SPL - Sound Performance Lab Phonos RIAA Phono Preamplifier

SPL phonos

RIAA phono preamp

This phono preamplifier for moving magnet (MM) and moving coil (MC) pick-up 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 create a small voltage by moving a magnet between copper coils. MM pickups have very high inductance and impedance.

The Phonos offers a choice of three capacities in order to be able 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.

moving coil

The MC cartridge is also a small electromagnetic generator, but in which the magnets are firmly anchored and the coils move between them, i.e. exactly the opposite of the MM cartridge.

However, the output voltage is very small, only a few hundred microvolts, and is therefore more sensitive to noise and induced hum. This makes the preamplifier design a challenge, because the very low output voltage must be preamplified in an extremely noise-free manner. With up to 71.5 dB of preamplification, Phonos offers one of the most powerful phono preamps for MC systems, which thanks to 120V technology are amplified with extremely low noise, linearly and phase-locked.

MC pickups have very low inductance and impedance. This means that the effects of cable capacitance (from turntable to preamp) are negligible.

The impedance, on the other hand, is relevant and can be set in six positions: 100, 220, 470, 2.2k, 4.7k, and 10 kOhm.

If there are doubts as to which impedance corresponds to that of the pickup, the impedances can simply be switched through until the linear frequency response is acoustically determined.

perfect level

The gain switch can be used to determine the amplifier power, i.e. the output level of the phono.
There are three values to choose from.
In the " Norm " position, the gain for MM systems is +46 dB and for MC systems +67 dB.

When the switch is set to " -10 ", the gain is reduced by 10 dB (MM = +36 dB, MC = +57 dB). This is optimal in combination with standard hi-fi devices that work 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).
The output level is about as loud as that of modern DA converters with a reference level of 0 dBfs = 15 dBu.

Subsonic filters

The rumble of the drive mechanism of the turntable is amplified in the playback by the high boost in the bass range by the RIAA equalization.

With the switchable subsonic filter, the Phonos offers the possibility of removing this rumble.

connections

Gold-plated cinch sockets are available as connections for connecting the record player and for forwarding to a preamplifier such as the Director Mk2 or the Elector.

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

Sounds good

With all devices in the Professional Fidelity series, SPL not only develops according to plan from the outset, but also by ear. Many of the basic components are mounted on the circuit boards in through-hole mounting (THT). This ensures that the components that sound best are installed.

RIAA equalization

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

When cutting the record, the RIAA equalization uses a pre-emphasis in which the low frequencies are reduced and the high frequencies are boosted (blue RIAA curve).

The bass is reduced by up to 20 dB to provide more space and a longer record life.
The high-frequency range is boosted by up to 25 dB in order to increase the signal-to-noise ratio between the noise and the hiss of the record medium 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.

Douglas Self Design

The Phono's RIAA equalization was developed following the recommendations of Douglas Self.
Idea: Many small capacities instead of fewer large capacities.
Advantages: The capacities charge and discharge faster, which results in better resolution and faster pulse behavior.

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

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

The VOLTAiR technology

VOLTAiR is made up of the terms Volt and Air .
Volt is the unit of electrical voltage and Air is the English word for air.

VOLTAiR symbolizes the seemingly limitless dynamics resulting from the high audio tension.

120V technology is the SPL reference technology. It is unique in the world of audio because it works with a DC voltage of 120 volts. This corresponds to four times the operating voltage of IC-based semiconductor operational amplifiers. In our Professional Fidelity series, they refer to this unsurpassed technology as VOLTAiR technology.

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

120V technology operates at +/- 60V. To be able to handle such a high voltage, SPL engineers have developed special proprietary op amps capable of operating at +/- 60V DC - the SPL 120V SUPRA op amps . This high voltage would destroy conventional components and operational amplifiers.

120V technology achieves exceptional technical specifications and sonic benefits. From a technical point of view, in terms of dynamic range, signal-to-noise ratio and overload resistance. In terms of sound, in terms of richness of detail and an absolutely relaxed listening pleasure.

Incidentally, the "120V" in the name of the technology has nothing to do with the local mains voltage from the socket. This is about the operating voltage in the device with which the audio signals are processed.

The mains voltage from the 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 the DC voltages required in the audio device.

comparison

Most audio devices work with an internal operating voltage of +/-15 volts and can therefore process a maximum input level of +21.5 dBu. For example, if a DAC has an output level of +22 dBu at 0 dBFS, level peaks in the music material would already cause clipping in the input stage of the device. All components in the audio device often work at their limit. The result is a noisy sound that causes stress and faster hearing fatigue.

Devices from SPL with VOLTAiR technology can process input levels of +32.5 dBu thanks to the higher internal operating voltage of +/- 60 volts - i.e. offer 12 dB more headroom. As a result, all components work continuously in the optimum working range. The result is a very pleasant, natural and relaxed sound experience. So you can enjoy your music in every detail.