Boss RDD-20 Digital Delay Line


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Boss hit the ground running with the original Uber-Chorus, the legendary Boss CE-1, and has created many desirable chorus effects since

The RDD-20 Digital Delay is a half-width rack unit from the 1980s Boss Micro Rack range. It uses 12-Bit digital circuitry to get that proper 80s sound. 12-Bit circuits tend to sound more analogue and less hifi than 16-Bit and they have a characteristic “Old School” sound. The RDD-20 will create delay effects from a super-short delay via slapback through to long quarter-note delays & repeats

The RDD-20 has a dedicated modulation section with variable depth & rate controls so short chorus & phaser effects are easily done. In this resepct it duplicates much of the functionality of the RCE-10 Chorus

When you look harder at the RDD-20 it becomes clear that a lot of thought went into the design of the Micro Rack series. The power supply has a loop-through connector so units can be daisy-chained. There’s a footswitch socket for effect bypass. Inputs & outputs are on phonos as well as mono jacks and there’s a rear-panel switch to shift the nominal operating level between -10 and -20 dBm. Maximum delay time is 400 mS

Front panel controls are simple: Delay time is set in steps and fine-tuned via a delay time pot. Modulation Rate and Depth control Modulation and the dedicated Feedback control sets the amount of delay fed back to the input. At higher settings, with short delays you’ll hear typical resonant flanging effects and, with longer delays, slow, dub-style effects.The Delay output section has a simple lo / hi EQ control and an Effect Level control to set the balance of direct & effect. There’s an effect bypass switch and a power switch

Keys to the depth of the chorus effect are pre-delay and the modulation section. By adjusting these it’s possible to create very subtle effects with movement but very little pitch modulation, or you can wind up the depth to get a traditional chorus with lots of detuning. Unlike simple stomp boxes, there’s lots of opportunity to shape the effect through experimentation

“I just love it for its analog “spacy” sound. It’s adding the depth that I need to my sound. This is one of my secret weapons”

“It’s used to produce weird sounds, playing with all the knobs you can produce sounds that goes up to helicopters swirling, trapped in a giant leslie…”

“I just love it, I can describe the sound of the Delay as “spacy”, because it got some reverb in it, it adds a 3 dimentional aspect to the sound. What I like is its tone control, in fact it controls the way you want to make it sound: very analog or very digital, with everything in between”

Photos show a Boss RCE-10 Chorus and will be replaced with photos of the RDD-20

The RCE-10 has one input and two outputs. Inputs & outputs are on phono sockets as well as mono jacks and there's a rear-panel switch to shift the nominal operating level between -10 and -20 dBm. It uses an external 9 VDC power supply (included). Delay is variable from 1.5 to 400 mS and the unit uses 12-Bit digital processing
1/2U device suitable for mounting in a 19" rack tray (not supplied). External 9 VDC power supply included
Owners Manual  Harmony Central ★★★★★ Reviews  Muffwiggler discussion Dancetech review Synth demo (Chorus comes in at 0:16, and is panned left-right at 0:40) Youtube demo Youtube demo
1/2 U
In truly excellent condition for a vintage piece of kit. There are a couple of scratches on the underside but the rest of the unit looks like new