Adventures on the other side of zero

[Mark Hammer]

I finally got my deluxe TZF setup working...well....almost working (there seems to be a bum power-related capacitor that needs tending to), and it's pretty interesting.  Once I get the intermittent functioning working I'll record some sound clips.

I have a pair of Boss BF-1 flangers.  These are 4-knob units, using SAD-1024 chips.  The chassis says they run off 9v, but the service notes say 12vdc, and users say 12vdc yields better performance, which I have to agree with; the "performance" being wider sweep.

I lifted one end of the 47k resistor that mixes dry signal in with the wet, such that each unit provides ONLY a delayed signal.  If one turns the depth control down, the delay range can be adjusted with the manual control.  And here is where it gets interesting.

I whipped up a little splitter/mixer unit so that I combine the two pedals in parallel.  The manual control allows me to set one for a little fixed delay, which is longer than the minimum delay in the sweep of the other.  IN effect, one flanger serves as fixed staggered delay for the 2nd one.  And, true to form, when the swept unit sweeps upward to its shortest delay time, it sweeps past the fixed delay of the other signal, and crosses through zero.

The neat thing is that I can vary how much time it spends on the other side of zero.  I can also set the two units to slow-ish asynchronous sweeps such that one will be crossing over the other at various times, occasionally yielding double through-zeroes as one sweeps up and back again while the other one is just starting to sweep up.

We normally think of through-zero as something that uses a fixed delay, combined with a swept one, but having two asynchronously swept delays provides an interesting sound...well, when the damn pedal doesn't crap out on me.

The other thing to keep i mind is that sweep ratios - the ratio of the shortest delay time to the longest - become exaggerated when using a staggered fixed delay.  A unit that might only sweep from a half msec to 12msec (24:1 ratio), yields a near infinite ratio when combined with a 2msec fixed delay.  The sweeps make an A/DA seem positively limp.

If you're going to tinker with TZF, I recommend considering dual lfo's for the two BBDs, and play with the weaving of time back and forth.

[Morocotopo]

So, a nice project would be a Dimension C but flanging instead of chorusing? Hmmm...

[Mark Hammer]

Scott Stites has done this.  There are a great many threads and posts abut the topic in the archives here.  Do a rigorous search and you'll find them.

Keep in mind that the Dim-C uses a single LFO, and counter-sweeps the two BBDs with that LFO.  You CAN get TZF but note that it will be a periodic sweep,  The dual-flanger approach I took allows for far more variation, including unpredictable through-zero moments.  That doesn't mean you will prefer the sounds, just that there are more sounds to choose from, to see which ones you prefer.

Also note that, as desirable a flanger as the BF-1 is, what I did can be accomplished with any garden variety flangers.  What impresses us about any flanger is it's ability to achieve ultra-short delay times, such that it appears to swoop down from out of the blue.  Achieving those swoops can often require more circuitry to buffer the clock and permit shorter delays.  All other things being equal, a flanger that sweeps from 300usec to 10msec will impress far more than one which sweeps from 1msec to 10msec.  But remember, that 300usec is relative to the real-time signal.  If your "real-time signal" is, itself, slightly delayed, then even a cheap and poorly designed flanger (heck, even a chorus) may be able to sweep to the same, or a shorter delay time, than the fixed/reference delay.

The quirky thng about the arrangement I used is that the regeneration/feedback controls in the two flangers should probably be set to minimum to avoid problems.  At the very least, whichever flanger you wish to use as your staggered/reference, should have no feedback.  Feedback in any flanger is either restricted to the swept-delay signal only, or else taken from the point after they are mixed and fed back to the input, before they are split.

[Morocotopo]

You know, I DO have two flangers, and one has an LFO that can be stopped (Electric Mistress and FL 301)

Hmm.

And I Do have a splitter-blend.

Hmmmmm.

And I DO have some spare time.

HMMMMMMMMMMM!!!!

Damn, I just realized you need only the delayed signal in the static one. Dismantle time? Give me the Hammer, I mean, the hammer!

[Morocotopo]

Damn! you got me all fired up.

Wich is the simplest flanger to breadboard  a couple of them to test this?

[Mark Hammer]

If you already have them, just lift the dry signal.  Unsolder one end of whatever mixing resistor brings the dry signal to the mixing stage.  If you've installed a vibrato option, you already have that.