Internal Architecture - Lexicon PSP 42 Operation Manual

Lexicon PSP 42 Operation Manual 10

Internal architecture

The Lexicon PSP 42 is build around a delay line, operating with a variable sampling rate. The
rate can be adjusted continuously within the limits of 0,5 to 1,5 of the host sampling rate.
Activating the DLYx2 button, further reduces the delay line sampling rate to half of its value. To
make the Lexicon PSP 42 sound good when operating within such a wide range of sampling
rates, a 4-pole low-pass variable filter is applied to the input signal to attenuate frequencies that
could cause aliasing. The sample rate converters that are located before and after the delay buffer,
provide low harmonic distortion thanks to a superior interpolation algorithm. Such an architecture
allows for continuous modulation of the actual delay time. The modulation section, consisting of
a LFO and an envelope follower, is capable of generating sinus and square waveforms. The
Envelope follower and LFO signals can be mixed in any proportions to make up a final
modulation signal that is used to control the delay line sampling rate. Modulating the delay line
sampling rate results in the delay time and pitch to be altered.
The Saturation circuit enriches the harmonic contents of the input and feedback signals, adding
warmth and punch. The saturation effect is almost not perceptible when the signal level is low,
but becomes clearly audible when it rises. Its main purpose is to simulate magnetic tape
characteristics for convincingly sounding tape delay emulation, but it can also be used to add
punch or distortion to the signal as well, provided that the signal level is high enough.
The Signal path is 32-bit float all the way through, to preserve the bit-depth and the dynamic
range of the input signal.