newbie questions, have searched for answers.

[ibanezts808]

First off, I'd like to thank aron and all moderators for such an amazing site, i love seeing that you're willing to provide knowledge and not go corporate on us to the point of charging membership fees, this is what music is about, a willingness to share.

To begin, i want to let you know I have researched these questions but have not found adequate answers.

1.  Transistors:  I know how they work, but don't know how they work in the context of pedals.  My understanding is they are used to amplify the signal, is this correct?  if not, what do they do?

2.  Op-Amps:  I have no clue as to what these do, by the name i'm assuming they amplify.

3.  Caps:  I also know how these work, but do not know what their use is in pedal design.  I know that may sound incorrect, but maybe i do not fully understand what they really do.  probably due to half-assed internet sites that want money for a full explanation.

I tried to make a beginners distortion pedal, and i followed the schematics exactly but all that happend was my signal was weak on the output.  I also tried doing my own design, basically i just ran the signal through to wires, a hot and a ground, i connected two diodes to the hot and ground going in opposite directions and i got nothing, I know i probably did something stupid and there is no way that idea could've worked, but i'm just beginning, any help would be so greatly appreciated, thank you all.[/i]

[aron]

1. Transistors: I know how they work, but don't know how they work in the context of pedals. My understanding is they are used to amplify the signal, is this correct? if not, what do they do?

Transistors can be used to buffer, amplify, switch - well all sorts of things. For a distortion pedal, they are usually used to amplify and buffer the signals.

2. Op-Amps: I have no clue as to what these do, by the name i'm assuming they amplify.

Again, could be a lot of things. Usually to amplify and buffer.

3. Caps: I also know how these work, but do not know what their use is in pedal design. I know that may sound incorrect, but maybe i do not fully understand what they really do. probably due to half-assed internet sites that want money for a full explanation.

Check out my simple mods page for a few examples of how capacitor values might affect a circuit:

http://www.diystompboxes.com/cnews/mods.html

[Hal]

simply put, capacitors block DC and allow AC to pass.  This is what they are used for in coupling stages.  However, they have a frequency dependance - that is, they impede differently based on frequency.  Using this property, they are also used for frequency pass filters.

[The Tone God]

There alot of different answers to your questions and the funny thing is all of them can be right. For example an opamp can be used as a buffer, amplifier, attenuator, summing amplifier, differential amplifier, etc. A capacitor can be a filter for noise in the power supply or a band of frequencies in a tone control, a "charge bucket" in an oscilator, DC decoupling between stages, etc. So to answer your questions fully would take some time.

The function of a part in a circuit can depend on the circuitry surrounding it. Understanding the part's inner working on its own is understand "how a part works" while understand the part's role in a circuit is "what a part does". I'm sure that is making things clear. :roll:

Let me try this another way. You understand how a screw works but then you are asking what does a screw do in a car. Well it can hold parts together like the engine, it can make an electrical connection like ground to the chassis, it can be use as a calibration setting like in a carburator. The screw is a fastener in general but depending on the context it can do different things.

You can't always say a particular part does only one thing so your question is kind of vague. Why don't you pick a simple circuit that you want to understand abd pop off some questions ? The beginner project might a good place to start.

Andrew

[Transmogrifox]

If enough of us reply with something about the parts, at least you'll have it all on one page, so here' my 2 cents:

Transistors are like a water valve in some ways. The base is like the crank, or knob/valve control thing, the collector is like the part where the high pressure water supply connects, the emitter is a low pressure place, like the output of the valve to a filling tank or reservoir or something.

As you open the valve, more current flows through, and when it's all the way open, there is a maximum possible flow of water no matter how much you crank the valve after that.  Likewise, when you shut the valve off, current stops flowing.

For a transistor, it's the same:  when you apply a voltage to the base (turn the valve), electrical current flows from the collector to emitter if you have a positive charge (say 9V in a pedal) connected to the collector and the emitter connected to ground.

You can see that if you turned it, say, half way on, there would be some "water current" flowing through a valve with quite a bit of play before it either maxed out or turned off.  As long as you're between the max and minimum range, whatever wiggle happens at the valve handle also happens in the water flow through the valve.  When a wiggle on the input is much greater than the play on the valve handle, the water current stops following the pattern of the valve handle motion as long as it is beyond its limit.  This is called clipping, or distortion...whatever have you.

That's why a transistor, in function is an amplifier.  It can be used as a "follower" otherwise known as a "buffer", which takes the voltage on the input and repeats it on the output with a gain of 1, in other words, it doesn't "amplify" the voltage.  It is used to amplify the current, so that you can drive lower impedance loads at the same voltage.

It can also be used as a distorting device since you can amplify the signal so much that the output limits at either "rail" and distorts the signal.  

A transistor also has some interesting input and output impedance (current-voltage relationship) characteristics that make it useful for active filtering and variable gain amplifiers, yadda yadda...

The op amp, then, is a very very very high gain amplifier made up of a bunch of transistors.  Circuit designers use negative feedback (feed output back to input in the opposite direction)  to reduce the gain, increase bandwidth, and generally make it useable.  You can control the overall gain of an op amp with external resistors (and capacitors).

Caps are kinda like frequency-dependent resistors.  They have a very low "resistance" (almost a short-circuit) at high frequencies, and a very high "resistance" at low frequencies (like, they don't pass any DC through)--so maybe you can see how they are used in filtering certain frequencies like in a tone control.


About the diode thing you tried:  Probably the only reason it didn't work is that you didn't amplify the signal enough to clip significantly so that it was audible distortion--probably just sounded like you didn't do anything to the signal.  If you amplify it with an op amp, and put a volume pot on the output, then you have an MXR dist +

[niftydog]

half-assed internet sites that want money for a full explanation

my friend, you are looking in the wrong places if that's the case. Check out this thread (and others via the search function) for some useful links!