? about scope clipping and thd

[nauc 10+ year member]

i have a velleman hps10, when i turn up my gain to clip the signal, when it clips, what is that = to as far as thd goes

cause if the 300/4 does say 97 watts per channel at 1% thd, how many watts will it be putting out when it clips my scopes signal

Click to read more...

 

[helotaxi 5,000+ posts]

THD and clipping are two separate things and don't have anything to do with eachother. THD is a measure of harmonic distortion. Basically signal introduced by resonance within the electronics of the amplifier. Harmonics are whole integer multiples of the fundamental frequency. So say you feed a 100Hz sine wave to the amp, it would ideally only output the signal fed to it, but in reality it will produce some harmonics as well. These harmonics alter the sound produced by the amp. Even order harmonics are generally considered pleasant sounding and odd order harmonics tend to sound harsh. When you clip the signal, the distortion is not really harmonic. Typically what you end up with is ripple on the top of the clipped waveform. In many amps this has the sound of high odd order harmonic distortion, but not all.

 

[nauc 10+ year member]

so im guessing thd will be heard before clipping when increasing the volume

 

[helotaxi 5,000+ posts]

Yes. But considering even the best speakers produce on the order of 10% THD, most amp distortion is inaudible. Once the signal is clipped, depending on how bad it is clipped you are talking well over 50% distortion (just not harmonic distortion). Using a clipped signal, you can get a lot more power out of an amp, BUT that power will be lost as heat in the speaker rather than giving you any more volume. This is a matter of how AC power is measured since it is constantly fluctuating. You will increase the average voltage and current going to the driver but not the peak, so instead of only touching the peak voltage for an instant, it goes there a stays there until the cycle reverses and goes to the neg rail voltage and stays there. The whole time that the clipped peak is present, you are effectively sending DC to the sub. DC produces nothing but heat from a driver.