Cambridge Audio Alva Duo silver

Launched alongside the Alva Solo in 2018, the Alva Duo is Cambridge Audio’s phono preamp for turntables fitted with a moving magnet or moving coil cartridge. This silver version uses the electronics of the original model, with no changes to the circuit design. The front-panel headphone amplifier, subsonic filter, and rear balance control are therefore all still present, in a compact metal chassis.

The role of a dedicated phono preamp

A turntable cartridge outputs only a signal of a few millivolts at best, and around one hundred times less for a moving coil. Without specific amplification and RIAA equalization correction, this signal remains unusable by a standard line input. The phono preamplifier handles this double task: boosting the level and applying the inverse correction to that engraved on the record. The Alva Duo sits at this exact point in the chain, between the turntable and the integrated amplifier or preamplifier in the system.

MM and MC compatibility in a single unit

A front-panel switch toggles between the two operating modes. In moving magnet mode, gain reaches 39 dB and input impedance is set at 47 kΩ with a capacitance of 100 pF, standard values for the majority of MM cartridges on the market. Moving coil mode offers 60 dB of gain and an impedance of 100 Ω, which corresponds to a reasonable compromise for many medium-output MC cartridges. Very low-output MCs or those with more specific loading requirements may, however, reach the limits of this fixed, non-customizable setting.

Dedicated front-panel headphone output

A 6.35 mm connector occupies the front panel, accompanied by a slightly offset volume potentiometer. The built-in headphone amplifier lets you listen to your vinyl without turning on the main amplifier, which is useful during late-night sessions or when sharing a home. The potentiometer offers more noticeable resistance past the halfway point, acting as a safeguard against excessive listening levels.

Electrical design and quiet operation

The switch-mode power supply chosen by Cambridge Audio operates outside the audible band. This principle is intended to limit the mains hum often blamed on this type of gain stage. The components are surface-mounted (SMT technology), which shortens the traces and reduces the pickup of stray noise. The stated signal-to-noise ratio exceeds 90 dB in moving magnet mode and 70 dB in moving coil mode, values consistent with the intended use. Total harmonic distortion remains below 0.0025% in MM and rises to 0.20% in MC, a direct consequence of the much higher gain required to amplify the signal from a moving coil. Overload margin exceeds 30 dB, enough to handle the sharpest transients from a well-cut record without clipping.

Subsonic filter and balance control

A subsonic filter cuts very low frequencies, below the useful band. Stray vibrations from warped records or a vibration-prone environment are attenuated before reaching the speakers: low-frequency woofers are protected and the sound becomes more stable. At the rear, a balance potentiometer adjusts the balance between the two channels. This control is mainly used to compensate for a possible level imbalance between the left and right channels, which may come from the cartridge itself.

Compact format and connections

The chassis measures 48 × 215 × 159 mm and weighs 0.95 kg, a format that makes it easy to place on a shelf or next to a turntable. The new silver finish is added to the black and graphite gray versions already available. At the rear, the stereo RCA input accepts the turntable cables, accompanied by a ground terminal for connecting the tonearm ground wire. The RCA line output remains fixed in level: only the front-panel potentiometer affects the headphone output. The internal power supply supports mains voltages worldwide. Maximum power consumption is capped at 10 watts, and automatic standby activates after 20 minutes without a signal.

Technical Specifications

Type

• Stereo MM / MC phono preamplifier

Cartridge compatibility

• Moving Magnet (MM)
• Moving Coil (MC)

Audio performance

• Gain: 39 dB (MM) / 60 dB (MC)
• RIAA response: ±0.3 dB (30 Hz – 20 kHz)
• Signal-to-noise ratio: >90 dB (MM) / >70 dB (MC)
• Total harmonic distortion (THD+N)
  • <0.0025% (MM)
  • <0.20% (MC)
• Overload margin: >30 dB
• Crosstalk at 10 kHz
  • 85 dB (MM)
  • 75 dB (MC)

Built-in functions

• Built-in headphone amplifier
• Subsonic filter to reduce unwanted vibrations and rumble
• Automatic standby after 20 minutes of inactivity

Inputs / outputs

• RCA phono input
• Stereo RCA line output
• 6.35 mm jack headphone output
• Ground terminal for turntable

Impedance and capacitance

• Input impedance
  • 47 kΩ (MM)
  • 100 Ω (MC)
• Input capacitance: 100 pF

Power supply

• Low-noise switching power supply
• Maximum power consumption: 10 W
• Automatic power-off

Chassis

• Compact and elegant chassis
• Dimensions (H × W × D): 48 × 215 × 159 mm
• Weight: 0.95 kg