Phonos

The RIAA Phono Preamplifier

This phono preamplifier for Moving Magnet (MM) and Moving Coil (MC) pickup systems is based on the legendary Douglas-Self-Design.

MM & MC

There are two pickup systems for record players:

 

Moving Magnet (MM) and Moving Coil (MC).

 

Moving Magnet

Moving magnet pickups generate a small voltage by moving a magnet between copper coils. MM pickups have a very high inductance and impedance. The Phonos offers a choice of three capacitors to correct the linearity of the frequency and phase response. The capacitances are 150 pF, 220 pF and 330 pF. In the off-position the capacitance is determined by the capacitance of the cable.

The output voltage, however, is very low at only a few hundred microvolts and is therefore more sensitive to noise and induced hum. This makes preamplifier design a challenge, because the very low output voltage must be pre-amplified extremely noise-free. Phonos offers one of the most powerful phono preamplifiers for MC systems with up to 71.5 dB preamplification. Thanks to the 120V technology, the preamplifiers are extremely low-noise, linear and phase-locked.

MC pickups have a very low inductance and impedance.

 

This means that the effects of cable capacitance (from turntable to preamplifier) are negligible. The impedance, however, is relevant and can be set in six positions: 100, 220, 470, 2.2 k, 4.7 k, and 10 kOhm.

 

If there is any doubt as to which impedance matches that of the pickup, the impedances can also simply be switched through until the linear frequency response is acoustically determined.

Perfect level

The gain control can be used to determine the amplifier power, in other words, the output level of the Phonos.

There are three values to choose from.

In the “Norm” position, the gain is +46 dB for MM systems and +67 dB for MC systems.

 

With the switch set to “-10”, the gain is reduced by 10 dB (MM = +36 dB, MC = +57 dB). This is optimal in combination with standard HiFi equipment that works with a reference level of -10 dBV.

 

If the switch is in the “+4” position, the gain is increased by +4 dB (MM = +50 dB, MC = +71 dB).

So the output level is about as loud as that of modern DA-converters at a reference level of 0 dBfs = 15 dBu.

Subsonic Filter

The rumbling of the turntable’s drive mechanism is also amplified by the high amplification of the bass range due to RIAA equalization in playback.

The Phonos offers a switchable subsonic filter to remove this rumble.

Connections

Gold-plated RCA sockets are available for connecting the turntable and for outputting to a preamplifier such as the Director Mk2 or the Elector.

 

A ground connection for the turntable is designed as banana plug socket. The ground lead can be either clamped or plugged in.

 

Douglas Self Design

The RIAA equalization of the Phonos was developed according to the recommendations of Douglas Self.

Idea: Many small capacities instead of a few large capacities.

Advantages: The capacitors charge and discharge faster, which results in better resolution and faster impulse response.

Only audiophile Styroflex capacitors are used in the entire RIAA equalizer.

About the person: Douglas Self is a British electronics engineer with a strong penchant for audio. He holds honorary degrees from Cambridge University and teaches psychoacoustics at the University of Sussex.

RIAA Equalization

RIAA equalization is a specification for the recording and playback of records proposed by the Recording Industry Association of America (RIAA). The RIAA equalization curves introduced a global de facto industry standard for vinyl records in 1954.

 

RIAA equalization uses pre-emphasis to reduce low frequencies and boost high frequencies when the record is cut (blue RIAA curve).

 

 

The bass is reduced by up to 20 dB to provide more space and longer record play time.

 

The high frequencies are boosted by up to 25 dB to increase the signal-to-noise ratio between the noise of the record media to the audio signal.

 

During playback, exactly the opposite happens in the Phonos. The de-emphasis filter (red RIAA curve) compensates for the pre-emphasis and the result is a linear frequency response.

 

The VOLTAiR Technology

The 120V technology is our reference technology. The 120V technology is unique in the world. It operates at a DC voltage of 120 volts. This is four times that of IC-based semiconductor op-amps. In our Professional Fidelity series, we refer to this unsurpassed technology as VOLTAiR technology.

The highest possible audio quality requires the highest possible audio operating voltage.

The 120V technology works with +/-60 V. To be able to handle such a high voltage, we have developed special proprietary operational amplifiers that can operate with a DC voltage of +/-60 V: the SPL 120V SUPRA operational amplifiers. This high voltage would destroy conventional components and operational amplifiers.

 

The 120V technology achieves exceptional technical specifications and sonic benefits. Technically, in terms of dynamic range, signal-to-noise ratio and headroom. Sonically, in terms of richness of detail and an absolutely relaxed listening experience.

 

By the way, the “120V” in the name of the technology has nothing to do with the local mains voltage from the mains power socket. This is about the operating voltage inside the device with which the audio signals are processed.

 

The mains voltage from the mains power socket is transformed to the required secondary voltage in the device’s internal linear power supply with toroidal transformer. Rectifiers convert this AC voltage into DC voltage required in the audio device.

 

Comparison

Most audio devices work with an internal operating voltage of +/-15 volts and can thus process a maximum input level of +21.5 dBu. If a DAC, for example, has an output level of +22 dBu at 0 dBFS, level peaks of the music material would already cause overloads in the input stage of the device. All components in the audio device often operate at their limits. The result is an unsteady sound that causes stress and faster ear fatigue.

SPL devices with VOLTAiR technology can handle input levels of +32.5 dBu thanks to the higher internal operating voltage of +/- 60 volts – thus offering 12 dB more headroom. All components consequently operate continuously in the optimum operating range. The result is a very pleasant, natural and relaxed sound experience. So you can enjoy your music in every detail.

These diagrams clearly show the superiority of the VOLTAiR technology in comparison to other circuits with lower, common operating voltages.

For audiophiles and vinyl enthusiasts striving to extract the purest sound from their turntables, the SPL Audio Phonos phono preamplifier presents an unparalleled solution. It addresses the critical challenge of preserving the delicate nuances and dynamic range inherent in analog recordings while providing the precise amplification necessary for both moving magnet (MM) and moving coil (MC) cartridges. This device is designed to elevate your vinyl listening experience by delivering crystal-clear audio with minimal noise and distortion, ensuring that every detail of your favorite records is faithfully reproduced.

One of the standout features of the SPL Audio Phonos is its highly versatile input impedance settings for both MM and MC cartridges. The MM input impedance is fixed at 47 kΩ, which is ideal for most standard cartridges, while the MC impedance is switchable across a wide range—from 100 Ω to 10 kΩ. This flexibility allows you to fine-tune the preamplifier to match your cartridge’s specifications precisely, resulting in optimal signal transfer and tonal balance. The selectable capacitance options for MM cartridges (off, 150 pF, 220 pF, and 330 pF) further enhance this customization, enabling you to counteract cable capacitance and refine the frequency response for a more natural sound.

Amplification levels are another critical aspect where the SPL Audio Phonos excels. For MM cartridges, the unit offers three amplification settings: 36 dB, 46 dB (normal), and 50 dB, accommodating a wide range of cartridge outputs and ensuring that even low-output cartridges receive adequate gain without sacrificing clarity. For MC cartridges, amplification ranges from 56 dB to 71.5 dB, making it suitable for very low-output designs. This broad gain spectrum ensures that regardless of your cartridge type or output level, your vinyl playback will be loud, dynamic, and free from unwanted noise. Speaking of noise, the device boasts exceptionally low noise levels—down to -85.3 dBu at 46 dB amplification for MM and -61.7 dBu at 67 dB amplification for MC—meaning your listening experience remains clean and immersive, even during quiet passages.

Behind its superior audio performance is a robust internal linear power supply equipped with a shielded toroidal transformer and operating voltages of ±60 V for analog audio circuits. This design minimizes electromagnetic interference and provides consistent, stable power, which translates into improved dynamic range (up to 131.3 dB for MM and 128.7 dB for MC) and lower distortion. The output impedance is a low 75 Ω, ensuring compatibility with a wide range of downstream audio equipment while preserving signal integrity.

Physically, the SPL Audio Phonos is thoughtfully engineered with dimensions of 278 mm wide, 100 mm high, and 300 mm deep, and a weight of 3.2 kg. This size and weight reflect the quality components housed within, including precision relay switching and a robust chassis that reduces vibration and interference. The mains power supply is user-selectable for 115 V or 230 V operation, with low power consumption—only 30 VA at maximum and less than 0.3 W in standby—making it energy-efficient and adaptable to different electrical environments.

This phono preamplifier is ideal for serious audiophiles who demand uncompromising sound quality from their vinyl collections, whether at home in a high-fidelity stereo setup or in a professional listening environment. Its ability to handle both MM and MC cartridges with precision, combined with customizable settings and an advanced power supply, ensures that users can tailor the sound to their preferences while enjoying exceptional clarity and detail.

In summary, the SPL Audio Phonos phono preamplifier is a meticulously designed component that transforms your vinyl playback by offering outstanding flexibility, ultra-low noise, and a wide dynamic range. Its robust construction and thoughtful engineering provide confidence in its durability and performance. Priced at ₹199,800, this preamplifier represents a worthwhile investment for anyone serious about achieving the highest audio fidelity from their analog sources. With the SPL Audio Phonos, you’re not just listening to records—you’re experiencing them as the artists intended.