The listing details are for only 1 box so double any shipping estimates.

I'm planning to list my DMA-150S2 in the near future. This is essentially a stereo version of the DMA-360 Mk 1 as they share common boards and parts. Interior photos show boards labeled DMA 360 / 150S2. Contact me if you are interested in that amplifier.

From the Spectral website:

UNMISTAKABLY SPECTRAL
The DMA-90 is an unmistakably Spectral product in the iconoclasm of its approach and the elegance of its solution. Spectral amplifiers combine the oft-praised "musicality" and naturalness of the best tube designs with solid state's low level detail, powerful output capabilities and long term stability. The DMA-90's extraordinary accuracy in the measurable dimensions is matched by sonics of incomparable clarity, transparency and musical coherence.
Every new Spectral product marks a chapter in Spectral's ongoing quest to identify and eliminate subtle musical distortions and noise. The DMA-90's speed and wide stable bandwidth are signature traits of a Spectral amplifier. So also is circuitry incorporating design features and high technology components which reflect the most advanced practices of the electronic instrumentation, microwave communications and master recording fields.
Total electronic modularity is another Spectral hallmark. With its miniaturized components and convenient plug-in circuit modules, the DMA-90 is made for quick and efficient servicing. More importantly for the satisfactions of long-term ownership, these modular circuits also permit it to be upgraded as its underlying design evolves. The DMA-90's predecessor, the DMA-80, is fully upgradable to DMA-90 specifications and performance at moderate cost and with minimal disruption of the owner's listening enjoyment.
THE EVOLUTION OF THE DMA-90 DESIGN
The DMA-90 is Spectral's latest response to the distortion issues which gave rise to a generation of high-bias, Class A solid state amplifiers some year ago.
Class A works, but at considerable cost. It is very inefficient, generating large amounts of heat. Class A amplifiers require massive heat sinks and massive power supplies, therefore a larger chassis to support the whole operation. In circuit design, everything is related to everything else. Bigger parts and larger circuit configurations mean longer signal paths, which tend to radiate and interfere with one another.
The design of the DMA-90 is an exercise in taut, spare, sophisticated simplicity. The amplifier utilizes a floating bias current which follows the music signal. Because a relatively low bias is normally needed to keep the output devices within their linear range, the DMA-90 is quite efficient. It generates little heat. The DMA-90's rise and settle times are on the order of a few hundred nanoseconds - this is a few ten millionths of a second. This is well below the threshold of audibility.

THE MULTIPLE DIMENSIONS OF QUALITY
The DMA-90 is built to all applicable military and NASA specifications for parts quality, PC board fabrication, assembly and soldering. Selected stainless steel hardware, high purity copper conductors and high current gold plated connectors are used throughout. One percent metal film resistors are standard except where handmade, bulk metal film Vishay resistors are used in sensitive circuit positions. The lightweight, high quality aluminum chassis, with its Class A Polane paint finish and handmade, hand ground heli-arc welded seams contributes to the DMA-90's sonic performance by eliminating hysteresis, eddy current effects and the arcing which sometimes results from anodizing. The front panel is milled from solid imported Swiss stock and glows softly with Spectral's unique natural camera finish.
The DMA-90 is the amplifier of choice for speakers which present a complex load, such as fine electrostatic, hybrid and ribbon speakers. How an amplifier starts and stops - how quickly it stabilizes itself from inevitable overload - is especially important with speakers such as these, which react strongly, capacitively and inductively, with the amplifier driving them.
SPECIFICATIONS

DMA-90 High Resolution Amplifier

Power Output:
(continuous)
Stereo:

@ 8 ohms - 100 Watts RMS
@ 4 ohms - 200 Watts RMS
Bridged:
@ 8 ohms - 180 Watts RMS
@ 4 ohms - 250 Watts
Power Output
(minimum at clipping)
Stereo:

@ 8 ohms - 159 Watts RMS
@ 4 ohms - 240 Watts RMS
Bridged:
@ 8 ohms - 255 Watts RMS
@ 4 ohms - 306 Watts
Output Current:

22 Amps per channel
Frequency Response:

±0.1 dB, DC-150 KHz
±1 dB, DC-1 MHz
±3 dB, DC-1.8 MHz

Distortion:
Static:

Less than 0.015 from DC to 100 KHz Typically 0.009 @ 100 Watts RMS/8 ohms
Dynamic:
8 Tone Cluster Test 20 KHz @ 500 Hz separation; 0.01% 8 ohms; 0.015% 4 ohms

Speed:
Rise Time:

Less than 300 nanoseconds
Settling Time:
1.5 microseconds to -40dB
Slew Rate:
1000 volts/microsecond

Noise:
Signal to Noise:

97dB unweighted, 107dB ASA A
Crosstalk:
98dB @ full power 8 ohms

Input:
Impedence:

10K ohms in parallel with 100 pf
Sensitivity:
1.5 volts/nominal output

Power Supply:
Line Voltage:

100 volts, 120 volts, 240 volts (factory wired)
AC Voltage Range:
±10%
Maximum Consumption:
800 Watts
Quiescent Consumption:
125 Watts