readings for concepts behind effects circuits

[cnspedalbuilder]

In the past few months I've learned a lot about the mechanics of pedal building and troubleshooting  But I still feel like I don't really understand what I'm doing. I have a fairly good understanding of the simple principles, but I wonder if there are some sources on the conceptual aspects of these circuits. For instance, I think the experts on the board can look at a circuit, break it down into meaningful chunks, and get an idea of why the components are connected in that particular way and what the pedal will do. Maybe another way to think about it is that experts can probably hear "fuzz circuit", get a general idea of the layout in their head--knowledge of what connections and kinds of components must be there and what that can be tweaked to get an individualized sound.  Is there a source out there that can help me think about circuits this way? Or do I just have to spend a few months on a breadboard until I get an intuitive idea?

[Ice-9]

Take a look at R.G. Keen's webpage. At the top left on the home page there is I link title 'FX Technology'  Go there and click on tubescreamer.

The whole effect is broken down into block and every parts is explained in detail.

www.geofex.com

[GibsonGM]

Hi CNS....read a lot at GEOFEX, great stuff!  You'll start to see patterns...learn the patterns, so to speak.

You'll eventually note that some stages of circuits are buffering, amplifying, RE-amplifying, oscillating, changing resistances...shaping the tone with R-C networks of all kinds, some with pots to change frequency...some things like diodes clipping signals...these are the basic blocks that most everything is made from.  Inside those blocks, there will be differences; what makes a fuzz a fuzz and not a distortion, and vice versa, etc.

Transistor gain stages, opamp gain stages, buffers...nice to learn how those operate.  After a while, you will look and go "Oh, that's an input buffer, goes to that gain stage...these parts put a little mid scoop in, there's a gain control, and another gain stage with clipping diodes to get us some distortion"!    Just familiarity   

And don't worry, there will always be new things to learn which you've forgotten, overlooked, or didn't think mattered, ha ha!   

[deadastronaut]

good advice as above...but breadboard a lot too.

so you hear those differences/tweaks..adding tone controls...different clipping etc

most of all have fun...

[lars-musik]

If you have inhaled the geofex stuff deeply and gone through all posts of at least RG Keen and Mark Hammer here in the forum (after that there are some more members you'll like to follow....) then take a look at the circuit analysis at Electrosmash, for example the Rat http://www.electrosmash.com/proco-rat, the Phase 90: http://www.electrosmash.com/mxr-phase90 and the others you find there. It helped me quite a lot and is VERY comprehensive.

[PBE6]

I would also suggest the Electrosmash website, analysis inspired by RG's approach with some extra math and graphs thrown in for good measure.

You're on the right track. Stompbox circuit design for  seems heavily focused on the following:

1. Selecting the appropriate subcircuits to achieve the required function (i.e. gain stages, filters, rectifiers, clippers, etc...).

2. Choosing the order that works best to achieve the desired sound (i.e. cutting bass before clipping, boosting bass after clipping, low-pass filtering at the end, etc...).

3. Dealing with subcircuit interactions. This usually boils down to impedance matching and the judicious use and/or exploitation of high impedance elements in the chain.

If you cover those bases, chances are good that you'll have a functional design.

I find it easy to study subcircuits in isolation, but to study the placement of subcircuits and impedance matching you really need to look at existing designs. Once you feel comfortable with RG's explanations and others like it, try analyzing some simple designs at General Guitar Gadgets or Runoffgroove. Lots of people here willing to help if you get stuck, too.


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[PRR]

> conceptual aspects of these circuits.

There's good audio circuits which do no damage to the audio.

And then there are the bad ones.

Usually the *same* circuit can be "good" or "bad" depending how big the audio is.

The first goal of most audio circuits is Amplification. The study of audio is largely about knowing amplifiers. A skinny iron string 2mm away from a magnet induces a teeny electrical power in a coil. A "loud"speaker requires considerably more power. So the essential guitar amplifier amplifies-up from small to large signal.

You can adjust any decent guitar amp "dead clean", negligible distortion. If you paid for 10 Watts output, design the amplifier so nothing distorts much up to 10 Watts.

But those rhythm guitarists in the back of the bandstand had to push their 10 Watts to be heard over the brass, sax, even a clarinet. When they exceeded 10 Watts the sound changed, "distorted". Note that this is somewhat similar to what happens when brass/sax/voice is "pushed". The timbre gets sharp, extra overtones. Non-electric musicians usually have such an effect and use it for musical emphasis.

So e-guitarists pushed to and past the edge of distortion. On the simple mellow amps of the day, this was hard work. And often considered "rude". Guitar was back with bass and drums and never out-front (unless the brass needed a beer-break). But the edge of distortion has musical seductiveness, also the economics of large touring bands changed, Les Paul distorted with grace, and distorted guitar became THE sound of popular music.

So how do you distort? Play your amp louder than it can go cleanly.

Guitar signal is 0.020V to 0.200V. It's a little hard to get distortion at such low levels consistently. But we are going to amplify anyway. Boost by factor of 100. Now we have 2V to 20V. If we use an amplifier with a few-Volt power source, it won't make 20V clean, may be getting a bit "colored" at 2V.

I like the car in the garage analogy. A car up to 6 feet wide can be put in a 7 foot garage without damage. But an 8 foot wide truck will get bent mirrors and corners.

"How" it mangles the signal is important. Any over-driven amplifier will distort (there are no infinite-output amplifiers). But many ways to do this, and each variant distorts different. "Soft" clippers give less-harsh overtones. "Hard" clippers throw shrill overtones far up the spectrum.

For musical reasons we often add tone-shaping. Multiple bass tones distorted together make non-harmonic partials which confuse the ear and are annoying, so we usually bass-cut in front. Most distorters get too shrill, so we often high-cut afterward. Many elaborations.

So you need to understand how an amplifier amplifies, how it over-drives, and how you can modify the damage it has done. It is in some ways the highest art of the electronic designer, requiring deep understanding of psycho-acoustics. OTOH many classic distorters are ordinary amplifiers, abused and tweaked by guess-and-gosh.

[cnspedalbuilder]

Thanks everyone, there are great resources at GeoFX and Electrosmash. I realized that I had looked at GeoFX a few months back, but forgot to go back after learning a bit about the building process. Thanks to those of you who have contributed to these and other resource sites

[dschwartz]

Search for teemuk's book..it's amazing!

Also look for basic electronic circuits, they are the building bloks..

Pedal design is much like playing Lego..you have a lot of blocks for specific jobs..better yet, you have many options for a functional block, and if you are creative, you can design your own blocks...

Read about buffers, opamp amplifiers, transistor amplifiers, and other active device amplifiers.. Then read about filters, RC, Twin tee, multiple feedback, sallen key, etc... Then oscillators, power supplies, etc..

Bredboard these things and build circuits with different topologies and you will get an idea of the flavour of each one..in time you will be trained to recognize a topology by ear.. Or better yet..to imagine a sound and being able to reproduce it with a circuit..

[Fast Pistoleros]

If you have inhaled the geofex stuff deeply and gone through all posts of at least RG Keen and Mark Hammer here in the forum (after that there are some more members you'll like to follow....) then take a look at the circuit analysis at Electrosmash, for example the Rat http://www.electrosmash.com/proco-rat, the Phase 90: http://www.electrosmash.com/mxr-phase90 and the others you find there. It helped me quite a lot and is VERY comprehensive.

electrosmash looks more interesting than beavis! thats a great website!

[amz-fx]

You may also find a few items of interest here:

http://www.muzique.com/lab/main.htm

Best regards, Jack