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<blockquote data-quote="thylantyr" data-source="post: 4148724" data-attributes="member: 560358">A car audio power supply can &#039;squeek&#039; in sound under load. For instance, lets say youtook the cover off and placed your ear next to the transformer, the toriod. Operate theamp under heavy load, burp it, you may hear a squeel........ chirp chirp..... for every burp.This is because the switching frequency is dropping under load and the switching frequencyis suppose to be outside the audible range, way beyond 20khz. Under load, the switchermay drop in frequency to the audible range, hence the chirp...This is not a good design and a good amplifier shouldn&#039;t do this unless it&#039;s broken or something else weird is going on.But in your case, you hear the amp squeel when the input voltage rises from 12v to 14v,it also seems like the switcher is having problems with it&#039;s switching frequency. The lowervoltage is tweaking the amplifier out when it shouldn&#039;t. Maybe something is broke....Broke-back amplifier?<img src="http://www.theage.com.au/ffximage/2006/01/23/Brokeback_051213015328053_wideweb__300x298.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />That&#039;s my weird take on this.</blockquote>

[QUOTE="thylantyr, post: 4148724, member: 560358"] A car audio power supply can 'squeek' in sound under load. For instance, lets say you took the cover off and placed your ear next to the transformer, the toriod. Operate the amp under heavy load, burp it, you may hear a squeel........ chirp chirp..... for every burp. This is because the switching frequency is dropping under load and the switching frequency is suppose to be outside the audible range, way beyond 20khz. Under load, the switcher may drop in frequency to the audible range, hence the chirp... This is not a good design and a good amplifier shouldn't do this unless it's broken or something else weird is going on. But in your case, you hear the amp squeel when the input voltage rises from 12v to 14v, it also seems like the switcher is having problems with it's switching frequency. The lower voltage is tweaking the amplifier out when it shouldn't. Maybe something is broke.... Broke-back amplifier? [IMG]http://www.theage.com.au/ffximage/2006/01/23/Brokeback_051213015328053_wideweb__300x298.jpg[/IMG] That's my weird take on this. [/QUOTE]

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