i use to call this handy little circuit: "bipolarizer"...
(official German name: "Bipolares Koeffizientenglied" [Tietze-Schenk])

Right I've got a site up. My HTML knowledge sucks though so be kind

http://www.geocities.com/smoguzbenjamin/morpher.html
Is that right?

ahem... i`m not so sure, but to me it seems, if you put the "morpher" there, there will be no signal fedback through the 470k resistor, when the morph-pot is in middle-position (= no signal passes the morpher; gain=0),
that means, the 470k+morpher act like a very huge-valued resistor, which
would turn IC1b to amplify near infinity, with all the nasty noize involved...

but i may be wrong here...

You're right. Damn, I missed that. Howabout moving it in front of that? Hold on a sec, gotta update the pic.

Quote from: Mark HammerElektrojänis,

I don't know if you are familiar with the Gretsch Controfuzz (part of Jamie Heilman's original Leper's archive of schematics), but it uses an interesting subtractive arrangement where a straight signal and Blue-Clipper/Dist+ type diode clipper are each fed to different inputs of a mixing stage (one goes to the - input and the other goes to the + input).  The output level control of the fuzz/clipper section determines how much fuzz is subtracted from the straight signal.  Because of how fuzzes work, and the compression they introduce, the straight signal decays faster than the fuzz signal so the fuzz appears to "creep into" the output.

I have actually tried to build the controfuzz but it was quite long time ago... I could not get it to behave properly. On signal peaks it seemed to work but then it faded to strange blurpy noise and then back to the signal for the last part of the decay. (This is from my memory... It was something like 6 or 7 years ago.) Part of this could be explained with my sloppy soldering technique on veroboard. Partly it could have been because I could not stabilize the opamps properly (I used the some version of the 748 that the schematic called, now I would probably try TL072 or 5534 or something). Hmmm... Maybe I should try it again now. My soldering should have improved since then (partly because of better tools).

However my idea for subtracting one distorted signal from another should sound quite different. When the two signals are distorted by the same amount but one is more asymmetric (biased differently) it should give quite strong octave. Strength of the octave effect is strongly dependent on how well the levels of the two signals are matched. In software that is easy. With opamps it should be possible. With discrete transistors as the distortion stages... some trimmers will probably be needed (they could be needed for opamp versions too as the resistors around them have tolerances too). My software tests on this kind of system actually sound a bit like my ampeg scrambler clone.

Hmmm... I'm drifting a bit offtopic... :oops:

About biasing that phase changer thingy... shouldnt it work if you just tie the other end of the pot to Vref instead of ground?

Edit: Hmmm... on another thougth... Biasing it like that might not work Because the bias could get to the inverting input too... And it would probably make the pot scratchy too.  Then again, I'm not sure...

How about putting this kind of control in place of the range pot in the Dr. Quack? Some kind of bias would be probably needed to be mixed with the control signal though.

Quote from: Mark HammerSame goes for flangers, etc.  I suspect you could also use it for a regen control, such that regeneration could vary between entirely negative or entirely positive.  Again, both intensity and polarity in one knob.  If you're going to use it in a regen path it doesn't even have to take up another pot/knob or panel space!

This describes exactly the control I use in the infinitphase for resonance - I tried it after reading about Pauls' use of it in the Funk-a-Duck for the drive control (I think, is that right Paul?) and it works a treat.

here's a schematic portion:
http://prophecysound.com/images/ifmkii/rez.jpg

Mike

I think you'd want to change the phase of the dry signal and not the envelope to create notches & peaks etc. I think it'd be better if Mark'd chime in on this.

Quote from: smoguzbenjaminI think you'd want to change the phase of the dry signal and not the envelope to create notches & peaks etc. I think it'd be better if Mark'd chime in on this.

Was this about my suggestion above? I meant it to be a different thing... If you use it on the envelope signal you should be able to change the sweep from upwards to downwards. Marks original post actually says it has been used like that already in some EH-pedal.

You could even do both for extra versatility.

I might try those some day when I have time to build Dr. Quack... I think I might have an etched PCB for it somewhere...

i think you want the morpher to replace the range pot.

good luck

There are essentially two kinds of "morphers" being discussed here.  One varies between two antiphase versions of the same audio signal, and the other (in the YTF case) pans between two versions of an envelope signal.

Why aren't these the same?  Because the inverted audio signal covers the exact same peak-to-peak zone as the noninverted one.  

In the case of envelope voltages, one envelope signal is *added* to zero volts and the other is *subtracted* from some designated maximum.  Neither covers the exact same voltage range even though they consist of the exact same amount of voltage sweep....if that makes sense.  Look at the dowanward sweep stage in the Mutron (or many other EF's that produce bidirectional sweep) and you'll see that a reference voltage is provided (using the 180k/120k resistive divider), from which the envelope signal is subtracted.  Different beast.

The YTF's circuit (now there is a circuit in desperate need of a redraw for comprehensibility) essentially mixes two envelope signals in a manner that results in cancellation in the middle position.  The morpher feeds the same signal to two inputs which result in varying degrees of cancellation depending on how much attenuation of input is applied to the in-phase vs out-of-phase copy.

I was looking at tim escobedo's phuncgnosis... would it be possible to add the LED/switch combo that tim uses there to the Dr. quack?

Me and Dr. Quack :mrgreen: I'm a nightmare I think :mrgreen: