SAE 2500 / XXV power amplifier

Solid State Power Amplifier

At  the very top of our amplifier line are the Mark 2500 (XXV) Professional Power Amplifier , with 300 watts per channel, min. RMS into 8 Ω  at less than 0,05% Total Harmonic Distortion , both channels driven, 20 Hz to 20 kHz), these amplifiers represent years of sound reinforcement experience. They are offered in our traditional satin-gold and black version (Mark XXV) for home music systems, and the professional version (Mark 2500) complete with black rack-mountable front panel and custom handles. They are easily transported since they weigh less than sixty (60) pounds each.

Along with the fully complementary input circuitry designed into all SAE amplifiers, a unique Parallel-Series-Output circuit utilizes 16 output devices and combines the inherent advantages of both parallel and series connected output stages.

Unit-to-unit repeatability, ease of service, and minimal wiring are the benefits accuring from plug-in drive, input, and relay boards. A massive heat sink of 1/8" aluminum, and built-in forced-air cooling ensure cool operation under the most demanding power and load conditions.

Amplifier Protection

Four means of protection are included: Avolt/amp limiter which senses load impedances below 2 Ω  (without being affected by reactive loads such as electrostatic speakers which are rated at 4 Ω  or higher). A thermal cut-out device  for sensing  of abnormal heat-sink temperature, 4 B-supply fuses, and an AC-line fuse.

Circuitry

The Mark 2500 (XXV) are completely balanced from input to output utilizing full complementary double differential inputs, complementary drives and full complementary series connected output stages. Eight output devices per channel (in paralll/series) are utilized for higher than normal safe-area operation. The output devices are run so conservatively that failure is improbable.

Feedback Level Controls

This type of level control assures a constant input impedance of 50  kohm and reduces the noise figure to less than -100 dB below rated output at all positions.

Meters

The meters in the Mark 2500 (XXV) are direct power reading in Watts. They are extremely useful and easy to read requiring no conversion charts. A dB reference is provided for professional applications. In conjunction with the range switch, they cover output levels from 20 mW to over 400 Watts

Plug-in Board Design

Easily accessible input, drive , and relay boards make the amplifiers both simple to service and consistant in performance from one amplifier to another in production. All boards are constructed with military-grade, FR-10 glass-epoxy material to ensure circuit integrity.

Loudspeaker Protection

In case of subsonic pulses or ±DC outputs the amplifier incorporates a relay activated disconnect circuit, which will automatically disconnected the loudspeakers from the amplifier. Used also during turn-on prevent annoying turn-on transients, this dual relay circuit incorporates features unique to SAE products. The most important of these alleviates high frequency distortion developed by the relay due to "contact diode effect"

Power Supply

The engineering goal was to develop a transformer which was small in size yet have a greater copper-to-iron ratio resulting in better regulation. This was achieved by using thicker square-section copper windings and special laminations which  have extended window openings effecting lower heat generation and greater efficiency. This transformer which is manufactured within the SAE plant is coupled to 4 computer-grade capacitors totaling 40,000 microfarads. This combination creates a power supply which will very no more than 10% from no load to full load.

Forced Air Cooling

A quiet, high-output integral fan provides the necessary cooling for continuous operation under demanding situations or confined installations. The Mark 2500 is equipped with an extra high-speed fan.

Specifications

Continuous Power Output per Channel (20 Hz -20 kHz both channels driven, 8 Ω , RMS min.):  300 Watts at 0,05% (T.H.D)

45Continuous Power Output per Channel (20 Hz -20 kHz both channels driven, 4 Ω , RMS min.):  450 Watts at 0,1% (T.H.D)

Total Harmonic Distortion (from 20 Hz to 20 kHz at 250 mW to rated power)

 at 8 Ω :  0,05% Max.

 at 4 Ω :  0,1% Max.

Intermodulation Distortion (from 250 mW to rated power at 8 Ω  with any 2 mixed frequencies between 20 Hz to 20 kHz at 4/1 voltage ratio):  0,05% Max.

Frequency response (at rated power):  20 Hz - 20,000 Hz ±0,25 dB

Noise:  greater than 100 dB below rated power

Transient Response of any Square Wave:  2,5 microseconds rise and fall time

Slew Rate:  40 Volts per microsecond

Stability:  unconditionally stable with any type of load or no load inclding full-range electrostatic loudspeakers

Damping Factor:  150 Min (100 Hz)

Input Sensitivity:  1,84 V RMS for rated output at 8 Ω

Input Impedance:  50 k Ω

Semiconductor Complement:  46 Transistors, 49 Diodes

Overload Protection  

Low impedance electronic-sensing circuit limits with output current below 2 Ω  without limiting with 4 Ω  or higher (or reactive loads)

Thermal sensing of inadequate ventilation

Internal B+, B- suppy fuses

Loudspeaker protection

Relay circuit protects loudspeakers fom low frequency oscilations and plus or minus DC output. Five second turn on/off delay eliminates on/off disturbances

Power Requirements:  110 - 125 V, 50/60 Hz 100 watts at idling to 1100  watts at rated output

Dimensions (W x H x D):  483 x 178 x 400 mm ( 19" x 7" x 15,75") excluding handles controls, and connections)

Weight (Shipping):  30,9 kg (68 pounds)

Options:  Walnut Cabinet WC-25