6 ms·

Low THD PWM audio amp, DIY friendly

catseyechandra 4y ago
I'm both an IT and audio geek, does HN likes audio geekery? I'm not affiliated with the company behind this website BTW..
- amelius 4y ago
  > does HN likes audio geekery Only if scientifically backed.
  - aquarium87 4y ago
    Hahaha! I can't imagine discussing the finer points of optimization on here. "the electromagnetic signal of course rides half outside the wire in a world increasingly filled with RF/EMF noise. Be sure to keep your cables off the floor or there WILL be impedence changes. Also, the Frequency Response is largely not relevant as 95+% of audiophiles don't have effective bass traps or ways to remove excess energy from the room. Intelligibility is the better metric, and no one uses it because it requires bass trapping and that's just to ugly and expensive." Are you ready to rip my head off yet for all these largely unknown but completely true scientific facts? :)
    - amelius 4y ago
      Of course science would also require a blind perception test ...
  - the_third_wave 4y ago
    When talking about high-end audio it is more of The Science™ than about the scientific method. The former is also far more profitable so it is not surprising to find so little of the latter in this field.
rektide 4y ago
DIY as in assemble yourself? I tried finding parts or info or schematics or designs for their other amps, but nothing of any real detail seems available. Cool potential offering here, but based on their other offerings, looks like it will probably be phenomenally expensive even in kit form. And not at all in the kind of hacker-ish open form we might hope. It'd be great to see some real open-source wonkery start eith some of the modern chipamp chips. TI's latest tpa3255 is a beastly chip, and there's some pretty good sub $100 ~400W designs about based on it's advanced magic. Trying to get a bit more geeky, to share & tune & profile boards & builds together for modern chip-amps could really open up some new frontiers of affordable quality.
- KennyBlanken 4y ago
  My money is on "tax and/or tariff avoidance ploy." Taxes and tariffs are responsible for "tariff engineering" to get around the definitions used for many tariffs. For example, a lot of early DSLRs couldn't record video continuously for more than 20 minutes, because this would qualify them as camcorders. Either that or they're selling this for people who have the skills to create a chassis (or have one made) and then put these guts into. Sort of a "crate engine" of the audio world, I guess. I liked the "affordable" claims. The complete kit is $1200...
al2o3cr 4y ago
Audiophool class-D amplifier. Now I've seen EVERYTHING :P
- zihotki 4y ago
  I assume you meant "audiophile", not audiophool, right? If so, I wonder what makes an amplifier to be an audiophile amplifier in your opinion? Objective and measurable parameters of the amplifier in question are phenomenal.
  - rasz 4y ago
    There is a picture of special, braided IEC power cable on there.
    - aquarium87 4y ago
      Geometry. Rigidity. It's POTENTIALLY legit. Here is a pretty science based primer on some of the things going on in the cable world. https://www.gcaudio.com/tips-tricks/why-power-cords-are-important/ https://www.gcaudio.com/tips-tricks/why-power-cords-are-impo... One thing to understand about this niche high end cable market is that intellectual property just isn't a thing. There isn't enough money to fight lawsuits and wage war against copycats. Everyone loses throwing money away. The end result is that only large companies like AudioQuest can afford to "give away" the science behind their products by patenting them. Other companies have to talk around and obscure what ACTUALLY makes their cable sound good. This is a pretty raw deal for consumers who are left exposed and vulnerable to bad designers, fraudsters, and tricking themselves into thinking something sounds better when it's not. And that's not even getting into value judgements about what a cable is worth based on how much closer to perfection it gets the user! The system does seem to be working as intended by small niche cable makers who spend lifetimes accumulating arcane knowledge and handbuilding quality cables while keeping the bar for entry to the market high. Another neat tidbit about cables is that the product lines and price points are not linear. They just can't be in reality from a design perspective. The people that say a cable is a cable are half correct. It's impossible to have a cable lineup of 7 levels and improve on the induction, capacitance and resistance all at the same time in each level. So there are tradeoffs, and occasionally a cheaper cable from the same company will sound better than a more expensive cable because one or two of the parameters were improved while another got worse. Depending on the interactions between the connected equipment and their deviation from perfect, if the parameter that took a step backwards in a more premium cable happens to be the weak point of the equipment as well, then an objectively better and more expensive cable can sound the same or worse.
eqvinox 4y ago
From the title, I expected an audio amp project with schematics and layouts available that was "DIY friendly" to build yourself. I was left disappointed…
zihotki 4y ago
DIY in the site name is very misleading. There is nothing DIY there, they sell already assembled kits, no schematics or component list. From the site it looks like they work closely with NCORE which produces very good amps. Edit: clarification
amelius 4y ago
Wow, that's quite a lot of capacitors. Why so many?
- dreamcompiler 4y ago
  I'd guess it's because they have a high quality switching power supply, a power factor corrector, and a digital amplifier. All those things require good capacitors -- probably more than if all the circuitry was linear.
- klodolph 4y ago
  500W is a lot of juice. Consider that 120 times per second, the amp gets no power from the wall and has to rely solely on the power in capacitors. The capacitors have to supply the full 500W. Possibly more—something that’s nominally 500W “peak” but driving a speaker may see instantaneous loads much higher. Modern circuitry has increased efficiency and reduced the heat dissipated by an amp, but the capacitors still need to supply the full amount of power between mains cycles. It is sometimes easier to get the desired performance out of paralleled banks of capacitors rather than just use one large capacitor. This does look a bit excessive, though.
  - amelius 4y ago
    Perhaps it's a measure against failure? Do these capacitors fail open? Or price, although that would raise new questions. Another is availability of components. Or perhaps the form factor (these capacitors seem slightly less tall than the ones on the other board in the picture).
    - klodolph 4y ago
      Designing for failure seems unlikely here. I think they just wanted lots of capacitance and a low ESR. Lots of capacitors is a cheap way to get that.
pengaru 4y ago
Too bad it's not actually DIY. Does anyone remember the 80s-era catalog of DIY HiFi kits? I can't remember the name, it was electronics geek+audiophile porn. Maybe it was Craven? something like that?
- michaelteter 4y ago
  Crutchfield? https://en.wikipedia.org/wiki/Crutchfield_Corporation https://en.wikipedia.org/wiki/Crutchfield_Corporation
  - pengaru 4y ago
    They seem too focused on automotive/car stereos to be it. The catalog I'm recalling was cover to cover populated amplifier circuit boards accompanied by specs and prices. Lots of huge toroidal transformers... maybe it was a local thing back in IL. The cover was mostly black with glowy green text IIRC, nothing like the vintage Crutchfield catalogs I can find via GIS/ebay. Oh well.
    - snozolli 4y ago
      Possibly Madisound. Their site says they've been around since '72. I have vague recollections of them having a print catalog in the 90s before everything went online.
      - pengaru 4y ago
        It might have been an 80s refresh hifi-leaning variant of eico's catalog: https://www.ebay.com/itm/255457806571 https://www.ebay.com/itm/255457806571 That cover seems very familiar to me, and I do remember there being a bunch of green on a black background.
- wesapien 4y ago
  Google or Youtube GR Research. They supply bookshelf speaker kits and large open baffle towers.
DiabloD3 4y ago
Don't see the point of this when I can just build a Kevin Gilmore Dynalo or Dynahi. Very low part count, almost BOM golf like; multiple variations by him and others to cover any case. Closest you will ever get to a wire with gain. Not to slight Hypex (the company behind the Ncore family of Class D chip amps), mind you, they're probably the only chip amp to ever succeed in making low distortion high output high efficiency chip amps (and if it is a class D and doesn't have a Ncore, it probably sucks, unless it's that new THX design family); but it will never outperform a Dynalo/Dynahi built correctly.
- djmips 4y ago
  aren't the Dnyaxx amps headphone amps?
  - DiabloD3 4y ago
    Yes and no. People have built speaker amps out of Dynahis. Due to the small size of the PCBs, it is trivial to do bi/tri-amped designs (with the woofer using a different amp or multiple stacked Dynahis). The Dynahi is, admittedly, a ~25w amp (at least, at near-zero distortion and clipping conditions) when firing into an 8 ohm typical load, which means it isn't a headphone amp either; the Dynamite configuration (balanced Dynahi) doubles this output. Note: the best tweeters ever made have rather strange electrical characteristics, in the same vein that some headphones do. The Dynaxx family tends to handle anything, high or low ohm (even speakers that are 4ohm nominal or headphones that are 1000+ohm), but also ones with ridiculous impedance curves. People have realized that due to its exceptional tolerance of weirdly designed speakers, it makes for a good speaker amp too. 25w is enough to drive these tweeters loud enough, and some mids as well; woofers, no, not with a single board. Kevin Gilmore also has sequels to his Dynaxx family (these being, themselves, improved versions of the KG Dynamic), due to some parts being replaced as they've fallen out of production and are hard to buy now.
amluto 4y ago
There are quite a few very, very good class D amplifier designs out there. “Very good” means highly efficient and with good enough fidelity (noise, distortion, etc) that no one will ever be able to distinguish them from perfect. But, IMO quite annoyingly, these things generally have analog inputs. This means you need a good DAC (which exists and isn’t terribly expensive) and a good connection from the DAC to the amp. You can make a good connection out of inexpensive cables, but you still need to worry about ground loops and possibly signal levels. So why aren’t there comparably good amplifiers with digital inputs and a DAC integrated directly? Fancy preamp features are unnecessary — if the input resolution is 24-bit, then volume control and such can be done digitally with effectively no loss.
- wdfx 4y ago
  Searching for "plate amplifier module" you can find integrated digital/amp/crossover units suitable for DIY builds.
  - amluto 4y ago
    That’s a great form factor for building a speaker but a rather annoying form factor for driving an existing passive speaker.
- Gordonjcp 4y ago
  Given that it's just phase-correct PWM, you'd think feeding the bits you'd stuff into a DAC directly into the PWM counter would do the job nicely. You could probably do that with a fast microcontroller these days. Some golden-eared audiophool pillock would complain they could hear jitter caused by the pins not being gold-plated or something, but who cares?
  - aquarium87 4y ago
    It takes a lot of computing power to reconstruct an audio sample well. Once reconstructed it takes massive massive amounts of storage. It's all about the Shannon Nyquist sampling theorum. "Strictly speaking, the theorem only applies to a class of mathematical functions having a Fourier transform that is zero outside of a finite region of frequencies. Intuitively we expect that when one reduces a continuous function to a discrete sequence and interpolates back to a continuous function, the fidelity of the result depends on the density (or sample rate) of the original samples. The sampling theorem introduces the concept of a sample rate that is sufficient for perfect fidelity for the class of functions that are band-limited to a given bandwidth, such that no actual information is lost in the sampling process. It expresses the sufficient sample rate in terms of the bandwidth for the class of functions. The theorem also leads to a formula for perfectly reconstructing the original continuous-time function from the samples." [1] But, HOLD ON: "Practical digital-to-analog converters produce neither scaled and delayed sinc functions, nor ideal Dirac pulses. Instead they produce a piecewise-constant sequence of scaled and delayed rectangular pulses (the zero-order hold), usually followed by a lowpass filter (called an "anti-imaging filter") to remove spurious high-frequency replicas (images) of the original baseband signal." [1] In case that was too verbose..... "sample rate that is sufficient for perfect fidelity".... "such that no actual information is lost in the sampling process"... "theorem also leads to a formula for perfectly reconstructing the original continuous-time function from the samples" PERFECTLY!!! Zero information loss between sampling and reconstruction. Still WTFs me to this day. So yeah, you can feed bits to a PWM. But that not music. [1] https://en.m.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem https://en.m.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_samp...
SomeoneFromCA 4y ago
I can reliably distinguish even very high-end Class D from a decent class AB amp. I perceive sand-grain in the sound of class D.
cramjabsyn 4y ago
I’m a huge fan of class D amps, although usually on the cheap end of the spectrum. Recently I purchased a “fosi audio” (brand names seem to rotate) stereo amp with bluetooth. It’s about the size of a raspberry pi. It is plenty powerful to drive a pair of bookshelf speakers, sounds good, and connects to a turntable and bluetooth source at the same time. $25 on ebay. Really hard to beat for the price and size

I'm both an IT and audio geek, does HN likes audio geekery? I'm not affiliated with the company behind this website BTW..

amelius 4y ago
> does HN likes audio geekery Only if scientifically backed.
- aquarium87 4y ago
  Hahaha! I can't imagine discussing the finer points of optimization on here. "the electromagnetic signal of course rides half outside the wire in a world increasingly filled with RF/EMF noise. Be sure to keep your cables off the floor or there WILL be impedence changes. Also, the Frequency Response is largely not relevant as 95+% of audiophiles don't have effective bass traps or ways to remove excess energy from the room. Intelligibility is the better metric, and no one uses it because it requires bass trapping and that's just to ugly and expensive." Are you ready to rip my head off yet for all these largely unknown but completely true scientific facts? :)
  - amelius 4y ago
    Of course science would also require a blind perception test ...
- the_third_wave 4y ago
  When talking about high-end audio it is more of The Science™ than about the scientific method. The former is also far more profitable so it is not surprising to find so little of the latter in this field.

rektide 4y ago

DIY as in assemble yourself? I tried finding parts or info or schematics or designs for their other amps, but nothing of any real detail seems available. Cool potential offering here, but based on their other offerings, looks like it will probably be phenomenally expensive even in kit form. And not at all in the kind of hacker-ish open form we might hope. It'd be great to see some real open-source wonkery start eith some of the modern chipamp chips. TI's latest tpa3255 is a beastly chip, and there's some pretty good sub $100 ~400W designs about based on it's advanced magic. Trying to get a bit more geeky, to share & tune & profile boards & builds together for modern chip-amps could really open up some new frontiers of affordable quality.

KennyBlanken 4y ago
My money is on "tax and/or tariff avoidance ploy." Taxes and tariffs are responsible for "tariff engineering" to get around the definitions used for many tariffs. For example, a lot of early DSLRs couldn't record video continuously for more than 20 minutes, because this would qualify them as camcorders. Either that or they're selling this for people who have the skills to create a chassis (or have one made) and then put these guts into. Sort of a "crate engine" of the audio world, I guess. I liked the "affordable" claims. The complete kit is $1200...

al2o3cr 4y ago

Audiophool class-D amplifier. Now I've seen EVERYTHING :P

zihotki 4y ago
I assume you meant "audiophile", not audiophool, right? If so, I wonder what makes an amplifier to be an audiophile amplifier in your opinion? Objective and measurable parameters of the amplifier in question are phenomenal.
- rasz 4y ago
  There is a picture of special, braided IEC power cable on there.
  - aquarium87 4y ago
    Geometry. Rigidity. It's POTENTIALLY legit. Here is a pretty science based primer on some of the things going on in the cable world. https://www.gcaudio.com/tips-tricks/why-power-cords-are-important/ https://www.gcaudio.com/tips-tricks/why-power-cords-are-impo... One thing to understand about this niche high end cable market is that intellectual property just isn't a thing. There isn't enough money to fight lawsuits and wage war against copycats. Everyone loses throwing money away. The end result is that only large companies like AudioQuest can afford to "give away" the science behind their products by patenting them. Other companies have to talk around and obscure what ACTUALLY makes their cable sound good. This is a pretty raw deal for consumers who are left exposed and vulnerable to bad designers, fraudsters, and tricking themselves into thinking something sounds better when it's not. And that's not even getting into value judgements about what a cable is worth based on how much closer to perfection it gets the user! The system does seem to be working as intended by small niche cable makers who spend lifetimes accumulating arcane knowledge and handbuilding quality cables while keeping the bar for entry to the market high. Another neat tidbit about cables is that the product lines and price points are not linear. They just can't be in reality from a design perspective. The people that say a cable is a cable are half correct. It's impossible to have a cable lineup of 7 levels and improve on the induction, capacitance and resistance all at the same time in each level. So there are tradeoffs, and occasionally a cheaper cable from the same company will sound better than a more expensive cable because one or two of the parameters were improved while another got worse. Depending on the interactions between the connected equipment and their deviation from perfect, if the parameter that took a step backwards in a more premium cable happens to be the weak point of the equipment as well, then an objectively better and more expensive cable can sound the same or worse.

eqvinox 4y ago

From the title, I expected an audio amp project with schematics and layouts available that was "DIY friendly" to build yourself. I was left disappointed…

zihotki 4y ago

DIY in the site name is very misleading. There is nothing DIY there, they sell already assembled kits, no schematics or component list. From the site it looks like they work closely with NCORE which produces very good amps. Edit: clarification

amelius 4y ago

Wow, that's quite a lot of capacitors. Why so many?

dreamcompiler 4y ago
I'd guess it's because they have a high quality switching power supply, a power factor corrector, and a digital amplifier. All those things require good capacitors -- probably more than if all the circuitry was linear.
klodolph 4y ago
500W is a lot of juice. Consider that 120 times per second, the amp gets no power from the wall and has to rely solely on the power in capacitors. The capacitors have to supply the full 500W. Possibly more—something that’s nominally 500W “peak” but driving a speaker may see instantaneous loads much higher. Modern circuitry has increased efficiency and reduced the heat dissipated by an amp, but the capacitors still need to supply the full amount of power between mains cycles. It is sometimes easier to get the desired performance out of paralleled banks of capacitors rather than just use one large capacitor. This does look a bit excessive, though.
- amelius 4y ago
  Perhaps it's a measure against failure? Do these capacitors fail open? Or price, although that would raise new questions. Another is availability of components. Or perhaps the form factor (these capacitors seem slightly less tall than the ones on the other board in the picture).
  - klodolph 4y ago
    Designing for failure seems unlikely here. I think they just wanted lots of capacitance and a low ESR. Lots of capacitors is a cheap way to get that.

pengaru 4y ago

Too bad it's not actually DIY. Does anyone remember the 80s-era catalog of DIY HiFi kits? I can't remember the name, it was electronics geek+audiophile porn. Maybe it was Craven? something like that?

michaelteter 4y ago
Crutchfield? https://en.wikipedia.org/wiki/Crutchfield_Corporation https://en.wikipedia.org/wiki/Crutchfield_Corporation
- pengaru 4y ago
  They seem too focused on automotive/car stereos to be it. The catalog I'm recalling was cover to cover populated amplifier circuit boards accompanied by specs and prices. Lots of huge toroidal transformers... maybe it was a local thing back in IL. The cover was mostly black with glowy green text IIRC, nothing like the vintage Crutchfield catalogs I can find via GIS/ebay. Oh well.
  - snozolli 4y ago
    Possibly Madisound. Their site says they've been around since '72. I have vague recollections of them having a print catalog in the 90s before everything went online.
    - pengaru 4y ago
      It might have been an 80s refresh hifi-leaning variant of eico's catalog: https://www.ebay.com/itm/255457806571 https://www.ebay.com/itm/255457806571 That cover seems very familiar to me, and I do remember there being a bunch of green on a black background.
wesapien 4y ago
Google or Youtube GR Research. They supply bookshelf speaker kits and large open baffle towers.

DiabloD3 4y ago

Don't see the point of this when I can just build a Kevin Gilmore Dynalo or Dynahi. Very low part count, almost BOM golf like; multiple variations by him and others to cover any case. Closest you will ever get to a wire with gain. Not to slight Hypex (the company behind the Ncore family of Class D chip amps), mind you, they're probably the only chip amp to ever succeed in making low distortion high output high efficiency chip amps (and if it is a class D and doesn't have a Ncore, it probably sucks, unless it's that new THX design family); but it will never outperform a Dynalo/Dynahi built correctly.

djmips 4y ago
aren't the Dnyaxx amps headphone amps?
- DiabloD3 4y ago
  Yes and no. People have built speaker amps out of Dynahis. Due to the small size of the PCBs, it is trivial to do bi/tri-amped designs (with the woofer using a different amp or multiple stacked Dynahis). The Dynahi is, admittedly, a ~25w amp (at least, at near-zero distortion and clipping conditions) when firing into an 8 ohm typical load, which means it isn't a headphone amp either; the Dynamite configuration (balanced Dynahi) doubles this output. Note: the best tweeters ever made have rather strange electrical characteristics, in the same vein that some headphones do. The Dynaxx family tends to handle anything, high or low ohm (even speakers that are 4ohm nominal or headphones that are 1000+ohm), but also ones with ridiculous impedance curves. People have realized that due to its exceptional tolerance of weirdly designed speakers, it makes for a good speaker amp too. 25w is enough to drive these tweeters loud enough, and some mids as well; woofers, no, not with a single board. Kevin Gilmore also has sequels to his Dynaxx family (these being, themselves, improved versions of the KG Dynamic), due to some parts being replaced as they've fallen out of production and are hard to buy now.

amluto 4y ago

There are quite a few very, very good class D amplifier designs out there. “Very good” means highly efficient and with good enough fidelity (noise, distortion, etc) that no one will ever be able to distinguish them from perfect. But, IMO quite annoyingly, these things generally have analog inputs. This means you need a good DAC (which exists and isn’t terribly expensive) and a good connection from the DAC to the amp. You can make a good connection out of inexpensive cables, but you still need to worry about ground loops and possibly signal levels. So why aren’t there comparably good amplifiers with digital inputs and a DAC integrated directly? Fancy preamp features are unnecessary — if the input resolution is 24-bit, then volume control and such can be done digitally with effectively no loss.

wdfx 4y ago
Searching for "plate amplifier module" you can find integrated digital/amp/crossover units suitable for DIY builds.
- amluto 4y ago
  That’s a great form factor for building a speaker but a rather annoying form factor for driving an existing passive speaker.
Gordonjcp 4y ago
Given that it's just phase-correct PWM, you'd think feeding the bits you'd stuff into a DAC directly into the PWM counter would do the job nicely. You could probably do that with a fast microcontroller these days. Some golden-eared audiophool pillock would complain they could hear jitter caused by the pins not being gold-plated or something, but who cares?
- aquarium87 4y ago
  It takes a lot of computing power to reconstruct an audio sample well. Once reconstructed it takes massive massive amounts of storage. It's all about the Shannon Nyquist sampling theorum. "Strictly speaking, the theorem only applies to a class of mathematical functions having a Fourier transform that is zero outside of a finite region of frequencies. Intuitively we expect that when one reduces a continuous function to a discrete sequence and interpolates back to a continuous function, the fidelity of the result depends on the density (or sample rate) of the original samples. The sampling theorem introduces the concept of a sample rate that is sufficient for perfect fidelity for the class of functions that are band-limited to a given bandwidth, such that no actual information is lost in the sampling process. It expresses the sufficient sample rate in terms of the bandwidth for the class of functions. The theorem also leads to a formula for perfectly reconstructing the original continuous-time function from the samples." [1] But, HOLD ON: "Practical digital-to-analog converters produce neither scaled and delayed sinc functions, nor ideal Dirac pulses. Instead they produce a piecewise-constant sequence of scaled and delayed rectangular pulses (the zero-order hold), usually followed by a lowpass filter (called an "anti-imaging filter") to remove spurious high-frequency replicas (images) of the original baseband signal." [1] In case that was too verbose..... "sample rate that is sufficient for perfect fidelity".... "such that no actual information is lost in the sampling process"... "theorem also leads to a formula for perfectly reconstructing the original continuous-time function from the samples" PERFECTLY!!! Zero information loss between sampling and reconstruction. Still WTFs me to this day. So yeah, you can feed bits to a PWM. But that not music. [1] https://en.m.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem https://en.m.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_samp...

SomeoneFromCA 4y ago

I can reliably distinguish even very high-end Class D from a decent class AB amp. I perceive sand-grain in the sound of class D.

cramjabsyn 4y ago

I’m a huge fan of class D amps, although usually on the cheap end of the spectrum. Recently I purchased a “fosi audio” (brand names seem to rotate) stereo amp with bluetooth. It’s about the size of a raspberry pi. It is plenty powerful to drive a pair of bookshelf speakers, sounds good, and connects to a turntable and bluetooth source at the same time. $25 on ebay. Really hard to beat for the price and size