Bad clipping?

You should be OK - unless:
1) The amp is underrated.
2) The cab is overrated.
3) The cab has a tweeter.

 

I've said this before so I apologise to those who may have already read it....

Clipping is like smoking. Some say it causes cancer, some say it doesnt, some say it only causes cancer of you smoke a certain amount.

Me, I won't smoke. Nor will I send a clipped signal at any speaker.

 

Good advice.

 

So, you never use any kind of fuzz or overdrive? Jeez, us old farts from back before there were "master volumes" musta cooked a mess of speakers what with overdriving the outputs of them tube amps like we did for guitar and the occasional heavy bass sound.

 

Clipping and distortion are not the same thing. A distortion effect doesn't clip the signal. And yes, I use overdrives where appropriate........

 

I beg to differ. Overdrive and distortion effects are basically the same thing: deliberate clipping. If you turn an overdriven (by a stomp box) signal up to the maximum output of your power amp, while the amp itself is not clipping, but just on the onset of it, it would be the same as if the amp itself was clipping.

There's one thing different actually: an overdriven signal (by a preamp of stomp box) it usually EQ'ed, so it will contain less high frequency content. But increased high freq content due to clipping harmonics is (by some) not believed to cause damage to tweeters nor woofers.

 

I don't know where you heard this, but clipping anywhere in the signal chain will do the trick. A power amp will take a clipped input and happily amplify it and pass it on to your speakers.

 

No offense, Pete, but this is 100% wrong. Clipping is distortion, by definition, and distortion boxes do clip signals. That's how they work, and they couldn't do what they do otherwise.

Check out this for starters, from a boutique pedal maker:

http://www.mindspring.com/~j.blackstone/dist101.htm

 

There are lots of threads covering this topic. Basically, the cause of blowing your speakers is delivering too much energy (that is too much power over a specified period of time) to your speakers.

Because severely clipped signals "approach" the shape of square waves, and because the energy in a square wave (i.e. the area under the wave, as those with some calculus and electrical engineering education understand) is the maximum possible for the root frequency of that wave, this is the most energy you can deliver to the speaker for the given volume. At low volumes, of course, you can be well within the speaker's tolerance.

When this is done at high volumes, then the results can be much worse, particularly for bass frequencies. If you look at the impedance/frequency charts for most speakers they are non-linear. Often at the lowest bass frequencies speakers have much lower impedance than the nominal spec, and therefore are in more danger of being blown than at higher frequencies.

This is much less of a factor at higher frequencies, (i.e. guitar) where the energy being delivered to the speakers for each wave half-cycle is significantly less.

Having said this, I agree with PETEBASS - don't clip your signal at the preamp!

There are some good articles linked in other parts of this forum - do a search!

 

Oh wow, like thanks Dude! I better get rid of this Samsamp preamp I have - and the Blue Tube pre, and the V-Amp. With all that clippin' I been doin' with 'em I'm surly goin' straight to Hell!

 

So much for my Synth pedal too... dang.

 

Yup, that's primarily why the whole "clipping of any kind will destroy speakers" argument doesn't hold any water. Distortion from stomp boxes is clipping. They either drive an amplifying device outside its linear range or use didoes to artificially clip the tops off the waveforms.

Speakers don't care about waveform. They only care about how much power is being dissipated in them and about mechanical excursion.

 

OK if I'm wrong I'm wrong. I don't pretent to be an expert in electronics. However, my comment above came from a discussion on TB a long time ago involving a highly regarded electronics engineer who works works a highly regarded amplifier manufacturer that starts with Q (sorry Bob). Maybe I misinterpreted him. Someone actually asked "Does a distortion effect pedal have the same affect as clipping the amp?". His answer implied that they were 2 very different types of distortion and that the pedal should not deliver the same harmful heat and energy as a clipped power amp. I'll hunt around for the thread........

 

Hi Pete,

When your power amp clips, you can be sure it's putting out more power than it's rated for. That could be more power than the loudspeaker can handle.

When your stomp box clips, your amp might be running at full power, at hardly-any-power, or whatever.

 

Exactly.
The stompbox thing tends to reinforce the idea that speakers don't care about waveform but about how much power is being dissipated in them.

 

Thankew. I believe this is as succinct as this has been stated here. I've got a hunch even Mark will agree with this.

 

No, it's all wrong.....


Actually, it's exactly right. Pure square waves have twice as much energy as pure sine waves of the same frequency and amplitude, so it's theoretically possible that a given amp could put out twice as much as its rated clean power under heavy clipping.

 

Let me see if I understand this.

Lets say we have a 100w amp pumping out 100w of clean signal into a 100w speaker. Then we stomp on the distortion pedal. The amp is now receiving a clipped signal courtesy of the pedal, but still pumps out 100w, therfore the speakers are safe. However if we got our distortion by clipping the power amp instead, the amp would pump out 200w+ and possibly hurt the speaker.

Question time:-

1) The clip light on a power amp comes on when you're clipping the output, but the clip light on a bass head comes on when you're clipping the input. PA mixing desks also warn you when you're clipping the input. If the above is correct, then clipping the input shouldn't present too much drama, why do we then have so many warning lights trying to prevent us doing it?

2) I did sound recently at a venue with a PA instalation that uses a Yammy 01v digital desk. The owner of the gear was particularly fussy about clipping the inputs because the distortion from a digital desk is more lethal than the distortion from an analog desk. I respected her wishes of course. What's the expert opinion on this?

 

A little correction to your preamble there Pete - The amp is not putting out more power under heavy clipping - it is delivering more energy. Power is an instantaneous measure. Energy is the accumulation of power over time.

Delivering too much energy in a short period of time is what causes the problem. Think of it this way - a sine wave only delivers maximum power at its peak, the square wave delivers maximum power continuously throughout each cycle. Total energy delivered by a square wave is ~ twice that of a sine wave at the same power level.