Audio Graveyard

I have a question about guitar distortion pedals?

Posted by admin in Friday, October 2nd 2009

the_dude asked:

Many players (including myself) prefer the sound of distorted tube amp circuitry vs. transistor circuitry. I know the distortion is produced from the overdriven tubes, whether preamp or power amp, and adjusting the guitars volume as well as the amps volume (channel and master) will effect the distortion as well.

All this said, why then, do so many of us use distortion pedals? What exactly is the pedal doing? Is it increasing the gain of the guitar signal to overdrive the tubes, or is it processing a synthetic “distortion” tone?

Example: If a guitarist with a Marshall JCM 800 plays his guitar through its clean channel and steps on his distortion pedal, (lets say it’s a Boss OS-2) is he getting tube distortion (is the pedal now overdriving the tube by increasing the gain) or is he actually getting transistor distortion introduced into the signal via the pedals transistor circuitry?

Anyone? I’m interested in the basis for your answer as well. Thanks!
Thanks for the responses, but perhaps I should clarify the question- I’m wondering if using a distortion “effect” of any type- actually overdrives the tubes in a tube amp to produce the “distortion” or if it introduces a “processed signal” into the chain.

I am completely aware that the tone will be different from setup to setup, and that overdriving the tubes with high gain/volume will cause them to distort.

That’s the basis for my question- does an effects pedal (if it’s built into the amp and you have to “click” or “switch” it on I consider that an effect) overdrive the tubes to produce distortion or does it simply alter the guitar signal the way a transistor effect would- by introducing a square wave?

Would it be accurate to say that if you use a distortion pedal with a tube amp and aren’t playing at high volume, then you aren’t getting tube distortion, but rather transistor distortion?

Again, I’m not searching for a “sound”, just an answer to a technical question.

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3 Comments

Master U said in October 2nd, 2009 at 7:53 pm

I used to build these pedals in the 70’s, we called them Fuzz Boxes, all you do is get an pre-amplifier, then pass it through a simple circuit to convert it to a sawtooth wave (Even Harmonics) or a Square wave (Odd harmonics), this is then mixed back to the original signal to give you the depth of distortion you need..

Normally they are built into foot controls, the Button switch turns it on (when off the signal goes straight through), and the pedal is connected to the mixing potentiometer, to vary the amount of distortion.

draciron said in October 4th, 2009 at 2:39 pm

I play a wide variety of sounds. Some I like a nice dirty distortion, others I like just a trace of distortion. Actually the faster I’m playing the less I want heavy distortion as the sound gets muddy where a good slow riff I can lay it on thick and still have the notes resonate through all the effects.

Then I want more than a clean channel. I want depending on the sound some chorus, reverb, delay, etc.

Different sounds call for different distortions. I want to play what I want to play not be limited by what my single pedal/amp can do. Often I use as many as 3-4 effects changes in a single song. It might be going from a heavy distortion to a lighter distortion for the fast part or it might be 3 or 4 very distinct effects.

So for me it’s kind of a non-question as I never liked strait amp distortions anyway. I use a multi-effects pedal and love the variety and range I can get. I tinker with the invidual settings and amp models until I get something I like then. Tinker some more when the rest of the band critques the sound or complains

As for what the pedal is doing. Even with a single pedal you are customizign the distortion. If you use amp X with this kind of head and play through this kind of pickup at this kind of volume you get X distortion. This is modified by changing your EQ, adding or subtracting things like reverb. Still you have a pretty set distortion that varies quite a bit with volume. Unless your mic’ing the cab/amp for compensation your sound changes a whole lot with just a small increase in gain. So by going through a pedal and using the pedal to provide distortion you are creating a consistant distortion that will sound pretty close whether on your practice amp or your stack. If you borrow another guitarists rig you’ll still with that distortion pedal and guitar get something close to your sound. Add in a series of pedals or go to a multi-effects pedal and your sound gains in repertoir and customizability.

Tubes to me have a warm sound but they are not as consistant. I play a tube amp as a practice amp but my head on my stack is solid state. I have a problem with the outs getting too warm on the tube amp and cutting out after a couple hours of playing. Also the sound on most tube amps is different. Assuming you let it warm up (good idea unless your rich enough to replace the tubes fairly often) until they are really warm the sound will change. So until it’s warm I don’t even want to do a sound check. Then after playing for a bit the sound changes and I have to make some changes to compensate for the tubes heating up. The tube amps have a warmer sound but I can mimic that in my pedal so I go with solid state for my head. At a gig I don’t want to spend alot of time messing with my sound. Too much confusion as it is. Hard to see the knobs, alot of background noise going on and experimenting live is not something like to do with my sound. I’ll improv notes and even write a song on the spot but I want to know what my sound will be before I play my first note. I want it to stay that way the whole gig.

sasquatchpuppeteer said in October 6th, 2009 at 11:59 am

That’s a good question, I pondered the same thing a long time back. A distortion pedal does not overdrive the tubes of an amp; if this was the case then distortion pedals wouldn’t work with solid state amplifiers! And neither is it producing a ‘distortion tone’ so to speak. Rather, it is distorting the waveform that is being produced, and the resulting wave distortion creates the ‘fuzz’ that we now call ‘distortion’. Additionally, some do (as you say) increase the gain and then clip the waveform to reduce the overall volume, resulting in an altered waveform that emphasises certain tones and harmonics, though these are usually known as Overdrive pedals rather than distortion pedals (my preferred choice of pedal on top of a valve amp).

So in the case of your example, the guitarist is getting distortion introduced into the clean wave form via the pedal, which is either changing the wave form from one shape to another, or boosting and clipping it to produce an altered shape. Have a look at the following links if you want to know a bit more about distortion types and effects.