SPL Phonos silver

SPL Phonos: The High-Performance MM and MC Phono Preamp

The SPL Phonos is a high-end phono preamplifier designed for moving magnet (MM) and moving coil (MC) turntables. Equipped with SPL’s exclusive VOLTAiR technology, this preamp delivers exceptional amplification of up to 71.5 dB for MC cartridges and 50 dB for MM cartridges, making it one of the most powerful phono preamplifiers on the market. Its meticulous design, based on Douglas Self’s recommendations, uses audiophile-grade Styroflex capacitors for precise RIAA equalization, ensuring natural, detailed, and dynamic sound reproduction.

Exceptional Amplification Technology

At the heart of the SPL Phonos lies VOLTAiR technology, which operates with a continuous voltage of 120 volts (+/- 60V), double the voltage of the best discrete operational amplifiers and four times that of conventional semiconductor amplifiers. This high operating voltage provides a dynamic range 12 dB higher, offering a natural and relaxed listening experience where every musical detail is preserved.

The Phonos employs an efficient two-stage concept: first amplify, then equalize. For active components, it uses SPL’s exclusive high-voltage operational amplifier modules, built with discrete SMD technology components mounted on small separate boards. For each channel, three of these modules generate a maximum total amplification of approximately 72 dB in MC mode and 50 dB in MM mode, more than sufficient to drive even the least sensitive high-level inputs.

Reference RIAA Equalization

The RIAA equalization of the Phonos was developed following the recommendations of Douglas Self, a British electronics engineer specializing in audio. Instead of using a few large capacitors, SPL opted for numerous small audiophile-grade Styroflex capacitors connected in parallel. This approach allows the capacitors to charge and discharge more quickly, resulting in better resolution and faster impulse response.

RIAA equalization is essential for vinyl playback. During recording, low frequencies are reduced by up to 20 dB to save space and increase playback time, while high frequencies are boosted by up to 25 dB to improve the signal-to-noise ratio. During playback, the Phonos performs the exact opposite operation: the de-emphasis filter compensates for the pre-emphasis, resulting in a perfectly linear frequency response.

Remarkable Adaptability

The SPL Phonos stands out for its great adaptability to different types of phono cartridges. For MM cartridges, which have high inductance and impedance, the preamp offers a choice of three capacitors (150 pF, 220 pF, and 330 pF) to correct the linearity of the frequency and phase response. In the “off” position, the capacitance is determined solely by the cable.

For MC cartridges, which have very low inductance and impedance but minimal output voltage (a few hundred microvolts), the Phonos offers six different impedance settings: 100, 220, 470, 2.2k, 4.7k, and 10 kOhms. This flexibility allows precise adjustment of the preamp to each cartridge for optimal frequency response.

The Phonos also features a three-position switch to adjust the output level: “Normal” corresponds to standard amplification, “-10 dB” is designed for more sensitive high-level inputs, and “+4 dB” is suitable for less sensitive equipment or studio use.

Meticulous Construction for Optimal Sound Quality

The quality of components is crucial in a phono preamplifier, particularly due to the extremely low input signals. The SPL Phonos exclusively uses high-quality Styroflex capacitors in its equalization network. These components were chosen not only for their precision but also for their lesser-known but equally important characteristics, such as low loss angle.

The Phonos’ casing is robust, with a powder-coated steel chassis and an aluminum cover, as well as aluminum knobs and front panel. The latter is available in three colors: black, silver, and red. This solid construction helps minimize interference and maximize sound quality.

Intuitive User Interface

Unlike many phono preamplifiers that require opening the casing to modify settings via jumpers, the SPL Phonos offers all its settings via front-accessible switches. This practical design allows vinyl enthusiasts to easily experiment with different configurations and immediately hear the effects while playing a record.

The aluminum front panel features a cartridge type selector (MM/MC), a capacitance selector for MM cartridges, a gain switch to adjust the output level, and a switch to activate the subsonic filter. The latter is particularly useful for eliminating background noise potentially caused by the turntable mechanism.

Exceptional Sound Performance

The SPL Phonos stands out for its energetic and dynamic sound signature. It delivers detailed reproduction with natural and full tonal colors, as well as lively and authoritative dynamics. As one tester summarized, this preamp “rocks.”

Thanks to its VOLTAiR technology and meticulous RIAA equalization, the Phonos delivers a sound rich in detail with a relaxed listening pleasure. Its ability to handle high input levels (+32.5 dBu) due to its high internal operating voltage ensures that all components remain within their optimal operating range.

Frequently Asked Questions

What is the difference between MM and MC cartridges, and why does the SPL Phonos offer different settings for each?
Moving magnet (MM) cartridges generate voltage by moving a small magnet between copper coils, producing a relatively high output signal but with high impedance. Moving coil (MC) cartridges work inversely, with fixed magnets and moving coils, producing a much weaker signal (a few hundred microvolts) but with very low impedance. The Phonos offers specific settings for each type: variable capacitance for MM and adjustable impedance for MC, allowing the frequency response to be optimized according to the cartridge type used.

What is the purpose of the SPL Phonos’ subsonic filter?
The subsonic filter eliminates very low inaudible frequencies (below 20 Hz) that can be generated by vinyl irregularities or mechanical vibrations of the turntable. These frequencies, though inaudible, can overload amplifiers and speakers, causing audible distortion and wasting power. Activating this filter protects your equipment while potentially improving overall sound quality.

Why is the VOLTAiR 120V technology important for a phono preamp?
The VOLTAiR technology, with its 120V operating voltage (+/- 60V), offers a dynamic range 12 dB higher than conventional circuits. For a phono preamp that needs to amplify extremely weak signals (especially with MC cartridges), this additional headroom keeps all components within their optimal operating range, reducing distortion and improving the signal-to-noise ratio. The result is a more natural, detailed, and dynamic sound reproduction.

How to choose the right impedance for my MC cartridge with the SPL Phonos?
If you know the impedance recommended by your MC cartridge manufacturer, start with that setting. Otherwise, a general rule of thumb is to multiply the coil impedance of the cartridge by 10 to 100. For example, for a cartridge with an impedance of 10 ohms, try between 100 and 1000 ohms. The Phonos allows you to easily experiment by changing the impedance during playback until you find the setting that offers the best frequency response and the most balanced sound for your specific cartridge.

What is the importance of RIAA equalization in a phono preamp?
RIAA equalization is essential because it compensates for the emphasis curve applied during vinyl record cutting. Without this precise equalization, the sound would be unbalanced, with insufficient bass frequencies and excessive high frequencies. The quality of the RIAA implementation directly affects the fidelity of sound reproduction. The SPL Phonos uses a sophisticated approach with multiple small high-quality Styroflex capacitors for more precise equalization and better transient response.

Is the SPL Phonos suitable for MC cartridges with very low output levels?
Although the Phonos offers impressive amplification up to 71.5 dB for MC cartridges, some tests suggest it may not be ideal for extremely quiet MC cartridges. Its noise level, while very good, could be noticeable with cartridges producing the lowest output voltages. However, for the vast majority of MC cartridges on the market, the Phonos delivers excellent performance with remarkable dynamics and tonal richness.

Why does the SPL Phonos use multiple small Styroflex capacitors instead of a few large capacitors?
This approach, based on Douglas Self’s recommendations, offers several advantages. Small capacitors charge and discharge faster than large ones, improving resolution and speeding up impulse response. This design contributes to more precise reproduction of musical transients and better overall sound definition. Additionally, Styroflex capacitors are renowned for their low loss angle and stability, crucial characteristics for maintaining precise RIAA equalization.

Technical Specifications

Phono Preamplifiers

• MM Preamplifier (Moving Magnet)

  • Gain: 46 dB (Normal), 36 dB (-10 dB), 50 dB (+4 dB)
  • Switchable capacitance: Off, 150 pF, 220 pF, and 330 pF
  • Noise (A-weighted): -85.3 dB
  • Input impedance: 47 kΩ

• MC Preamplifier (Moving Coil)

  • Gain: 67 dB (Normal), 57 dB (-10 dB), 71.5 dB (+4 dB)
  • Switchable impedances: 100 / 220 / 470 Ω; 2.2 / 4.7 / 10 kΩ
  • Noise (A-weighted): -61.7 dB

Technologies and Filters

• RIAA Technology
  • RIAA equalization (Douglas Self design)
  • Use of small audiophile-grade capacitors for better resolution
  • Faster and more linear response
• VOLTAiR Technology
  • 120V SUPRA operational amplifiers operating at high voltage (+/- 60V)
  • Dynamic range exceeding 12 dB
  • Exceptional performance in terms of dynamics and signal-to-noise ratio
  • Natural and detailed sound with wide dynamic space
• Subsonic Filter
  • Switchable to eliminate low-frequency noise (rumble)

Connectivity

• Inputs and Outputs
  • Gold-plated unbalanced RCA connectors
  • Ground connection via banana plug
  • Output impedance: < 5 Ω
  • Crosstalk: -80 dB (at 1 kHz)

Power Supply

• Switchable mains voltage: 230 V AC / 50 Hz or 115 V AC / 60 Hz
• Power consumption: max. 30 VA
• Standby power consumption: 0.7 W
• Fuses
  • 230 V: T 500 mA
  • 115 V: T 1 A
• Internal operating voltage (analog): +/- 60 V

Physical Characteristics

• Dimensions (including feet)
  • 278 x 57 x 335 mm (W x H x D)
• Weight
  • 3.2 kg (unit only)
  • 4.3 kg (with packaging)
• Construction
  • Audiophile-grade components with through-hole mounting technology
  • Robust casing with simple interface for quick adjustments