Modified Cat 22 Dolby Trick Card


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This Cat 22 Dolby A card has been modified as a “Dolby Trick” card. In this modified card bands 1 & 2 have been disabled so only bands 3 & 4 – the mid & high frequencies – are processed. Use in encode (record) mode to process audio

I have 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

For sale is a modified & tested Cat 22 (Dolby A) card. The Dolby 361 is not included

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

Cat.22 card only. Requires a compatible interface such as the Dolby 360 or 361

Modified Cat.22 card only

Setup guide


Cat.22 card only. Modified to disable bands 1 & 2. Tested to encode only, working 100%. Dolby 361 not included