A stereo reverse reverberator with cascading multitap pre-delays.

I wanted to try and make a reverse-ish reverb for a while, and I think this one turned out pretty cool!
It uses 4 short linear delay lines (maximum 100ms -> 200ms -> 400ms -> 800ms) as a pre-delay before a full-wet Plate Reverb module. The delays are feeding into each other in such a way that all taps are evenly spaced, and every subsequent tap is 2dB louder, so you get 15 taps increasing in level, feeding into the verb. This way, the longest ‘reverse’ time is about 1.5s. There’s even a button to delay the dry audio so it ends up at the end of this pre-delay, so with a short decay time for the reverb this makes a quite convincing reverse reverb! If you turn down the reverb mix you can blend in this strange, reversed multi-tap pre-delay. It’s fully stereo (both dry and wet retain stereo image), and you can skew the left and right pre-delay paths for a huge stereo field. There’s also modulation of the pre-delay, and if you crank the feedback and reduce the pre-delay time to minimum you can get some very strange and unique flanger-like tones out of this thing. The feedback is ducked with an envelope follower, so things never get out of hand (too much), so turn the knobs, go nuts, make strange sounds!

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[OVERVIEW]
-Input/Output: Stereo in/Stereo out (or Mono in/Stereo out)
-CPU load: Around 102%
-Build: Initial version built with firmware 2.80
-MIDI: All MIDI related modules (in PEACH colour) are on the 3rd page marked MIDI. I always use channel 10. If controls are set to CC’s I use CC channels 21/36 (see CONTROLS section for details).
-CV Inputs: Unused.
-CV Inputs: Unused.

[REVISIONS]
1.0: Initial patch.

[CONTROLS]
All the main controls are on PAGE0 and are labeled and starred (see below for a “Picture Manual” in the comments). The Stereo Output module with gain parameter is on PAGE1.

MIX (sets the mix between dry and wet signal)
VERB MIX (set the mix between the pre-delay taps and reverb)
VERB DECAY (sets the reverb decay length)
REVERSAL TIME (sets the delay time of the pre-delays)
FEEDBACK (sets the feedback of the pre-delays; ducked by output of last pre-delay taps)

MOD RATE/DEPTH (sets the rate/depth of pre-delay modulation)
LPF/HPF (sets the low-pass/high-pass filtering of the pre-delays
DRY DELAY (toggles a delay of the dry sound; enable this for most realistic reverse reverb)

SKEW (sets the asymmetry of Left and Rights paths; found on PAGE1)
DUCK (sets the amount of ducking of the FEEDBACK); found on PAGE1)

ZEBU LEFT/RIGHT button = Unused
ZOIA LEFT / MID / RIGHT stomp = Unused

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[PATCH STRUCTURE]
This looks like a complex patch but it’s actually pretty straightforward. There are 4 pre-delays (on each side, L and R), and they cascade into each other in such a way that each tap is 2dB louder:
Tap1 to Output = -14dB
Tap2 to Output = -12dB
Tap3 to Output = -8dB
Tap4 to Output = -0dB
Tap1 to Tap2 = +2dB
Tap1 to Tap3 = +2dB
Tap1 to Tap4 = +2dB
Tap2 to Tap3 = +4dB
Tap2 to Tap4 = +4dB
Tap3 to Tap4 = +8dB

So that gives:
Tap1 = -14dB
Tap2 = -12dB
Tap1+2 = -10dB
Tap3 = -8dB
Tap3+1 = -6dB
Tap3+2 = -4dB
Tap3+2+1 = -2dB
Tap4 = -0dB
Tap4+1 = +2dB
Tap4+2 = +4dB
Tap4+2+1 = +6dB
Tap4+3 = +8dB
Tap4+3+1 = +10dB
Tap4+3+2 = +12dB
Tap4+3+2+1 = +14dB

Of course, with this many delay lines, the audio feeding into all those taps must be heavily attenuated (I think also -14dB?). I guess balancing all the gain stage from all these taps was the main challenge for this patch!

All this feeds into a Plate Reverb, very straightforward. I added a SKEW value for the pre-delay times, which only affects the Right signal path and makes those delays a bit shorter which makes the stereo image very big. Finally, the feedback path was tricky, and I ended up only feeding the last few pre-delays back into each other and had to add an envelope follower so things could be retrained a bit better, so it ended up a bit different than I expected, but still a pleasant addition, I think.

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[TIPS/TRICKS]
>>> Set REVERSAL TIME to taste, set VERB MIX full wet and enable the DRY DELAY toggle for most realistic reverse reverb sounds. Don’t forget, your main MIX control still controls the balance between the verb and dry sound!
>>> Now reduce the VERB MIX to hear those individual taps peek through.
>>> Set REVERSAL TIME very short (near minimum), and turn FEEDBACK up for strange, flanger-like tones. Can get messy!

[THOUGHTS/IDEAS/PLANS]
This one turned out pretty well, and I don’t think I’ve seen something like this on PS yet. It sounds great with vocals or other complex harmonic sounds going in, or with short plucky things! For now, I want to play around with it, so no future plans yet.

If there’s any bugs/questions/remarks/requests or suggestions for improvement, please let me know!
Enjoy!

(Image: Tom Hegen)