- Firstly the dual gain pot (which controls both the overall gain in the overdrive section and the ratio of clean signal to overdriven signal at the input to the boost/mix stage) has been split into two separate pots. This allows you to not only mimic the original Klon tones but also mix up your own varieties of overdrive/clean tone and come up with something totally unique for a Klon pedal. This mod is useful when used carefully and with the gain below 75% I'd say, any higher gain and the Klon loses what it's best at anyway and becomes just another overdrive.
- Second we've got the diode clipping switch, this switches between stock klon (Ge diodes with forward voltage .35 ~ .4v), silicon diodes (FV ~ .7v) and LEDs (FV ~ 1-1.2v). As you can see this allows you to greatly adjust the clipping threshold of the circuit. With the LEDs in place you get a much rockier, aggressive tone - it becomes quite a distortion pedal!
- Thirdly, I've socketed all of the opamps. This allows you to pick and choose your favourite clipping chips to stick in the klon, any dual opamp will do really. I liked the LM1458 and the LF353 (If I remember correctly!) in the overdrive portion of the circuit and a hi-fi burr brown op amp in the boost section (OPA 2132). However, it is also noted that a TLC2262 cmos rail to rail op amp also sounds decent when used in place of the first op amp. If you can't get hold of the burr brown opamp use a TL082 for the boost and treble control opamp.
- Soulsonic also posted up his extra gain mod: "Change R10 to 680 ohm, R11 to 4k99, and C7 to 180nF. This is my boosted gain mod. You get more gain, but the frequency response remains essentially the same at max gain. When used in tandem with the red LEDs, it can get some pretty rippin' distortion that's way more interesting than the stock boring dull overdrive."
- Dual Channel Klon??! - Earthtonesaudio suggested this simple but interesting mod. When used in conjunction with the split gain/blend pot mod it's especially useful. Basically you split up the bypass switching and and wire it to two separate footswitches, then you can use one to activate the bypass and one to switch in the clipping section - you now have three settings - clean (pedal not engaged), clean boost (pedal engaged but with clipping section switch grounded) and overdrive (pedal engaged and clipping section switched in). It works well too
- Finally. I'm not sure whether or not to do this mod, I'm tempted to add an extra switch to place in some "Tubescreamer" style soft clipping diodes over the op-amp. I'll have a play with it and decide if it's worth it (Probably will add an extra dimension to the sound, so it'll probably get done..... hmmmm.)
And here's some more images of one I just made:
