Dual Phaser Pedal Question

[mindcapsule]

Hi,

I was thinking of building a Phaser pedal from a kit however I would like to be able to switch between two sweep settings via footswitch with one of the rates being full on (fastest setting). Can I do this with an additional DPDT or 3PDT switch?

So basically the pedal would have one switch to turn the pedal on and off, and another switch to go between the sweep rates.  I'm guessing that I should be connecting the switch between the middle lug and ground of the pot.  

Any help would be greatly appreciated.

Thanks,

Robert

[petemoore]

I did something like this recently on a phase 45 with an SPST/parallel resistor to the 10k?...anyway I can't get the schem up right now...that resistor which sets the Min rate with the Rate control pot, in fact connected To the rate Pot IIRC.
 At faster settings it becomes a speed increase knob, the faster the setting the more the speed increase the switch does, unfortunately, 10k is a small figure [compared to the 500k? rate pot]...I'd planned at one point to increase the 10k to say 25k or  100k [which would probably make super slow *slightly faster] to give more room for the switch to mess with changing the resistance of that resistor.
 Perhaps two parallel speed pots would be independantly settable, and Now that I just thought of this, I might just scrap the above speed increase mod and use the added pot and switch for achieving [gazuntheit] independant presettable switched speed control.
 The other speed control I love using is the Speed pot of the SS phaser, the circuit in and being controlled by a wah treadle/case. Getting the right taper on the pot...I used a 'ratio gear' string/spring drive [EB Volume pedal type drive...string around/through a potshaft one end sprung the other to the toe of the pedal] the string goes through a 'cone', this changes the rate between toe down distance and potshaft rotation distance near toe down.

[Mark Hammer]

The ease would depend on what sort of LFO you're using.  Some of the "classic" 2 op-amp LFO circuits use a pot in voltage-divider mode to set the speed, where others use a pot as a variable resistor.  The voltage-divider format provides a greater range of frequencies for the same parts count, as far as I know, hence it tends to be the more commonly found.

The variable resistor format, however, is obviously the easier one to switch.  Indeed, all it would really take to do the switching would be a SPST switch to select between a higher resistance (the slow speed) and the additiona of a parallel resistance to set the "fast" speed (the added parallel resistance drops the entire resistance down to achieve a faster charge-up time of that capacitor in the feedback loop of the op-amp).

If the idea of having a gradual, rather than instantaneous, speed change appeals to you, take a look at the LERA circuit over at GEOFEX (http://www.geofex.com/Article_Folders/lera/lera.htm).

Finally, the "bonehead" way to do it is to simply add another cap in parallel with what is already there.  For instance, if you wanted to drop the speed of a CE-2 (http://home.hetnet.nl/~chrisdus/download/ce2.gif) by half, you could simply add another 0.1uf cap in parallel with C19.  Alternatively, stick another 0.1uf cap in series with C19, and use a footswitch to shunt it.  The down-side is that you probably need to know what speed factor will work for you, in advance.

[mindcapsule]

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