What Is It?

One of the truly wonderful things about living in the global village is that genius and craftsmanship now know no national boundaries. We've seen some amazing digital tools coming out of Germany, France, Israel, Spain, and now with the advent of Professional Sound Projects (PSP), from Poland. PSP is a small company, but as their first collection of products demonstrates, they know their stuff.

Following their first successful release, Vintage Warmer (to be discussed in a future article), PSP introduced (initially via the company's own Web site and now through international distribution) the PSP42, a software emulation of the classic Lexicon PCM42 delay. PSP did such a good job that Lexicon blessed the product by allowing it to be called the "Lexicon PSP42." In most respects this is a feature-by feature sound-alike (though there are a few small differences to be discussed later). It was an immediate hit, and PSP have followed it with an expanded version, the PSP84, and several other products. The plug-ins come in both mono and stereo versions and run under both Macintosh and PC host applications at sampling rates up to 192kHz.

Installation, Documentation, and Support

Installation for all PSP plug-ins is by the familiar click-through installer method. You'll be given a choice of installing different operating system versions (in my case Mac OS 8/9 or X) and PDF documentation, after which the installer will present you with a list of possible plug-in folders for your various host applications. PSP plug-ins come in VST and DXi for Windows users and VST and MAS (and soon RTAS and Audio Units) for Macintosh. The first time you run each plug-in you'll have to enter your authorization name and a 10-digit authorization key. That's it.

The documentation is well-organized clearly written, with only a slight tinge of "translation blur." Tweakers should be pleased by some of the deeper technical discussion and clear block diagrams. The PSP84 manual in particular has some useful discussions on the technical particulars and design
philosophy.

Because PSP's technical support department is in Piaseczno Poland, you may prefer to use their on-line support system or to communicate via e-mail. Still, the company does provide telephone and fax numbers (hint: Poland is in the Central European Time Zone, one hour later than London). My own e-mail was answered promptly and I had a series of very productive exchanges with the developer. I'm quite pleased to report that this correspondence resulted in the correction of some shortcomings in the design of the Infinite Repeat function, leading to a new update of PSP42!

PSP42

The Lexicon PCM42 was designed by signal processing maestro Gary Hall and was released in 1981 on the heels of a popular series of Lexicon Prime Time delays. In addition to having that "Lexicon sound" integral to so many current recordings, the PCM42 was designed with performance in mind, with external control and synchronization features that were quite revolutionary. Although they never really disappeared from many studios, these instruments have experienced a renaissance that has driven the cost of used units back up to the original list price and beyond.

With PSP42 we can now fulfill our fantasies and run as many instances as our computer will support. The software emulation has several other advantages over the original hardware. For one thing, PSP42 can run in stereo, for another it has twice the memory of the original. It can also run under complete automation control within a host sequencer program, and of course it has presets (something all the old timers longed for in the PCM42).

Signal Path

PSP42 is based on the model of a single delay line with feedback that was the standard architecture for the PCM42 and most monophonic delay processors of the day. The audio input is protected by a combination of an anti-aliasing filter and a "saturator" (analog tape simulation). The delay time is specified through a combination of the playback clock rate (continuously adjustable from 0.5 to 1.5 of the nominal rate) and the delay tap (this being the point along the delay line where the output signal is extracted - not to be confused with "tap tempo"). There is also a button to switch between normal delay time (at full bandwidth) and double delay time (at half bandwidth of 8kHz).

On the PCM42 the clock rate could be controlled with a front panel knob or from an external input that could accommodate a pedal or an control voltage, and PSP42 emulates these functions. The clock can also be modulated by either an input envelope follower or a sine/square wave LFO (with continuous blending between the two). This variable clock rate is what sets vintage delays apart from later designs based on a fixed clock. Varying a clock in real time results in smooth frequency changes similar to the effects of varispeed on an analog tape deck. Variations in delay time resulting from changing the delay tap result in discontinuities in the signal, i.e. "glitches." It takes a good bit of crafty programming to avoid such artifacts and to emulate that "analog" sound. Happily, PSP have done a marvelous job. The clock sweeps in PSP42 sound like the real thing.

Sound

For this review I didn't have the benefit of a PCM42 for A/B comparison, but if I can trust my ancient ears and sonic memory I will declare PSP42 to be damned close to the original. The PCM2 had that "suave" Lexicon sound that allowed it to sit comfortably in a mix without cluttering up the high frequencies (its nominal bandwidth was 16kHz). PSP42 has a sound carefully modeled on its forebearer, including that forgiving input saturation and the hi cut filter and phase invert in the feedback path. It comes with a set of 16 factory presets that run it through its paces. "Light flanger," "wow tape," and "doubler" all sound as you'd expect. "Didgee" gives a deep static resonance like a didgeridu and while "lezlie" may not sound exactly like a Leslie cabinet, it sounds exactly like a PCM42 imitating a Leslie!

Automation and Control

All parameters can be automated or externally controlled using MIDI Control Change messages, hard-coded in the controller range of 102 to 118. The MIDI CC resolution of 7 bits is adequate for all parameters except Delay Time, which requires two controllers for coarse and fine adjustments. In addition, Delay Time can be slaved to System Tempo.

Looping and Sync

Although people will use PSP42 for its delay and modulation function, there is a cadre of PCM42 looping enthusiasts who will be keenly interested in how the PSP stacks up. The Lexicon PCM42 was perhaps the first digital delay that was designed from the get-go to work as a performance looper. It offered up to 4.8 seconds of memory and five parameters could be dynamically controlled by a foot pedal or an external control voltage source. The 42 could also be modified with additional memory and other functions offered initially by its designer Gary Hall and later by fellow-Lexiconian Bob Sellon.

The initial release of PSP42 did not emulate the PCM42s Infinite Repeat function precisely, though this was largely a conscious decision. One difference (in my opinion an improvement) is that when PSP42 is put into Repeat mode the length of the loop equals the current delay setting. The PCM42 always looped the entire contents of memory so you could never capture a short loop. This did have its advantages, though. By setting the delay time to a subdivision of the full memory length you could play with a short echo but loop a longer phrase, and the loop would contain the echoed material (you can still do this by running two instances of PSP42 in series).

I also discovered a few anomalies in the way the repeat function related to the input and feedback signals, but these problems have since been corrected by a quick response by the developer to my "bug" report. The forthcoming version 1.3 will capture running feedback into a loop and will apply echo effects to the contents of a loop when it is released. Hats off to software designers who go that extra mile!

Another difference in implementation is in the programmable clock feature. The PCM42 provided a timing pulse, suitable for driving an analog sequencer or a drum machine. This could be set as a proportion (e.g. 1/2, 3/16, 7/32) of the entire memory time and it was independent of the delay setting as defined by the inc/dec buttons. PSP42 uses ostensibly the same interface to set both clock output and delay time. This is more consistent with contemporary sync practice but it sacrifices the polyrhythmic possibilities of the original (I'm not sure how significant this might be, since I never actually used the original feature myself!). PSP42 also can act as a slave to system clock, so the repeat rate will automatically lock to tempo.

PSP84

What if Lexicon hadn't shifted its focus in the mid 1980s to high-end digital reverberation units and had continued development of digital delays? We might have had a hardware version of the PSP84! This plug-in is at heart a two channel evolution from the PSP42, but with the addition of a multimode dynamic filter, overdrive, and reverberator and with a greatly enhanced modulation section. All the components of the PSP84 have been designed with a consistent awareness of producing a vintage sound characteristic of the early 1980s (Ah yes, I remember it well!). To my ear they have done an excellent job.

The two delay lines can be feed individually by the left and right channels of a stereo send or insert. They can be linked or can run independently with different delay and feedback settings. Delay times can be set manually or slaved to the clock rate, with a maximum time of 5 seconds. Outputs of the two feedback paths can be panned independently. The filter section can be placed at the input, in the feedback path, or at the output, and the filter characteristic can be low pass, band pass, or high pass. Filter resonance is fully adjustable and cutoff frequency can be set throughout the full range up to 15kHz. The Saturation, or Drive, module is at the input to the delay line and affects both the input signal and the feedback signal. It has a single control that regulates both the saturation amount and the input envelope follower sensitivity.

The modulation section can be used to control both the delay clock and the filter cutoff frequency. It offers a choice of envelope follower and LFO with sine, pulse, triangle, sawtooth, and random waveforms, with a rate from 0.01 to 15 Hz. The reverb section offers a choice of vintage spring or plate characteristics. The spring setting has a periodicity or "sproing" that works well in certain situations, while the plate gives a denser and smoother sound. A damping control regulates the decay characteristics. The reverb can be placed either in the delay path or at the output mix.

Just as with PSP42, all parameters of PSP84 can be controlled in real time either from a VST host program or via MIDI. Each parameter is hard-coded to a particular MIDI Continuous Controller message in the range of 20 and above (keeping them out of the way of the more common dedicated controllers).

Summary

Those of us who have been kicking ourselves for not buy a used PCM42 when they were still cheep can rejoice. The PSP42 is a worthy emulation of the sound and functionality of the Lexicon classic, at about 10% of the price. The PSP84 builds on this basic architecture to provide a stereo processor with analog-style filter, vintage reverberation, and a greatly enhanced modulation section. As a company, PSP is small, dedicated, and responsive to their customers, with excellent support, an appreciation of good-quality sonics, and creative ideas. PSP have brought back an old friend and have introduced us to some new ones!

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