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distortion

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Josh

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when an audio wave hits the rails and causes distortion, which is effectively DC voltage, it stuffs the speakers. so my question is how do distortion pedals work? if a square wave goes though an amp does it not stuff the speakers?

cheers

Josh.
 
If the distortion generated in small signal stage, this is no dangerous for speaker.
 
Sebi said:
If the distortion generated in small signal stage, this is no dangerous for speaker.

Unless you turn it up loud :lol:

The reason for blowing the speaker is pretty straight forward, and just requires simple maths.

Assume your amplifier has an HT rail of 100V, so the maximum peak to peak output is 100V p-p. To convert this to RMS volts for a sinewave, you divide it by 2.828 giving 35.36V RMS. To calculate power you square this, and divide it by the speaker impedance - giving 156W into 8 ohms.

For a square wave, either clipped in the output stages, or clipped in the input stages and turned up to full level, the RMS voltage output is 100 divied by 2 - giving 50V RMS. The output power from this is 312W, double that for a sinewave.

So using a squarewave rather than a sinewave doubles the power in the speaker.

However, it's 'nicer' to clip in the preamp stages, rather than overdrive the
output stages massively - your amplifier will love you for it :lol:
 
I have no idea how a modern (last 20 yrs) distortion pedal works however when I was a kid (late 60's, early 70's) a popular electronics project was a fuzz box - simply a diode that clipped/rectified the signal. It worked, sounded neat, etc. As suggested, the resulting waveform has more "on" time and had the potential to deliver more power to a speaker under a given set of conditions.
 
stevez said:
I have no idea how a modern (last 20 yrs) distortion pedal works however when I was a kid (late 60's, early 70's) a popular electronics project was a fuzz box - simply a diode that clipped/rectified the signal.

They are still much the same, in fact modern copies of old designs are particularly popular these days - there are even lots of websites where you can download circuits for effects pedals, some even sell bare PCB's to build them.
 
so if ya build a distortion pedal that just clips the wave and use it at a line level (as they are normally used), and then crank the guts out with an amp and big speaker, that's allright? coz i'd still be putting DC across the speaker! ???

Cheers

Josh.
 
Josh said:
so if ya build a distortion pedal that just clips the wave and use it at a line level (as they are normally used), and then crank the guts out with an amp and big speaker, that's allright? coz i'd still be putting DC across the speaker! ???

No! - if you feed it a squarewave at full power it's no different to clipping the output stage - you're still feeding twice the rated power out of the amplifier. A suarewave isn't putting DC across the speaker, by definition a squarewave is AC - it's just double the power of a sinewave.

A valve amplifier survives this better, because the transformers won't pass a high power square wave like a transistor will - the edges will roll off, in a much more 'speaker friendly' way :lol:
 
Josh-the distortion or "fuzz" is separate from the power applied in this sense.

The distortion or fuzz alters the input signal by clipping it. That clipping, by itself, creates a unique sound. That sound is intended to be amplified to a level that is within the power handling limits of the equipment and systems that follow. If you take any signal and overdrive an amplifier or speakers you certainly will add to the uniqueness however, as has already been expressed, you run the risk of damaging the equipment.

The limits of any amplifier are governed by the design and the components used in the construction. Music, by it's nature, is of varying amplitude and frequency with lots of what I'll call "off time" and limited amounts of full "on time." The average power at the input is relatively low and momentary peaks allow the amplifier designer to make use of the short term power handling ability of components. If presented with input waveforms that are more continuously "on" then the amplifier might exceed the limits of one or more components or simply it's ability to deliver the power required. An amplifier could be designed to handle a waveform that includes DC without a problem however the cost would be much higher.

The thoughts in the preceeding paragraph apply to just about anything in the system including the speakers, wiring, power supplies. They all have limits and designs are often based on something less than DC being applied. Let me say that I use DC to illustrate what might appear to be the greatest extreme however it may not actually be the case in every situtation.
 
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