Pre-amplifier tubes are the first line of amplification and pass the signal on to the output tubes. They are relatively inexpensive and easy to replace, no biasing, no fuss.

All PM pre-amplifier tubes are double triodes (two valves in one). PM has already selected and discarded any pre-amp tubes with unpleasant microphonic ring, mechanical noise, hiss and squeals. The average PM pre-amp tube life is about 3000 hours.