Dolby 361 Processor with Modified Cat 22 Dolby Trick Card


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SKU: dbx-361-cat-22-dolby-trick Categories: , Tags: , , , ,


Standard Dolby 361 processor with a modified Cat 22 “Dolby Trick” card. Bands 1 & 2 have been disabled so that the card only processes mid & high frequencies. Use in encode (record) mode to process audio

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

These Dolby 361s date back to the 1970s & 80s and are likely have missing switch caps & bulbs. This does not affect operation. Tested to encode only, working 100%. Supplied with a modified & tested Cat 22

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 subtle. We have modified the Cat 22, bypassing processing on the lower two frequency bands, to create a more pronounced effect

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 1U device weighing in at 5.5 Kg. There are no electronics in the 361 but inputs & outputs are transformer-coupled. It contains a power supply, dedicated input / output switching section and a slot for the noise reduction card Many 361s came with a non-standard power connector for which a suitable power cable will be supplied. Later models used a standard IEC socket in which case a UK, USA or Euro Schuko power cable will be supplied on request. Voltage is switchable 110 / 220 VAC
Standard 1U device suitable for rack-mounting. The 361 is heavy (5.5 Kg) so should be mounted with care
In good condition for a vintage piece of kit. Has been tested for encoding. These Dolby 361s date back to the 1970s & 80s and may have missing switch caps & bulbs. As shown the photos, the cover panel for the NR card slot may be missing. Meters and/or meter illumination may not work. None of these affect operation Tested to encode only, working 100%. Supplied with a modified & tested Cat 22