amp noobie question about dirtortion?

[Rod]

Hi everyone!

How distortion is produced from a amp circuit point of view? is it with a variable voltage in the cathode resistor?

What are the components in a amp circuit, that produce distortion?

How modern high gain amps, produce their distortion?

[überfuzz]

When tubes, gain stages, aren't capable of amplifying the signal correctly, the signal is distorted. (Also known as break up.)

[defaced]

When the output voltage wants to exceed the supply voltage minus any losses due to the amplifying device, you get clipping. Basically, the output signal runs out of room between the supply rails. How the amplifiying stage is configured (supply voltage, resistors, capacitors, etc), and what amplifying device is used, will determine how and when the stage will clip. Modern high gain amps use many (commonly 3 and 4, and to a lesser extent 5 and I believe I've run across someone using 6) amplifying stages in series, which all can clip, to produce the final "high gain" or more appropriately "heavily distorted" signal.

[Enzo]

ANy circuits have limits, be they power supply voltages, or the ability to amplify, or whatever. WHen we ask the circuit to try to go beyond those limits, it distorts the sound. Distortion is not some particular thing, it is a general term for loss of fidelity - the output is not identical to the input. It can take many forms and has many causes. There is no one way.

[anson]

Distortion is when the waveform of the input signal becomes changed in shape from its original form. When a signal is driven into a valve (or mosfet or what ever) that is larger in voltage swing than what the component can handle, then the waveform becomes compressed, or "clipped". That's one kind of "distortion". Another kind is when the amplifier circuit can hande the size of the input signal fine, but it changes the shape of the waveform because of the non-linear characteristics of the circuit.

[Chuck H]

This isn't entirely accurate to what's happening, but the visual helped me at one time. If you picture a sound wave (a wavey line like an AC signal) and imagine it's "volume" is represented by the height of the wave (which it sort of is). Now imagine a hole that is smaller than the wave height and suppose that when the wave passes through the hole the rounded ends get clipped off. If you make the hole small enough, or the wave big enough, the wave can begin to look almost square. Modern high gain amps do this to a signal several times to get the sound they have. As noted, three, four or even five gain stages may be used in series. Asking how an amp makes distortion is a very complicated question that can't be properly summed up in a single post. There are lifetime hobbies based on the subject and several fat books written about it. I do find it interesting that you proposed a particular circuit as responsible though. Unfortunately it's nowhere near that simple. But welcome to the forum. If you search here and the archives you can find answers to almost any circuit questions that you might have. And if you decide you really want to know about this stuff, you'll have plenty of questions. More and more as you continue to learn what you still don't know.