Prisma 750 Monoblock Power Amplifier

The Prisma Series 750 is a high quality, reference, 750W monoblock hifi audio power amplifier, incorporating true-balanced circuit topology and custom designed toroid power supply.

General Features

Rugged Build Quality

Mechanical strength has been a hallmark of Perreaux products since the company first started production back in 1974. The concept behind the physical design and construction is that each structural member should contribute to both rigidity and performance.

Ultra Stiff Power Supply

The 750 incorporates a massive custom designed, toroidal power transformer, employing unusually heavy gauge wire that reduces copper losses to a minimum. An electrostatic shield prevents AC line borne interference from entering the signal path. The power supply filter capacitors, totaling 60,000uF, have exceptionally low inductance and internal resistance. They charge and discharge in response to load demand far more rapidly than conventional storage capacitors and are capable of delivering the instantaneous current required by the output stages, providing optimum dynamic range and transient response. The wiring from the power supplies to the output boards is designed for unimpeded transmission of the required current and voltage and utilizes heavy gauge, tinned copper wire cables. Since power supply leads radiate at signal frequencies, all wiring is carefully loomed to minimise this effect.

Hybrid Class-A/AB

The bi-polar transistors used in the 750 are operatin in Class-A. This avoids the crossover notch distortion and the resulting odd-order harmonics present, to some degree, in all other classes of operation. The devices used in the 750 output stage are MOSFETs, which with high quiescent current circuitry, are run in the equivalent of Class-A to 10 watts. Beyond this point the output class is technically Class-AB (hence the hybrid nomenclature), but with a major difference. The combination of MOSFET characteristics and their application in this circuitry, result in crossover distortion so minimal that it is virtually non-existent.

Bi-Wiring Made Easy

2 pairs of binding posts make bi-wiring speakers as simple as "A-B-C".

MOSFET Output Stage

The 750 output stage takes full advantage of the unique qualities of MOSFET devices and in many ways they are superior to bi-polar transistors. A major advantage is their tendency to draw less current over a large section of the power bandwidth as their temperature rises (Negative Temperature Coefficient), hence self stabilising thermally, whereas bi-polar transistors draw more current as their temperature rises (Positive Temperature Coefficient) and protection circuits become mandatory to prevent thermal runaway and eventual self destruction. MOSFETs have the ability to swing fully across the amplifier’s internal DC voltage and are therefore true "rail-to-rail" devices. Using MOSFETs encourages the highest performance from the balance of the internal amplifier circuitry.

Multiple Protection Systems

The 750 incorporates a full range of protection circuits, isolated from all signal carrying circuits via opto-couplers. However, these circuits are aimed at ensuring an extremely high safety margin for these high-powered products rather than as a mandatory addition to correct for poor or overloaded circuit topologies.

Soft Start

The 750 utilises soft start circuitry to protect the fuses and/or circuit breakers in your home’s mains power supply. Without this circuit, the huge inrush current required to charge the 60,000uF of power supply capacitance, would blow the fuses or trip the circuit breakers.

Earthing

We pay particular attention to designing the product to ensure maximum separation between internal signal and power earths, only meeting at a central starred point.

Highest Quality PCBs and Components

Quality fiberglass PCBs, featuring heavy copper tracks and high quality audiophile grade components, are used throughout the 750.

User Controls

Balanced/Unbalanced Input Select
Rear Mounted Power Switch
Earth Isolation Switch

I/O Compliment

1 Unbalanced Input (RCA)
1 Balanced Input (XLR)
2 pairs Speaker Binding Posts
2 Remote Trigger Inputs (5VDC)
Continuous Power Ouput: 750Wrms into 8Ω
  1300Wrms into 4Ω
Total Harmonic Distortion (THD+N):  
  Typically 0.008% @ 1kHz into 8Ω
  20Hz to 20kHz <0.04% into 8Ω
Frequency Response: 20Hz to 25kHz, ±0.25dB
Signal to Noise Ratio  
  Rated Output (unweighted): 100dB
Dynamic Headroom (rated with music): >1.1dB
Maximum Current Output: 160A
Damping Factor: >700 @ 1kHz into 8Ω
Input Impedance:  
  Unbalanced 22kΩ
  Balanced 3.3kΩ
Input Sensitivity:  
  Unbalanced 1.50Vrms
  Balanced ±0.77Vrms
Dimensions:
  Width
  Height
  Depth

430mm (16.9")
186mm (7.3")
497mm (19.6")
Weight: 31.0kg (68.3lb)

Brochures & Manuals

Manual for Prisma 750

2015 PDF 659 KB

Reviews