Digital Delay 59A

The Digital Delay 59A is Modcan's first foray into the world of 16 bit, high sample rate Digital Signal Processing (DSP). In the past most modular delays used Bucket Brigade ICs or BBDs for time based effects. The demise of BBD ICs in the late 90's resulted in us turning to digital methods for creating delays. Some of the benefits of Digital Delay over BBDs are very low noise, 20Hz - 20kHz frequency response, delay time synchronized to tempo and stereo effects.

While the 59A is able to provide a high dynamic range and wide/flat frequency response, it also provides some selectable filtering to emulate the warmth and resonance of analogue delay units. In OFF position, no filtering is applied and the module provides delay with mirror-like accuracy. For emulation of analogue units, a lowpass filter ( LP II ) with a 2kHz rolloff provides a somewhat warmer color. A 3kHz filter ( LP I ) with slight peaking is reminiscent of the resonance found in analogue delay units.

This design uses a high performance stereo 24bit Codec for A/D and D/A conversion with 105dB of dynamic range. State of the art DSP micro controller with external 512K x 8 SRAM on a high density SMD 4 layer board.

Features:
* Mono and stereo "ping pong" delay modes
* Delay times divided into 4 ranges for best resolution
* Additional Loop mode is a basic full bandwidth sampler
* Voltage control of Delay, Regen Amount and Wet/Dry Mix
* Internal Regen control with External analogue feedback path
* Tap Tempo override matches delay time to song tempo
* Trigger input syncs delay time to an external clock or LFO
* Two choices of switch selectable Low-pass DSP filtering for "analogue emulation"
* Indicator LED for input and Regen clipping also indicates sync tempo
* Ultra smooth glitch free delay time transitions

Modes:

Mono Mode: Mono mode as indicated by the "M" prefix on the mode range switch is mixed with the dry signal on the Left/ Mono output. The Right output is internally connected to the Feedback Loop Out Jack and contains the wet delay signal only. This allows the user to externally process the feedback signal path with filters or frequency shifter modules etc. The Feedback Amt pot controls the level of feedback. Listen to the Feedback.MP3 for an example of external feedback processing.
Delay times are divided into four ranges:

1/ 20uS - 50mS- flanger range
2/ 50mS - 600mS
3/ 600mS - 2.4Sec.
4/ 2.4Sec. - 5.8Sec.

Stereo or "Ping-pong" Mode: Stereo mode is indicated for those ranges with an "S" prefix. Delay times are the same as for Mono mode. From a mono input the delayed output is ping-ponged left and right adding movement to the sound. The Left and Right jacks are the outputs. The external feedback path is disconnected in this mode and the internal Regen controls the number of echo repeats.

Loop Mode: The input is sampled when the Tap Tempo is momentarily depressed and looped in an infinite cycle with the end loop point set by the Delay pot. The loop is output through the Left/mono channel.

Firmware design by Eric Brombaugh.

http://modcan.com/amodules/delay.html