5 ms·

If you want to just buy a thing that exists, you could look for one of the "high end" networked audio interfaces out there with on-board DSP mixing + network co

If you want to just buy a thing that exists, you could look for one of the "high end" networked audio interfaces out there with on-board DSP mixing + network control, e.g. MOTU AVB interfaces support that (e.g. MOTU 16A + some TOSlink to analog stereo out for the 17th/18th channel would be completely sufficient for your project). You would only have to develop the automation to remote control the volumes / routing and integrate it into your home automation, or if you want to get fancy, you could connect that to a PC and do literally anything you could imagine. Keep in mind that this will cost quite some money and I have no idea how much you want to spend on this project, but it will also give you high quality and low latency audio. If you want to build it yourself and if you want to keep it cheap and simple: integrating an ADC or DAC on a custom board isn't that hard, at least if you don't need "perfect" "audiophile" audio quality; usually the datasheets of the ADC / DAC chips already tell you exactly how you're supposed to use them + external components you need and so on. In your case, you'll probably want to use a cheap FPGA for mixing (think of Spartan-6 or newer), since that can easily handle dozens of channels, unlike cheap MCUs which usually don't support the number of channels you'd need. With MCUs the limit isn't necessarily how much you could mix in software, but how many ADC/DAC channels you can physically attach to the chip. For zigbee (or whatever network protocol you prefer) you can find dozens of small chips which can interact with that. Since it sounds like your system is wired anyway, you could also think about Ethernet for the network. When you start playing around with this, I'd recommend building a simple and minimal prototype first with e.g. a stereo in/out + network, to keep the manufacturing costs low in case you mess up the design, and once this works as intended, build the "full" 14x18ch module. Don't forget to add some simple debug port like e.g. RS232, it's cheap to add and it makes your life during development much easier.

coreyp_1 3y ago
Thank you for the reply! I'll look into the MOTU devices... I had not heard of them before! I was hoping to keep the cost at sub-$1k (although that is by no means a hard limit), but you are correct in that I already have the speakers wired in. Basically all cables come to a single location, which is where the amps need to go (speakers are not powered). It seems that the previous owner just ran the same 2 channels to all rooms in an on/off configuration. I didn't think about the RS232 for debugging, but that's a good idea. I know that the datasheets give external components, but when I was looking at this ~6 months ago, it seemed that most of the options were surface mount, and I've only done breadboard designs, so I didn't know how to work with that for prototyping purposes. This may be my biggest sticking point. Also, I didn't know if FPGA or something more familiar (such as a RPi) would be better for mixing. I have a PhD in CS, but I've never worked with FPGAs!!! lol I only know what they are in theory! I'm not against rolling up my sleeves and working, I just didn't know where to start. Even the smallest MVP (stereo in, mixer, stereo out) has too many parts with which I am unfamiliar.
- an-unknown 3y ago
  > when I was looking at this ~6 months ago, it seemed that most of the options were surface mount That's because most components today are only available as SMD. Once you play around with higher speed digital chips, breadboards are not really suitable anyway. But don't worry about SMD devices, there are manufacturers like e.g. JLCPCB which build the PCB and assemble it for you if you give them the manufacturing files. In that case you give them your Gerber + placement files and you get a board with all the SMD parts assembled already and you only have to solder e.g. connectors yourself. The board will be indistinguishable from something you'd buy in a commercial device. It's also cheap enough that it's totally fine to do this for prototypes, but it will usually take a while (think of 1-2 weeks) to get the board, so "prototyping" is a bit slow. If you have no idea about this / never did this before, maybe start with a simple test board where you figure out how to use e.g. KiCAD to design a PCB and how to get it assembled? It's quite easy, but you should be familiar with the process before you attempt to build anything more complex, simply because everything you build costs money in the end and if it doesn't work, it's annoying. > I didn't think about the RS232 for debugging, but that's a good idea. In case you wonder why I said RS232, it's probably the simplest protocol (electrical and logical) you can use, which makes it really hard to mess it up. In most cases all you need is an RS232 transceiver chip like an SP3232E and a UART interface on your FPGA/MCU/... > speakers are not powered Means: you'll need some amplifiers too. You again have two options: get some cheap commercially available amplifiers and only think about the mixer or completely build it yourself. If you build it yourself, you could look at Class D amplifiers, there are chips which directly translate digital I2S or TDM signals to the PWM signals for the speakers. > I have a PhD in CS, but I've never worked with FPGAs! In that case it will be quite the learning curve, because with FPGAs you don't write "software", you essentially describe a digital chip instead. A good starting point would probably be to get one of the cheap FPGA evaluation boards, ideally with an FPGA similar to what you want to use in the end. Keep in mind that if you put an FPGA onto your own board, you'll need some way to program it, like e.g. a JTAG programmer. That's the same with microcontrollers too btw, except you might need an SWD programmer then if it's some Cortex-M MCU. And if you get the one supported by the chip manufacturer (or a cheap Chinese clone of that one), things usually get easier because then it's supported by the development environment of the manufacturer. > I'll look into the MOTU devices... I had not heard of them before! You probably didn't hear about that before because it's "pro" audio hardware and not something an average consumer would ever buy/use. In this case it's only line level, so you still need amplifiers for the speakers afterwards. Maybe you'll find something that's even better for your specific use case. For commercially available amplifiers, you could again look at "pro" hardware which usually comes in 19" rackmount cases and sometimes there are even other options for "fixed" installations. That being said, be careful to not get an amplifier which is way too "powerful" for your speakers and you can also waste a lot of money on fancy things you don't need.

coreyp_1 3y ago

Thank you for the reply! I'll look into the MOTU devices... I had not heard of them before! I was hoping to keep the cost at sub-$1k (although that is by no means a hard limit), but you are correct in that I already have the speakers wired in. Basically all cables come to a single location, which is where the amps need to go (speakers are not powered). It seems that the previous owner just ran the same 2 channels to all rooms in an on/off configuration. I didn't think about the RS232 for debugging, but that's a good idea. I know that the datasheets give external components, but when I was looking at this ~6 months ago, it seemed that most of the options were surface mount, and I've only done breadboard designs, so I didn't know how to work with that for prototyping purposes. This may be my biggest sticking point. Also, I didn't know if FPGA or something more familiar (such as a RPi) would be better for mixing. I have a PhD in CS, but I've never worked with FPGAs!!! lol I only know what they are in theory! I'm not against rolling up my sleeves and working, I just didn't know where to start. Even the smallest MVP (stereo in, mixer, stereo out) has too many parts with which I am unfamiliar.

an-unknown 3y ago
> when I was looking at this ~6 months ago, it seemed that most of the options were surface mount That's because most components today are only available as SMD. Once you play around with higher speed digital chips, breadboards are not really suitable anyway. But don't worry about SMD devices, there are manufacturers like e.g. JLCPCB which build the PCB and assemble it for you if you give them the manufacturing files. In that case you give them your Gerber + placement files and you get a board with all the SMD parts assembled already and you only have to solder e.g. connectors yourself. The board will be indistinguishable from something you'd buy in a commercial device. It's also cheap enough that it's totally fine to do this for prototypes, but it will usually take a while (think of 1-2 weeks) to get the board, so "prototyping" is a bit slow. If you have no idea about this / never did this before, maybe start with a simple test board where you figure out how to use e.g. KiCAD to design a PCB and how to get it assembled? It's quite easy, but you should be familiar with the process before you attempt to build anything more complex, simply because everything you build costs money in the end and if it doesn't work, it's annoying. > I didn't think about the RS232 for debugging, but that's a good idea. In case you wonder why I said RS232, it's probably the simplest protocol (electrical and logical) you can use, which makes it really hard to mess it up. In most cases all you need is an RS232 transceiver chip like an SP3232E and a UART interface on your FPGA/MCU/... > speakers are not powered Means: you'll need some amplifiers too. You again have two options: get some cheap commercially available amplifiers and only think about the mixer or completely build it yourself. If you build it yourself, you could look at Class D amplifiers, there are chips which directly translate digital I2S or TDM signals to the PWM signals for the speakers. > I have a PhD in CS, but I've never worked with FPGAs! In that case it will be quite the learning curve, because with FPGAs you don't write "software", you essentially describe a digital chip instead. A good starting point would probably be to get one of the cheap FPGA evaluation boards, ideally with an FPGA similar to what you want to use in the end. Keep in mind that if you put an FPGA onto your own board, you'll need some way to program it, like e.g. a JTAG programmer. That's the same with microcontrollers too btw, except you might need an SWD programmer then if it's some Cortex-M MCU. And if you get the one supported by the chip manufacturer (or a cheap Chinese clone of that one), things usually get easier because then it's supported by the development environment of the manufacturer. > I'll look into the MOTU devices... I had not heard of them before! You probably didn't hear about that before because it's "pro" audio hardware and not something an average consumer would ever buy/use. In this case it's only line level, so you still need amplifiers for the speakers afterwards. Maybe you'll find something that's even better for your specific use case. For commercially available amplifiers, you could again look at "pro" hardware which usually comes in 19" rackmount cases and sometimes there are even other options for "fixed" installations. That being said, be careful to not get an amplifier which is way too "powerful" for your speakers and you can also waste a lot of money on fancy things you don't need.