wiring clipping diodes

[bonkdav]

im planning on putting a device together that allows many selections of diodes but i was wondering does it matter if you put them in series or in parallel. i know this has a huge effect on resistors and capacitors so im just curious with the forward voltage of diodes and if it does matter if there are any "rules" you can follow. im planning on using it to find the clipping in a ts808 or maybe in a big muff for example.

thanks,

davis

[aron]

Whatever way you intend to wire them, you need to take them out of circuit when you don't want them.

[ambulancevoice]

if there just output clipping diodes, you must put them after the output cap so the diodes dont short (i think thats the term) the transistor

really, you can them in any configuration

[tcio]

Rather than starting a new topic I figured I'd just post here. I am having problems using clipping diodes. I have tried placing them just as they are on the MXR Distortion Plus schematics and have tried this on a few boosters. It seems to be a hit or miss situation and when it is a miss I cannot seem to ever get a hit.

Shouldn't I basically be able to throw this configuration (D1, D2, .001uF Cap) on the output of any circuit to clip the output?

http://www.muzique.com/schem/mxrdist2.gif

[Mark Hammer]

Shouldn't I basically be able to throw this configuration (D1, D2, .001uF Cap) on the output of any circuit to clip the output?

No.  There has to be sufficient gain and corresponding signal level for the diodes to do what they do.  Diodes clip at specific absolute amplitudes, not relative ones.  If the signal is not at the amplitude required for the diode to begin conducting, they won't conduct.  Otherwise it's a bit like having a deep deep bucket with a tiny bit of water at the bottom, and you're sitting there wondering why tilting the bucket a bit to the side doesn't result in any water pouring out. 

Now, you do have the option of selecting your diodes and diode type such that the critical threshold at which they conduct are low enough to suit a circuit with very modest gain.  Indeed, the infamous Black Ice overdrive uses selected diodes that clip at such a low signal amplitude you can insert them at the guitar's volume control and get clipping without any active boost at all.  Of course, the pickups have to be hot humbuckers, and you have to pick/strum hard, but you can still get some clipping.  Those same (Schottky type) diodes inserted on the output of a pedal that provided a modest 10x boost might work more effectively.  Of course, if you plunked in a pair of 1N914 diodes, and was hoping for some good sizzle with single-coil pickups, you'd probably want to up the gain to something over 200x.

[tcio]

Whew! I was really wondering what was going on there. I have some studying to do but now I have a base of understanding to start at rather than where I was before (a total "no clue" basis).

I have learned quite a bit already from a few of your excellent informative posts on this forum and also want to thank you for your post on lowering the output by placing resistors in series around the output pot. I have been struggling with this issue since the start of my DIY project building. Seems I have a really sensitive preamp and it gets a real garbly sizzly sound whenever I plug into a pedal with a loud output level.

I tried the resistor in series around the output pot just tonight and got exactly what I was hoping to get after finding the right values.

Thanks Mark for your time.   

[Mark Hammer]

Oh no!!  I've given you a little knowledge.  Now you're really dangerous.

As always, glad to help out.

[tcio]

LOL!

Not yet but hopefully someday soon.

I seem to be doing really well at whipping things together by swapping values and listening to the results but I cannot do near the tampering I would like to do, like how to tweak the gain stages, calculating (like voltage, impedance, stuff like that) as I don't understand whats really going on with the circuits yet.

But with the help of the wonderful people on this forum and continuing with my reading some day I just may be able to build my own pedal 100% totally from scratch to my own personal specifications and know exactly why each and every part is in the circuit and their purpose.