Dolby 361 Processor with Cat 22 Dolby A Noise Reduction Card


Out of stock

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This Dolby 361 is out of stock. I have a similar Dolby 360-1 here

There is a setup guide for using this hardware here

The Dolby 361 was ubiquitous throughout the 1970s, 80s and 90s. It was the standard single-channel Dolby mother unit, compatible with the original 1965 Cat 22 Dolby A card and the later Cat 280 Dolby SR cards. Every studio had a couple of 361s but they are now surprisingly rare on the secondhand market

As a double-ended noise reduction system, Dolby A encoded the signal and applied reciprocal decoding on playback. If the tape machine was aligned correctly the system was pretty transparent and gave a significant noise reduction, particularly at higher frequencies

Post-digital, Dolbys are obsolete except for archiving and for doing the Dolby Trick. Dolby A splits the audio spectrum into four bands, applying varying amounts of compression to each. Compression is level-dependent so, as levels rise, compression backs off. At higher frequencies, where tape hiss is more obvious and average signal levels are relatively low, a fair amount of compression could be used, resulting in a dramatic perceived reduction in tape noise & hiss

The Dolby Trick
The Dolby Trick uses the high-frequency compression of Dolby A as an audio effect. By encoding the signal, but not decoding it, it lifts the harmonics & airiness of sounds in an attractive way. It works like a charm on backing vocals but it’s also useful on guitars, drum ambience & etc

Used with standard Cat 22 cards the effect is most pronounced at high frequencies. By modifying the cards to bypass processing on each frequency band it’s possible to create different effects

I’ll have modified cards for sale soon

The 361 was patched into tape machine feeds & returns and switched from record to replay mode as required. There's a remote socket on the back panel for automatic record / repro switching but most 361s were switched manually Built like a brick outhouse, the 361 is a hefty 1U device weighing in at 5.5 Kg. There are no electronics in the 361, it's a housing for the NR card. It has a power supply, dedicated input / output switching section and a slot for the noise reduction card. Inputs & outputs are transformer-coupled 361s came with a non-standard power connector which is almost impossible to find. These units have been modified with standard IEC sockets. A UK or Euro Schuko power cable will be supplied on request
Standard 1U device suitable for rack-mounting. The 361 is heavy (5.5 Kg) so should be mounted with care
In excellent condition for a vintage piece of kit. Has been tested for encoding. Some front panel switch indicator bulbs are blown but the relevant switches for encoding (NR in/out, Rec, Normal) are illuminated. Meter illumination does not work. Otherwise works 100%. Cover panels for the NR card slots are supplied