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Quality micro amplifiers (class D) are extremely difficult to design. They are way outside the possibilities of amateurs or boutique shops, unlike classical am

Quality micro amplifiers (class D) are extremely difficult to design. They are way outside the possibilities of amateurs or boutique shops, unlike classical amps (class A, ...)

baybal2 7y ago
> They are way outside the possibilities of amateurs or boutique shops I disagree, take a look at what that guy does: https://twitter.com/amiteque https://twitter.com/amiteque
kragen 7y ago
What are the pitfalls?
- analog31 7y ago
  Owning a good enough oscilloscope is actually an issue. The switching signals are high speed, and subtle variations impinge on both the efficiency and stability of the amplifier. Many of the components are operating in their regime of non ideal behavior, e.g., a capacitor is not just a capacitor. Circuit board layout is also a big deal. Even the commercial amplifier makers have mostly reverted to buy-in modules. Most of the "mini amps" sold for bass guitar contain IcePower modules made by a division of Bang & Olufsen. I've gone so far as to simulate a switchmode amplifier in LTSpice just for fun. I'm quite heavily into electronics, but have made it a personal rule not to mess around with homemade line powered equipment that I would actually take to a performance. I don't want to become known as the whiz kid whose homemade gear blew up on stage. ;-) At lower power levels, there are some IC's made by Texas Instruments and others that shouldn't be too difficult to apply, but you can also get entire amplifier boards with these chips from online suppliers for next to nothing.
  - nwallin 7y ago
    Define "good enough oscilloscope"? A rigol 1054z can be had for $4-500. What do you need from an oscilloscope that the 1054z doesn't provide? I'm not saying you're wrong, I just don't understand.
    - analog31 7y ago
      That's probably good enough, but certainly better than what I have at home. In fact, I bought a couple of those for my workplace.
  - rasz 7y ago
    How is owning an oscilloscope capable of <~50KHz BW an issue? Those are the only frequencies you should be worried about in an audio amp.
    - detaro 7y ago
      Not for testing a class-D amp, which switches in the MHz range, and you do want to test if it's stable, if your filters actually get rid of the HF parts, ... And even for an analog design 50kHz wouldn't really be enough for many potential problems which happen above that. Worrying just about the audio range is not enough.
      - analog31 7y ago
        Indeed, and it's the high frequency behavior where you see if you're getting charge on and off the gates of the MOSFETs fast enough with just the right timing.

Quality micro amplifiers (class D) are extremely difficult to design. They are way outside the possibilities of amateurs or boutique shops, unlike classical amps (class A, ...)

baybal2 7y ago

> They are way outside the possibilities of amateurs or boutique shops I disagree, take a look at what that guy does: https://twitter.com/amiteque https://twitter.com/amiteque

kragen 7y ago

What are the pitfalls?

analog31 7y ago
Owning a good enough oscilloscope is actually an issue. The switching signals are high speed, and subtle variations impinge on both the efficiency and stability of the amplifier. Many of the components are operating in their regime of non ideal behavior, e.g., a capacitor is not just a capacitor. Circuit board layout is also a big deal. Even the commercial amplifier makers have mostly reverted to buy-in modules. Most of the "mini amps" sold for bass guitar contain IcePower modules made by a division of Bang & Olufsen. I've gone so far as to simulate a switchmode amplifier in LTSpice just for fun. I'm quite heavily into electronics, but have made it a personal rule not to mess around with homemade line powered equipment that I would actually take to a performance. I don't want to become known as the whiz kid whose homemade gear blew up on stage. ;-) At lower power levels, there are some IC's made by Texas Instruments and others that shouldn't be too difficult to apply, but you can also get entire amplifier boards with these chips from online suppliers for next to nothing.
- nwallin 7y ago
  Define "good enough oscilloscope"? A rigol 1054z can be had for $4-500. What do you need from an oscilloscope that the 1054z doesn't provide? I'm not saying you're wrong, I just don't understand.
  - analog31 7y ago
    That's probably good enough, but certainly better than what I have at home. In fact, I bought a couple of those for my workplace.
- rasz 7y ago
  How is owning an oscilloscope capable of <~50KHz BW an issue? Those are the only frequencies you should be worried about in an audio amp.
  - detaro 7y ago
    Not for testing a class-D amp, which switches in the MHz range, and you do want to test if it's stable, if your filters actually get rid of the HF parts, ... And even for an analog design 50kHz wouldn't really be enough for many potential problems which happen above that. Worrying just about the audio range is not enough.
    - analog31 7y ago
      Indeed, and it's the high frequency behavior where you see if you're getting charge on and off the gates of the MOSFETs fast enough with just the right timing.