The P38 Stereo Compressor
The P38 is a stereo mastering and record production compressor with advanced optical compression, in a substantial 2U rack mounting format. It has balanced line inputs and outputs operating at line levels.
ORIGINS
Ted's original compressor was developed in 1963; in those days it was a simple optical device driven by a valve amplifier. It sounded good, but it was, to say the least, not very adaptable. During the Alice days (The 'Alice' mixer company was founded by Ted and friends in 1969) there were a number of simple compressors developed, mainly for automatic control and none were marketed as record production tools. It was not until 1993 that Ted needed a stereo compressor for his own recording work, and developed an optical compressor based on the ones used in the early days of Joe Meek's studio in Holloway Road, and his own studio in Denmark Street, London.
In recognition of Joe, Ted named the compressor the 'Joemeek' SC2. This compressor was an enormous success, particularly with producers in the United States.
The first tfpro compressor was a further development of the original design concept, but introducing some novel features including M/S matrix compression (to give perfect stereo imaging) and a variable width control. The use of a new type of light dependent resistor allowed much higher speeds of operation and so Ted ivas able to emulate some other popular compressors using variations of speed and attack/release profiles. But the P8 'Edward', as the compressor was called, retained a single VU meter and following some further experimental work stretching the use of optical systems even further, Ted decided to update the P8 to produce the definitive compressor that will last as a standard in the music production business.
The new P38 is built to last; from its heavy gauge front panel to the steel chassis; the construction is 'substantial'. Terminations are via both XLR connectors and conventional 1/4 inch jack sockets, and the power supply is built in. As with all top-end TFPRO equipment, the inputs are transformer coupled using double wound audio current transformers giving transparent performance, total isolation and freedom from hum and buzz.
The stereo input gain control is a feedback type with extremely low self noise, and incorporates a '+14dB' switch to allow for lower level inputs. To maintain perfection in stereo imaging, the stereo signal is processed into 'sum and difference' signals and these signals are compressed separately. Immediately before the output, the sum and difference are reprocessed into left and right signals. The compressor retains the optical concept that gives such an amazing sound, but Ted has incorporated novel and original design features giving extreme control of compression, with selectable ratios from 1.2:1 up to 100:1, so that the P38 is like having all the historic compressors at once! To achieve these different 'flavours' there is a 'model' switch to select four distinct compression types (detailed in the handbook). Some of the model types incorporate an element of automatic release so that programme material influences compression; this facility is modified by the TR REL button (Transient Release). Immediately following the compressor there is another innovation; this is the 'soft clip' option where transient overloads can be 'clipped' without audible distortion. An LED indicator shows when these transients are being affected.
METERING
Unlike Ted's earlier compressors, the P38 has a pair of meters that read final output level. A meter change-over switch alters the status so that the left meter reads 'mono input' while the right meter reads 'CR' (gain reduction).
PERFORMANCE
The P38 follows current TFPRO thinking and has a much extended frequency range. The Low frequencies remain flat down to 8Hz, while the HF end extends beyond 4OKHz without filtering so that there is substantial response up to 75KHz and beyond.
Noise and distortion performance are to professional standards with impulsive distortion minimised by the use of integrated class A amplifiers.
IMAGING AND BALANCE
While the M/S matrix system takes care of the stability of the stereo imagef and provides the ability to go from mono, right through to full stereo and beyond to an enhanced stereo (15O% stereo), there are often times when there are slight gain differences and imbalances between left and right. The P38 provides for this with a balance adjustment capable of plus and minus 6dB on each side.