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Audio Effects from modulating an Echo or Delay signal
Audio Effects from modulating an Echo or Delay signal
● Designing a dual 90° mod. Chorus & Flanger, using Reason 9.5
● DIY Electric Mistress / Dimension D, using Reason's CF-101
-: How it works :-
Let's start with a recording of you saying "Hello". When you play back the recording, the sound says "Hello".
If we now play back the original but add a delay of maybe 3 seconds to a copy, we get "Hello... Hello". It's an echo.
But if we play back the original but add a tiny delay of maybe 20 milliseconds to a copy, we get "Hello" but this would sound strangely hollow.
Chorus and Flanger effects are about adding a tiny delay to the original signal.
The graph shows an audio signal of a triangle wave. It's played at "A3" which is the "A note" just below "middle C". "A3" is pitched at 220Hz and so that graph represents 30ms (or 6.6 cycles).
Here is the same audio signal of triangle wave except it is delayed by 10ms (or 2.2 cycles).
The next 3 graphs show the result of adding the first two graphs together.
Here the delayed signal is 9ms.
The result of adding a delayed signal (to the original) causes interference. In this 9ms example, the interference happens to be constructive; resulting in a larger amplitude signal.
Here the delayed signal is 10ms.
The interference basically becomes changes the waveform.
Here the delayed signal is 11ms.
Different delay amounts create different resultant waveforms. In this 11ms example, the interference happens to be destructive; resulting in a smaller amplitude signal.
Here is an animation of the 3 summed signals for 9ms, 10ms and 11ms.
By changing the delay times, we can create some "motion" to change the resultant waveform.
-: Controlling the effect :-
We create the "motion" in Flangers and Chorus by modulating the delay time using a Low Frequency Oscillator (LFO). The parameters available for LFO are usually Frequency of oscillation and Modulation Amount. LFO Frequency is sometimes labelled as Rate or Speed. LFO Modulation Amount is sometimes labelled as Depth or Width.
We can mostly assume that the LFO will use a triangle-wave or a sine-wave.
The diagram below shows parameters for Flanger and Chorus devices which are typical to Boss and Ibanez models.
Flangers have a Feedback parameter (sometimes labelled as Resonance or Regeneration or Enhance), which Choruses tend to not have. Feedback is when some of the delayed signal is added back to the input; creating a string of delayed copies; causing a whoosh-like effect.
Flangers and Choruses also tend to use different Delay Times. Delay Time is sometimes labelled as Manual or Effect. Flangers use very short delays which accentuates movement in the high tones; causing a "metallic whirl" effect. Chorus uses a longer delay time which accentuates movement in the mid tones; causing a shimmer-like effect.
Some devices have pre-set Delay Times (which you cannot change).
Parameter controls labelled as Effect-Level or Delay-Level determine the amount of the delayed signal which is added to the original signal.
-: How it sounds :-
As the delay time increases or decreases, the delayed copy creates interference which is changing over time. There are many descriptions of the sound of flanging or chorusing which mostly involve fluidity. It could be something from a "fluttery shimmer" to a "swirly breeze" or from a "twinkly ripple" to a "wave swell". An ethereal quality: You get the idea. Whatever imagery it evokes, there are several generalisations we can garner:-
When the LFO speed is slow, you can push up the Delay Level and/or the LFO width (and/or the Feedback). It will still sound acceptably subtle.
When the LFO speed is fast, you have to turn down the Delay Level and/or the LFO width (and/ or the Feedback). At fast speeds, the effect becomes very noticeable.
Most of the time, the LFO is sweeping up or down. This modulation effect is subtly pleasant. But at the "ends" of the sine-wave (or tri-wave), the delay-time "bounces back" to change direction. These "turning-points" create a noticeable whir-like sound. This is the "dead giveaway" that you are using a Chorus or Flanger. Too much of the whir will spoil the magic. The "sweep" is like swaying through water while the "whir" makes you a bit seasick... maybe.
Short delay times accentuate the high timbres; medium delay times accentuate the middle timbres, and; long delays accentuate the low timbres. Because Flangers have a Feedback control, short delay times are better suited for pleasant sound control. If you add Feedback to long delay times, you end up with Vibrato (and that is another story).
-: Guides and References :-
Guides : Delay times for Flanger & Chorus
Notable articles on Chorus and Flangers : from Reverb, Making Music, Premier Guitar, Presonus, Strymon, Mr Black, Wampler, Electro Harmonix, GearPage [1] & [2].
These are only guides. Is it a Chorus or Flanger? In the end, it's really a question of what sound we are after. What device are we trying to emulate? Let's look at some popular Chorus & Flanger devices for a better idea of the "sound" we want.
Specifications of popular devices:
Flanger : Delay times
0.0039 - 4 ms MXR Micro Flanger MX-152 0.4 - 3.2 ms Boss RBF-10 MicroRack Flanger 0.4 - 14ms A/DA Flanger 0.5 - 6.5 ms Boss BF-2B 0.5 - 15 ms Roland SBF-325 Fl.mode 0.5 - 16 ms (mid= 3ms) Boss BF-1 0.6 - 10 ms Moog MF-108M Fl.mode 0.8 - 16 ms Ibanez FL-305 1 - 12.8 ms Ibanez FL9 1 - 13 ms Boss BF-2 1 - 15 ms Tokai TFL-1 2.4 - 2.8 ms EHX Electric Mistress (Flanger)^ 2.5 - 12 ms Ibanez FL-301 5 ms Ibanez AD-202 Fl.mode
LFO range
0.025 - 5 Hz Roland SBF-325 0.04 - 10 Hz A/DA Flanger 0.05 - 10 Hz Boss BF-1 0.057 - 11 Hz Ibanez FL-301 0.06 - 13 Hz Ibanez FL9 0.0625 - 10 Hz Boss BF-2B 0.0625 - 10 Hz Boss RBF-10 Microrack Flanger 0.08 - 8.8 Hz Ibanez FL-305 0.1 - 8 Hz MXR Micro Chorus 0.1 - 10 Hz Guyatone MC3 0.1 - 14 Hz Boss MicroRack Ensemble Chorus 0.1 - 20 Hz Yamaha SPX90 0.25 - 1 Hz SR&D Rockman Stereo Chorus 0.2 - 5.5 Hz MXR Micro Flanger 0.25-1 Hz Scholz Rockman St. Ch./ Delay 0.33 - 10 Hz Seymour Duncan Catalina
Chorus : Delay times
0.5 - 35 ms Boss RCE-10 MicroRack Ensemble Chorus 0.9 - 6.4 ms Ibanez CS9 re-issue 1 - 8 ms Guyatone MC3 1.2 - 12.8 ms Ibanez BC10 Bass Chorus 3.2 - 8.5 ms Ibanez CS9 original 4 ms Boss CE-300* 5 - 15 ms Roland SBF-325 Ch.mode 5 - 50 ms Moog MF-108M Ch.mode 5.1 - 7.3 ms MXR Micro Chorus MX-148 6 - 60 ms Seymour Duncan Catalina 10 - 50 ms Ibanez AD-202 Ch.mode 16 ms MXR M-134 St. Chorus 20~24 / 40~44 ms Scholz Rockman Stereo Chorus 20~24 / 50~54 ms Scholz Rockman St. Ch./ Delay
* not verified
^ depends on version. Delay estimated from CombFilter chart.
From the above tables, we can guess at some typical settings:- Effect Type Delay Mod.Range Flanger High 0.5ms +4ms Flanger Low 2ms +4ms Chorus High 8ms +4ms Chorus Low 16ms +4ms
Links: Boss manuals, Manuals Lib, Effects Database, Tone Home, Rockman Fr, SynthManuals
-: Designing a dual 90° mod. Chorus & Flanger, using Reason 9.5
This design takes inspiration from Electro-Harmonix Electric Mistress -&- Roland SDD-320 Dimension D (plus a bit from Tom Scholz Rockman Stereo Chorus).
The Design : We will use one LFO but take two outputs which are 90° out-of-phase. These will modulate the two devices (1 Chorus & 1 Flanger). So the devices will be 90° out-of-phase; when one device "sweeps", the other device will "whir", and vice-versa.
The dual 90° phase-locked Chorus & Flanger will be created within Propellerhead Reason 9.5 using the CF-101 Chorus/Flanger. The same principles apply if you're using another Digital Audi Workstation (DAW).
Electro Harmonix's Electric Mistress is the "Holy Grail" in the Flanger/ Chorus world. Since the beginning of time (around 1976), the Electric Mistress has been consistently voted into the top "Best Flanger" and "Best Chorus" category. There are many devices which can switch between a Flanger OR a Chorus. But the Electric Mistress is a Flanger AND a Chorus.
Roland's SDD-320 Dimension D is a studio Chorus device from 1979 and it only has 4 buttons to select your sound. So you could select [1] or [2] or [3] or [4], from softest effect to strongest. Why bother with knobs for twiddling when the sounds are already beautiful? Actually, you could also select combinations of [1 + 4], [2 + 4] and [3 + 4] too. The same Chorus design idea was later released as Boss Dimension C (in pedal form). The Dimension effects devices create dual Chorus by using a single LFO with 2 outputs at 90° phase-difference to modulate 2 delay devices.
For our design, we will use one LFO, take 2 outputs at 90° to modulate a Chorus and a Flanger.
Delay time for Flanger = 2.7ms {like E. Mistress}
Delay time for Chorus = 17ms {close to Rockman}
LFO rate = slow to medium
Block Diagram of Roland SDD-320 DimensionD - using 2 Delays modulated by 1 LFO at 90° phase shift [source- WiKi UserManuals].
Photos source- Electro Harmonix
The CF-101 is a Chorus/ Flanger from Propellerhead for use within their Reason music and audio software environment.
We will be using the Reason CF-101 Chorus/ Flanger as the main device. We will use 2 x CF-101; one for Flanger and one for Chorus.
But first, let's get some idea of the delay times in milliseconds...
Propellerhead Reason CF-101 Chorus/ Flanger - in milliseconds:-
CF - 0 1 2 3 4 5 6 7 9 11 13 15 ms - 0.16 0.31 0.47 0.63 0.78 0.94 1.09 1.25 1.56 1.88 2.19 2.5 CF - 17 19 21 23 27 31 35 39 43 47 51 ms - 2.81 3.13 3.44 3.75 4.38 5.0 5.63 6.25 6.88 7.5 8.13 CF - 55 63 71 79 87 95 103 111 119 127 ms - 8.75 10.0 11.25 12.5 13.75 15.0 16.25 17.5 18.75 20.0
CF-101 Delay settings:-
Flanger appx 2.7ms = 16
Chorus appx 17ms = 110
For the phase offset LFO, we will use 4 Phase LFO by Spectral Scan.
-: DIY Electric Mistress / Dimension D, using Reason's CF-101
4 Phase LFO dual 90° modulated delay:
4 Phase LFO dual 90° modulated delay:
Device List :-
● Combinator (Rack Device Holder) - so we can Save the set-up.
● ID8 Instruments (Standard MIDI) - so we can test and hear the set-up.
● Spider - Audio Merger Splitter - We're using the Splitter to split the signal for the Chorus & Flanger separately. We're also using the Merger as a mixer to merge the Chorus & Flanger signals into one.
● CF-101 Chorus/ Flanger x 2
Shopping/ Download List:-
● 4 Phase LFO by Spectral Scan. This device can have 3 phase-offset outputs from 1 main LFO.
Alternatively:-
○ Elements DS-LFO by AirRaid Audio.
Procedure to create our dual Chorus & Flanger device.
○ Open a Combinator
○ Drop in the ID8.
○ Below that, drop in the Spider Audio Merger Splitter.
○ Below that, drop in BOTH the CF-101s.
○ Below that, drop in the 4 Phase LFO.
I've arranged it as the Chorus on top and the Flanger below it. It's a good time to rename the devices.
Wiring
○ ID8 outputs ->- Spider Splitter inputs A,B
○ Spider will split outputs for Chorus & Flanger
- Spider Split outputs-2 ->- Chorus (top-CF) inputs
- Spider Split outputs-4 ->- Flanger (bottom-CF) inputs
○ Chorus (top-CF) outputs ->- Spider Merge input-1
○ Flanger (bottom-CF) outputs ->- Spider Merge input-3
○ Spider Merge outputs ->- Combinator inputs (This is your end result signal).
○ 4 Phase LFO will modulate delay times of the Chorus & Flanger
- 4 Phase LFO 01 CV-out ->- Chorus Delay CV-in
- 4 Phase LFO 02 CV-out ->- Flanger Delay CV-in
4 Phase LFO set-up:-
○ Rate = 0.88 Hz
○ Type = N (non-linear)
○ Level = 25%
○ 02 Level = 25%
○ 02 Offset = 90 degrees
Chorus [top-CF] set-up:-
○ Delay = 110
○ Feedback = 0
○ Rate = 0 / Sync = Off / Mod = 0
○ Send Mode = On
Flanger [bottom-CF] set-up:-
○ Delay = 16
○ Feedback = 35
○ Rate = 0 / Sync = Off / Mod = 0
○ Send Mode = On
This version is for using as Effects Send/ Return (so Send Mode = On).
For stand-alone effect use, switch both Send Modes = Off.
That's it! Have fun!
Epilogue:
I am quite pleased with this "Dimension Mistress". I am using it for all my mixer set-ups as an "always On" Effects Send/ Return.
As an effects project, this has involved obtaining a lot of information on many devices. To summarise what we've done, the concept is as follows:-
a) Use one LFO to synchronise the modulation of 2 Delay devices.
b) The LFO outputs are to be out-of-phase with each other.
c) We've chosen the LFO phase-shift to be 90°.
d) The first Delay device is chosen to be a Chorus,
e) using an uncommonly long delay time of 17ms {close to SR&D Rockman}.
f) The second Delay device is chosen to be a Flanger,
g) using a medium delay time of 2.7ms {like E Mistress}.
h) with medium Feedback (set by ear)
i) For the LFO, we selected a slow comfortable rate of 0.88 Hz.
j) The modulation levels of both devices were decided by ear,
k) and selected to be the same for both devices.
Apart from (a) & (b), everything can be adjusted or changed to suit whatever effect you want to achieve. For your sanity, I would advise that you adjust the parameters in the same order as above. Just be aware that slower LFO rate can use larger modulation amounts without the effect sounding obvious.
If you want to use this more like SDD-320 Dimension D, then use both Delay devices as Chorus use the "Checking Output Waveforms" diagram as your guide to delay times and modulation amount.
Looking at (e), I chose a long delay time because I'm used to the Rockman X100 sound. The contrast of delay times gives the effect a wide shimmery feel. Just a note: For my Chorus device, I'm actually using a Feedback= -5, which is similar to SDD-320 Mode4.
Elements DS LFO dual 90° modulated delay:
Here is another more version of the above using Elements DS-LFO (for a bit of variety).
DS-LFO set-up:-
○ LFO1: Freq = 0.88 Hz
○ LFO1: Phase = 90
○ Global: Amp = 20%
In DS-LFO, the Right CV-out is affected by Phase (LFO Left CV-out is not affected).
Chorus -&- Flanger set-up:-
Rear: Delay CV (knob) = 64
The Delay CV is adjusted to half (64) because the CV-output of DS-LFO is double that of the 4 Phase LFO.
Mono version - dual 90° modulated delay:
Here's an even simpler version for Effects Send/ Return:
The Chorus is Mono and panned hard Left.
The Flanger is Mono and panned hard Right.
Notes about 70s & 80s analogue electronic circuits:
We mostly think of setting the delay-time in "the middle" and using the LFOs to modulate that delay-time. In 70s & 80s, components to create delays were expensive. As such, the reality was to set the delay-time to the "maximum" (allowed for in the circuit) and then use the LFO to modulate the delay-time downwards (ie shorter)... Some devices would modulate upwards.
We mostly think of the delayed-signal as a pristine clone of the original signal. In the 70s & 80s, the delayed-signal was more like a "blurred shadow" of the original. Delay was created by using a long series of capacitors (called Bucket-Brigade Device) which generally would not guarantee a clear copy. But it didn't matter if the delayed signal was clear or not: The flange and chorus effect still works. In fact, this added more character to the sound... as well as some (unintentional) noise!
Elements DS LFO dual 90° modulated delay:
Mono version - dual 90° modulated delay:
Additional Info
Full conversion table for CF-101 to milliseconds
CF-101 0 10 20 30 40 50 60 70 80 90 100 110 120 0 0.156 1.719 3.281 4.844 6.406 7.969 9.531 11.094 12.656 14.219 15.781 17.344 18.906 1 0.313 1.875 3.438 5.000 6.563 8.125 9.688 11.250 12.813 14.375 15.938 17.500 19.063 2 0.469 2.031 3.594 5.156 6.719 8.281 9.844 11.406 12.969 14.531 16.094 17.656 19.219 3 0.625 2.188 3.750 5.313 6.875 8.438 10.000 11.563 13.125 14.688 16.250 17.813 19.375 4 0.781 2.344 3.906 5.469 7.031 8.594 10.156 11.719 13.281 14.844 16.406 17.969 19.531 5 0.938 2.500 4.063 5.625 7.188 8.750 10.313 11.875 13.438 15.000 16.563 18.125 19.688 6 1.094 2.656 4.219 5.781 7.344 8.906 10.469 12.031 13.594 15.156 16.719 18.281 19.844 7 1.250 2.813 4.375 5.938 7.500 9.063 10.625 12.188 13.750 15.313 16.875 18.438 20.000 8 1.406 2.969 4.531 6.094 7.656 9.219 10.781 12.344 13.906 15.469 17.031 18.594 9 1.563 3.125 4.688 6.250 7.813 9.375 10.938 12.500 14.063 15.625 17.188 18.750
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