转发一个关于功放功率的观点

pseudo

solderdude写的，我觉得很有道理，转发一下，


Why people consider other amps ?
Portability, desktop or 'home stereo', minimum or maximum requirements, looks, brand, sales pitches, recommendations, functionality, in-output connections, tube/hybrid/SS, size/weight, price, price/performance ratio to name but a few.

High power amplifiers with low output impedances are abundant and cheap. Any speaker amp does this. Not recommended for sensitive headphones !!!!
Then there is the reason that people CLAIM things about SQ based on whatever floats their boat.

The quoted output power of an amplifier is a max rating. How much power one requires depends on listening level, efficiency.
The trouble is most people confuse the words 'needs power' with volume control settings and required voltage.
A high voltage (say 10V) and low current ( say 20mA) is the same 'power' as 1V with 200mA of current.
In case 1 the volume control needs to be set higher as in case 2 yet the same 'power' is drawn by the headphone.

An amplifier is a VOLTAGE source with a finite (maximum) output voltage and is CURRENT limited. Voltage X Current = Power
A headphone needs a voltage and at a certain voltage a headphone draws current depending on the impedance of the headphone.
A headphone thus draws current depending on applied voltage and impedance.
The amplifier needs to be able to supply enough voltage (to avoid clipping) and enough current.

When a current limit is reached there can't be a higher voltage so no higher SPL either.
When a voltage limit is reached there can't be a higher current so no higher SPL either.

The impedance plays a role here. Higher impedance headphones require a higher voltage (higher vol. control position) and draw less current.
Lower impedance headphones require less voltage (lower vol. control position) but draw more current.

You have different impedance headphones and some are inefficient ? You need an amp that can deliver a high voltage (higher Wattage in 300 Ohm) and one that can deliver enough current (higher wattage in 16 Ohm).

You only have high impedance headphones ? You only need enough voltage. Only have low impedance headphones you need more current.
Because of this some amplifiers are better suited for specific headphone(s)

A higher power amplifier does NOT deliver more power nor can it drive headphones 'better' or different from a lower power amplifier as long as the both amplifiers can reach the same output voltage under the same load and other conditions.
The higher power amplifier can play louder. So when one turns up the volume the low power amplifier may 'clip' short peaks where the higher power one doesn't.
A peak that is clipped doesn't need to sound like clipping/distortion (depends on circumstances) but can sound 'compressed' or 'less dynamic' when the clipping is not too severe. That's where the 'needs power' comes from.

Most planars have 'flat' bass response. Due to the way our hearing works planars will sound 'fuller' and more powerfull in the bass at higher levels compared to headphones with boosted bass. People liking 'bass' thus turn up the power with these headphones. To ensure clipping does not occur you need a lot of power. As SOME planars are notoriously inefficient this is where the 'opinion' comes from. Planars usually continue to sound 'good' at higher SPL's and so people turn them up louder than 'normal' phones (your HD800 is closer to planar than dynamic in this aspect)
Usually this talk comes from the 'more subjective' people that have no real clue how headphones and amplifiers work.

zhangjie

英语六级，求翻译