Stereo flanger project recommendation?

[Stompe Le Monde]

I did a search for this without much luck so I'm guessing either I'm stupid/blind or there really isn't much floating around out here for stereo flanger projects.  So, I'm basically looking for a couple suggestions, advice, ideas, hugs, or whatever else you might like to give me.  I can't really explain why, but I just really want a stereo flanger right now, maybe because I've been listening to loads of Rentals bootlegs this week...

I saw the stereo mod in Tonepad's package for the Small Clone and I was wondering if this could be used or modified to work with an existing flanger project, or maybe if I could also slap that onto my already heavily modified AD3208?  I would think that would be pretty simple really, but I can't say that I even come close to remotely knowing what I'm talking about so hopefully one of you would care to enlighten me.

Thanks in advance...

[Mark Hammer]

First question to answer is what do you mean by "stereo"?  There are several different types:

"Stereo" A: One output is wet, the other dry.
"Stereo" B: One output is wet+dry, the other is dry only.
"Stereo" C: One output is dry minus wet, the other is dry plus wet.
"Stereo" D: One output is dry+plus wet with one delay, the other is the same thing with a different delay.

There are probably other configurations but that gives you some idea of the variety.  What do you want your stereo flanger to do for you?  Anbswer that and we can point you in the appropriate direction of either complete projects or mods to existing ones.

[Karmasound]

I have been curious about this too.


It's hard to know what to choice to pick since I haven't heard them.

Maybe D?


I want to do this for my clone chorus and the Flanger 301


I was going to built 2 and have a polarity reverser built to the output of one and then they could be run to seperate amps.


I don't even know if this will work. I would love to hear from someone who uses stereo effects so I can get this right.

[Karmasound]

Not to hijack..

But what I had in mind was running my Fuzz od boost on mono.


Then splitting the signal and running on chorus, phaser ,flanger, delay, maybe univibe to one amp and the same for the other.


I'm not sure how it would sound or if I would get phase cancellation.


But I would really like to know how to make this work before I invest alot of money into it.





All suggestions are welcome, thanks

[Mark Hammer]

In some cases, all people really need is an active splitter.

Given my penchant for making little battery-powered practice amps, I am often tempted to try out stereo things involving parallel processing.  Recently, I ran two outputs from a 1-in-3-out splitter to two different choruses, which ran to two separate amps.  Sounded huge and glorious.  Lots of animation, no cancellation, and very aperiodic (i.e., repetitive up and down) because the two separate LFOs were not synced.  Did the same thing with a chorus to one amp and a Small Stone to the other.  Worked just as well, and actually better than some of the more standard quasi-stereo arangements where dry goes left and wet goes right.

Worth considering.  Splitters are easier to make than stereo modulation pedals.

[Karmasound]

Couple of questions for you. That just made my day.


1. Where is a schematic or something for a nice active splitter(verified)?

2. what constitutes and active splitter versus passive?

3.would it be worth it to put a polarity flipper on one channel?


I think that is it for now. Thanks

[gorohon]

Splitter? Is that like the EPFM "Spluffer" project by chance?

[Stompe Le Monde]

First question to answer is what do you mean by "stereo"?  There are several different types:

"Stereo" A: One output is wet, the other dry.
"Stereo" B: One output is wet+dry, the other is dry only.
"Stereo" C: One output is dry minus wet, the other is dry plus wet.
"Stereo" D: One output is dry+plus wet with one delay, the other is the same thing with a different delay.

Well, my original thought was A.  I was thinking about sending the dry signal to two different amps and panning the wet between the two, I've been listening to that effect used (I think) quite a bit lately and really love it.  D sounds like it would have some really cool results by itself and panning the two signals, I think that is the choice I would make now if I could run this in "mono" mode as well.

Would it be possible or efficient to put two stomp switches on your option "D" to turn the modulation on or off for each channel?  If so that is definitely the route I would choose.  It kind of seems like the ADA flanger is the gold standard from what I've read doing searches, so would it be possible to modify the ADA to work in this manner?

I'll be the first to admit that when it comes to modulation effects I'm stepping a little out of my league here so sorry if these questions seem a little stupid or basic.  If anybody could recommend some good articles about modulation effects to help my fairly basic knowledge of them improve I would greatly appreciate it.

Mark, you're the man.  Thanks.  That's all I got to say for now.

[Mark Hammer]

Splitters:  The Spluffer project isn't too bad though it needs updating from the dinosaur era of 4739's.  My own splitter at home is the ultra-simple 1-in-3-out you'll find in the datasheet for the TL074 quad op-amp.  Since the input buffer stage on that one has a gain of 11 (easily modifiable), I tacked a 10uf output cap and 10k output level pot on the output of each of the 3 output stages to be able to match or alter levels.  Works great.

Option D: The sum vs difference stereo option (C), and its problems when listened to by means other than headphones (cancellation in "mono air space"), has come up before.  Option D is feasible when you have a means of yoking several different time delays to the same master clock, such as with a multi-tap chip like and MN3011 or MN3214, both highly unavailable these days.  

One *could* for instance produce a circuit in which two identical BBDs are tied to the same LFO but have their own clock circuits.  Small differences in the tolerances of the passive components would no doubt produce small differences in the delay range achieved, and location of notches and peaks.  If each of these BBD outputs was mixed with the same dry signal and fed to its own output jack, there would be a stereo effect, though no side to side movement, simply a sense of it being "bigger".  The use of two clock circuits very close in frequency, though, creates the potential for heterodyning artifacts and requires special attention to board layout, etc.

So, how can one easily create the impression of two different delayed outputs without the problems and cost incurred by running two separate BBDs, or the risk of mono cancellation when using option C? By combining the best of both phase-shift and BBD worlds.

Imagine the following.  Dry signal goes to two mixing stages.  BBD output goes o mixing stage A and also goes to a simple two-stage phase-shift network and then on to mixing stage B.  The phase shift network is exactly as you might see anywhere - op-amp with 10k feedback and input resistor, plus cap on the other input and resistance to ground.  That resistance to ground can be fixed or swept, your choice.  What it does is add more phase-delay to SOME frequencies, which will be enough to make that wet signal be different than what went to mixing stage A.  If you don't want to sweep it, you can at least tinker with the cap values or use a dual-ganged pot to vary resistance to ground and where the phase-shift starts and maxes out at (i.e., the interchannel difference).

(Once Steve Giles has finished toilet training his new family member, he might chime in with some comments regarding Eventide's use of fixed phase-shift stages.)

When sent to multiple amps, this would certainly sound bigger.  If side to side movement is critical to your needs, you could always yoke the phase-shift stages to its own LFO, or maybe even use a quadrature LFO with one output driving the BBD clock and the other sweeping the resistive elements of the phase-shift stages, or simply hook up a footpedal as an "expression" controller to manually sweep the phase shift and alter side-to-side differences.

Though the A/DA is kind of a "gold standard" for flanging, one needn't get that complicated for experiments.  For instance, a single dual op-amp added to the basic structure of John Hollis' "Zombie" chorus could probably get what you're striving for.  Since the Zombie uses passive mixing, it would probably be a breeze to use the basic posted layout (whether R.G.'s or someone else's), draw in the extra traces needed for two phase shift stages and the aditional passive mixing components, route a few wires to the right place, and away you go.

Though not a "beginner" project, it is well within the capabilities of many to build a Zombie.  It is also well within the capabilities of many to hand draw some extra traces on a basic PCB layout (my choice would be to draw them alongside the edge where the pads for control leads are currently situated so you have a this-side/that-side arrangement of traces/pads - if you don't like it, simply cut off the extra stuff so you have a basic Zomibe board).  Best of all, the time and cost from thinking about it to using it and tinkering with it is relative little.

Does that sort of fit the description of what you're aiming for?

[StephenGiles]

Mark Hammer said:

(Once Steve Giles has finished toilet training his new family member, he might chime in with some comments regarding Eventide's use of fixed phase-shift stages.)

Yes, we have been approved by the awful old bat sent to inspect! No actually she was apparently quite nice, and we collect Bonzo on Sunday.

Now, let me mull this over a little. Tomorrow, my wife is having some "fusion" on a finger which was set mis-shapen after an accident many years ago, so I will have my lap top with me in the hospital. Let me say that I havn't built the Eventide Instant Phaser yet, but thanks to TI that may now be a possibility.
Stephen

[walters]

1.) just use a A/B box for each channel to if you want to have
        2 amps in stereo


   2.) Take your mono flanger output and run it through a splitter and on
        one channel just put a Inverter pedal thats it you got stereo

[puretube]

2.) total sonic cancellation?

sorry for this parking-lot-like answer, but that`s the way it is IMHO...

:?

[Karmasound]

1.) just use a A/B box for each channel to if you want to have
        2 amps in stereo


   2.) Take your mono flanger output and run it through a splitter and on
        one channel just put a Inverter pedal thats it you got stereo

Wouldn't inverting it make it out of phase with the other and cancel?

Do you mean reverse polarity?

The peak of the wave would be in the + and the peak of the second would be in the - if the polarity was reversed , right. Therefore they wouldn't cancel.


If it was inverted the + and - peaks would hit at the same time and cancel out.

I'm not a tech though. So i'm just making a educated guess.

[Mark Hammer]

If you are privileged to listen through headphones, then Walters' #2 suggestion would work.  It wouldn't sound fantastic, but if your intention is to have it simply not sound mono, yes it would work.  So, he's not entirely wrong.

The problem occurs with listening to it WITHOUT headphones.  Air is essentially monophonic.  Our ears can detect if there are phase differences between ears or sound sources when it comes to portions of signals, but when two antiphase versions of the same entire signal meet in mid-air they cancel each other out.  There may be places you can stand where they won't do this, but heaven help you if you move and lose the "sweet spot".

Indeed, that is the entire principle behind noise-cancelling headphones.  Your ears detect ambient sound, and the built-in microphones feed the SAME ambient sound through the headphones with the polarity reversed.  When the headphone and acoustic signal meet on the way to the eardrums, they cancel each other out (not perfectly, but mostly).

My suggestion for adding some phase shift to the delayed sound in one channel alows for the creation of just enough phase difference and time delay between copies of the same signal at each output for it to sound different without having two antiphase signal sources cancel each other out if the listener is standing 20 feet back between two amps.  

Incidentally, while sum and difference channels used for quasi stereo outputs (a VERY common approach; my DOD FX-20 phaser is designed in exactly that way) have the problem of cancelling out in mono air, adding a stage or two of fixed phase shift creates enough channel to channel difference to avoid complete cancellation in the absence of headphones.

The basic principle here is "What can you do to make sure that the two signals comng from stereo outputs are not exact copies of each other, OR the complete opposite of each other?"  Just about anything in between those two polar extremes will permit some sort of stereo effect to be heard when listening, sans headphones, to two amps.

[Karmasound]

So if you had two amps one with it's own phaser or chorus pedal and had the settings different enough, then you would get a nice stereo sound?

But if you set them the same chances are cancellation might occur?

[Mark Hammer]

So if you had two amps one with it's own phaser or chorus pedal and had the settings different enough, then you would get a nice stereo sound?

But if you set them the same chances are cancellation might occur?

Technically, yes.  Just recognize that there are gradations of "the same".  I might have two phasers driven/swept by the same LFO, but component-to-component variation due to tolerances might make the notches produced at slightly different locations/frequencies for each.

On a 1-10 scale of the two channels being entirely-the-same (1) to completely-the-opposite (10), you probably want to be somewhere between a 4 and 8.

My posting on another recent thread discusses the Ibanez Flying Pan, noting that what I call "wet panning" is a suggested antidote to the way that the two output channels on the FP are TOO different from each other.  Someting that extreme CAN be useful, but is is rarely something you turn on and leave on the way you leave a chorus or phaser on.

[walters]

1.) Put a Inverter Pedal not a 90 degrees make it like 80 degrees
      You have to have 2 amps for stereo


 2.) And then Put a Delay on the inverted output just short delay
      its up to just experiment this is called ADT

[Karmasound]

1.) Put a Inverter Pedal not a 90 degrees make it like 80 degrees
      You have to have 2 amps for stereo


 2.) And then Put a Delay on the inverted output just short delay
      its up to just experiment this is called ADT

What's ADT stand for? :?:



That sounds like it would be the hard way, not the most efficient and economical way.

Do you have any schems or some thing I can look at. I don't know how to build all of that right know.



I also don't want to do anything that will color the tone or deviate from it to much cause then i'm not sure if it would be teh same thing then. :?

[walters]

1.) ok tell me what you want to do really basic

[puretube]

90 degrees, or 80 would be very ok for the stereo-purpose...

but 180 is not OK. (IMHO, Mark...)

An inverter flips exactly 180 degrees (not 90!).
(I prefer the term "flip", to avoid: "shift" - which doesn`t hit the nail here).


ADT = Auto Double Tracking
(supposed to sound like a singer sings the same thing onto a 2nd tape-track)