The Signal Transfer Stereo Phono Preamplifier is a stand-alone version of the phono system used in the Precision Preamplifier. It offers both moving-magnet and moving-coil inputs, the latter with two gain options for optimal performance. It gives extremely accurate RIAA equalisation, a noise performance that approaches the theoretical limits, and superb linearity. This version has fully balanced low-impedance outputs and is designed to interface with equipment of the highest performance. PCB 007: £33:50 each

F E A T U R E S

• Moving magnet and moving coil inputs. Separate input connectors are provided for the two inputs so two sources can remain permanently connected. Selection between the two is by a switch on the PCB.
• The moving coil input has two gain options to match a wide range of cartridges.
  Selection between the two is by a switch on the PCB.
• Fully balanced outputs with high-quality male XLR connectors. Low output impedance to maximise common-mode rejection of interconnect.
• Integral 3rd-order Butterworth subsonic filter: -3 dB at 20 Hz
• Power indicator LED
• Exceptional RIAA equalisation accuracy of +/-0.05 dB. Surprisingly, this does not require specialised and expensive components. This accuracy is obtained done by design rather than just spending money.
• Very low noise.
• Extremely low interchannel crosstalk. Better than -100 dB in moving-magnet mode. This performance is built into the PCB layout.
• Very low distortion. THD better than 0.002% at 6 Vrms. This is about forty times the normal operating level, so in real use the distortion introduced is vanishingly small. It is certainly too low to measure.
• PCB positions are provided on both moving magnet and moving coil inputs to allow both capacitance and resistance to be added across the input so cartridge loading can be altered as desired
• Absolute phase is preserved from all inputs to output.
• Easily obtainable parts. The only op-amps used are the 5534, the 5532 and the TL072, both of which are easy to find world-wide. Their performance is exceptional here because of the way they are used.
• Provision for standard-footprint gold-plated phono sockets.
• High-quality double-sided plated-through-hole PCB with solder mask both sides and full screen print.
  All solder pads gold-plated. PCB size is 220 by 98 mm.
• Fully ROHS compliant in both PCB and all components.

S P E C I F I C A T I O N S

• Input sensitivity: (moving-magnet) 5 mV rms for 150 mV rms out at 1 kHz
  Gain= +29.5 dB (30 times) at 1 kHz
• Input sensitivity: (moving-coil) 0.1 or 0.5 mV rms for 150 mV rms out at 1 kHz (switchable)
  Gain= +49.5 dB or +54.5 dB (300 or 1500 times) at 1 kHz
  
• Maximum input level: (moving-magnet) greater than 350 mV rms at 1% THD
• Maximum input level: (moving-coil, gain 10x) greater than 53 mV rms at 1% THD
• Maximum input level: (moving-coil, gain 50x) greater than 11 mV rms at 1% THD
• Input impedance: (moving-magnet) 47K in parallel with 100pF (customisable)
• Input impedance: (moving-coil) 100 Ohms (customisable)
• Maximum output level: (unbalanced) greater than 10 V rms at 1% clipping THD
• Maximum output level: (balanced) greater than 20 V rms at 1% clipping THD
• Output impedance: 100 Ohms
• Minimum load on output: 600 Ohms
  
• Distortion (moving-magnet input): Less than 0.002% THD 50Hz - 7kHz, at 6 Vrms output.
  Level in actual use is approx 150 mV rms so real-life distortion will be much lower.
• Distortion (moving-coil input at 10x gain): Less than 0.006% THD 1kHz, at 1.6 Vrms output.
  Level in actual use is 150 mV rms so real-life distortion will be much lower.
  
• RIAA equalisation accuracy +/-0.05 dB 100Hz - 50kHz
  
• Noise out (moving-magnet, Rs=50R) Less than -95 dBu (20-22kHz bandwidth, rms sensing)
• Noise out (moving-magnet, cartridge load 610R + 450mH) Less than -88.5 dBu (22-22kHz, rms
• Noise out (moving-coil, gain 10x, Rs=10R) Less than -90 dBu (22-22kHz bandwidth, rms)
• Noise out (moving-coil, gain 50x, Rs=10R) Less than -75 dBu (22-22kHz bandwidth, rms)
  
• L - R crosstalk (moving magnet input) better than -100 dB at 1 kHz
• L - R crosstalk (moving coil input at 10x gain) better than -75 dB at 1 kHz
  
• Power supply: +/-15V to +/-18V; an +/-18V supply is recommended to maximise headroom.
• Power consumption: 45mA from +/-18V supply.

This graph shows the typical RIAA equalisation accuracy. The error is less than 0.1 dB from 100 Hz to 40 kHz. Please note that the scale is enormously expanded and covers only 1.5 dB. The response rolls off very slowly below 100 Hz due to action of the subsonic filter, but is still accurate to -0.5 dB at 50 Hz. Measurement system: Audio Precision SYS-2702.