Pedal sequence explanation

[gmaslin]

I've run into this pedal sequence issue too. An audio amp designer offered the following to me:

A distortion effect squares the signal and a square wave is much easier to reverb well since most of the infinite tone vector variations in the sine wave are not there. When the since wave is clipped, so are these tonal variations. As a consequence, all the tonal richness is either lost or muted. This effect is exacerbated when the impedances of the circuits don't mate well. Mismatched output impedances of the pedals/pre-amps and amps also degrades the signal (tone sucking) by clamping the resonant peaks of the pickups.

Since we're on the subject of mating pedals/effects. I'm looking for advice on a modulating pedal to match my wah, reverb and distortion pedals. More than a few musicians have suggested to me that a phase shift pedal would fit perfectly with the other effects I have and will enable me to dial in chorus and flanging effects without duplication. Their arguments claim a flange or chorus pedal would only introduce unnecessary complexity and mostly unusable tones with the other pedals I have. What the opinion of the readers here? If the mods feel like this belongs in its own thread, feel free to move it and email me the new location.

[EBK]

Welcome to the forum!

We'll have to carefully parse what you wrote into some more technical terms that don't make engineers nervous ("infinite tone vector variations" sounds like someone was trying to sell you something instead of teach you something...).  Give us a while.   The fact that you're here means you are willing to learn, and most of us are excited to impart what wisdom we happen to have.

[Transmogrifox]

The term that engineers like is:
Linear Time-invariant Systems (LTI)

Unfortunately we engineers (just like everybody else) don't get a free lunch, so most of our guitar stomp boxes are:
Non-Linear Time-variant Systems (let's not use an acronym here).  We design certain systems to reduce distortion and time-variance so that we can approximate LTI systems for certain types of circuits, but then (like distortion) intentionally violate these properties to make an interesting effect.

The one commonly-used effect I can think of that intentionally approximates LTI behavior:
Graphic Equalizer

A Parametric Equalizer is technically not time-invariant, but it's practical use is meant to be time-invariant (set andforget).

Here are the types of effects that might be considered mostly linear but Time-Variant systems:
Compressors (linear amplification that is modulated over time)
Tremolo (same as above)
Wah & envelope filters & other clean filter effects
Chorus (linear filtering that is modulated over time)
Flange (like Chorus)
Phaser (like Chorus)
Delay (approximately LTI, but often delay time is modulated)

Nonlinear time-invariant systems:
Fuzz
Distortion
Pitch shift

Example of a nonlinear time-variant system:
Ring modulator
Fuzz octaver (duty cycle often signal-level (time) modulated)

All of this techno-babble has a purpose...

LTI systems are commutative (can be arranged in any order and the same effect is achieved). Like, a*b*c*d = a*d*c*b.

Linear Time-variant systems generally can be arranged interchangeably when the delay involved in the time variation is slow enough that there is very little change between the non-delayed and delayed paths of the signal, AND the change is much slower than the impulse response of the system (for example a wah).

For example, if you put a wah after an echo effect, you get everything coherently wah'd in unison.  If you put a wah in front of an echo effect, it's like having 2 wah pedals going at different times because the sweep position on the delayed signal is different than the current sweep position clean path.

The effect of wah sequence on choruses and flangers is much more subtle because the rate at which you change the pedal position doesn't cause there to be a very big difference in frequency response between clean and delayed parts of the signal.

Nonlinear systems are where things get interesting.
As a general rule, the best sounds come from placing non-LTI stuff ahead of LTI stuff.  In some cases you can get a decent effect from going the other way around.
In general reverbs and delays in front of distortion or time-varying systems sound like trash.
Chorus in front of distortion can sound ok, but usually it is overwhelmed by the nonlinear response of the distortion pedal (doesn't come through as much)
Phasers and flangers can have a unique sound when placed ahead of distortion (but the effect is much more pronounced when placed after).
Wahs before and after distortion have their own sounds:
  Before:  pre-filters the signal and changes which harmonics and cross-modulation terms are generated by the distortion (additive synthesis)
  After:  The distortion creates more harmonic (and non-harmonic) mess and the filter emphasizes a certain band of generated frequencies (subtractive synthesis)
EQ's have the same general effect as wahs.  Often it is good to have an EQ before AND after a distortion.  Most distortion pedals have this pre and post EQ function built-in.

Compressors are a good example of an exception to the rule of Non-LTI-->LTI.  A compressor is time-variant, but usually sounds the best when it is at the start of the signal chain.

[Transmogrifox]

... most of the infinite tone vector variations in the sine wave are not there.

This is hilarious    I need to quote this somewhere ...
Oh, I did

[gmaslin]

@Transmogrifox
Thanks for the well thought out response. It provides a different explanation for the same conclusion that is useful to know. Unfortunately, it doesn't really answer my question. Given the following effects (stompboxes):
1. Wah pedal
2. Digitech Hothead (distortion)
3. Digitech Timebender (delay)
4.
Will a plain old phase shifting pedal with rate, level and effect intensity, combined with the other effects above allow me to produce chorus and flanging sounds?

[nocentelli]

That depends on whether you consider a phaser to be capable of recreating what you might perceive as chorus or flanging sounds. Some chorus pedals can approximate flanging and vice-versa, some phasers can produce what you might call a univibe-ish chorus-y swirl, but I would not say that a phaser can do flanging.

[gmaslin]

@nocentelli
As I understand the waveform manipulation, phasing effects shift the signal to create notches or gaps in the waveform without adding back any pitch or harmonic distortion. These missing distortions can be introduced with the wah (pitch variations) and the Timebender (harmonic variations). Here is the theory:
1. All the chorus effects can be achieved by slightly manipulating the Wah with a short delay and repeat (<40ms) on the Timebender.
2. Flanging effects are no more than chorus effects with shorter delays (<15ms) and greater pitch variation (more Wah range).
If the information above is true, then it would seem to suggest I can achieve most, if not all of the usable tones available with a flanger or chorus pedal. If the theory is faulty, then please explain how it is.

[ElectricDruid]

The theory is faulty. Here's why:

A wah produces a significant peak in the frequency response, whereas both phasers and flangers produce multiple notches in the frequency response. Those different modifications produce very different sounds.

You might be able to get a "proper" flanger or chorus sound out of the Timebender. It has some limited modulation options, so if you set up a delay with a short enough length and then add the modulation, you'll be getting close. For chorus, you want the delay a bit longer (say 10-30msecs) and no or very little delay feedback (repeats). For flanging, you want the delay shorter (0.5-20msecs is good) and you want much deeper modulation and probably a significant amount of feedback.

HTH,
Tom

[gmaslin]

@ElectricDruid
Thanks for the most helpful answer so far. I'm assuming you read and understood the minimal use of Wah described above to achieve the slight pitch variations required and determined it was impractical/ineffective to work. Okay, so it sounds like I may not even need any phase shifting pedal with the Timebender. It has numerous pitch shifting and modulating options, including octaves. I will be experimenting with the settings you describe to see what kind of chorus and flanging results I get. In my pursuit of a flange effect on the Timebender, what parameter increases feedback? I recognize electronic feedback as the "Presence" knob on my amp. Is this the feedback I need to dial in or do you mean something different by "feedback"?

[Transmogrifox]

Sorry, your question wasn't clear.  With a topic like "Pedal sequence explanation" it looked like you were looking for advice on -where- in the pedal chain to put phasers/chorus/flange effects, and did not pick up that you were really asking about whether you can abuse certain effects to get the sound of another effect.

First -- Read RG Keen's excellent "technology of the..." series on geofex:  http://www.geofex.com/fxtech.htm
This will give you a lot better understanding of what these effects actually do rather than trying to decipher what "infinite tone vector variations" means.

You won't get anything pitch-modulated from a wah pedal (well, you can with about 64 of them synchronously modulated in the right way -- I know this because I have done it digitally https://www.youtube.com/watch?v=CzA3SYhKkIw).

For flanging and chorus sounds, the Digitech TimeBender is the correct tool if it lets you configure delay times down in the 1ms to 50ms range.
Because of the voicing and delay modes you might even be able to get some sounds that have a curling swoosh like a phaser.  Either way it looks to me like the TimeBender is a pretty versatile effect so it will probably cover 90% of what you might want to do.  More than getting advice from a forum, take a day and just play with the thing.  Go through the tutorials in the user's manual (available online) and take some time to understand what it can do.  Browse youtube & other online forums.

Feedback is "repeats".

A typical flanger sound would be wet/dry set to 50%, delay set to around 5ms and adjust modulation to taste.  To make it more intense increase the "repeats" knob.

A chorus sound can be had with about any delay setting -- just add modulation.  Short delays (<20ms) will give you a more classic chorus sound and longer delay times will give you the chorus sound in the repeats.

A phaser will give you the swooshing sounds like a flanger, but the notches in the filtering are spaced on a logarithmic interval.  Flanger notches are spaced harmonically.  In my opinion the phaser generally sounds a little darker than the flange.

You can get an ok chorus-like sound out of a phaser, but it helps to have something like a 12-stage phaser.

One trick with the wah -- you can get a mild phaser-like sound out of it by putting it into an op-amp feedack loop.  This creates a mild univibe-like sound when the feedback level is set correctly.

Finally, if you're looking for a 1-stop shop modulation pedal (you already have the timebender), then a flanger would be probably the most versatile to add to your pedal chain.

[ElectricDruid]

@ElectricDruid
Thanks for the most helpful answer so far. I'm assuming you read and understood the minimal use of Wah described above to achieve the slight pitch variations required and determined it was impractical/ineffective to work. Okay, so it sounds like I may not even need any phase shifting pedal with the Timebender. It has numerous pitch shifting and modulating options, including octaves. I will be experimenting with the settings you describe to see what kind of chorus and flanging results I get. In my pursuit of a flange effect on the Timebender, what parameter increases feedback? I recognize electronic feedback as the "Presence" knob on my amp. Is this the feedback I need to dial in or do you mean something different by "feedback"?

On the Timebender (in common with many delay pedals) feedback is labelled "Repeats", since feeding back some of the delayed signal back into the delay turns a single delay into multiple repeats.

HTH,
Tom

[gmaslin]

@Transmogrifox
I owe you an explanation. My opening post was originally intended as an addition to the 'Passive volume pedal' thread in this same forum section. The issue of pedal order effect on tone was there and that is why I referenced the mods to move it to its own thread. I am happy that it ended up here because the answers have given me the information much more quickly than I anticipated. The Timebender is proving to be much more pedal than I originally thought it would be when I bought it. I am getting some very credible chorus sounds and the repeat patterning options create an almost infinite tonal variety of those sounds. I will be experimenting all weekend with flanging sounds but if those are as promising as my experience so far with chorus sounds, I am very optimistic. I, like many, would like to settle on as few pedals as possible to credibly recreate the sounds required. I suspect the Timebender will eliminate the need for a chorus pedal. I'll know more later.

@ElectricDruid
Thanks again. :hugs:

I have been looking at a Moosapotamus DIY flanger/modulator and am impressed. I happen to have a gutted old Crate amp that has those troublesome MN3xxx chips so if I can't get the flange effect I want from the Timebender, I'll try putting one together. Are there other flanger pedal projects that have surpassed it? Also, I'm considering a compressor pedal. Are there any DIY compressor projects I should be looking at? What about the idea of using the level without gain on my distortion pedal to get a compression effect, will it work?

[gmaslin]

Final update:
The Timebender cannot go lower than a 10ms delay. As a consequence, I am unable to find any settings that will produce a smooth flange effect. I can get some barely passable flange effect sounds but they are too wobbly (chorusy?) to be considered good. This time delay limitation will not allow a phaser introduced in the pedal chain to effect a flange sound so it looks like I need a real flanger to get a real flange sound. Anyone know better? If not, I'll be starting a new thread asking about the competency of the moosapotamus project to do flange sounds.

[ElectricDruid]

Yep, 10msecs definitely puts you into "chorus" territory, not "flange". Tough luck. The wobbliness is probably caused by the LFO modulation not being slow enough. Flangers often use very slow LFOs, with a 10 second cycle or longer (0.1Hz or so). As you speed up the LFO, the pitch distortion (wobble) gets worse. The technical reason for this is that the rate-of-change-of-delay increases. This is notable on several chorus pedal designs, where faster LFO rates give a "seasick" sound unless you can back the modulation depth off a bit.

If you're looking for a flanger to build and you'll allow me to blow my own trumpet for a moment:

http://electricdruid.net/flangelicious-a-super-dooper-flanger/

This project came out of a thread here originally:

http://www.diystompboxes.com/smfforum/index.php?topic=105807

The aim was to design a simple-to-build flanger - most aren't exactly a beginner's project. Ask around to get an objective opinion - lots of people here have built one, and there are various threads about it.

Tom