The amp shown is nowhere near "professional grade".
Professional means it does the right thing in unusual circumstances - naughty inputs, naughty outputs, naughty mains power, running at full power on the grass under a pile of coats and scarves, pumping through old and fraying speaker leads lying on the ground, ...
The design is missing all sorts of safety features apart from the most basic (prevent electrocution from broken mains wires touching the chassis).
A 200VA transformer with a 350W amplifier is just asking for a transfomer meltdown (or fire, if the transformer doesn't have a functioning thermal fuse), unless there is a limiter in place to limit the output to 120W or less. (Fuses are also recommended, but in the professional environment you don't want them to blow, ever. Hence, a limiter is mandatory.)
The bridge rectifier is undersized.
In traditional mains-frequency rectification such as shown, the diodes only conduct for about 10% - 20% of the time, so the peak current in them is can be more than 10 times the average. At 36V and 10A output average, the rectifier current peaks are in the neighbourhood of 100A. A BR35 (35A 1000V) will provide a reasonable working life. At up to 36W dissipation, you can probably just bolt it to the chassis with some thermal compound.
The design is also missing speaker protection features and surge/spike protection/EMI prevention, and RF intereference filters on the inputs.
The design is also missing convenience features one expects of a professional amp, such as "power good" and "fault" lamps/circuitry. And handles.
It's nice that there are good inexpensive amplification modules now. But as with software, the difference between a toy example and professional grade is thought, time and money spent on reliability, safety, and usability.
> The design is also missing speaker protection features and surge/spike protection/EMI prevention, and RF intereference filters on the inputs.
1.) TPA325x have built-in speaker protection circuits.
2.) Do balanced inputs need RF interference filters?
For this project: After blowing the bridge rectifier a few times (for the reason you mentioned above), I ended up replacing the linear supply with a SMPS instead.
If you want TPA3250 amps without having to build your own, they're widely available from the usual cheap vendors for less than $100.
The victory of class D is now total; extremely low distortion numbers can be achieved without heroic board layout or expensive passives made of unobtanium. All available in the tiny packages of AirPods, smartphones etc. And power levels in the tens of watts can be done with a single chip.
I disagree that the "victory is total". First of all, distortion in the upper part of the audio range is not that stellar. Secondly - I personally can tell apart Class-D, Class-AB and Class-A. Class-D has grainy sound, even the best ones, $3000+ I tried; I get fatigued pretty quickly from them.
I built this project myself last spring. That 3e-Audio TPA3250 board isn't sold anymore, so I built my own custom variant amplifier using similar parts with a TP3251:
It sounds MUCH better than my existing cheap vendor Fosi TPA3116 did -- the cheap vendor ones don't use quality components, especially for the power supply, so you're not going to see the expected performance.
That power supply board (diode bridge + filtering caps) was designed with a friend in KiCAD and fabricated by JLCPCB (I have a few boards leftover). The speakers are also DIY -- Hivi 3.1 with cherry wood veneer!
I showed article author Zorpette my work, and he gave it his blessing =)
EDIT: If you do try to build this, be VERY careful around the high-voltage power supply electronics.
I recently ventured into the Campervan world. A friend gave me a couple of older nice waterproof Polk audio speakers. Mounted them in the back of the van on a custom rubber shock mount I build from random pieces at the hardware store.
I wanted a way to power the speakers and send music via bluetooth 5. All powered off my 12v solar system. Looked around at all the 'commercial' offerings and found nothing attractive. Everything was over priced or just didn't have modern features.
So... I searched around on Amazon for the right keywords. Ended up getting one of these little class D 100w+100w amps with treble and bass knobs off Amazon for $30 [1]. Got a 12v->24v step up for $16 [2] to give the amp a bit more power and less distortion.
Works amazingly well for a fraction of the price of anything else.
But it looks like there was a commercial offering. You say it yourself that you could find a solution on amazon. Or I’m missunderstand what the quotes around ‘commercial’ mean?
Since this isn't explicitly clarified in the article, it's worth mentioning that THD (or THD+N for that matter) is not always a helpful spec to compare two amps. You can easily have two amps where the one with the worse THD is actually the superior one because its distortion is in low-order even harmonics, while the nominally lower THD amp has more distortion in odd or higher-order harmonics. The distribution of distortion over harmonics is as important as the raw sum. (For the layperson who doesn't care about the math: this is why tube amps sound good even when their nominal THD spec may be higher than low-end solid-state amps.)
If your amplifier's distortion is less than 0.1%, you probably won't hear it, whatever it is.
The main reason people like the sound of tube amps (the "warmth") is due to the fact that most of them can't amplify high audio frequencies very well.
For reference, the frequency range of human hearing is taken to be 20 Hz to 20,000 Hz. Hearing is logarithmic in frequency, i.e. the perceived difference in pitch between 100 Hz and 200 Hz is the same as between 10,000 Hz and 20,000 Hz - an octave.
Tube amps have output transformers. It's difficult to design wideband power transformers (heck, designing any transformer is difficult), so most of them have reduced output in the top octave. (AKA "high frequency rolloff".)
One reason for the bad reputation of transistor amps is this: -
Many early transistor amps (and some still today) were prone to oscillation at MHz frequencies under some circumstances. The oscillation itself is inaudible but it affects the linearity control of the amplifier (negative feedback). Amplifiers were oscillating at MHz frequencies for a millisecond or two and losing control, which had a noticeable effect on the sound.
The oscillation wasn't picked up by the designers (of the early transistor amplifiers), because who needs a 100MHz oscilloscope for designing audio circuits that only go up to 20kHz? That's just silly. (Until, of course, it isn't.) And in those days, 100MHz scopes were expensive.
There are other reasons. For example, tube amps withstand some overload; transistor ones don't. Exceed the output transistors' second breakdown rating for a tenth of a second, and suddenly you have no sound. Your new speakers you just brought home from the store killed your amp. "But they're 8 ohms, same as the old ones!" (Another long story there.)
It took a while to figure out all this stuff and how to protect against it, and in the meantime, reputations were made and lost. Tube good, transistor bad.
The article covers some of the alternatives below, so take this rant with a grain of salt.
I don't understand the need to connect a massive linear power supply to a class D power amplifier. That seems completely backwards to me. If you're going class D, then why not eliminate what is often one of the biggest and most obvious expenses and replace the linear power supply with a switching power supply?
Typically in these projects you spend some chunk of the BOM cost on a few nice transistors or an amp chip, another big chunk on the transformer, smaller chunks of money on capacitors, then miscellaneous ICs/amps/hardware/etc. There's some variation here between components, but it just seems bonkers to pay for a big hunk of metal for a 1960s era solution for your power supply, when you are already using super fancy high-speed switching circuits in the amp.
There is no reason that these devices should have any appreciable mass beyond the heat sink. If you've got a massive transformer, you're building an amp like you've traveled in time back to the 1980s, before class D amps existed (well, before they were feasible for these applications). Nothing wrong with that, it's just that the linear power supply adds a lot of cost and mass for no reason.
At my last company, we tested tons of combinations of class D modules with various power supplies, and the best sounding results tended to be with linear power supplies. Don't get me wrong, there's tons of tricky stuff when it comes to the subjective side of audio, so it may be at least partially placebo effect. But we pretty consistently found that off the shelf switching PSUs sounded worse subjectively, even if they measured the same on the bench.
I haven't been doing audio for a while, so I don't remember more of the details. But audio signals tend to need all their power in short bursts all at once, when a low frequency bass note hits for example, and so the transient current tends to be much more important than a stable voltage rail. A lot of switching supplies do not optimize for this. Well designed versions can both sound great, but a cheap linear supply is going to sound much better than a cheap switcher. Audio is stuck with 1960s technology for the most part anyway though.
>I don't understand the need to connect a massive linear power supply to a class D power amplifier.
Generally from what I understand, linear, unregulated (gasp) supplies are preferred over anything else. I think the reasoning is that the PSRR is great at lower frequencies so having a bit of 120Hz ripple isn't a big deal.
Though this is a bit of antiquated advice, IMO, since you can get amazing performance out of SMPS supplies with a bit of filtering.
Although they are conceptually related, it is harder to engineer switching power supplies than it is to engineer class-D amplifiers, so I could sort of understand a hobbyist drawing up a design that uses 1960s technology to make DC to go in to 1990s technology.
What I've been looking for is a not-outrageously priced home theatre system that supports all the latest standards, like DTS-X, Dolby Atmos, etc... and has proper, decent speakers, not tiny little tin cans or a soundbar or something.
However, nobody seems to make the "proper" speakers that have the up-firing part needed for Dolby Atmos and are also wireless so I don't have to run cables from the TV to the rear speakers.
The few that I've found so far are crazy expensive.
I think home audio needs an IKEA-type manufacturer to upend the traditional economics of the products.
The expensive part of home theatre audio is that proper wood speakers are big and expensive to ship.
Someone needs to figure out a way to flat-pack full size speakers that consumers can assemble at home, but without requiring soldering irons and power tools.
If you want good value for money, Dayton Audio is your best bet. They used to do some kits, IIRC, but their FBU speakers are reasonably priced for what they are.
For kits there's Madisound (high-end[1]), and in Australasia, The Loudspeaker Kit[2] for more moderately priced kits -- often using Dayton drivers.
You can get cabinet makers (kitchen designers and the like) to make up the boxes locally for you if you can supply them plans in a format they can use.
1. "High end": Buy components for a total of $1k, build your own box to the plans, and get the equivalent of a $10k pair of speakers.
People had a lot of success buying cheap amps from AliExpress based on a known chipset, like the TPA3250 mentioned in the article, and change the few components that matter.
Usually, it is about changing the cheap knockoff caps by proper audio-grade ones.
Now you are left with the 90% of the work, that is getting a good power supply ;) The easy way is battery power, but then you need to charge the batteries. Linear power supplies are big, expensive and inefficient, but relatively easy to get right.
Switching power supplies are tricky as they tend to introduce all sorts of noise, in fact, they work almost in the same way as the amplifier itself, so you are basically powering an amplifier with an amplifier, both with their own feedback loops.
Counterargument: The power supply is overrated. You want to start with high-power but lousy switching power supply. You want to position it far and shielded from your amplifier. You want a decent ferrite bead on the cable, and a decent bypass filter in the box (both electrolytic and ceramic). The high-frequency stuff should mostly be gone. You can then use a linear regulator and a pretty basic filter to clean up the rest, and introduce an extra volt-or-so of drop on the output.
I understand the DIY allure, I really do (I do some electronics DIY myself - guitar pedals, tube amps, that kind of thing), but if you want to get great sound and save money at the same time, then just get a used QSC amp from Craigslist for $400 or so. It's better than pretty much anything you'll be able to build on your own for "reasonable" money, and it doesn't look "DIY".
I used to be pretty into audio (I used to have bi-amped Vandersteen 2Cs). I've kind of wanted to build a new setup, speakers following the Tech Ingredients "World's Best Speakers" or "World's Second Best Speakers" at https://www.youtube.com/watch?v=CKIye4RZ-5k&t=18s
I had looked at building this amp to power it, but I realized I really want something that can do HDMI-CEC, where my TV can power the amp on and off and control the volume. You know, how my current Yamaha soundbar works. But I haven't for the life of me been able to find any boards that would allow me to add HDMI-CEC into the project. I did find USB modules that would allow a computer to send CEC commands, but no pre-amp or class-D board that could take CEC input.
Building speakers and a soundbar would be pretty fun though. Been really getting into DIY projects.
I was under impression that class A amplifiers generally have the best amplifier characteristics (linearity, THD), and class D was mainly used in applications preferring efficiency/size/price over audio quality. Apparently class D has gotten lot better for the majority of applications.
Class A architecture's main advantage is it is very easy to achieve high objective performance, while trading away heat and power (and consequently size and mass). You can easily get 3rd harmonic below -80dB and you can eliminate even harmonics entirely. All you have to do it spend a lot on heat sinks and commit to a large power bill.
The problem is going to be reaching really stellar objective performance with the Class A design, because all those space age (not in a good way) power transistors are very slow and hard to drive, and that limits your error correction techniques. That's where these fancy designs are better. Basically they're using lightning-fast transistors and a DSP to bridge a power supply directly into a speaker. Objectively these designs have 3 orders of magnitude less total distortion, unmeasurable 2nd and 3rd harmonics, inaudible (-120dB or better) intermodulation products. The space age designs have simply no chance.
It's actually class B that has the best performance. A lot of people say class B is bad because crossover distortion, but what they are actually referring to is class C (the classic picture where a bit of the waveform is conducted by the top one and a bit of the waveform is conducted by the bottom one, with some flat spots in between) Class AB is bad because near the crossover, both top and bottom devices conduct and that actually causes an assload of crossover distortion. Properly biased class B precisely hands over conduction from one side to the other, making crossover distortion practically negligible.
Class A is theoretically the best but you can get good performance, and perhaps even better performance than A with a properly designed class B amplifier.
(I don't know much about this stuff.) I've been wondering why "audio interfaces" are so expensive. Even the cheapest one is $100. Can you explain what makes these expensive? How much would it cost to DIY one of those?
It seems like a lot of money is spent on the power supply. Small Bluetooth speakers draw power from lithium ion batteries which are, in turn, topped up with a cheap external power source. I understand that you can draw very high current from these batteries even if only briefly. Why don’t high end amps use the same trick instead of these giant toroidal coils and smoothing capacitors?
A dark secret of power amp design is that the power supply is half the battle. Note that this design uses a conventional line frequency transformer rather than a switchmode power supply. Making an all-switchmode amp is actually a bit of a challenge. I've been there. My home stereo is a cheap switchmode power amp board, but the power supply is line frequency, as a concession after I discovered that powering it from a switchmode power supply makes it put out all sort of weird noises.
An extremely nice product are the "IcePower" modules made by Bang and Olufsen, which incorporate both power supply and power amp into a single board. So they've worked out the bugs of making the parts play nicely together. These are now the jellybean power amps in smaller musical instrument amplifiers, of which I own a couple.
Terminal voltage matters too; higher voltage is required to deliver more power. 3.7V into 4 ohm limits you to under a watt. So many systems have a boost converter in there too - which is a potential source of electrical noise.
You could certainly have a stack of 18650 cells do the job if you want a portable boombox...
I guess because batteries while being great for high current operations, are not the most environmentally friendly solution. My DIY power amp requires a +/- 20-40V power supply. That would be quite a lot of batteries. Toroidal transformers are the next best choice, since they are smaller than comparable regular transformers.
Large caps are not only for smoothing but also act as power bank for instantious large current needs.
Forgive me, I'm not an audiophile, but am curious about it.
What is the constraint(s) that makes good audio equipment expensive?
Is it about components that can handle enough power? Is it avoiding distortion? Or both of the above (or other factors) for the price that components are available on the market?
Looking at some of the photos of components in the amplifier, it looks way dumber and less sophisticated than a Raspberry Pi. Why has the cost of an amplifier not come down to say, $100?
And maybe related, why does a "good" pair of noise cancelling headphones cost $300 and not $50? Is there something related?
If you're the kind of person who equates harmonic distortion with "warmth" you're in for a big treat with these Nelson Pass designs. On objective measurements these are just about the worst amps you can buy (or build). We're talking about 2nd harmonics at only -50dB. Warm AF.
This is just a quibble, but most switchmode amplifier chips are analog. Granted the term "digital" has been adopted by the audio community for switchmode amplifiers, but it still raises eyebrows.
Class D amps are pretty amazing. the Fender class D bass amps are ridiculously good and light for the price now. like 20% of the weight of their predecessors light. Which, if you've lugged a tube 4x10 around, is pretty awesome.
At 84€ just for the plans I will give this a miss, but if you happen to have images and other opinions of the ones you made yourself I'd be very curious
It's effectively impossible to DIY anything with HDMI but if you can get an adequate 6-channel analog output from an HDMI line-level converter then at that point all you need is three 2-channel amps or design one with all 6 channels in one box.
HDMI audio is a huge pain. Optical Toslink should be doable; you might be able to find the right board. But there's a lot more involved in doing the digital 5.1 decode and having more channels.
Summarizing what jeffbee says in sibling comments: -
Yes, it is certainly possible. But you need to acquire the prerequisite seven to ten years' experience first for a project of that complexity. When you've got that experience...you'll just buy one.
[+] [-] tuatoru|5 years ago|reply
Professional means it does the right thing in unusual circumstances - naughty inputs, naughty outputs, naughty mains power, running at full power on the grass under a pile of coats and scarves, pumping through old and fraying speaker leads lying on the ground, ...
The design is missing all sorts of safety features apart from the most basic (prevent electrocution from broken mains wires touching the chassis).
A 200VA transformer with a 350W amplifier is just asking for a transfomer meltdown (or fire, if the transformer doesn't have a functioning thermal fuse), unless there is a limiter in place to limit the output to 120W or less. (Fuses are also recommended, but in the professional environment you don't want them to blow, ever. Hence, a limiter is mandatory.)
The bridge rectifier is undersized.
In traditional mains-frequency rectification such as shown, the diodes only conduct for about 10% - 20% of the time, so the peak current in them is can be more than 10 times the average. At 36V and 10A output average, the rectifier current peaks are in the neighbourhood of 100A. A BR35 (35A 1000V) will provide a reasonable working life. At up to 36W dissipation, you can probably just bolt it to the chassis with some thermal compound.
The design is also missing speaker protection features and surge/spike protection/EMI prevention, and RF intereference filters on the inputs.
The design is also missing convenience features one expects of a professional amp, such as "power good" and "fault" lamps/circuitry. And handles.
It's nice that there are good inexpensive amplification modules now. But as with software, the difference between a toy example and professional grade is thought, time and money spent on reliability, safety, and usability.
[+] [-] regularfry|5 years ago|reply
[+] [-] Hydraulix989|5 years ago|reply
1.) TPA325x have built-in speaker protection circuits.
2.) Do balanced inputs need RF interference filters?
For this project: After blowing the bridge rectifier a few times (for the reason you mentioned above), I ended up replacing the linear supply with a SMPS instead.
[+] [-] pjc50|5 years ago|reply
The victory of class D is now total; extremely low distortion numbers can be achieved without heroic board layout or expensive passives made of unobtanium. All available in the tiny packages of AirPods, smartphones etc. And power levels in the tens of watts can be done with a single chip.
[+] [-] SomeoneFromCA|5 years ago|reply
[+] [-] Hydraulix989|5 years ago|reply
https://photos.app.goo.gl/gPH8VZiaGRiNYWfL6
It sounds MUCH better than my existing cheap vendor Fosi TPA3116 did -- the cheap vendor ones don't use quality components, especially for the power supply, so you're not going to see the expected performance.
That power supply board (diode bridge + filtering caps) was designed with a friend in KiCAD and fabricated by JLCPCB (I have a few boards leftover). The speakers are also DIY -- Hivi 3.1 with cherry wood veneer!
I showed article author Zorpette my work, and he gave it his blessing =)
EDIT: If you do try to build this, be VERY careful around the high-voltage power supply electronics.
[+] [-] 2sk21|5 years ago|reply
[+] [-] latchkey|5 years ago|reply
I wanted a way to power the speakers and send music via bluetooth 5. All powered off my 12v solar system. Looked around at all the 'commercial' offerings and found nothing attractive. Everything was over priced or just didn't have modern features.
So... I searched around on Amazon for the right keywords. Ended up getting one of these little class D 100w+100w amps with treble and bass knobs off Amazon for $30 [1]. Got a 12v->24v step up for $16 [2] to give the amp a bit more power and less distortion.
Works amazingly well for a fraction of the price of anything else.
[1] https://www.amazon.com/gp/product/B089KVH9J1
[2] https://www.amazon.com/gp/product/B01EFUHFW6
[+] [-] krisoft|5 years ago|reply
[+] [-] xenocyon|5 years ago|reply
[+] [-] tuatoru|5 years ago|reply
Speaker distortion is in the 1% to 5% range.
If your amplifier's distortion is less than 0.1%, you probably won't hear it, whatever it is.
The main reason people like the sound of tube amps (the "warmth") is due to the fact that most of them can't amplify high audio frequencies very well.
For reference, the frequency range of human hearing is taken to be 20 Hz to 20,000 Hz. Hearing is logarithmic in frequency, i.e. the perceived difference in pitch between 100 Hz and 200 Hz is the same as between 10,000 Hz and 20,000 Hz - an octave.
Tube amps have output transformers. It's difficult to design wideband power transformers (heck, designing any transformer is difficult), so most of them have reduced output in the top octave. (AKA "high frequency rolloff".)
One reason for the bad reputation of transistor amps is this: -
Many early transistor amps (and some still today) were prone to oscillation at MHz frequencies under some circumstances. The oscillation itself is inaudible but it affects the linearity control of the amplifier (negative feedback). Amplifiers were oscillating at MHz frequencies for a millisecond or two and losing control, which had a noticeable effect on the sound.
The oscillation wasn't picked up by the designers (of the early transistor amplifiers), because who needs a 100MHz oscilloscope for designing audio circuits that only go up to 20kHz? That's just silly. (Until, of course, it isn't.) And in those days, 100MHz scopes were expensive.
There are other reasons. For example, tube amps withstand some overload; transistor ones don't. Exceed the output transistors' second breakdown rating for a tenth of a second, and suddenly you have no sound. Your new speakers you just brought home from the store killed your amp. "But they're 8 ohms, same as the old ones!" (Another long story there.)
It took a while to figure out all this stuff and how to protect against it, and in the meantime, reputations were made and lost. Tube good, transistor bad.
[+] [-] klodolph|5 years ago|reply
I don't understand the need to connect a massive linear power supply to a class D power amplifier. That seems completely backwards to me. If you're going class D, then why not eliminate what is often one of the biggest and most obvious expenses and replace the linear power supply with a switching power supply?
Typically in these projects you spend some chunk of the BOM cost on a few nice transistors or an amp chip, another big chunk on the transformer, smaller chunks of money on capacitors, then miscellaneous ICs/amps/hardware/etc. There's some variation here between components, but it just seems bonkers to pay for a big hunk of metal for a 1960s era solution for your power supply, when you are already using super fancy high-speed switching circuits in the amp.
There is no reason that these devices should have any appreciable mass beyond the heat sink. If you've got a massive transformer, you're building an amp like you've traveled in time back to the 1980s, before class D amps existed (well, before they were feasible for these applications). Nothing wrong with that, it's just that the linear power supply adds a lot of cost and mass for no reason.
[+] [-] p-funk|5 years ago|reply
I haven't been doing audio for a while, so I don't remember more of the details. But audio signals tend to need all their power in short bursts all at once, when a low frequency bass note hits for example, and so the transient current tends to be much more important than a stable voltage rail. A lot of switching supplies do not optimize for this. Well designed versions can both sound great, but a cheap linear supply is going to sound much better than a cheap switcher. Audio is stuck with 1960s technology for the most part anyway though.
[+] [-] hatsunearu|5 years ago|reply
Generally from what I understand, linear, unregulated (gasp) supplies are preferred over anything else. I think the reasoning is that the PSRR is great at lower frequencies so having a bit of 120Hz ripple isn't a big deal.
Though this is a bit of antiquated advice, IMO, since you can get amazing performance out of SMPS supplies with a bit of filtering.
[+] [-] whatshisface|5 years ago|reply
[+] [-] amelius|5 years ago|reply
[+] [-] jiggawatts|5 years ago|reply
However, nobody seems to make the "proper" speakers that have the up-firing part needed for Dolby Atmos and are also wireless so I don't have to run cables from the TV to the rear speakers.
The few that I've found so far are crazy expensive.
I think home audio needs an IKEA-type manufacturer to upend the traditional economics of the products.
The expensive part of home theatre audio is that proper wood speakers are big and expensive to ship.
Someone needs to figure out a way to flat-pack full size speakers that consumers can assemble at home, but without requiring soldering irons and power tools.
[+] [-] tuatoru|5 years ago|reply
For kits there's Madisound (high-end[1]), and in Australasia, The Loudspeaker Kit[2] for more moderately priced kits -- often using Dayton drivers.
You can get cabinet makers (kitchen designers and the like) to make up the boxes locally for you if you can supply them plans in a format they can use.
1. "High end": Buy components for a total of $1k, build your own box to the plans, and get the equivalent of a $10k pair of speakers.
2. http://www.theloudspeakerkit.com/
3. Dayton Audio: https://www.daytonaudio.com/
[+] [-] GuB-42|5 years ago|reply
Usually, it is about changing the cheap knockoff caps by proper audio-grade ones.
Now you are left with the 90% of the work, that is getting a good power supply ;) The easy way is battery power, but then you need to charge the batteries. Linear power supplies are big, expensive and inefficient, but relatively easy to get right.
Switching power supplies are tricky as they tend to introduce all sorts of noise, in fact, they work almost in the same way as the amplifier itself, so you are basically powering an amplifier with an amplifier, both with their own feedback loops.
[+] [-] woofie11|5 years ago|reply
It sounds like a lot, but it's not.
[+] [-] captn3m0|5 years ago|reply
https://www.headfonia.com/review-audioquest-jitterbug-usb-ma...
[+] [-] m0zg|5 years ago|reply
[+] [-] linsomniac|5 years ago|reply
I had looked at building this amp to power it, but I realized I really want something that can do HDMI-CEC, where my TV can power the amp on and off and control the volume. You know, how my current Yamaha soundbar works. But I haven't for the life of me been able to find any boards that would allow me to add HDMI-CEC into the project. I did find USB modules that would allow a computer to send CEC commands, but no pre-amp or class-D board that could take CEC input.
Building speakers and a soundbar would be pretty fun though. Been really getting into DIY projects.
[+] [-] fest|5 years ago|reply
[+] [-] jeffbee|5 years ago|reply
The problem is going to be reaching really stellar objective performance with the Class A design, because all those space age (not in a good way) power transistors are very slow and hard to drive, and that limits your error correction techniques. That's where these fancy designs are better. Basically they're using lightning-fast transistors and a DSP to bridge a power supply directly into a speaker. Objectively these designs have 3 orders of magnitude less total distortion, unmeasurable 2nd and 3rd harmonics, inaudible (-120dB or better) intermodulation products. The space age designs have simply no chance.
[+] [-] hatsunearu|5 years ago|reply
Class A is theoretically the best but you can get good performance, and perhaps even better performance than A with a properly designed class B amplifier.
[+] [-] de6u99er|5 years ago|reply
Here's my Pre-Amp (apavel Dudek's PA03) and Power Amp (Nelson Pass DCB1) that I built a couple of years ago.
I even went the extra mile and used discrete OpAmps from Burson Audio.
https://www.bursonaudio.com/pa03-gainclone-power-amp-by-pave...
For those who are not afraid to go down a rabbit hole. -> https://www.diyaudio.com/
[+] [-] neolog|5 years ago|reply
(I don't know much about this stuff.) I've been wondering why "audio interfaces" are so expensive. Even the cheapest one is $100. Can you explain what makes these expensive? How much would it cost to DIY one of those?
[1] https://www.amazon.com/PreSonus-AudioBox-USB-Audio-Interface...
[+] [-] de6u99er|5 years ago|reply
[+] [-] de6u99er|5 years ago|reply
Apologies for the typo
[+] [-] gswdh|5 years ago|reply
[deleted]
[+] [-] davidhyde|5 years ago|reply
[+] [-] analog31|5 years ago|reply
An extremely nice product are the "IcePower" modules made by Bang and Olufsen, which incorporate both power supply and power amp into a single board. So they've worked out the bugs of making the parts play nicely together. These are now the jellybean power amps in smaller musical instrument amplifiers, of which I own a couple.
[+] [-] pjc50|5 years ago|reply
Terminal voltage matters too; higher voltage is required to deliver more power. 3.7V into 4 ohm limits you to under a watt. So many systems have a boost converter in there too - which is a potential source of electrical noise.
You could certainly have a stack of 18650 cells do the job if you want a portable boombox...
[+] [-] de6u99er|5 years ago|reply
Large caps are not only for smoothing but also act as power bank for instantious large current needs.
[+] [-] unknown|5 years ago|reply
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[+] [-] supernova87a|5 years ago|reply
What is the constraint(s) that makes good audio equipment expensive?
Is it about components that can handle enough power? Is it avoiding distortion? Or both of the above (or other factors) for the price that components are available on the market?
Looking at some of the photos of components in the amplifier, it looks way dumber and less sophisticated than a Raspberry Pi. Why has the cost of an amplifier not come down to say, $100?
And maybe related, why does a "good" pair of noise cancelling headphones cost $300 and not $50? Is there something related?
[+] [-] dang|5 years ago|reply
[+] [-] PretzelFisch|5 years ago|reply
[+] [-] jeffbee|5 years ago|reply
[+] [-] analog31|5 years ago|reply
[+] [-] lowdose|5 years ago|reply
https://www.devialet.com/en-eu/phantom-speaker/phantom-premi...
[+] [-] iainctduncan|5 years ago|reply
[+] [-] HungSu|5 years ago|reply
[+] [-] mcwone|5 years ago|reply
[+] [-] HungSu|5 years ago|reply
http://www.linkwitzlab.com/LXmini/Introduction.htm
[+] [-] bestouff|5 years ago|reply
[+] [-] jeffbee|5 years ago|reply
[+] [-] pjc50|5 years ago|reply
[+] [-] tuatoru|5 years ago|reply
Yes, it is certainly possible. But you need to acquire the prerequisite seven to ten years' experience first for a project of that complexity. When you've got that experience...you'll just buy one.