freestompboxes.org

Hey, here is a noob question. I'm currently just looking at making some simple transistor based circuits (a clean boost first) and at the same time I'm trying my best to really learn about transistors from an engineering perspective.

Something has me a bit perplexed though - what is the general MAX current/voltage output of a stompbox? How do I know where to set my limits? Obviously I don't want to be spitting out +/- 15V swings, but what kind of range am I looking to use? Obviously some pedals are hotter and louder than others, but what is so loud it'll cause clipping in anything else?

Similarly, what tends to be a guitar's current output? I've heard people saying that really smacking on a guitar can give a peak to peak difference of about 1V but what does that tend to be in current? I know this is generally what the gain control on a pedal is for but it's still bugging me

Regarding voltage - the maximum 'acceptable' voltage depends on what the voltage source is pushing it into and what sound you want.
What will be clipped in the following circuit (and whether that sounds good) is largely up to the next thing in line. There are plenty of pedals that use an 18V supply to provide 'headroom' - this can allow a theoretical maximum 18V peak-peak output.
This is part of why gainy pedals usually have a voltage divider at the output for volume control.

Regarding current - the current produced will again be determined by the interaction of the current source (guitar or pedal) and the following input circuit.
Higher impedance inputs will require less current from the source, and lower impedance sources can more readily supply higher current if required.
This leads to the usual practice of designing circuits with high impedance inputs and low impedance outputs. Of course there are exceptions such as fuzz-face type circuits which get part of their character from loading a weak current source (passive pickups) with a low impedance input.

"What is the right way to do things?" is a much bigger question.
I go by "If it sounds good (and won't electrocute anyone), it is good."

Thanks! Very useful. I figured maximum voltage swing allowable would be +/- 4.5V generally for 9V stomp-box applications. What if you have high voltage swings and relatively high current though? This is where I get confused. My maths tells me that a signal that swings from 0mA - 2mA is going to make a very different voltage swing if it hits a 1Mohm input vs a 10kohm input.