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Want to go audiophile? 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

Want to go audiophile? 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-pavel-dudek-with-burson-v5-upgrade/ 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/ https://www.diyaudio.com/

gswdh 6y ago
Nahh the class D would be better: the distortion is beyond anyone at this point as has much better dynamic range which is very important for audio.
de6u99er 6y ago
should be: Pavel Dudek Apologies for the typo
de6u99er 6y ago
Another correction: Pre Amp is based on Nelson Pass's design, and Power Amp on Pavel Dudek's
neolog 6y ago
microphone -[XLR]-> interface -[USB]-> computer (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/dp/B00154KSA2 https://www.amazon.com/PreSonus-AudioBox-USB-Audio-Interface...
- barkingcat 6y ago
  I think for your application, you'll just need to separate the concerns out a bit You have the mic preamp, which can definitely be diy'able Then you have the AD/DA converter - this will convert the output from your diy'ed mic preamp into digital signals - this can't be done easily DIY, but you can purchase chips that does this : the ESS Sabre is one of the most popular AD/DA converters that you can probably source from aliexpress, etc - you might need to buy in bulk though otherwise the vendor might not talk to you. Then you have the usb interface itself, which comes with all the issues about certification, interface types and properly engineering/building a usb interface that works with consumer ports across different platforms is non-trivial for DIY'ers. You might be able to do something like "make a usb work for my specific computer, with a specific motherboard/platform" but for example, making something that adheres to the usb2.0 or 3.0 spec for both mac + pc + anything else that uses usb (for example, your cell phone, etc) - that's a totally different exercise that most diy'ers won't be able to easily do. Again, you can buy off-the-shelf chips to do this, but at that level, you're doing digital circuitboard design, and I'm not sure how well bread boarding works with things like usb. You might be able to layout a PCB and have someone etch it for you, etc. After that you'll need to build the output portions of the interface (after coming out of the DA chip). That can be DIY'ed. If you want to DIY an in-and-out audio interface you'll need to take on all these different aspects all at the same time. That's why you don't see many DIY projects of this kind. Rather, the DIY projects being talked about in this thread are one aspect of this chain: you want to drive some speakers, ok! we can build an amp diy. You want to do AD/DA ok you can do that one thing with a homebuilt board, with a chip, etc. But having all aspects being integrated together is non-trivial for a DIY. You might be able to use a Raspberry Pi zero or something like that for driving the AD/DA - USB portions, etc and that could be a way to go. In fact, I think using an RPi as a DAC would be a great way to DIY a usb audio interface, at least you've got all the chips integrated already, and you have an audio jack for getting inputs, etc, and you have the power source and usb OTG port[1] already designed, etc. And that's where you start to see $100 isn't all that bad for a usb audio interface. [1] https://gist.github.com/gbaman/50b6cca61dd1c3f88f41 https://gist.github.com/gbaman/50b6cca61dd1c3f88f41
  - iainctduncan 6y ago
    This. And if you're talking about audio cards, from a music production perspective, one substandard component in the chain makes all the rest kinda pointless. They all need to be up to snuff.
- bluGill 6y ago
  Two reasons, first, those who want XLR inputs (and outputs in many cases) want quality sounds so they are willing to pay for something a little more high end. If you there are cheap USB audio interfaces that are pretty good, but the next level up is really several levels up in quality (though I'm not sure if you can objectively tell). Second, the volumes sold need high prices to pay for the engineering.
  - amluto 6y ago
    The people who really want XLR are usually commercial, theatrical, etc. In those applications, you have a whole bunch of sources, a whole bunch of sinks, a whole bunch of devices and, critically, a lot of wire. RCA is single-ended, generally not isolated, and, no matter how much you gold-plate it and how much money you throw at silly cables, it will couple to 60 Hz AC, AM radio, and pretty much anything else. The effect in a large system isn’t some mystical loss of “airiness” — its obvious horrible garbage. I have personally listened to AM radio by accident — a theater setup had a little nonlinearity somewhere, and AM radio was being pickup up on a microphone wire, inadvertently demodulated, amplified, and it came out quite clearly from the speakers.
    - bluGill 6y ago
      That is a much higher price point. XLR is also used in tiny studios. The guy recording his guitar in the basement doesn't use RCA even though odds are very good none of the problems you cite would happen to him. Not that you are wrong, but you have moved up several more levels. In price to get all those inputs and long cables...
- tuatoru 6y ago
  > I've been wondering why "audio interfaces" are so expensive. They're a minority interest. Designing good DACs is a subtle art and the engineer costs are amortised over small production runs. The design of the ancillary circuits (analogue preamps, headphone monitoring, phantom power, input and output protection), and mechanical design and integration are also time-consuming and tricky (=expensive) to make reliable and within design goals. And marketing costs are probably as large as engineering. You certainly could do it yourself, but the component cost is the least of your worries. You'll need a fair bit of bench gear - oscilloscope, function generator, various power supplies, DVM, ... but even that's not the problem. You need a lot of knowledge about component selection and circuit design and layout, and a lot of experience with the tools of the trade. Making something like the Presonus (but probably six or ten times as big, because I can't do an all-in-one circuit board with all those functions on it and have it work in any reasonable timeframe), getting it to a state where I would let an unknown mic or computer be plugged into it, or let someone else use it, would easily take me more than three hundred hours. If you're new to this, multiply by n (n >=3).

gswdh 6y ago

Nahh the class D would be better: the distortion is beyond anyone at this point as has much better dynamic range which is very important for audio.

de6u99er 6y ago

should be: Pavel Dudek Apologies for the typo

de6u99er 6y ago

Another correction: Pre Amp is based on Nelson Pass's design, and Power Amp on Pavel Dudek's

neolog 6y ago

microphone -[XLR]-> interface -[USB]-> computer (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/dp/B00154KSA2 https://www.amazon.com/PreSonus-AudioBox-USB-Audio-Interface...

barkingcat 6y ago
I think for your application, you'll just need to separate the concerns out a bit You have the mic preamp, which can definitely be diy'able Then you have the AD/DA converter - this will convert the output from your diy'ed mic preamp into digital signals - this can't be done easily DIY, but you can purchase chips that does this : the ESS Sabre is one of the most popular AD/DA converters that you can probably source from aliexpress, etc - you might need to buy in bulk though otherwise the vendor might not talk to you. Then you have the usb interface itself, which comes with all the issues about certification, interface types and properly engineering/building a usb interface that works with consumer ports across different platforms is non-trivial for DIY'ers. You might be able to do something like "make a usb work for my specific computer, with a specific motherboard/platform" but for example, making something that adheres to the usb2.0 or 3.0 spec for both mac + pc + anything else that uses usb (for example, your cell phone, etc) - that's a totally different exercise that most diy'ers won't be able to easily do. Again, you can buy off-the-shelf chips to do this, but at that level, you're doing digital circuitboard design, and I'm not sure how well bread boarding works with things like usb. You might be able to layout a PCB and have someone etch it for you, etc. After that you'll need to build the output portions of the interface (after coming out of the DA chip). That can be DIY'ed. If you want to DIY an in-and-out audio interface you'll need to take on all these different aspects all at the same time. That's why you don't see many DIY projects of this kind. Rather, the DIY projects being talked about in this thread are one aspect of this chain: you want to drive some speakers, ok! we can build an amp diy. You want to do AD/DA ok you can do that one thing with a homebuilt board, with a chip, etc. But having all aspects being integrated together is non-trivial for a DIY. You might be able to use a Raspberry Pi zero or something like that for driving the AD/DA - USB portions, etc and that could be a way to go. In fact, I think using an RPi as a DAC would be a great way to DIY a usb audio interface, at least you've got all the chips integrated already, and you have an audio jack for getting inputs, etc, and you have the power source and usb OTG port[1] already designed, etc. And that's where you start to see $100 isn't all that bad for a usb audio interface. [1] https://gist.github.com/gbaman/50b6cca61dd1c3f88f41 https://gist.github.com/gbaman/50b6cca61dd1c3f88f41
- iainctduncan 6y ago
  This. And if you're talking about audio cards, from a music production perspective, one substandard component in the chain makes all the rest kinda pointless. They all need to be up to snuff.
bluGill 6y ago
Two reasons, first, those who want XLR inputs (and outputs in many cases) want quality sounds so they are willing to pay for something a little more high end. If you there are cheap USB audio interfaces that are pretty good, but the next level up is really several levels up in quality (though I'm not sure if you can objectively tell). Second, the volumes sold need high prices to pay for the engineering.
- amluto 6y ago
  The people who really want XLR are usually commercial, theatrical, etc. In those applications, you have a whole bunch of sources, a whole bunch of sinks, a whole bunch of devices and, critically, a lot of wire. RCA is single-ended, generally not isolated, and, no matter how much you gold-plate it and how much money you throw at silly cables, it will couple to 60 Hz AC, AM radio, and pretty much anything else. The effect in a large system isn’t some mystical loss of “airiness” — its obvious horrible garbage. I have personally listened to AM radio by accident — a theater setup had a little nonlinearity somewhere, and AM radio was being pickup up on a microphone wire, inadvertently demodulated, amplified, and it came out quite clearly from the speakers.
  - bluGill 6y ago
    That is a much higher price point. XLR is also used in tiny studios. The guy recording his guitar in the basement doesn't use RCA even though odds are very good none of the problems you cite would happen to him. Not that you are wrong, but you have moved up several more levels. In price to get all those inputs and long cables...
tuatoru 6y ago
> I've been wondering why "audio interfaces" are so expensive. They're a minority interest. Designing good DACs is a subtle art and the engineer costs are amortised over small production runs. The design of the ancillary circuits (analogue preamps, headphone monitoring, phantom power, input and output protection), and mechanical design and integration are also time-consuming and tricky (=expensive) to make reliable and within design goals. And marketing costs are probably as large as engineering. You certainly could do it yourself, but the component cost is the least of your worries. You'll need a fair bit of bench gear - oscilloscope, function generator, various power supplies, DVM, ... but even that's not the problem. You need a lot of knowledge about component selection and circuit design and layout, and a lot of experience with the tools of the trade. Making something like the Presonus (but probably six or ten times as big, because I can't do an all-in-one circuit board with all those functions on it and have it work in any reasonable timeframe), getting it to a state where I would let an unknown mic or computer be plugged into it, or let someone else use it, would easily take me more than three hundred hours. If you're new to this, multiply by n (n >=3).