Hands On - Lexicon PCM 70 (part 4)
Since the PCM70s primary function, to my mind at least, is as a digital reverb unit, I think I should start at Program 3.0 - the first of the twenty-two basic reverb Programs. The Programs in Row 3 of Figure 2 are designed to emulate real concert halls, and they do a pretty good job too. As the manual states, the reverb starts with a low initial density which builds up gradually over time. As well as the reverberation itself, the Concert Hall programs also have four early reflections, each of which can be independently adjusted for level and timing. There is also a gate for stopping the reverb abruptly, an effect which was especially popular on drum sounds at the time the PCM70 was introduced, but sounds a bit naff now.
Stepping down to Row 4 (you press the down key to increment the number) we find the Rich Chamber programs. I cant improve on Lexicons description: The Rich Chamber programs produce an even, relatively dimensionless reverberation, with little change in colour as the sound decays. The initial diffusion is similar to the Concert Hall programs, but the sense of space and size is much less obvious. This characteristic, along with the low colour in the decay tail make the Rich Chamber programs especially useful on spoken voice, giving a noticeable increase in loudness with very low colour. This is actually a very helpful description of the sound, not just an advertising copywriters message, which Lexicon provide in their manual for all the Program families. When you understand the designers intentions, it makes operation of the unit more rewarding (a lot more rewarding than simply flicking through presets). The programs in Row 5 are plate simulations with a high initial diffusion and bright sound. Lexicon recommend their use on percussion. Row 6 is dedicated to creative Inverse Room programs. Many of the reverb programs have editable parameters in common. Here is a selection which should indicate the power available in the PCM70:
- Attack sets the sharpness of the initial .response
- Chorusing randomises delay times, adding richness to the sound.
- Decay optimisation alters program characteristics according to input level to make the reverb decay more natural. This can be set On or Off. The off position is used if clicks are noticed.
- Definition controls the build up of echoes during the latter part of the decay.
- Diffusion controls the density of echoes.
- Delay master changes simultaneously the delay times of all the early reflections.
- Duration determines the length of time before cut off in the Inverse Room programs.
- Gate sets the time delay before reverb is stopped.
- HC (High frequency cut off) applies a 6dB/octave filter at a selectable frequency.
- Lo slope (Low frequency slope) determines the shape of the reverb envelope at low frequencies in the Inverse Room programs.
- MD slope (Mid frequency slope). Same as the above but for mid frequencies.
- L RFL DB (Left early reflection levels). The level of each early reflection in the left channel can be adjusted.
- R RFL DB (Right early reflection levels). Similar to the above.
- L RFL MS (Left early reflection delay times). The delay time of each early reflection can be adjusted.
- R RFL MS (Right early reflection delay times). Similar to the above.
- LVL MST (Level master) allows simultaneous changes in the early reflection levels without altering the relationship between individual reflections.
- Mix controls the ratio of dry and processed signal.
- PDelay (Pre delay) sets the time between the input signal and the onset of reverberation.
- Reverb time. I think you know this already.
- RT HC (Reverberation time high frequency cut off) sets the frequency above which sounds decay at a progressively faster rate.
- RT Low adjusts the low frequency reverberation time.
- RT Mid. Similar to the above.
- RTL stop sets a separate reverberation time for low frequency signals when input has ceased.
- RTM stop. Similar to the above but for mid frequencies.
- Size sets the room size.
- Xover (Crossover frequency) sets the frequency at which the transition from low frequency reverb time to mid frequency reverb time takes place.
As you can see, there is a good range of parameters available, but not I think too many to put the average user off editing the original programs. The one drawback is that the display is quite small and some of the parameter names have had to be abbreviated beyond the point where people can be expected to work out their meaning - but you have to remember that classic effects units have their failings, just as classic cars leak oil.
The other effects have a whole new set of adjustable parameters, far too many for me to go into here, but I must mention the PCM70s party trick. Every engineer will want to use it at least once and I recently placed it, suitably tailored, on the opening of the CD The Killing Tide by Sol Invictus. The effect is known as Resonant Chords.