Methods of distortion in stomp boxes

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TragicTravisty
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Post by TragicTravisty »

What are the pros/cons of different methods of implementing distiortion in stompboxes? (modfet, diodes, transistors, etc...)

By the way, this is my first post, im new to this stuff, i have extensive knowledge of internal guitar wiring and some basic pedal knowledge from jack orman, beavis, etc... but have yet to build a pedal.

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Post by borislavgajic »

wellcome TragicTravisty!

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Post by soulsonic »

Welcome,
I think all the different methods available have value and can get good sounds; it's just a matter of choosing the right one for the sound you want. Most of the time that seems to require experimentation. From my experience, it seems that using a simple op amp circuit with clipping diodes is the most straightforward and easily accomplished way of doing it. Op amps are very reliable and consistent, so you don't have to worry about tweak-y biasing or the inconsistencies that can come from using transistors - you just wire it up like in the schematic, and 99% of the time it will do exactly what it's intended to. Then you just fool around with different diodes to get the flavor of distortion you want.
That being said, I also love the classic transistor fuzzes and other things that rely on distorting discrete components to get the sound. JFET and MOSFET overdrives and distortions get some beautiful sounds too. My only complaint about the discrete circuits is that many times they require trimming and adjusting that can be a real headache for a beginner.
And there's other non-linear circuits, such as comparators, that can be used to convert the signal to a pure square wave for some intense fuzz. Experimenting with various signal shaping function circuits can yield some cool distortions too. I highly recommend checking out some basic books and app notes about op amp circuits for ideas about different functions to experiment with (and also just to learn more about circuits in general). National Electronics' AN-20 Applications Guide for Op Amps can be found as a free download on their site and it's a great resource for circuit knowledge and ideas.
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Post by DSV »

I think there is no 'best' method of distortion. As soulsonic said, some are easier to implement, in example JFETs. Others, like OpAmps with clipping diodes, are more consistent (that's why I prefer them).
But IMHO every distortion sound can be created through the combination of:
- a pre-equalizer, which cuts or boosts more some frequencies before clipping, thus giving the grain of the distortion.
- a clipping stage.
- a post-equalizer, for the final shaping and placement in the mix.
So what is more important in a distortion, rather than the type of technology used to clip the signal, is the filtering pre-, post-, and inter clipping (should more stages be used).

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TragicTravisty
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Post by TragicTravisty »

on a similar note, does led color affect its tonal characteristics? and if it does, shouldnt red have the bassiest tone, since its frequency is lowest, and blue be the trebliest?

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Post by soulsonic »

Different colors have different sounds, but that's because different colors have different voltage thresholds; not because of the different wavelengths of the colors. It's a difference that is more related to amplitude than frequency.
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Post by Fuzzer »

It has to do is with the Vforfard of the diode, I believe.

Edit: Oh, I'm sorry, I had left the window open with my comment written, I couldn't notice taht Soulksonic had answered already.
The Freestompboxes Forum search function is soo great, use the search function..., the S E A R C H function.

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TragicTravisty
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Post by TragicTravisty »

what are the actual differences in different leds?

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Post by Greg »

TragicTravisty wrote:what are the actual differences in different leds?
Do you mean what are the forward voltage differences ?
You can find them on the spec sheet, or if you're using bulk type LEDs, most DMMs can measure them I think... i know mine can.
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TragicTravisty
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Post by TragicTravisty »

i mean what are the differences in tone caused by the foward voltage?

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Post by Greg »

That was pretty much covered in this post by Soulsonic:-
soulsonic wrote:Different colors have different sounds, but that's because different colors have different voltage thresholds; not because of the different wavelengths of the colors. It's a difference that is more related to amplitude than frequency.
There isn't really any actual tone change. There's a change in where the signal gets clipped... affecting the feel and compression of the pedal more so than the tone.
To be honest, I think the differences between different LEDs is subtle compared to the difference in changing from Ge or Si diodes to LEDs.
Then you can try combining other diodes with LEDs. The possibilities are endless.
Once you try some different diodes and combinations, you'll start to get a feel for the characteristics of different types, and higher or lower voltage thresholds.
The effects will vary in different circuits, but the characteristics of different types tends to stay the same.
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Post by R.G. »

TragicTravisty wrote:What are the pros/cons of different methods of implementing distiortion in stompboxes? (modfet, diodes, transistors, etc...)

By the way, this is my first post, im new to this stuff, i have extensive knowledge of internal guitar wiring and some basic pedal knowledge from jack orman, beavis, etc... but have yet to build a pedal.
Go to the first source - go read The Guitar Effects FAQ at GEO (http://www.geofex.com), especially the Distortion 101 section.

In fact, read the rest of GEOFEX and that will answer lots of your followup questions.

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