Deeper chorus on an Ibanez SC-10?

[moro]

Hello,

I have an Ibanez SC-10 and the effect is a little too subtle for my liking. Is there a quick fix to getting a deeper chorus out of this thing? Here's the schematic:

http://www.freeinfosociety.com/electronics/schematics/audio/ibanezsc10.pdf

I tried replacing C27 with a 47pF cap (the smallest I had) and it got a little out of control. But am I on the right track here? Should I try 10pF? Also, comparing it to the CE-2 schematic, it looks like maybe I should increase the value of R29?

Thanks.

[jonathan perez]

what do you mean deeper? what do you mean subtle? is it not loud enough? more bass? more delay time?

[MartyMart]

C27 is the correct cap for the delaytime mod, perhaps 47p was just too close to "flanger" area ?
Try 10-22pf and see how that sounds.
MM

[Mark Hammer]

C27 is the correct cap for the delaytime mod, perhaps 47p was just too close to "flanger" area ?
Try 10-22pf and see how that sounds.MM

Actually, 47p would increase the delay time range well beyond what is probably acceptable for that circuit.  All other things being equal, the minimum delay time would increase proportional to the change in the value of C27.  Assuming that the minimum delay time was likely somewhere in the 3-4msec range, swapping 5pf for 47pf would bump you up to a hypothetical 30msec+, and that's for the minimum delay.  Keep in mind that as delay range goes upwards, the degree of modulation tolerable drops dramatically.  Not only that, but the lowpass filtering in the circuit is generally aimed at a much higher clock rate so the noise will likely become more objectionable as the pedal goes from swirl to boingy-boingy.

A suggestion.  The amount of capacitance change needed in the C27 position to produce a nudge of the delay range in an upwards direction and thicken/deepen it up a bit is likely to be fairly small, and likely involve less than a doubling of C27's value. Those familiar with Craig Anderton's EPFM II, and more specifically his "spluffer" project, may remember his idea for a "trick capacitor".  Since the intended cap was supposed to be on the order of a few pf, he suggests taking two short pieces of insulated wire and simply twisting them to fabricate a cap.  One end of each wire is soldered to the circuit, with the free ends of each wire sticking out (and hopefully covered so they don't short out against anything).  I doubt there is any way to predict the specific capacitance of the end result, but the nice thing is you can adjust the resulting capacitance by simply clipping off more of the twisted pair.  You also don't have to worry about removing anything from the board and risking damage.

Given the already packed interior of the pedal, you'll want to use small wire for the purpose.  Teflon-coated hookup wire is probably perfect.  Cut yourself two pieces about an inch to an inch and a half long and strip one end of each.  Solder the stripped ends to the pads where C27 goes.  Twist them around each other from the base all the way to the tip, making sure they don't short out at the tip.  Congrats, you have now made a capacitor.  Listen to the resulting tone and decide if it's deep enough or too deep for you, keeping in mind the depth will likely need to be decreased.  If it's too deep, chop a quarter inch off the twisted pair, and continue until you like what you have.

Or....you could simply adjust VR4 and bump it over in the delay range a bit.

[moro]

C27 is the correct cap for the delaytime mod, perhaps 47p was just too close to "flanger" area ?
Try 10-22pf and see how that sounds.
MM

Thanks!

To clarify, with the 47pF cap, it became a throbby distorted mess, even with the delay time turned all the way down.

[moro]

Given the already packed interior of the pedal, you'll want to use small wire for the purpose.  Teflon-coated hookup wire is probably perfect.  Cut yourself two pieces about an inch to an inch and a half long and strip one end of each.  Solder the stripped ends to the pads where C27 goes.  Twist them around each other from the base all the way to the tip, making sure they don't short out at the tip.  Congrats, you have now made a capacitor.  Listen to the resulting tone and decide if it's deep enough or too deep for you, keeping in mind the depth will likely need to be decreased.  If it's too deep, chop a quarter inch off the twisted pair, and continue until you like what you have.

Wow, what a great idea. Thank you--you just saved me a trip to Radio Shack.

Again, I am humbled by how clever and resourceful people are.

Or....you could simply adjust VR4 and bump it over in the delay range a bit.

Making my own capacitor sounds like more fun than twiddling a trim pot.