Voltage drop and no extra current = ?

[soydeedo 10+ year member]

Awhile back, before I did the big 3 and got rid of my failing battery, I sometimes heard a hollow sound when I didn't have enough juice to power the amp feeding my subs. When it happened, I measured my voltage at ~11 or so which is definitely not good.

I'm curious, though, what happens if an amp doesn't get the amperage it needs when the voltage drops? It obviously can't put out the power it wants to, so assuming it doesn't break down does it just clip the signal or something? Or does it send out the full waveform just without the amplitude it wants?

I'm assuming it clips just because of the hollow sound, but I'd like to know for sure.

PS - I've tried a search on this many times with no good results. I'm sure it's already been covered, but I couldn't find anything so sorry about that.

Click to read more...

 

[dipitydoo 10+ year member]

I'm not sure about the hollow sound, but an unregulated amp will output power dependent on the voltage up to a point where it will cease to function at a set minimum voltage

 

[helotaxi 5,000+ posts]

It will attempt to draw as much current as it needs when the voltage drops. The battery will take up the slack usually. Even an "unregulated" amp will attempt to draw more current most of the time. An unregulated amp will either clip or drop the rail voltage and not get as loud. A tightly regulated amp will draw excessive current until it either drops the voltage to the point that the protection circuits kick in or it exceeds the current capacity of its fusing or power supply FETs one of which will blow.

 

[soydeedo 10+ year member]

Thanks for the responses, fellas. I have an MTX 1501d which I've read is unregulated so that explains it. Since the battery was no good when it was doing this I guess it just couldn't get any more current so it was clipping like crazy, throwing out squared bass notes that give that hollow sound.

Thanks again. =) I feel lucky I didn't end up killing something major in my car during that interim period.

 

[n2audio 5,000+ posts]

http://www.audiogroupforum.com/csforum/showthread.php?t=65076&highlight=voltage

 

[soydeedo 10+ year member]

Hm...thanks, n2audio.

For unregulated supplies, the decreased input voltage means that the output voltage of the power supply will be decreased and the maximum output power of the amplifier will decrease as well.

That's very similar to what dipity and helotaxi said, except his wording makes it sound like it wouldn't clip at all, just the output would be very low. Maybe I'm reading it wrong or my limited knowledge on amps is biting me in the ***. Probably the latter. =P