All analog circuitry.
Get on the bus! The Double Deca bus that is. In order to get that classic analog delay sound, Vox selected the much-revered 3205 BBD chip. There are three delay modes in the Double Deca: “short”, “both” (short/long), and “long”. The “short” mode uses one BBD chip, providing a delay time of up to 300 ms with a clear delay sound and minimal decline in audio quality. The “long” mode uses all three of the BBD chips, allowing you to specify a delay time up to 900 ms for warm-sounding delay trails. The “both” mode mixes the short and long delays, giving an ambient tonal character. It's a multi-purpose design that lets you use either one or all three of the BBD chips. In addition, an independent modulation knob lets you adjust the chorus effect. For example in “both” mode, applying modulation will give you an amazing sound that's like a trinity of delay, reverb, and chorus.