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Topic: “some amps run out of current first and some run out of voltage” get me confused (Read 1436 times) previous topic - next topic
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“some amps run out of current first and some run out of voltage” get me confused

Hello everyone! I came across this passage:

Quote
When a headphone source runs out of power with typical compressed pop music you’ll typically either hear distortion or it simply won’t be loud enough with the volume all the way up. With more dynamic music, like classical or well recorded jazz, just the peaks may be clipped so it might not be as obvious there’s a power shortage. Power is a function of voltage and current. And some amps, with a given headphone, run out of current first and some run out of voltage first.

However, there is no mathematical calculation process to substantiate this statement, leading to my confusion about when distortion occurs and when the sound is simply too low. I would simply think that if the amplifier power is insufficient, the headphone's sound would be relatively low, and I couldn't imagine the possibility of clipping.
I would be very happy and grateful if I could receive guidance from everyone. Thank you.

Re: “some amps run out of current first and some run out of voltage” get me confused

Reply #1 –
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the headphone's sound would be relatively low, and I couldn't imagine the possibility of clipping.
Most, most amplifiers have enough gain to easily clip when you turn up the volume.

When it clips it continues to go louder because the average can go-up even though the peaks are clipped.   And the harmonic distortion adds to the perception of loudness.

Electric guitar players routinely drive their amps into clipping for an intentional distortion/saturation effect, and they tend to favor tube amplifiers because they tend to soft-clip before they hit a hard-limit.

A soundcard usually won't clip on the analog-side because there is usually headroom above the point where the digital clips (0dBFS is the "digital maximum").   A DAC with a built-in headphone amp may be similarly calibrated so the analog output doesn't clip. 

It's the voltage that's clipped but current, voltage, and resistance (or impedance) are related as described by Ohm's Law.   Resistance is "the resistance to current flow" so if you increase voltage or lower resistance you get more current. 

You can get clipping when the output voltage is limited by the power supply voltage (including any voltage-loss through the amplifier or if the amplifier can't supply the necessary current, the voltage will be limited for that reason (physics and Ohm's Law).

If an amplifier can put-out the voltage same voltage with a 4-Ohm load as an 8-Ohm load, you get twice the current and twice the power with the lower impedance speakers.    If an amplifier can't put-out twice the power at 4-Ohms, we'd say it's "current limited" although the voltage is also being "pulled down" or limited from what it was at 8-Ohms.

Re: “some amps run out of current first and some run out of voltage” get me confused

Reply #2 –
Duplicated deleted.

Re: “some amps run out of current first and some run out of voltage” get me confused

Reply #3 –
Quote from: DVDdoug on
Quote
the headphone's sound would be relatively low, and I couldn't imagine the possibility of clipping.
Most, most amplifiers have enough gain to easily clip when you turn up the volume.

When it clips it continues to go louder because the average can go-up even though the peaks are clipped.   And the harmonic distortion adds to the perception of loudness.

Electric guitar players routinely drive their amps into clipping for an intentional distortion/saturation effect, and they tend to favor tube amplifiers because they tend to soft-clip before they hit a hard-limit.

A soundcard usually won't clip on the analog-side because there is usually headroom above the point where the digital clips (0dBFS is the "digital maximum").   A DAC with a built-in headphone amp may be similarly calibrated so the analog output doesn't clip. 

It's the voltage that's clipped but current, voltage, and resistance (or impedance) are related as described by Ohm's Law.   Resistance is "the resistance to current flow" so if you increase voltage or lower resistance you get more current. 

You can get clipping when the output voltage is limited by the power supply voltage (including any voltage-loss through the amplifier or if the amplifier can't supply the necessary current, the voltage will be limited for that reason (physics and Ohm's Law).

If an amplifier can put-out the voltage same voltage with a 4-Ohm load as an 8-Ohm load, you get twice the current and twice the power with the lower impedance speakers.    If an amplifier can't put-out twice the power at 4-Ohms, we'd say it's "current limited" although the voltage is also being "pulled down" or limited from what it was at 8-Ohms.



@DVDdoug Thanks so much for your explanation with patience! The difference between dac/amp combo and dedicated amp is definitely something I ignored.
But I still got confused by some measurement graph like this:


I saw many graphs like this showed max. out put power/voltage of an dongle or a dedicated amp. How could they push the out put power far beyond to observe obvious distortion of some dongle?