Phonos duo

The RIAA Phono Preamplifier – Twice as nice

The SPL phono preamplifier Phonos duo expands the established

SPL phono preamplifier Phonos with a pair of balanced stereo inputs and outputs.

Phonos duo is thus even more versatile.

 

Whether moving magnet (MM) or moving coil (MC) cartridge systems –

the SPL VOLTAiR technology and the RIAA filter in the legendary Douglas-Self design

form the fundament for an outstanding phono sound.

Great design – a must have

Visually, the SPL Phonos duo Phono Preamplifier fits perfectly into the SPL HiFi line

Professional Fidelity – and is of course available in the three basic colors black, red or silver.

MM & MC

There are two cartridge systems for turntables:

 

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

 

Moving Magnet

Moving magnet cartridges generate a voltage by moving a magnet between copper coils. In order to achieve the best possible linearity of the frequency and phase response, the capacitance is modified to adjust the cartridge.

Phonos duo offers six different capacities for this adjustment:

 

12 pF, 47 pF, 100 pF, 150 pF, 220 pF und 330pF.

MC or MM ?

Moving coil cartridge systems are commonly regarded as the more audiophile systems, as they allow a faster and therefore a finer cartridge due to their low mass. They bring out the finest nuances of the record. The output voltage of a moving coil cartridge system is extremely low at just a few hundred microvolts and is therefore more sensitive to noise and induced hum.

 

The very low output voltage makes preamplifier design a challenge, because it has to be pre-amplified extremely noise-free. With up to 70 dB preamplification, Phonos duo offers one of the most powerful phono preamplifiers for moving coil systems. Thanks to SPL 120V technology, Phonos duo amplifies extremely low-noise, linear and phase-locked.

 

Moving coil cartridges have a very low inductance and impedance.

 

This means that the effects of cable capacitance (from the cartridge to the preamplifier) are not that significant. The impedance, however, is the relevant parameter here and can be set in six positions on the Phonos duo. The manufacturers specify the impedances of the cartridges. These should be followed as closely as possible.

 

Moving magnet cartridges, on the other hand, are more rugged and often less expensive.

The greater mass of the moving magnets causes more inertia, which results in less precise reading

of the record. However, modern moving magnet systems also use neodymium magnets, which have

a significantly lower mass. Such moving magnet systems can also keep up with

some moving coil systems in terms of accuracy.

 

Capacitance plays a significant role with moving magnet cartridges.

 

This means that the effects of cable capacitance (from the cartridge to the preamplifier)

can‘t be ignored here. The capacity for moving magnet cartridges can therefore be set to six values

on the Phonos duo to be optimally adapted to the system.

Free choice – balanced or unbalanced

Phonos duo offers two pairs of stereo inputs and outputs.

A pair of balanced inputs and outputs with XLR inputs and outputs and a pair

of unbalanced inputs and outputs with RCA connectors.

The INPUT switch on the front of the Phonos duo can be used to switch between the two stereo inputs.

The output signal is always present in parallel at both output – regardless of the selected input.

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 seeking the utmost fidelity in music reproduction, the SPL Audio Phonos Duo phono preamplifier offers a remarkable solution. Analog sources like turntables demand precise amplification to accurately capture the subtle nuances of each record groove. This preamplifier is meticulously engineered to elevate the listening experience by delivering pristine sound quality with exceptional clarity and minimal noise, ensuring your vinyl collection sounds as intended by the artist.

One of the standout features of the SPL Audio Phonos Duo is its dual capability to handle both Moving Magnet (MM) and Moving Coil (MC) cartridges with tailored settings. This versatility means you can use the preamplifier with a wide range of turntables without compromise. For MM cartridges, the device offers three amplification levels—30 dB, 40 dB, and 50 dB—and switchable capacitance options from 12 pF to 330 pF, allowing precise tuning to match your cartridge’s electrical characteristics. This level of customization results in optimal tonal balance and detail retrieval, so every subtle instrumental texture and vocal inflection is faithfully reproduced.

For MC cartridges, which often produce lower output signals, the Phonos Duo provides three amplification stages of 50 dB, 60 dB, and 70 dB alongside six selectable input impedances ranging from 20 Ω to 1000 Ω. This ensures that even the most delicate MC cartridges can be matched perfectly, reducing noise and distortion to a minimum. The amplifier’s extremely low noise floor, measured at -62 dBu (A-weighted) at 70 dB amplification for MC and -82 dBu at 50 dB for MM, guarantees that the signal remains clean and dynamic. The wide frequency response from 10 Hz to 100 kHz further ensures that the entire audio spectrum is reproduced without loss or coloration.

The SPL Phonos Duo also incorporates an internal linear power supply featuring a shielded toroidal transformer operating at ±60 V for analog audio circuits, which is crucial for maintaining signal purity and eliminating electromagnetic interference. This means that your music is amplified in an environment free from hum or buzz, preserving the integrity of your vinyl playback. With RCA input and output connectors and a low output impedance of 75 Ω, the Phonos Duo seamlessly integrates into existing high-end audio setups, providing reliable and consistent performance.

Physically, the preamplifier is crafted with precision in mind, measuring 278 mm in width, 57 mm in height, and 300 mm in depth, and weighing 3.2 kg. This compact yet robust form factor fits comfortably into any audio rack or shelf without compromising on build quality or operational stability. The device supports mains voltages of 115 V and 230 V with selectable fuses, consuming a maximum of only 30 VA and less than 0.3 W in standby mode, reflecting energy efficiency alongside high performance.

Whether you are upgrading your home audio system or building a dedicated vinyl rig, the SPL Audio Phonos Duo offers unmatched flexibility and sonic excellence. It is designed for discerning listeners who appreciate the difference that precise amplification and noise control make in revealing the full depth and emotion of analog recordings. By choosing this preamplifier, you invest in a component that not only enhances your enjoyment of vinyl but also respects the artistry behind every groove.

In summary, the SPL Audio Phonos Duo is a sophisticated phono preamplifier that delivers superior sound quality through its adaptable amplification stages, low noise operation, and robust power supply design. Its detailed feature set ensures compatibility with a broad range of cartridges and turntables while maintaining signal integrity and musicality. With practical dimensions and energy-efficient operation, it is a reliable and refined choice for anyone serious about vinyl playback. Experience your records as they were meant to be heard with confidence, knowing you have a premium preamplifier engineered for excellence.