Stereo flanger project recommendation?

[Karmasound]

I guess since I have two amps I would like to run modulation fx in stereo.

I will assume that i'll have to build one effect per amp.

I want a purtty stereo spread without phase cancellations, and I don't want the original sound of the effect to be colored, I just want it to sound like one awesome chorus or phaser not two.


So i'm guessing so far I need a splitter from my last mono pedal and put  chorus on amp A and one chorus on amp B.


Then from there is where i'm not sure. Put the setting so they vary slightly?
Do what you suggested?

i'm sure there are a lot of ways but i'm trying to go with the most practical.

I am building a pedal board and don't have all the parts yet. So the reason i'm asking all these ?'s is so when I order and do the layout and design I know what I am doing before hand.


I think i'm getting there, or just more confused. Thanks

[Stompe Le Monde]

Thank you Mark, I think I'll be able to manage that, it should be a good learning experience.  But, just for curiosities sake and tinkering once I get all my parts together, for option A (in the style of the Boss DM 3 I think?) would it essentially just involve sending the BBD output to one jack and dry to another, just skipping the mixing stage?  Could I wire it so when only one jack is plugged in it would still run everything through the mixing stage in "mono" mode?  Then separate the two signal when I plug in the second jack for this "stereo" mode?  Am I even remotely on the right track with that?

Thanks again for the help.  I have a feeling I'll be building a couple modulation effects this month just for experimentation's sake now.

[Stompe Le Monde]

I think i'm getting there, or just more confused.

You and me both.  I feel the coming weeks will be filled with a great deal of frustration followed by a whole mess of aural delight.

[Karmasound]

so just tacking a polarity reverser like on Geo's site on one side of the chain going to Amp A would do the 90 degree trick.

And that would get me a fat spread?



reverb creates depth, but what creates width?

[puretube]

it`ll do the 180 degree trick...

expanded stereo-width: add a little bit of inverted L-channel to the R-channel,
and add a little bit of inverted R-channel to the L-channel.
The more you add, the wider the speakers seem to be apart ("stereo-spread")...

[Karmasound]

ok I see.

Can you make it do 90?  Is there a different circuit to look at for that?

Half the R values?







Anyone ever used the Univibe in stereo?

[puretube]

halving the Rs halves the amplitudes, not the phases...

for shifting, or varying the phase (constant or modulated) :
that`s what allpasses are for...

find allpasses in almost every phaser (phasor/phaseshifter), and in so-called "vibes"

[Karmasound]

so I should study allpasses then?


would that put me on the right track?

[puretube]

read this:
http://www.geofex.com/Article_Folders/phasers/phase.html
(from R.G.`s site)

http://www.beitec.com/phase/phse.html
(by the great Mike Beigel)

[Mark Hammer]

Ton,

Re: 90n vs 180 degrees.  In total agreement.  One is shift, the other is flip.

KSound,

Each allpass filter (phase-shift) stage adds up to 90 degrees of phase shift, HOWEVER, that phase shift is not applied uniformly across the spectrum.  Like with anything involving a single capacitor and resistor, you see a gradual change as frequency increases or decreases.

Normally, with phase shifters, the value of a resistor is altered in some LFO-controlled way so that WHERE the phase-shift starts to be extensive enough to produce a notch, when combined with a dry signal, CHANGES.  If, given the sum total of all phase shift across all stages, for THAT frequency, given THAT cap and THAT resistance, ends up being 180 or 540 degrees for THAT momet, then you will hear a notch.

So, two fixed of phase shift CAN produce a "flipped" signal (180 degree shift) for some frequencies, but the net effect will also depend on the degree of time shift introduced by the BBD preceding it.  Maybe there is 180 degrees of phase shift and the *risk* of cancellation for a 5khz signal, but if one introduces 1msec delay at some point, that 180 degrees is supplemented by additional shift contributed by the delay. At least that's how I understand it.  The net result should be that where the notches fall will be different because of the combined effect of *time-based* and *group-delay* based phase shift.

I need an analogy here.

Imagine I cloned 100 people, and lined up all 200 at a starting line for a foot race.  The original 100 all vary in terms of running capacity/speed.  If I fire the starter's pistol and there are no systematic differences in where they are running or how far they have to run, the 17th fastest person should reach the finish line at the same time as their clone.  Suppose, however, I let loose a herd of cows on the side of the running field where the clones are all located.  It now becomes much less likely that the "originals" will arrive at the finish line at exactly the same time as their clones.  (Hot damn, I'm good!  :lol: )

This is the net effect of the added phase-shift stages.  I suppose to be certain to avoid some types of problems, sticking with only one allpass stage (max phase shift at any frequency of 90 degrees) might work well.

Incidentally, one of the things we have ALL foolishly neglected here is that phase can also also get changed in the amp itself.  Whether by virtue of the way the speakers are wired, or inversion in any of a number of stages in the amp, it is possible to NEED an additional stage of inversion between the guitar and that amp to assure amp 1 and amp 2 are in phase with each other.  In other words, you might get LESS cancellation by inverting the signal before going into a second amp!  Strange and wonderful world, isn't it?

[StephenGiles]

I'm trying to locate my Eventide Instant Flanger manual, I've got the Instant Phaser supplement which I must have separated out somewhere along the line, but the flanger section I'm sure provides some useful text regarding the fixed phase shift stages............so it's up in the attic I go!
Stephen

[DiyFreaque]

Mrs. Giles, if you can read this, Stephen went up into the attic and hasn't returned for some time.  We're getting worried - can you check on him please?  

Well, I certainly am interested in what the Eventide manual has in it.

In the meantime, JH (Juergen, not Jimi) wrote quite a bit about the phase shift function on his page covering his adaptation of the Eventide Flanger, dubbed the 'Storm Tide' flanger.  A very good read:

http://home.debitel.net/user/jhaible/jh_storm_tide_flanger.html

Cheers,
Scott

[StephenGiles]

Mrs Giles laughed!!

Yes, I am familiar with the Storm Tide. I've dug up a few pages, but not pages 13-24 which has a more detailed desciption of fixed phased shift matters. Perhaps this evening when I have a little more time I'll search a couple more piles of papers.
Stephen

[DiyFreaque]

I hope your wife's finger is healing OK.  She is brave - I think I would have just lived with the crooked finger (shudder).

Not to hijack the thread too much, but I was wondering - on your A/DA clone, did you stick with the op amps of the original design, or did you find some worthy/better substitutes?  This is a general "if you recall" question (no need to go look at the PCB if you don't remember off-hand).  

I plan to build one meself - I think, for one thing, having one of the greatest flangers ever made available to try these very interesting concepts out on will be wonderful.  In fact, it sounds like that's exactly the approach you've taken on some of these threads.

Take care,
Scott