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Post subject: Order of effects in signal chain: wah-wah vs phaser/flanger
Posted: Fri Mar 28, 2014 1:40 am
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Bit of a techy/geeky question, but I've been wondering the following. It's not Mustang-specific, but relates to all the effects in the Mustang and how we use them, so still valid for this forum I hope.

As we all know, effects that change the shape of the waveform (distortion, compression, etc) are usually put before the amp. Effects that modulate the waveform (ie combining two waves, either the sound and an external signal (eg as for tremolo) or two variants of the sound signal (eg chorus)) are usually put after the amp, in the fx loop.

So, thinking about the wah-wah effect versus phaser or flanger. These are similar-but-opposite. A wah-wah is a notch boost: ie it increases the amplitude of a narrow frequency band, and that band can be 'swept' across the frequency range, either with a foot pedal or some automatic means. Phasers and flangers are notch filters: ie they decrease the amplitude of a narrow frequency band, again sweeping that band across the frequency range. Phasers and flangers create the notch in different ways (hence their different sounds; a phaser does it by modulating the original signal with a phase-shifted version of itself, a flanger modulates the original sound with a delayed version of itself; the sweep is achieved by varying the amount of phase-shift or delay over time) but they both do basically the same thing for the purposes of this question.

Given those similarities, why is a wah-wah conventionally placed before the amp, and phasers/flangers in the fx loop? Or rather, I understand entirely why phasers/flangers are in the fx loop. What I don't understand is why the wah-wah shouldn't also be in the fx-loop?

Is it just many years trial-and-error experience that have led guitarists to conclude it sounds better having the wah-wah before the amp, for no particular scientific/electronic reason? Or is it because the wah-wah effect is being created in a completely different way to the other effects, making it fit better (in terms of the electrical / audio signal processing) with the other 'distortion' effects?

I think that's the answer: the 'notch' filter in a wah-wah isn't being created by the modulation of two signals. It's created by an ordinary band-pass filter/boost (think: one slider of a graphic equaliser). What makes it a 'wah' rather than just a fixed filter is that the (effective) capacitance values in the filter are varied by a clever transistor circuit that mimics a conventional capacitor. So think of quickly increasing one slider of the graphic eq, then increasing the next slider while reducing the first, and so on, back and forth across all the sliders.

Conclusion: although phaser/flanger and wah-wah are all notch effects, it's simply the electronic difference in the way the notches are created that determines where in the signal chain it's best to put each of these effects? If so, I find that an interesting thought: the type of sound created by an effect isn't the key factor in determining signal order, rather the way that sound is created. So if someone were ever to build a wah-wah effect that created the band-pass boost using modulation, it would be better to put it in the fx loop rather than before the amp?

I'm curious please for anyone who knows more about this than me to confirm/correct the above.


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Post subject: Re: Order of effects in signal chain: wah-wah vs phaser/flan
Posted: Fri Mar 28, 2014 1:53 am
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Then a further follow-up question is:

In the Mustangs, all these effects are created by DSP rather than conventional analogue phase-shift, delay and band-pass-boost circuits. So does the DSP create these effects by exactly mimicking the analogue signal processing? (eg for a Flanger, does the DSP take a copy of the audio signal, delay it a bit, then mix it back with the original?)

Or does the DSP process the audio signal in a completely different way, to create something that sounds the same as the equivalent analogue effect but with no relation to the way that analogue effect works?

If the latter is the case, then the interesting question is: if (as per OP) the effect order in the chain is best determined by the way the signal is being processed by analogue components, does that all become irrelevant in the DSP world, if the DSP is processing the signal in a completely different way? Or if not completely irrelevant, are the differences enough that there may be a 'better' overall effects order in a digital signal chain compared to the analogue equivalent?


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Post subject: Re: Order of effects in signal chain: wah-wah vs phaser/flan
Posted: Fri Mar 28, 2014 1:53 am
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Joined: Sun Jun 17, 2012 11:37 am
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Location: England
Note to self: spend less time thinking about such things and more time playing guitar :)


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Post subject: Re: Order of effects in signal chain: wah-wah vs phaser/flan
Posted: Fri Mar 28, 2014 4:37 am
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Joined: Tue Jul 26, 2011 5:27 am
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I use wah pre-amp for one simple reason. When you put it in your FX loop, it noticably changes the perceived volume (toe and heels). For instance - if I am playing an overdriven solo with a wah and put wah pre-amp, one will hear the "wah-wah", but the perceived volume will be roughly the same. If I put it in the FX loop, the perceived volume will vary greatly between toe and heels position. While this might not be as evident when playing clean stuff (the perceived volume also changes if you put it pre-amp here), it is certainly very evident for overdriven stuff. So I'd say that's the reason for most. But I used my ears to be the judge and tried out both possibilities and saw what works better for me ;)

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Post subject: Re: Order of effects in signal chain: wah-wah vs phaser/flan
Posted: Sun Mar 30, 2014 11:28 am
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Joined: Fri Feb 08, 2013 7:58 am
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Hi,
you get a very different kind of effect if you put the wah wah (or an auto-wah) in pre-amp section of a chain and in the post-amp section:
if the amp is overdriven, and the effect in the preamp position :
the guitar tone is first filtered and then saturated ... so if the pedal or control it is in the mid position of the sweep ... a midrangey tone will be distorted ..
if the amp is overdriven, and the effect in post-amp position:
the distorted tone will be filtered by wah modulation, the resulting tone is harsh and the volume changes according with the filtering frequency.

As we know the vintage wah wah is that in the preamp position. i would say ,the other effect is more suitable for synthesizer sounds.. even though my guitar teacher bought a vintage wah/fuzz pedal by Danelectro (shaped like a vintage car) and in that case the wah circuit was after the fuzz so when engaged the distortion, the resulting tone was very harsh. I didn't appreciate that combination but both the wahwah and fuzz were very beatiful if used separately.

Dimitri


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