Phono Preamplifiers

While the highest output MMs are specified at ~6mV/5cm/sec, in practice all pick-ups will deliver far higher outputs when tracking the most highly modulated vinyl grooves. All phono stages should be designed to accommodate these higher inputs, with a value of +18dB typically taken to represent the wildest groove modulation likely to be encountered and, indeed, successfully tracked by the most secure of pick-ups. Using the IEC reference inputs of 5mV (MM) and 500µV (MC), this suggests that margins of 40mV and 4mV need to be 'built in' to the phono preamp – otherwise any clipping and distortion that occurs at the input will travel, uncorrected, right along the signal chain to the loudspeakers.

Exposure's +40dB, +46dB, +54dB and +55dB (MM), and +54dB, +60dB, +63dB and +66dB (MC) gain options available to the VXN Phono are partnered with input limits of 108mV, 53mV, 21.5mV and 17.5mV [MM, black, red, blue, green infills, inset Graph], and 20.0mV, 9.8mV, 7.1mV and 5.1mV [MC, dashed traces], respectively. Pure MM pick-ups should be used with the +40dB input, or +46dB for the lowest o/p MMs, while the +46dB/+54dB settings are better suited to 'high output' MC types. The +55dB MM input is largely redundant. Neither are the +54dB MM and MC settings equivalent as the latter employs an additional gain stage at the input with a proportionally lower 20mV overload margin. In practice, the MC settings will suit a broad range of 'coil pick-ups with the +60dB setting ideal for most, leaving the +66dB option for the lowest output types. PM