Firmware - FX Rack

FX Rack is a professional-quality effects processor designed to work with the 4mix's send/return setup. It provides delay, reverb, and comb filter effects with independent processing for two audio channels.

Features#

Channel A1 (Delay/Reverb)#

• Delay: Tempo-synced delay with adjustable length and feedback
• Reverb: Classic reverb algorithm with adjustable size (RT60)
• Pipe Delay Mode: Toggle mode that feeds the delay output into the reverb input for more complex textures
• Mix Control: Adjustable mix between delay and reverb outputs

Channel A2 (Comb Filter)#

• Comb Filter: Short delay effect (1ms to 50ms) with adjustable delay time and feedback

Controls#

CV Inputs#

CV1 (Delay Length)

• Controls the delay length for the delay processor
• Range: 0 to 1/2 beat
• Tempo-synced: Synced to MIDI tempo when MIDI clock is present

CV2 (Delay Feedback)

• Controls the feedback amount for the delay
• Range: 0.0 to 1.0

MIDI CC Controls (Bank A)#

To access these controls, you need to use the MCC module and select bank A:

1. CC 20 (Reverb Size): Controls the reverb size (RT60/reverb time)

   • Similar to Room Size, this controls the RT60 (reverb decay time)
   • Range: 0.1 to 3.0 seconds
   • Lower values = shorter decay, higher values = longer decay

2. CC 21 (Delay/Reverb Mix): Controls the mix between delay and reverb for output A1

   • Center position: Mixes delay and reverb equally
   • Turning clockwise: Mixes more reverb
   • Turning counter-clockwise: Mixes more delay
   • This determines the final output mix for the Delay/Reverb channel

3. CC 22 (Comb Length): Controls the delay length for the comb filter

   • Range: 1ms to 50ms
   • Short delay for creating stereo width and modulation effects

4. CC 23 (Comb Feedback): Controls the feedback amount for the comb filter

   • Range: 0.0 to 1.0
   • Higher values create more pronounced delay repeats

MODE Button#

• Hold for 200ms: Toggles Pipe Delay Mode
  • When enabled (LED ON): The A1 channel delay output is fed into the reverb input along with the dry signal
  • When disabled (LED OFF): Only the dry signal goes into the reverb
  • The state is saved and persists across power cycles

Audio Processing#

The FX Rack processes audio in the following way:

Input A1 (Delay/Reverb In):

• Audio input for both the Delay and Reverb processors
• Signal goes through delay first
• Depending on Pipe Delay Mode:
  • Enabled: Delay output + dry signal → Reverb
  • Disabled: Dry signal → Reverb
• Final output (A1) is a mix of delayed signal and reverb output, controlled by CC 21 (Delay/Reverb Mix)
• Output A1 is 100% wet signal

Input A2 (Comb In):

• Audio input for the Comb Filter
• Signal goes through comb filter delay
• Output A2 is the comb filter output (100% wet signal)

This design allows for creative effects processing: delay/reverb on channel A1 and comb filter effects on channel A2, perfect for use with the 4mix's send/return setup.