PYE 4061S

Ted Fletcher breathes new life into this venerable old name.

Ted Fletcher has been involved in a number of audio companies over the years. He designed the original Alice consoles, for example, and was behind both the original JoeMeek and TFPro brands, whose gear earned plaudits. Today, Ted’s again designing for Alice, who recently acquired the PYE brand name, and he was invited to design and build a high‑end stereo compressor that would be worthy of the old name. One of his aims was to keep the operation as simple as possible, in line with the ethos of hardware used in the 1960s, but to improve on the noise performance of those vintage devices. The result of his endeavours is the PYE 4061S, and while it may have little in common with the original PYE compressor’s circuitry, it is nonetheless impressive.

Design & Operation

Described as a 21st Century analogue levelling amplifier, the PYE 4061S is a stereo feed‑forward compressor that’s designed to sound as transparent as possible, both when controlling peak levels and when used for longer‑term levelling. It’s billed as being suitable in the recording chain for tracking, for track processing during mixing, and for mastering. The circuit employ’s Ted’s previously proven ‘sum and difference’ mode to eliminate stereo image shift when processing stereo signals.

The ‘feed‑forward’ description relates to the way the gain‑control circuitry is configured. Most compressors work by sensing the output level from the compression stage and then feeding it back to the side‑chain and gain‑control stage, which might be typically a FET, VCA or opto‑electronic circuit. By contrast, a feed‑forward compressor monitors the input signal’s envelope and then sends this information on to the gain‑control element, which in this instance uses a transconductance amplifier in the feedback path of a high‑performance BA4580 op‑amp. Ted says this feed‑forward analogue limiter/compressor design adjusts its compression ratio in a way similar to the old Altec compressor, but without introducing low‑frequency bumps and without the overshoots of the slower valve circuitry. By the way, there’s no external side‑chain access, as the topography of this circuit doesn’t have what you’d recognise as a conventional side‑chain.

The 4061S is housed in a 2U rackmount case, with a reassuringly thick, white‑painted front panel. On the front, a pair of illuminated moving‑coil meters monitors the levels and gain reduction. Levels of up to +28dBu can be handled by the output stage, which employs circuitry built around UK‑built Stevens & Billington transformers. Two illuminated buttons bypass the compressor and switch the metering from showing either the left and right levels, or showing the mono level on the leftmost meter and gain reduction on the right.

The controls are set out clearly, with an input gain knob...