COT 50 build

[jonnygreentrees]

Just building a COT 50 clone from Fuzzdog

http://pedalparts.co.uk/docs/BoxOfTone50.pdf

and I primarily want to use it for low gain. Just wondering if there's a simple component swap I can do so it has less gain?

[Maroslav]

Maybe put trimmer in series with diodes?

[jonnygreentrees]

Thanks for the idea, it's PCB so anything I could outright swap would be better!

[induction]

What do you mean by 'gain'? Do you want less volume, less distortion, or something else?

[jonnygreentrees]

sorry, less distortion

[PBE6]

You could try swapping the silicon diodes for red LEDs or any other diode (or series combination of diodes) with a higher clipping threshold. This will also raise the output volume, which will probably make you turn down the gain to compensate which will also result in less distortion.

[jonnygreentrees]

thanks!

[Mark Hammer]

Stick a 1k-5k pot between the ground side of the diodes, and ground.  That'll do what you want, as well as being able to get the original tone.  Note that inserting more resistance between the diodes and ground will raise your volume level as it reduces clipping.  Not a big penalty, AFAIC, but you'll want to be mindful of the volume setting if you play with the new control while plugged into an amp.

[jonnygreentrees]

thanks Mark, could I use a mini trimmer pot or similar?

[duck_arse]

+1 wot mark said, add the warp control. also, yes, any sorta pot you can get/fit. connect it as a variable resistor.

[Mark Hammer]

thanks Mark, could I use a mini trimmer pot or similar?

You can use whatever you want, although given the simplicity of the circuit, there is no harm in panel-mounting an additional control.  You may find you have a purpose for the harder clipping of the stock circuit once in a while, so it's useful to have that easily available, without having to open up the chassis and dicker with a trimmer.

Alternatively, stick a 4k7 resistor in there instead, and use a 3-position (on-off-on) SPDT toggle to put a 2k2-2k7 resistor in parallel with the 4k7, or bridge the 4k7 completely.  That way you get a choice of stock (bridge) medium (4k7+2k2), or softer (4k7) clipping.

Some folks are fine with presets like that, and others like to have continuous controls.  Your choice.

Since ducky mentioned "warp control", yet another alternative is to connect your diode ground-ends to the wiper of a 5k linear pot.  One outside lug of the pot goes to ground, and the other goes to a single germanium or schottky diode to ground.  Orientation doesn't matter.  Full rotation to one end connects your stock diodes to ground, yielding stock clipping.  As you rotate in the other direction, you're adding series resistance to those diodes, and softening their impact, but still placing resistance in series with that additional diode.  Rotate even more in that direction, and that added diode starts to become a viable path to ground for half the waveform, while clipping for the other half of the waveform is reduced more by the resistance added on that side.

Essentially you end up with a control that can give you stock, softer clipping, and more asymmetrical clipping.  The same added diode that results in the asymmetry will also raise the clipping threshold, yielding a little more output, and a bit less clipping.

[jonnygreentrees]

brilliant, thanks for all the ideas guys!

[bool]

Just throw away one schottky and replace it with a 1N4148. Or a 1N4007.