10 ms·

Building a Digital Audio Mixer

107 points by bo0tzz 3y ago

tpmx 3y ago
Meanwhile I've been wanting like a 4-channel stereo analog mixer with nice slide pots and a UV meter per channel since the 80s...
- rzzzt 3y ago
  The LM3914 is (was?) a frequently used part for voltage-to-LED bars conversion: https://www.ti.com/product/LM3914#features https://www.ti.com/product/LM3914#features
- jacquesm 3y ago
  You can buy that 80's gear for pennies on the dollar but: slides will get noisy due to dust ingestion, even if you're very careful. I've got a big Tascam here that is from the 90's (32 channel) and it absolutely rocks but it's also physically large enough that you won't be taking it anywhere. But you never have enough channels ;)
  - tpmx 3y ago
    slides will get noisy due to dust ingestion, even if you're very careful. I thought that phenomenon was primarily due to oxidation. Hmm, maybe get a used 80s mixer and use the hardware as UX for a digital mixer (with some algorithmic smoothing of the inputs)...
- conradfr 3y ago
  I think the Tascam Portastudio 244 would have fit the bill, but with the tape deck taking extra space.
JKCalhoun 3y ago
Anyone contemplating a cold winter and wanting to immerse themselves in a fun indoor project, pick up a Teensy and get project-ing. I have built several small projects with Teensies (?) and always find them enjoyable. We live in a magic time when there are so many projects online, you can easily breadboard up one with the Teensy (or other small devices) and go all the way to professional-looking PCB with very little outlay in cash.
- ChuckMcM 3y ago
  Many people don't realize just how powerful it is. I built an analog synth emulator (although this post gave some ideas about doing a web UI for it) for fun.
  - JKCalhoun 3y ago
    I used a single 4.1 to host a UART (MAX232) to give me hardware serial, scan a home-built keyboard, and maintain a text buffer and update a 3.5" LCD display. (In short I built a modern terminal around the Teensy 4.1.)
    - ChuckMcM 3y ago
      Nice, one of the things I'm doing in my "spare" time is building a framebuffer that is driven by quad-spi on a ULX3S board. The plan is to have it act as a terminal with both a character mode, a vector mode (ala Tek4016), and a pixel mode using sixel graphics. Given that it is planned to be attached to a computer system as it's "visual output device" I really hadn't given too much thought to making it a standalone terminal but that would be an interesting application for it.
  - hug 3y ago
    There's many synthesizers that use a Teensy as the brains of the thing. My favourite by far is the Dirtywave M8, which is an incredible bit of hardware & software design, in UI & UX. They're unfortunately sold out, now, but they're incredible bits of kit. If you have a Teensy and some spare time, check out the Headless version of the firmware: https://github.com/Dirtywave/M8HeadlessFirmware https://github.com/Dirtywave/M8HeadlessFirmware -- upload it to your Teensy, and head to https://m8.run https://m8.run to get a fully featured tracker in your browser. The Polyend Tracker is another portable synth that is backed by a Teensy -- not quite as neat, but still neat.
- jacquesm 3y ago
  It's insane. I was just commenting to colleagues earlier today that $10 now gets you more compute than I had for the first decade of my career. And not just a little bit more either. https://www.marktplaats.nl/v/hobby-en-vrije-tijd/elektronica-componenten/m2039522493-esp32-dual-core-wifi-bluetooth-ontwikkel-board-38-pins-cp210 https://www.marktplaats.nl/v/hobby-en-vrije-tijd/elektronica...
allanrbo 3y ago
The Teensy is awesome. Programmed one to slightly boost the bass of my audioengine a2’s. It’s been running reliably for years.
- jwx48 3y ago
  Now this is something I would love to learn more about. I feel like I'm always tinkering with audio hardware, and if I can bring a Teensy into the picture, then even better.
jacquesm 3y ago
What's really funny is that the connectors are almost as large as the board (each). This is well into 'infrastructure as code' territory, basically the hardware is doing the heavy lifting on a description that is cooked up using software. Of course you still need some hardware but all of the interconnects and functional blocks are soft. Very impressive work, and whoever built that library did an amazing job of it (and this person is essentially extending that library to full functionality devices).
- MartijnBraam 3y ago
  The Behringer XAir18 I used as inspiration for this adds an FPGA to the design so it really is fully software defined for the audio path. The only limitation is that behringer doesn't let you control any of it and adds a load of arbitrary limitations. Hopefully more open audio mixers will take off a bit :)
  - _kb 3y ago
    Open architecture DSPs have been a things for the past couple of decades in the installation audio space. Basically a 19” rack mount box loaded with FPGA’s, DSP chips and maybe some IO that you can adapt to whatever needs arise. Definitely not budget friendly for home hacking like this, but the tooling in those ecosystems is incredibly impressive.
    - ta988 3y ago
      Do you have references for that?
      - tcrenshaw 3y ago
        Looks into QSys and biamp DSPs. Folks run whole stadiums worth of dsp on them
        ta988 3y ago
        Nice! Thanks
analog31 3y ago
I'm a huge Teensy fan. Beyond the sheer computing power of each successive board generation, the documentation, code, and support, are just out of this world. As well, Paul has made some valuable contributions to the general Arduino ecosystem.
lukeh 3y ago
AES70/OCA [1] is an AES standard for remote control of professional audio devices. I wrote an open source Swift implementation here [2] which I'm using for a similar digital audio mixer project. (The actual MCU running the mixer will talk to the AES70 control plane using a simpler SPI or I2C protocol.) [1] https://ocaalliance.com https://ocaalliance.com [2] https://github.com/PADL/SwiftOCA https://github.com/PADL/SwiftOCA
- MartijnBraam 3y ago
  Sadly a paid standard though :(
tcrenshaw 3y ago
I've been working on a similar project but several layers of abstraction higher. Instead of using microcontroller level DSP I'm using Linux running a real-time kernel on a nuc type device and using the DAW, reaper, as the primary mixer component. IO is done via USB soundcards; right now I'm using a tascam 2x2 interface but plan to expand to a 16x8 interface soon. I'm eventually targeting around 2 milliseconds of latency, but for now I'd be happy with around 10 (need to tinker more with real-time priorities and pipewire configs). I'm mostly using it as a bass rig for now, feeding either my headphones or speakers with an SVT sim with IR cabinet sims or straight out of the SVT sim out to a QSC power amp and a 2x10 cab. When I get my studio space finished I'll hopefully use it as a mixer/ recorder for band practice.
- PaulDavisThe1st 3y ago
  ... and you could of course use a libre open source DAW like ardour to gain even more control over your signal path, interactions with the hardware and more. But that might not be necessary, depending on your actual goals. There are also smaller projects like Carla, which would allow you to host plugins as part of the signal processing chain (up to and including things like PlugData or Rack/Cardinal), but that make no attempt at "DAW-like" features. Disclaimer: I'm the lead author of Ardour.
  - thedanbob 3y ago
    I actually encountered just this sort of setup recently: a Linux PC with a real-time kernel running JACK and Ardour, connected to an 18x20 USB interface. It was part of a live translation setup that was routing English audio to up to four translators, receiving their foreign language audio, sending it to IR headsets, and recording everything with Ardour. Unfortunately, it didn't work very well; I tentatively put the blame on JACK but some other part of the system could have been interfering, or maybe the PC itself just wasn't powerful enough. I didn't have time to troubleshoot properly so I just substituted in my MBA running Reaper, ironically.
  - linuxontheweb 3y ago
    Ardour is epic. I'd love to start building something as solid as it for web-based audio tooling purposes on https://linuxontheweb.github.io/ https://linuxontheweb.github.io/.
varispeed 3y ago
I don't think Teensy is a viable platform for this. For digital audio mixer, one of the most important factors is latency and this is where Teensy solution falls apart. More reasonable approach would be to use something like XMOS chip to handle the streaming and FPGA for signal processing. That being said, it's still looking like a fun project.
- chabad360 3y ago
  Yea, maybe (although I'm not able to quickly find what the teensy DSP's latency looks like), for the same price you can complain that its pre-amps are gonna suck. But on the other hand, this is much easier to implement and work with (and be cheaper) than most/any fpga systems.
- MartijnBraam 3y ago
  The Behringer X-air mixer does everything realtime with a lot of processing for 18 channels on a bog standard 400Mhz arm core, no special hardware needed.
  - varispeed 3y ago
    According to this: https://vogelchr.blogspot.com/2015/11/behringer-x-air-xr18-teardown.html https://vogelchr.blogspot.com/2015/11/behringer-x-air-xr18-t... It utilises XMOS and FPGA and 400MHz ARM is only to handle the user interface.
    - MartijnBraam 3y ago
      The fpga probably only does routing, it certainly can't handle effects
chaosprint 3y ago
heard of teensey for a while but I decide to use Daisy Seed for my project for a better latency. have you considered this alternative?
- tonyarkles 3y ago
  https://moogaudio.com/products/electrosmith-daisy-seed-header-separate https://moogaudio.com/products/electrosmith-daisy-seed-heade... This unit I assume? How’s the development experience been? I’m more of an embedded guy than an audio guy and this looks pretty cool! I’ve used the Teensy4 for a couple of projects in the past. Do they provide schematics?
- scrumper 3y ago
  I didn't know the latency was better on Daisy. Is that published spec or from experience? They're both M7 SOCs as far as I can tell? I am trying to decide now between Daisy or Teensy for a piece of music hardware I have an idea for. The decision will probably be more about developer experience (so tooling, support, etc.) but I'm at step one on the journey and am having a hard time telling them apart.

107 points by bo0tzz 3y ago

tpmx 3y ago

Meanwhile I've been wanting like a 4-channel stereo analog mixer with nice slide pots and a UV meter per channel since the 80s...

rzzzt 3y ago
The LM3914 is (was?) a frequently used part for voltage-to-LED bars conversion: https://www.ti.com/product/LM3914#features https://www.ti.com/product/LM3914#features
jacquesm 3y ago
You can buy that 80's gear for pennies on the dollar but: slides will get noisy due to dust ingestion, even if you're very careful. I've got a big Tascam here that is from the 90's (32 channel) and it absolutely rocks but it's also physically large enough that you won't be taking it anywhere. But you never have enough channels ;)
- tpmx 3y ago
  slides will get noisy due to dust ingestion, even if you're very careful. I thought that phenomenon was primarily due to oxidation. Hmm, maybe get a used 80s mixer and use the hardware as UX for a digital mixer (with some algorithmic smoothing of the inputs)...
conradfr 3y ago
I think the Tascam Portastudio 244 would have fit the bill, but with the tape deck taking extra space.

JKCalhoun 3y ago

Anyone contemplating a cold winter and wanting to immerse themselves in a fun indoor project, pick up a Teensy and get project-ing. I have built several small projects with Teensies (?) and always find them enjoyable. We live in a magic time when there are so many projects online, you can easily breadboard up one with the Teensy (or other small devices) and go all the way to professional-looking PCB with very little outlay in cash.

ChuckMcM 3y ago
Many people don't realize just how powerful it is. I built an analog synth emulator (although this post gave some ideas about doing a web UI for it) for fun.
- JKCalhoun 3y ago
  I used a single 4.1 to host a UART (MAX232) to give me hardware serial, scan a home-built keyboard, and maintain a text buffer and update a 3.5" LCD display. (In short I built a modern terminal around the Teensy 4.1.)
  - ChuckMcM 3y ago
    Nice, one of the things I'm doing in my "spare" time is building a framebuffer that is driven by quad-spi on a ULX3S board. The plan is to have it act as a terminal with both a character mode, a vector mode (ala Tek4016), and a pixel mode using sixel graphics. Given that it is planned to be attached to a computer system as it's "visual output device" I really hadn't given too much thought to making it a standalone terminal but that would be an interesting application for it.
- hug 3y ago
  There's many synthesizers that use a Teensy as the brains of the thing. My favourite by far is the Dirtywave M8, which is an incredible bit of hardware & software design, in UI & UX. They're unfortunately sold out, now, but they're incredible bits of kit. If you have a Teensy and some spare time, check out the Headless version of the firmware: https://github.com/Dirtywave/M8HeadlessFirmware https://github.com/Dirtywave/M8HeadlessFirmware -- upload it to your Teensy, and head to https://m8.run https://m8.run to get a fully featured tracker in your browser. The Polyend Tracker is another portable synth that is backed by a Teensy -- not quite as neat, but still neat.
jacquesm 3y ago
It's insane. I was just commenting to colleagues earlier today that $10 now gets you more compute than I had for the first decade of my career. And not just a little bit more either. https://www.marktplaats.nl/v/hobby-en-vrije-tijd/elektronica-componenten/m2039522493-esp32-dual-core-wifi-bluetooth-ontwikkel-board-38-pins-cp210 https://www.marktplaats.nl/v/hobby-en-vrije-tijd/elektronica...

allanrbo 3y ago

The Teensy is awesome. Programmed one to slightly boost the bass of my audioengine a2’s. It’s been running reliably for years.

jwx48 3y ago
Now this is something I would love to learn more about. I feel like I'm always tinkering with audio hardware, and if I can bring a Teensy into the picture, then even better.

jacquesm 3y ago

What's really funny is that the connectors are almost as large as the board (each). This is well into 'infrastructure as code' territory, basically the hardware is doing the heavy lifting on a description that is cooked up using software. Of course you still need some hardware but all of the interconnects and functional blocks are soft. Very impressive work, and whoever built that library did an amazing job of it (and this person is essentially extending that library to full functionality devices).

MartijnBraam 3y ago
The Behringer XAir18 I used as inspiration for this adds an FPGA to the design so it really is fully software defined for the audio path. The only limitation is that behringer doesn't let you control any of it and adds a load of arbitrary limitations. Hopefully more open audio mixers will take off a bit :)
- _kb 3y ago
  Open architecture DSPs have been a things for the past couple of decades in the installation audio space. Basically a 19” rack mount box loaded with FPGA’s, DSP chips and maybe some IO that you can adapt to whatever needs arise. Definitely not budget friendly for home hacking like this, but the tooling in those ecosystems is incredibly impressive.
  - ta988 3y ago
    Do you have references for that?
    - tcrenshaw 3y ago
      Looks into QSys and biamp DSPs. Folks run whole stadiums worth of dsp on them
      - ta988 3y ago
        Nice! Thanks

analog31 3y ago

I'm a huge Teensy fan. Beyond the sheer computing power of each successive board generation, the documentation, code, and support, are just out of this world. As well, Paul has made some valuable contributions to the general Arduino ecosystem.

lukeh 3y ago

AES70/OCA [1] is an AES standard for remote control of professional audio devices. I wrote an open source Swift implementation here [2] which I'm using for a similar digital audio mixer project. (The actual MCU running the mixer will talk to the AES70 control plane using a simpler SPI or I2C protocol.) [1] https://ocaalliance.com https://ocaalliance.com [2] https://github.com/PADL/SwiftOCA https://github.com/PADL/SwiftOCA

MartijnBraam 3y ago
Sadly a paid standard though :(

tcrenshaw 3y ago

I've been working on a similar project but several layers of abstraction higher. Instead of using microcontroller level DSP I'm using Linux running a real-time kernel on a nuc type device and using the DAW, reaper, as the primary mixer component. IO is done via USB soundcards; right now I'm using a tascam 2x2 interface but plan to expand to a 16x8 interface soon. I'm eventually targeting around 2 milliseconds of latency, but for now I'd be happy with around 10 (need to tinker more with real-time priorities and pipewire configs). I'm mostly using it as a bass rig for now, feeding either my headphones or speakers with an SVT sim with IR cabinet sims or straight out of the SVT sim out to a QSC power amp and a 2x10 cab. When I get my studio space finished I'll hopefully use it as a mixer/ recorder for band practice.

PaulDavisThe1st 3y ago
... and you could of course use a libre open source DAW like ardour to gain even more control over your signal path, interactions with the hardware and more. But that might not be necessary, depending on your actual goals. There are also smaller projects like Carla, which would allow you to host plugins as part of the signal processing chain (up to and including things like PlugData or Rack/Cardinal), but that make no attempt at "DAW-like" features. Disclaimer: I'm the lead author of Ardour.
- thedanbob 3y ago
  I actually encountered just this sort of setup recently: a Linux PC with a real-time kernel running JACK and Ardour, connected to an 18x20 USB interface. It was part of a live translation setup that was routing English audio to up to four translators, receiving their foreign language audio, sending it to IR headsets, and recording everything with Ardour. Unfortunately, it didn't work very well; I tentatively put the blame on JACK but some other part of the system could have been interfering, or maybe the PC itself just wasn't powerful enough. I didn't have time to troubleshoot properly so I just substituted in my MBA running Reaper, ironically.
- linuxontheweb 3y ago
  Ardour is epic. I'd love to start building something as solid as it for web-based audio tooling purposes on https://linuxontheweb.github.io/ https://linuxontheweb.github.io/.

varispeed 3y ago

I don't think Teensy is a viable platform for this. For digital audio mixer, one of the most important factors is latency and this is where Teensy solution falls apart. More reasonable approach would be to use something like XMOS chip to handle the streaming and FPGA for signal processing. That being said, it's still looking like a fun project.

chabad360 3y ago
Yea, maybe (although I'm not able to quickly find what the teensy DSP's latency looks like), for the same price you can complain that its pre-amps are gonna suck. But on the other hand, this is much easier to implement and work with (and be cheaper) than most/any fpga systems.
MartijnBraam 3y ago
The Behringer X-air mixer does everything realtime with a lot of processing for 18 channels on a bog standard 400Mhz arm core, no special hardware needed.
- varispeed 3y ago
  According to this: https://vogelchr.blogspot.com/2015/11/behringer-x-air-xr18-teardown.html https://vogelchr.blogspot.com/2015/11/behringer-x-air-xr18-t... It utilises XMOS and FPGA and 400MHz ARM is only to handle the user interface.
  - MartijnBraam 3y ago
    The fpga probably only does routing, it certainly can't handle effects

chaosprint 3y ago

heard of teensey for a while but I decide to use Daisy Seed for my project for a better latency. have you considered this alternative?

tonyarkles 3y ago
https://moogaudio.com/products/electrosmith-daisy-seed-header-separate https://moogaudio.com/products/electrosmith-daisy-seed-heade... This unit I assume? How’s the development experience been? I’m more of an embedded guy than an audio guy and this looks pretty cool! I’ve used the Teensy4 for a couple of projects in the past. Do they provide schematics?
scrumper 3y ago
I didn't know the latency was better on Daisy. Is that published spec or from experience? They're both M7 SOCs as far as I can tell? I am trying to decide now between Daisy or Teensy for a piece of music hardware I have an idea for. The decision will probably be more about developer experience (so tooling, support, etc.) but I'm at step one on the journey and am having a hard time telling them apart.