Phono Preamplifiers

The evergreen 2M Red from Ortofon [HFN Oct '08], one of the highest output MMs available, produces a very healthy 6.7mV (re. 1kHz/5cm/sec). Furthermore, with extreme LP groove excursions (up to +18dB), it'll go on to deliver peak outputs of some 50mV into the V10 and other phono preamps. Now, any phono stage with insufficient input headroom will clip and send a burst of distortion that's boosted through your system from these mere millivolts to the tens of watts – or more – feeding your loudspeakers.

The higher the phono stage's gain setting, the lower the input headroom – in the V10's case its maximum +73dB MC gain represents a boost of x4467, so even with its massive 24V (balanced) output it only requires an input of 5.4mV to clip the output stage. This is why it's important to carefully select the optimum gain for your choice of cartridge. Fortunately the V10 has more than enough headroom for every type of pick-up – the inset Graph shows the point at which it clips when set at the default +40dB MM gain [green trace], plus the additional +5dB [blue], +10dB [red] and +12dB [black] settings, offering 238mV, 123mV, 71mV and 56mV of input headroom, respectively. MC pick-ups are treated to similarly generous margins: the default +60dB MC gain [dotted green], +5dB [dotted blue], +10dB [dotted red] and +12dB [dotted black] options representing maximum MC levels of 22mV, 12.5mV, 6.8mV and 5.4mV, respectively. PM