Restored Phase Linear 1000 Autocorrelator Noise Reduction System

Restored Phase Linear 1000 Autocorrelator Noise Reduction System

82 capacitors replaced. All switches cleaned and lubricated. Most of these units have many loose solder joints. 6 boards are attached to the circuit board and are not supported properly on the top. Most of these will be loose and "intermittent" until re-soldered. Many parts (capacitors) were used in this restoration and lots of time and labor.

Restored February 2023

*****All functions work fine with the exception of the "Auto Correlator button" which when depressed does not always want to release***** I was always able to get the button to come back to the "out" position but sometimes it takes a few tries. It the button doesn't release a push and "quick" release will get it back to position after a few tries. A bit of patience goes a long way. These units are very old and mechanisms are not perfect after such a long service life. Some of the face plate print with the words "Peak Unlimiter Down Expander" is partially worn off (upper left hand corner). With that said Bob Carver was an audio and Gadget Genius and all his products are precious

The Phase Linear Autocorrelator Noise Reduction and Dynamic Range Recovery System is a signal processor that often makes good music sound better. Don't knock it until you've auditioned it; today in 2011, it really does make many good recordings sound even better.

It was wildly expensive when new in the 1970s, about $1,500 corrected for inflation, and has only a subtle but powerful effect. These are for careful listeners, not for impressing people with quick demos in the "retail" stereo stores of old, so few people actually bought them.

The Phase Linear Model 1000 and Model 4000 are very subtle processors, which is their magic. What they do won't be obvious unless you listen carefully, and if you listen carefully, these can add more to your music than just about anything else.

These brilliant circuits were envisioned and designed by perennial audio genius Bob Carver, founder of Phase Linear in 1970, and then Carver Corporation in 1979, as well as today's Sunfire, founded in 1994.

These processors were included in the Phase Linear Model 4000 preamplifier, and the same were also sold as the stand-alone Model 1000 processor reviewed here.

These processors are:

The Autocorrelator is a single-ended noise reduction processor. It's not really an autocorrelator; "Autocorrelator" was used as a fancy marketing name for a patented and very clever system of noise gates.

The Autocorrelator greatly reduces noise in tapes, FM radio, CDs and SACDs recorded in the 1970s and before. I haven't tried it with LPs, with which it was originally designed to work best.

The Autocorrelator is amazing: it really does reduce noise significantly, doesn't affect the music or frequency response and has no audible artifacts.

It just makes noise go away. It has separate circuits to remove hiss and to remove rumble.

Dynamic Range Recovery System

The Dynamic Range Recovery system is really two processors controlled with one knob, a Peak Unlimiter and Downward Expander.

It has a subtle effect. It improves immediate dynamics, adding life and impact to most sources, without adding any audible artifacts.

It is quite different from the processors sold by dbx, which have a stronger effect overall, but less effect note-to-note. Instead of expanding by a small amount, like 1.5:1 or less, over a large dynamic range, this Phase Linear expands by a larger about, up to 2:1, over only a very narrow dynamic range. This lets this Phase Linear processor add more to most recordings with no artifacts, but it's also so subtle that few people were sophisticated enough to hear it, and thus dbx won out in the market while this excellent processor went out of production.

This Phase Linear system is better for use most of the time, and is better for trying to get some note-to-note life back out of dynamically compressed recordings.

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