I disagree, most amps will not let you clip them bad enough to get true DC, however clipping does cause DC. I have seen a PA loudspeaker catch fire and a cone leave the basket tearing the surround and the spider because of true DC, it may only be for a few milliseconds but it’s still DC. The reason the guy in the other forum could turn the 'clipped' signal into a sin wave is because of the shelving effect in a cross-over, think about it. You’re not going to agree with me I know but, who really cares anyway. Everyone has his/her own opinion of things.
That is another topic. The famous how do you blow up speakers, ie by
mechanical damage or thermal damage. I can drive any speakers with
square waves all day if I don't exceed 'mechanical or thermal' abilities.
The speakers you seen blow violated one or both of the rules, not by DC, but by overdriving
the speaker beyond it's limits due to power. A clipped sinewave is 2x more power.
http://sound.westhost.com/clipping.htm
He said
There is no doubt that a clipped asymmetrical waveform will generate a DC component in the output of an amplifier.
He walks the fine line by saying 'generates a DC component'.
It's a fine line subject matter. For instance, if I expand a sine wave eventually it may appear to be flat at the peak.
On the other hand, if we sample the signal over a longer time we clearly see the AC waveform. If you examine
clipping for a brief time it also appears to be DC, but if you sample the signal over time, it's not a DC signal over that
period of sampling.
A bad analogy would be looking through a telescope and a person seeing the object claims he sees dirt. But zoom out,
hey, it's the moon. /lol
Here also is a little tid-bit from QSC's history.
"...Over the next five years, reliability became synonymous with the QSC name thanks to several technological advances developed by Pat. In 1978 Pat's revolutionary "AC Coupled Amplifier Circuit," which allows high-voltage transistors to mount directly on a grounded metal heatsink, earned him a patent. The advance made manufacturing easier and less expensive by decreasing the chance that an amp would fail because of an insulator breakdown. It also increased cooling efficiency and current flow, resulting in better overall amp performance, and ultimately proved safer than conventional technologies. The design guaranteed that no DC voltage would pass through the amplifier, causing speakers to blow or amp failure. Competitors' amps at the time always sent DC voltage to speakers when output devices failed - a dangerous flaw that could severely damage speakers and potentially cause fires...."
There is three topics there. AC coupled amplifier means that it's not a DC
amplifier. A direct coupled amplifiers sometimes is called a DC amplifier because
if you apply a DC voltage on the input, it amplifies the voltage as DC. Some high
end manufacturers who fear capacitors in the signal path will opt to remove them
forcing their amp to be DC coupled. This isn't a problem unless your source sends
a DC voltage on the input. But the amplifier may have stability problems holding
the output at near zero volts so they install servos on the DC amp or hand
tweak offset with a pot as some DIY freaks do.
Making the amplifier AC coupled is more or less the common approach for
the majority of product because nobody needs an audio amplifier to amplify
1Hz or less and the capacitor issue can be resolved.
The second issue in that statement is amplifier failure. If the common amp
fails you force rail voltage on the speaker. This DC voltage isn't a guarantee
that a driver will fail. It depends on if the driver received mechanical damage
by being overdriven or is the voice coil able to dissipate the power in the
'stuck position'.
The third topic is amplifier cooling.
Clipping bad, DC good, we can all live together!
Nobody is arguing, it's just normal 'lets post controversial subject matter' and wing poo in the fan :lol:
