1N5817 diode question

[timd]

I am working on this layout for the lofomofo -

http://tagboardeffects.blogspot.com/2010/03/and-few-more.html

and I don't have the 1N5817 diode. I do have a 1N5408 and a bunch of 1N400X types. Are these suitable replacements, or do I need that exact diode to capture the sound?

[IvIark]

Use the 1N4001

[CynicalMan]

The point of the 1N5817 and the pot is to provide some controllable clipping before the circuit's gain stage. The 1N5817 diode is a Schottky diode, which means that it will clip at around 0.15V instead of 0.3V for germanium diodes and 0.7V for normal silicon diodes. With a loud guitar signal, you can have clipping, but it's quite subtle. I remember breadboarding the LofoMofo, and the distortion knob didn't sound like it did anything. The 1N5408 and 1N400x are normal silicon diodes, so their clipping will be imperceptible unless you have a booster before the circuit. Personally, I'd just leave out the distortion pot and diode, or experiment with putting clipping diodes after the circuit.

(For future posters, the schematic is here: http://folkurban.com/Site/LofoMofo-724.html)

[darron]

the 1n400x won't do much of anything because it has the typical forward voltage mentioned of about 700mA

Any schottky will do the trick.

CynicalMan says he gets very little clipping, but if you have hot output pickups you can get quite a bit of break-up. it only clips one side of the wave too to make it all the more nasty. i suppose the effect kind of sounds like a guitar playing down the telephone line or overdriving a little pocket radio or something.

[timd]

Thanks for all the help. I used the 4001, and got some interesting results using a strat copy guitar. the "distortion" knob's is very subtle and and seems to add a little mid/bass/slight overdrive on the highest pot settings. What I found to be most interesting is that the guitar volume pot is setting is highly interactive. On 10 you can get a heavy fuzz no matter what distortion setting you use. Fun circuit for minimal part count.