Putting an effects loop into ANY effects pedal

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puppiesonacid
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Post by puppiesonacid »

Hey guys,


I have been wondering how to do this for a while now...I've always wanted to expirment with inserting effects loops into different pedals (besides delay) and messing with sounds that might be possible. I remember when the line 6 dl4 came out and had the mod delay setting, which had a phaser sweeping the repeats... I thought it was awesome!!! And then I read about keeleys mods to the dd3's/6's for adding effects loop and achieve similar results with that mod by putting a phaser in the loop.

So that got me thinking what other pedals could benifit from an effects loop to come up with new or different cominations of effects to achieve a new sound. For example what about putting an effects loop into a wah so that you can put say a ring modulator in the loop?( i know snarling dogs had an effect like this) or a delay in the loop of a wah? idk... just trying to think of how it would sound different if at all.

Anyways... I was just wondering if there are general guidelines to go by or if integrating this into any circuit would be different with each one. I would also want to have a level for the effects loop to control the amount of the effect in the loop and maybe even a series parallel switch for good measure. I have a loose understanding of how effects loops are integrated into tube amps but not so much in the pedal department.

idk... maybe this is retarded but I want to try it out and see what happens.

puppiesonacid

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Post by floris »

- Try to always use standard "send & return" combos with two female jacks that work on the same (guitar) signal-level.
- If there is no male jack plugged-in the "send", route the signal internally to the "return". This can be done easily with a "mono jack that has a switch".
- Control only the "send" volume (if needed at all) and not the "return", or vice versa, and stick to that. That reduces the amount of "gain"/"volume" stages that you need.

This way, it all conforms to the same and plugging stuff into each other should be a blast.
Also, create a few dedicated FX pedals that do looping / splitting / merging / mixing / gain / volume for some added flexibility.
This is not "retarded" but a lot of fun! Go for it and enjoy!

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Post by JiM »

Good candidates are enveloppe-controlled effects. Some of them already have an FX loop, look for example at the MeatBall. What you'd classically want in an enveloppe filter is a clean signal with a lot of dynamics for enveloppe detection, and a lot of harmonics to filter ... so a big compressed fuzz sits well in such a loop.
A loop can also be used to route separate signals in two parts of an FX. For example, trigger a noise gate with the bass drum, but process the bass : an old studio trick if bassist's groove is not as good as drummer's.

But for sure you're not into classics :wink: so feel free to experiment weired things !

Still, some FX are not easy to "split", either because parts of the circuit work closely together, or because some parts does not directly affect the sound.
For example, there's no point in putting an FX loop between the input buffer of an overdrive, and the clipping stage ; especially if the FX loop is buffered itself. Just put the other FX in front, it should sound the same.
Another example, if i understand well this article : http://www.geofex.com/article_folders/w ... wahped.htm By putting an FX loop between the two transistor of a standard (= inductor-based) wah, you'll mess with the biasing of the second transistor and the pedal might not act as a wah anymore.
Please try anyway, because only "impossible" things may lead to something completely new ! :twisted:

So there is no general rule to insert an FX loop in a circuit, each has it specificities ... Just make sure there's no bias offset in the loop (use coupling caps where needed)

I think of it as i type, putting an FX loop in the feedback loop of an opamp (for example, instead of diodes in a tubescreamer) could lead to really strange results ... and a lot of squealing ! :mrgreen:
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Post by puppiesonacid »

hmmm... i dont know if i'm getting my point acrossed or maybe i just dont understand how your presenting your thoughts on the subject. I thought that adding an effects loop was somewhat of a simple thing, like just tapping the the in's and outs of the signal and inserting a loop in, sort of like a having two pathway's for the signal to go and having one signal that is "open" or "empty" so you can inject another effect into it, like with the effects loop mod for a dd3/6 9 that whole phased repeats thing ya know? I never considered, nor really am I knowledgeable enough about loops to even think that they can be inserted into minute parts of an existing circuit. I just thought they were added in a similar fashion as the delay loop mods, so that you can layer sounds into new ones.

Im thinking about it from an tube amp perspective, ( or at least this is what I have knocking around in my head correct me if im off ) I know that an effects loop is inserted into the circuit so that its just getting amplified and input into the audio signal before hitting the preamp, so its a clean signal feeding the effect( i have a 5150, and im not one for the dissonant raspy distorted delay sounds that you get when running the delay into the front of the amp, so the typical solo delay lead i shoot for is the steve vai thing so its clean and articulate with gain)

so anyways, im sitting here wondering... ok so if you can do that with an amp, why not a pedal? shouldn't you be able to tap into the input stage of the circuit, insert a loop , drill the holes, label send and return and call it a day? :scratch: probably way more compicated than that right? :|

The ideas I had were like for instance, with that DODfx45 I started a thread about... I was wondering, would it sound cool to inject a phaser, into the repeats of the reverb and be able to mix it just ever so slightly into that signal via an effects loop? or stick your favorite chorus in the loop for your own modulated reverb brew?

or like the wah with the ring mod idea i mentioned eariler basically a homebrew of the snarling dogs moldy spore wah ( or whatever the heck it was called )

or putting loop into a slow gear circuit and again sticking someother modulation type effect in it... or even a delay? idk... does this make any sense? im giving examples of things I thought would be worthwhile to try out while was at work today.


idk... i'll go mumble things to myself now .... lol... :horsey:

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Post by JiM »

puppiesonacid wrote: maybe i just dont understand how your presenting your thoughts on the subject.
Maybe my thoughts where not clear enough :blackeye
My point is, you can put an FX loop between "building blocs" of a circuit, but harldy in the middle of a single building block. And some FX are made from a single building block (i think of fuzz and wah as examples).
an effects loop is inserted into the circuit so that its just getting amplified and input into the audio signal before hitting the preamp, so its a clean signal feeding the effect
so its clean and articulate with gain)
Just a bit inexact here : the FX send does not provide a totally clean signal, especially in a tube amp. It provides a preamplified signal, which is (more or less) distorted, compressed, and equalized. The loop is usually between the preamp and the power amp, and in modern amps most of the tone-shaping is done in the preamp (not true for vintage, tweed or single-ended amps).
A delay sounds muddy in front because the distortion is after the delay, and articulate in the loop (distortion before delay).
so anyways, im sitting here wondering... ok so if you can do that with an amp, why not a pedal?
Sure !
In most of the examples you give, there are strategic points in the circuits that are suitable (or sonically interesting) for an FX loop. I think the interesting thing of it is to modify by other effects a signal partially processed, in a way you could not do otherwise.

As for phasing the repeats of a delay, (correct me if it's not what I think, i don't have a DL4 nor looked at the keeley mods) you could do without a loop by phasing the 100% wet (just the repeats) output of the delay, and mixing that with the dry signal taken before the delay.
Or is each repeat passing thru the phaser again and again ?
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Post by floris »

When cutting into a signal path and make a "send & return" at that point, you have to take care about signal level and impedance.

Lets call your FX with the "send & return": FX.
Lets call the circuit that you put between the "send & return": LoopCircuit.

The "send" of your FX needs to send the signal with a level that is "expected" by the LoopCircuit in order for the LoopCircuit to work properly. That LoopCircuit also presents an impedance (or load) to the "send" of your FX. Preferably the input impedance of the LoopCircuit is bigger (>10x) than the output impedance of the "send". To put it differently, the "send" output needs to be low-impedance and the LoopCircuit input needs to be high-impedance. Usually that is done with a simple buffer/gain circuit in the "send". Probably also a simple buffer in the input of the LoopCircuit.

The same applies to the output of the LoopCircuit with regard to the "return" of your FX.

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Post by puppiesonacid »

JiM
you can put an FX loop between "building blocs" of a circuit, but harldy in the middle of a single building block
ok, i get that. That makes sense. I wasn't even considering trying to insert one in the middle of single building block, although that gets my thoughts going all the more... but am i wrong in thinking that although you can view a wah circuit as a single building block, I see it as having an input/output buffer "block"( optional ofcourse but Im thinking a stock dunlop wah here), a band pass filter "block" as well as gain stages ( ie transistors ) ? Or how about this... is it possible to put an effects loop "outside" of any circuit, only grazing the input and output stages, instead of between blocks, but viewing the whole circuit as a block unto itself, or do FX Loops have to be between two building blocks? ( i might have to stick my foot in my mouth for that last bit....)
A delay sounds muddy in front because the distortion is after the delay, and articulate in the loop (distortion before delay).
yes that is what I was trying to say... :roll: sometimes I mean one thing and say something like it all while not really getting my true thoughts acrossed.

In most of the examples you give, there are strategic points in the circuits that are suitable (or sonically interesting) for an FX loop. I think the interesting thing of it is to modify by other effects a signal partially processed, in a way you could not do otherwise.
Thank you, and thank you for seeing the value of what I'm thinking about. I hate it when I get ideas like this, b/c I know they are intresting and worth persuing but I have no great understanding on how to do it electronically ( although I'm trying like hell to read as many articles and view schematics of known circuits that function in the manners I seek and to implement them, all the while trying to understand what hell I am learning) I get how circuits work from a surface level, but the electronics guru, I am not.

I don't want to sound pretentious but I have "sonic visions" of stuff I would love to hear or see in real life, I can picture it in my mind and imagine how the pedal might react and what kind of features and functions I would like it to do but again, a nikoli tesla I am not. So can you hint or just flat out tell me where in the afformentioned circuits where I can insert a loop ? I don't know where to look or identify these "sweet spots" whats proper? whats "right"? what's wrong?"


is each repeat passing thru the phaser again and again ?

From what my ear tells me its a delay whose repeats have a modulated signal ( in this case a phaser) and that has its own LFO thing going on which is NOT dependent on any sort of playing dynamics. Very interesting and cool to play with.


OK now responses to FLORIS...

I get your point about taking care to properly work out the impedence issues and all the inbetweens, but I have no idea how to calculate/measure/test this by any means. I want to build these pedals for myself but I'm not satisfied with settling for fuzzes, overdrives and boosters or even with just the stock pedals ( especially when I get an idea like this that I want to scratch.) Although the ideas I have are ambitious I know I am a novice and I don't have the knowledge to match it, at least not yet. :lol:

The initial question that I posed here has seemed to have opened a pandora's box of electronic ignorance that I have. :scratch: It quite discouraging, b/c for some reason I really thought I kinda knew my way around schematics and circuits. I mean I know a little but ... no where near the kind of knowledge I have read here. :oops: But then again the types of circuits I'm investigating and the features I want are more advance in design. :thumbsup


To put it differently, the "send" output needs to be low-impedance and the LoopCircuit input needs to be high-impedance. Usually that is done with a simple buffer/gain circuit in the "send". Probably also a simple buffer in the input of the LoopCircuit.
I have read this before in Craig Andertons books and I get it for the most part, its an important thing that many guitarists don't consider into the equation.

The same applies to the output of the LoopCircuit with regard to the "return" of your FX.
You mean that the output needs a simple gain/buffer circuit in the "return" and not that the impedance has to go from high to low in the loop right? ( maybe both?)



thanks,


puppiesonacid

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Post by floris »

Perhaps you can take one practical example of a specific circuit where you want to break a signal path and insert a "send & return". That would help things along.

But basically:
- Put a buffer /gain circuit just before each output jack: "send" jack & LoopCircuit output jack.
- Put a buffer just after an input jack: : "return" jack & LoopCircuit input jack.

You can see this in almost every effect circuit so there are many examples. This is called: "Impedance bridging":
http://en.wikipedia.org/wiki/Impedance_bridging
"In electronics, especially audio and sound recording, a high impedance bridging, voltage bridging, or simply bridging connection is one which maximizes transfer of a voltage signal to the load."

Take a look at a tubescreamer circuit. It has a transistor input buffer which provides a high-impedance-input (it does not need draw a lot of current from the previous stage) and and it has a transistor output buffer which provides a low-impedance-output (it can provide current to the next circuit).
http://www.geofex.com/Article_Folders/T ... sxtech.htm
Input buffer example:
http://www.geofex.com/Article_Folders/T ... xtech1.gif
Output buffer example:
http://www.geofex.com/Article_Folders/T ... xtech4.gif

Example buffers:
http://www.muzique.com/lab/buffers.htm
Example gain circuits:
http://www.muzique.com/lab/boost.htm

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Post by JiM »

puppiesonacid wrote:but am i wrong in thinking that although you can view a wah circuit as a single building block, I see it as having an input/output buffer "block"( optional ofcourse but Im thinking a stock dunlop wah here), a band pass filter "block" as well as gain stages ( ie transistors ) ?
If you look at the link i've posted above, explaining how a classic wah works, i hope it will become clear.
First, let's ignore the input/output buffers if present, they're meant to be transparent sounding. The first transistor is really the heart of an active LC resonnant filter. And the second transistor makes a variable capacitor for the aforementionned filter.

So where could we break such a tightly coupled circuit ?
Between the buffer(s) and the wah makes no sense, as you'll want to add another buffer for the send or the return. It's exactly like connecting (buffer)->(FX)->(wah) or (wah)->(FX)->(buffer). And as long as the buffers are not distorting, they do not change the sound, they avoid it to be changed by parasitic effects.
In the middle, between both transistors ? First, that might separate the L and the C of the filter. So it's no more a LC filter. :slap: And also, as explained by R.G., the second transistor base is biased by the collector resistor of the first one. This bias voltage might not pass thru an external FX (as soon as there is a cap in the signal path), and the wah effect might again disappear.
So, for now, i'll forget adding an FX loop to an inductor-based wah.
is it possible to put an effects loop "outside" of any circuit, only grazing the input and output stages, instead of between blocks, but viewing the whole circuit as a block unto itself, or do FX Loops have to be between two building blocks?
What makes a loop interesting, is that you pick the signal after a first part of the processing, process it further outside of the box, then re-inject it where it were for final modifications. If the first or the last part are missing or sonically transparent (like buffers), it will not sound different than classic chaining. You might just try some parallel things with splitters and mixers.
So can you hint or just flat out tell me where in the afformentioned circuits where I can insert a loop ? I don't know where to look or identify these "sweet spots" whats proper? whats "right"? what's wrong?"
As Floris said, let's look at some examples.
  • inject a phaser, into the repeats of the reverb
    Not easy in a digital reverb (unless you code it), on the DOD FX45 you have to find the summing amplifier who mixes the delayed signal(s) with the dry signal. Put a buffered FX loop just before it, on the wet signal(s). You might need to pre-mix several delay taps before the send, then mix the return with dry signal. It might be simpler to modulate directly the delay on the BBD ... but that's beyond my skills.
  • stick your favorite chorus in the loop for your own modulated reverb brew?
    Just the same as the phaser above.
  • wah with the ring mod / snarling dogs moldy spore wah ( or whatever the heck it was called )
    As I said, i don't know how the ring mod could be "in" the wah. Either it is a truely specific design, or an inductor-less wah, or the ring modulator is just in series with the wah (before or after). A schematic could be very instructing.
  • or putting loop into a slow gear circuit and again sticking someother modulation type effect in it... or even a delay?
    This one looks like the enveloppe-filter example. Or a compressor, a noise-gate, etc. In these effects, the first "block" is an enveloppe detector, which then commands a VCF or a VCA. The detector has no audio output (hum, except in a BassBalls : it's used as a fuzzz :twisted:), but you can do strange things by detecting something else than the signal processed. You could put dynamics-bashing FX after the enveloppe detection (like a full-on fuzz, for example). Or the opposite : put a modulated signal in the enveloppe detector, but process a clean signal.
  • On FX who mix the dry signal with a delayed signal (phasers, flangers, etc.), you could add a loop on one branch, before mixing. It could lessen or cancel the original effect (e.g. vibrato instead of phaser), but that might still sound cool. Beware of phase inversion, it could lead to horrible squeals. 8)
  • Why not process non-audio signals ? For example, put a delay on the LFO who pilots a phaser or a tremolo.
There's no "right" or "wrong" in guitar FX. There is things you like or not. And new, interesting ideas are often things said to be impossible by the ones-who-know. So don't believe what I say. Just try on your breadboard, until you find something you like.
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Post by modman »

Had we gotten around to tracing Paul C's Tim, we would have had an example schematic to look at.

Image

But interesting thread, will move this one in the FAQ folder

EDIT: Split off the discussion on Tim to this thread.
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Post by puppiesonacid »

ok, so instead of the tim I found the mods for adding an effects loop for the BYOC delay pedal kit. Its for the older board, not the newer ping pong delay. modman, would this help in figuring out how to put an effects loop into any pedal or just this one haha?
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