The PL-1 demonstrated a smooth, full-bodied sound with a composed cadence and a touch of warmth. It proved itself an adept performer under pressing conditions across the middle frequencies. The treble satisfied on fundamentals and harmonics, albeit they were a bit dry at the very top end…. Timpani, bassoons, and basses exhibited solid low-end weight with tonal definition. Designed for low output cartridge.
The first device in line with the input signal is one half of a Russian 6N1P dual-triode tube, used in fixed bias (as opposed to autobias) mode: The cathode is tied directly to ground, without a resistor in line, and the grid is tied to a fixed DC supply, alongside the AC music signal. In an interesting design twist, the bias voltage for the 6N1P is supplied by two N-style 1.5V batteries, one for each half of the tube.
A passive RIAA equalization circuit follows that first gain stage, then the signal is amplified by two more stages: one half of a 12AX7 dual-triode followed by one half of a 5687 dual-triode, both in autobias mode. The 5687 was selected as the last stage because its low plate resistance allows for a lowish output impedance without the need for a cathode follower, and its plate is loaded with a Lundahl C-core choke, for increased operating headroom and consequent lower distortion.
In fact, the PL-1 has five tubes altogether: a single 6N1P, plus two 12AX7s and two 5687s. Because the 12AX7 and 5687 have split heaters, one side of each tube—which is to say, one triode within each dual-triode envelope—can be used independently of the other. The PL-1’s designer has taken advantage of that by wiring the tube sockets so that one channel uses one tube half and the other channel uses the other half. Thus the individual tubes run cooler, and the owner can get most of the sonic benefits of a fresh set of tubes just by swapping one channel’s 12AX7 and 5687 for the other’s, after such time as tube deterioration becomes sonically apparent. (The 6N1P is exempt from this “Cool-Swap” design.)
Good Condition. No box.