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What is clipping

 

Anonymous
I know it is bad, and I know It can harm speakers, but what is it, And what is soft clipping Tech.
 

Hawk
Musical transients, those instant bursts of musical information that are loud, can cause an amp to reach its operating limits. When that happens, the sound wave from the amp is corrupted and it can take the speaker out of its operating limits, thus causing damage to the speaker. It can be seen on an ocilliscope because a square sine wave will become jagged when the amp clips.

This is something that is very avoidable as long as you get a sufficiently powerful amp. Trouble is most people buy a mass market japanese receiver which is rated at a typical 100 wpc. But it turns out that they are rated using no more than two channels at a time. When faced with driving five, six or seven channels, the receiver's power supply can only put out enough current to give perhaps 50% of the rated power. So a typical 100 wpc amp may only put out 50 wpc into five channels. To show you how pervasive this problem is, look at the following chart which is the results of Sound & Vision magazine's tests of the rated power of home audio receivers for the past 5 years:

http://www.geocities.com/Area51/Hollow/3401/ratevsac.htm

Sony's vaunted DA4ES home theater receiver wasn't even tested because sony admits it wasn't designed to drive five channels at the same time. (Am I missing something here?).

Soft clipping tech is something NAD came out with about 25 years ago and it works very well (I think they have it protected by patent, but I am not sure). NAD does two things--first, their receivers have two rails to supply power to the output transistors, so there is sufficient power for the musical transients. Second, they have a circuit that rounds off the electrical wave so that there is no jagged edges to the sine wave--and that protects the speaker from damage.

I hope this helps.
 

G-Man
Speaker damage is far more likely to occur from your amplifier or receiver amp section clipping than from listening to your loudspeakers very loud. Almost all well-built speakers will inform the listener when they are distorting too much from being played too loud, well before any damage is done. Of course if you are tone deaf and keep cranking the volume up, unless there is protection built into the speaker and the amp section, you could well do damage to the speaker (besides your hearing).

Standard loudspeakers are very energy inefficient. They probably dispel as heat and mechanical energy over 90% of the "wattage" they receive. Thankfully (with most speakers)they play medium to loud from 1 to 20 watts. Problems can occur when there is a high energy transient in the music or movie that requires a burst of 50 to over 100 watts. While this burst rarely lasts more than a few milliseconds it can potentially cause a lot of problems if you are using an underpowered amplifier-I don't necessarily mean insuffiecient power--I mean insufficient headroom or amps. The push or amperage behind the wattage is what gives the amplifier extra headroom to comfortably hit these burst transients without overloading the amp and supplying the speaker with clean undistorted (not clipped) power.

From looking at the graphs from Sound and Vision that Hawk highlighted, in addition to the NAD T752 there are some other fine receivers with output higher than listed. The Harman Kardon line seems very good and conservatively rated, some of the Denon line, and if you can afford it--the Pioneer Elite VSX-D49TXi stands out. It seems to have a hellaciously good amplification section--even with 6 channels driven---not to mention all the other goodies it has. Now I know why it performs basically the same as my Aragon system downstairs.

Of course other receivers perform well too. Just remember that a watt on one can be quite different than a watt on another. Like a 100 watt Kenwood looks equivalent to the 80 watt NAD T752.

And if you want to be very safe while not spending too much money on a receiver or amplification---buy fairly efficient 8 ohm speakers. Anything 85 db or higher should be more than adequate.
 

Derek
Ususally, clipping is caused by the power supply running out of steam or the output transisters reaching thier limit.

Under normal output levels, you could imagine a single sinewave section of any music. The voltage will rise steeply from 0-Volts. Taper off at the top of the sinewave then slowly fall toward 0=volts, getting steaper as it approaches 0-Volts. After passing 0-Volts the voltage becomes negative and does the same thing it did on its positive swing.

If the input signal (volume knob) continues to increase some part of the amp will run into a brick wall where no more power is available and the initial rise will suddenly stop. Most of the other parts of the amp will try to push the output to where is SHOULD be. The resulting waveform will look like a bump with its peak "clipped" off - totally flat. This will sound very compressed and grungy. Increadably most amps are at their lowest distortion just before clipping.

Usually, when the power supply or transisters run out of headroom, they repeatedly will bounce against the "brick wall of no more power" at a much higher frequency than the original signal. This "ringing" is what kills tweaters because now you have a maximum-power high frequency output signal that the speaker's crossover rightfully passes to the appropriate driver - the tweater. This is one of the many advantages of bi-amping. If the woofer amp looses its composure, the rest of the speakers is uneffected.

Clipping can happen to any elctrical device, not neccesarily an amp. Microphones, analog or digital recorders, output stages of a pre-amp or input stages of active speakers (like subwoofers) can all be clipped before the signal gets to an amp or driver. At that point the highly distorted signal will be faithfully reproduced by the amp and sound like crap.

Hope that helps.
 

Anonymous
I just bought a used adcom amp from a friend who never had any problems with it. When I got it home it sounded great but at very low volumes I would hear a clipping sound. when turned up I didn't seem to hear it. dose anyone have any idea what's causing this.
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