5 ms·

You can get a $30 class D amp which will sound indistinguishable and use way less power

squarefoot 5y ago
I never did any close comparison, but a class D amp, if well built, sounds really clean with no audible noise in background, drawing a fraction of the power and costing a fraction of the money. Some people think they're of inferior quality for being "digital", but class D amps aren't digital at all, they're 100% analog just like traditional ones. The best way to explain how they work is comparing them to power supplies: a traditional class A/B amplifier is to a linear power supply what a class D is to a switching one: they work as PWM drivers wrt the load, but being the frequency really high (hundreds of KHz) there's no way they could produce unwanted noises, which would be easy to filter anyway using small cap+inductors networks. Those filters usually are also enough to avoid inaudible rf noises and audible heterodyne-generated noises in case two different amps in the same room work at slightly different frequencies. That however is not the case for amps enclosed in the same box (stereo or multi channel amps) as they have their clock sync signal in common and wouldn't generate any unwanted signals anyway.
- hakfoo 5y ago
  It feels like it's hard to find a "well built" Class D product. A lot of what's on the market seems to have ambitious or vague specs. It makes me suspicious when I see those Lepai-style amplifiers that are the size of a CD-ROM drive and claim "30 watts per channel... at 10% distortion." Would it even be able to meet those numbers under the test conditions, used for rating amplifiers in the '70s? I suspect they get much tighter numbers at less ambitious wattages, and honestly, most real world listening isn't going to break 1 watt, but it feels like they're not really starting from a place of credibility. From there, even a competent design seems to usually be sold as half a unit-- typically paired with a laptop-style PSU. I'm sure there's a huge range of quality and suitability of pairing, and it's another ugly cable management game to play. It's not going to fit neatly anywhere designed for traditional-sized components. There are probably some decent all-inclusive units once you move past the $50 AliExpress market, but then you're looking at more complex products and more elaborate competition: the fact it's Class D architecture is one bullet point among things like the number of inputs and outputs, video handling capability, and user experience.
  - squarefoot 5y ago
    > It makes me suspicious when I see those Lepai-style amplifiers that are the size of a CD-ROM drive and claim "30 watts per channel... at 10% distortion." I know what you're referring to; I bought one of those years ago and it sounds terrible at any volume, no matter the power supply, the input or what pair of speakers I connect it to. I believe it's a defective unit since the high distortion is audible at any volume. However, I tried some of those small modules sold on Ebay and other (more costly) class D speakers or amps for instruments, and they're generally really good. The modules in particular cost peanuts for what they offer quality wise. But yeah, the chance to save on BOM costs is too appealing, so there are manufacturers going further then making class D amps with junk power supplies or no filtering at the output to save pennies.

I never did any close comparison, but a class D amp, if well built, sounds really clean with no audible noise in background, drawing a fraction of the power and costing a fraction of the money. Some people think they're of inferior quality for being "digital", but class D amps aren't digital at all, they're 100% analog just like traditional ones. The best way to explain how they work is comparing them to power supplies: a traditional class A/B amplifier is to a linear power supply what a class D is to a switching one: they work as PWM drivers wrt the load, but being the frequency really high (hundreds of KHz) there's no way they could produce unwanted noises, which would be easy to filter anyway using small cap+inductors networks. Those filters usually are also enough to avoid inaudible rf noises and audible heterodyne-generated noises in case two different amps in the same room work at slightly different frequencies. That however is not the case for amps enclosed in the same box (stereo or multi channel amps) as they have their clock sync signal in common and wouldn't generate any unwanted signals anyway.

hakfoo 5y ago
It feels like it's hard to find a "well built" Class D product. A lot of what's on the market seems to have ambitious or vague specs. It makes me suspicious when I see those Lepai-style amplifiers that are the size of a CD-ROM drive and claim "30 watts per channel... at 10% distortion." Would it even be able to meet those numbers under the test conditions, used for rating amplifiers in the '70s? I suspect they get much tighter numbers at less ambitious wattages, and honestly, most real world listening isn't going to break 1 watt, but it feels like they're not really starting from a place of credibility. From there, even a competent design seems to usually be sold as half a unit-- typically paired with a laptop-style PSU. I'm sure there's a huge range of quality and suitability of pairing, and it's another ugly cable management game to play. It's not going to fit neatly anywhere designed for traditional-sized components. There are probably some decent all-inclusive units once you move past the $50 AliExpress market, but then you're looking at more complex products and more elaborate competition: the fact it's Class D architecture is one bullet point among things like the number of inputs and outputs, video handling capability, and user experience.
- squarefoot 5y ago
  > It makes me suspicious when I see those Lepai-style amplifiers that are the size of a CD-ROM drive and claim "30 watts per channel... at 10% distortion." I know what you're referring to; I bought one of those years ago and it sounds terrible at any volume, no matter the power supply, the input or what pair of speakers I connect it to. I believe it's a defective unit since the high distortion is audible at any volume. However, I tried some of those small modules sold on Ebay and other (more costly) class D speakers or amps for instruments, and they're generally really good. The modules in particular cost peanuts for what they offer quality wise. But yeah, the chance to save on BOM costs is too appealing, so there are manufacturers going further then making class D amps with junk power supplies or no filtering at the output to save pennies.