SPL Performer s900 red

SPL Performer s900: stereo power amplifier

Fitting 200 watts per channel into an eleven-inch-wide enclosure, narrower than most audio components, is an engineering challenge. SPL, founded in 1983 to equip recording studios, has met it with its Performer range. The s900 sits in the middle of this range and adopts the design of its bigger sibling, the s1200, in a reduced format. Its distinctive feature lies in an unusual internal voltage.

120-volt VOLTAiR technology

Most operational amplifiers operate with a supply voltage of plus or minus 15 volts. SPL manufactures its own, the 120V SUPRA, capable of operating at plus or minus 60 volts, four times the standard for semiconductor components. This high operating voltage is what the brand calls VOLTAiR.

The benefit can be heard. Between the average level of a track and the point at which the circuit saturates, an amplifier retains a margin called dynamic headroom. By raising the internal voltage, the s900 handles the strongest musical peaks while remaining far from this limit. Its components operate within their optimal range rather than at the edge of saturation, where distortion artifacts audible on amplifiers pushed to their limits arise.

Two separate stages for voltage and power

The s900 physically separates voltage amplification from power amplification. Each stage has its own feedback loop, the mechanism that corrects discrepancies between the input signal and the output signal. This separation prevents signals reflected by the speakers from travelling back to the input stage and disrupting signal processing.

The output stage operates in Class AB, a mode that combines the efficiency of Class B with some of the linearity of Class A. It is a common compromise in hi-fi: less heat dissipation than pure Class A, with distortion that remains controlled even at high power.

Power suited to most speakers

Into 8 ohms, the s900 delivers 2 x 200 watts. Output rises to 2 x 370 watts into 4 ohms and 2 x 420 watts into 2 ohms. It should be noted that power does not double when impedance is halved: the power supply is not designed to behave as an unlimited current generator. In practice, the s900 drives the vast majority of speakers with ease, whether compact models or floorstanders of normal sensitivity. The least sensitive loads and those with the most demanding impedance remain the domain of the more powerful s1200.

The damping factor exceeds 280 into 8 ohms. This value reflects the amplifier’s ability to control driver movement, especially in the bass, where the cone tends to continue moving after the signal ends. An output impedance below 0.035 ohms points in the same direction: firm control over the cones.

A linear power supply with toroidal transformer

The power supply is linear, with a shielded 866 VA toroidal transformer and 48,000 microfarads of filtering capacitance. SPL rejects switch-mode power supplies in favour of this bulkier, heavier approach. The role of this energy reserve becomes apparent during transients: when a track suddenly demands a great deal of current, such as a bass drum hit, the capacitors release stored energy without the voltage sagging. This partly explains the 14.6 kg weight for such a compact enclosure.

XLR and RCA inputs, sensitivity adjustment

The s900 accepts a balanced XLR source and an unbalanced RCA source, selected by a switch on the rear panel. This dual input makes it compatible with most preamplifiers, without an adapter.

Each channel has an input sensitivity adjustment, adjustable from 0 to -5.5 dB in 0.5 dB increments. This is not a volume control, but a fine attenuation set once to match the gain to the preamplifier. SPL prefers this solution to a potentiometer permanently placed in the signal path. The adjustment is useful for balancing two amplifiers in a bi-amp setup.

A 12-volt trigger input (AMP CTL, on a 3.5 mm jack) allows an SPL preamplifier, such as the Director Mk2, to automatically bring the s900 out of standby and return it to standby. In standby, power consumption remains below 0.3 watt. The speaker terminals accept banana plugs as well as bare cables up to 4 mm in diameter.

A compact format in the Performer range

The s900 measures 278 mm wide, 114 mm high and 345 mm deep, weighing 14.6 kg. This width of around eleven inches sets it apart from the seventeen-inch standard that governs most hi-fi furniture and racks. Used alone alongside full-width components, the enclosure may look out of place. However, it stacks naturally with other SPL components in the Professional Fidelity series, such as the Director Mk2 preamplifier or a phono preamp, which share its dimensions.

Three finishes are available—black, red and silver—thanks to an interchangeable front panel fitted into a central groove. Manufacturing takes place in Germany. SPL fits a significant proportion of components using through-hole mounting, a technique that allows the selection of parts chosen by ear during development.

On the safety side, a circuit monitors the presence of DC current at the output and disconnects the power stage if necessary: the Protect indicator then lights up red. A thermal sensor placed on the heatsinks switches off the amplifier in the event of overheating, indicated by the Temp indicator. The s900 is cooled by convection, without a fan, and therefore requires some ventilation space around it.

Technical Specifications

General

• Class AB stereo power amplifier
• Proprietary SPL VOLTAiR 120 V technology
• Separate-stage design for voltage and power amplification

Highlights

• High power suitable for most Hi-Fi speakers
• VOLTAiR 120 V technology providing very high dynamic headroom
• Low-distortion Class AB amplification
• Balanced XLR and unbalanced RCA inputs
• Input selection via rear switch
• Input sensitivity adjustment from 0 to -5.5 dB in 0.5 dB steps
• 12 V Trigger input (AMP CTL) for automatic standby mode
• Compatible with SPL preamplifiers and third-party equipment

Audio Performance

• RMS power:
  • 2 × 420 W into 2 Ω
  • 2 × 370 W into 4 Ω
  • 2 × 200 W into 8 Ω
• Harmonic distortion (1 kHz):
  • < 0.07 % into 2 Ω
  • < 0.06 % into 4 Ω
  • < 0.04 % into 8 Ω
• Frequency response (-3 dB): 10 Hz – 80 kHz
• Gain: 26 dB
• Output voltage:
  • 112 V peak-to-peak
  • 40.2 V RMS
• Output impedance: < 0.035 Ω
• Damping factor (8 Ω, 1 kHz): > 280
• Signal-to-noise ratio (A-weighted): -123 dB

Connectivity

• Inputs:
  • 1 balanced XLR pair
  • 1 unbalanced RCA pair
  • XLR / RCA input selector
• Speaker outputs:
  • Binding posts compatible with banana plugs
  • Screw terminals accepting cables up to 4 mm
• AMP CTL 12 V Trigger input (3.5 mm jack)

Settings

• Input sensitivity: 8 dBu
• Level adjustment:
  • From 0 dB to -5.5 dB
  • In 0.5 dB steps

Power Supply

• Linear power supply with shielded toroidal transformer
• Filter capacitance: 48,000 µF
• Toroidal transformer: 866 VA
• Input stage supply voltage: ±60 V
• Power stage supply voltage: ±64 V
• Relay / LED / Trigger supply: +12 V
• Mains power supply:
  • 230 V AC / 50 Hz
  • 115 V AC / 60 Hz
• 230 V fuse: T 4 A
• 115 V fuse: T 8 A
• Maximum power consumption: 900 VA
• Idle power consumption: 20 W
• Standby power consumption: < 0.3 W

Protection

• Protection against direct current (DC)
• Thermal protection with heatsink monitoring
• Automatic shutdown in case of overheating
• Protect and Temp diagnostic indicators

Dimensions and Weight

• Dimensions (W × H × D): 278 × 114 × 345 mm
• Net weight: 14.6 kg
• Weight with packaging: 15.8 kg