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> In amplifiers we care about efficiency, That is at odds with what the blog post says. I'm now confused - for the best sound quality, are we to maximise effi

> In amplifiers we care about efficiency, That is at odds with what the blog post says. I'm now confused - for the best sound quality, are we to maximise efficiency of power usage or maximise accuracy of signal reproduction? I didn't think you can do both.

kazinator 3y ago
You are right. Audio amplifiers have not historically been power efficient. In the case of a headphone amplifier on AC power, we don't have to think about efficiency, as long as it isn't ridiculous, like drawing 100W. Class B amplifiers are only efficient when producing no output, or when producing output clipped to the power rails (like a square wave). Due to being almost fully off or fully on. For a sinusoidal signal, the worst case efficiency occurs at about 40% of the output power delivered to the load, when the transistors will dissipate another 20%. Source: https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Book%3A_Semiconductor_Devices_-_Theory_and_Application_(Fiore)/09%3A_BJT_Class_B_Power_Amplifiers/9.2%3A_The_Class_B_Configuration https://eng.libretexts.org/Bookshelves/Electrical_Engineerin... Section 9.2.4: Class B Power Dissipation
- lelanthran 3y ago
  Okay, since you appear to know what you're talking about, if I wanted to maximise signal reproduction (with absolutely zero consideration for efficiency) when matching amplifiers with speakers (for car audio), what numbers should I be looking at when choosing components? (Yes, I checked a few youtube videos and blogs, but car audiophiles don't really get too scientific and it's hard to tell whether they really know what they are talking about).
  - SomeoneFromCA 3y ago
    What you want is low THD and low output impedance.
  - kazinator 3y ago
    In audio, the speakers are much more important than the amplifier. You will not easily hear a difference between two good power amplifiers, but you can easily hear the difference between pretty much any two speakers. As far as matching goes, you want amp power > speaker power handling. If the amp distorts before the speakers do, you're not getting the most out of the speakers, and clipping can be bad for some speakers too, especially tweeters. Also, the THD figures quoted for amplifiers are usually at moderate output levels; they get worse with higher voltage swing. An amp that is getting close to clipping will generally have worse THD than one which is nowhere near clipping. (As well, THD gets worse with rising frequency.)

kazinator 3y ago

You are right. Audio amplifiers have not historically been power efficient. In the case of a headphone amplifier on AC power, we don't have to think about efficiency, as long as it isn't ridiculous, like drawing 100W. Class B amplifiers are only efficient when producing no output, or when producing output clipped to the power rails (like a square wave). Due to being almost fully off or fully on. For a sinusoidal signal, the worst case efficiency occurs at about 40% of the output power delivered to the load, when the transistors will dissipate another 20%. Source: https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Book%3A_Semiconductor_Devices_-_Theory_and_Application_(Fiore)/09%3A_BJT_Class_B_Power_Amplifiers/9.2%3A_The_Class_B_Configuration https://eng.libretexts.org/Bookshelves/Electrical_Engineerin... Section 9.2.4: Class B Power Dissipation

lelanthran 3y ago
Okay, since you appear to know what you're talking about, if I wanted to maximise signal reproduction (with absolutely zero consideration for efficiency) when matching amplifiers with speakers (for car audio), what numbers should I be looking at when choosing components? (Yes, I checked a few youtube videos and blogs, but car audiophiles don't really get too scientific and it's hard to tell whether they really know what they are talking about).
- SomeoneFromCA 3y ago
  What you want is low THD and low output impedance.
- kazinator 3y ago
  In audio, the speakers are much more important than the amplifier. You will not easily hear a difference between two good power amplifiers, but you can easily hear the difference between pretty much any two speakers. As far as matching goes, you want amp power > speaker power handling. If the amp distorts before the speakers do, you're not getting the most out of the speakers, and clipping can be bad for some speakers too, especially tweeters. Also, the THD figures quoted for amplifiers are usually at moderate output levels; they get worse with higher voltage swing. An amp that is getting close to clipping will generally have worse THD than one which is nowhere near clipping. (As well, THD gets worse with rising frequency.)