4 ms·

The timing issue between the microphones doesn't surprise me. Multi channel soundcards require a single ADC that processes all of the channels in unison (same f

The timing issue between the microphones doesn't surprise me. Multi channel soundcards require a single ADC that processes all of the channels in unison (same for the DAC). This is also why you can't just plug four stereo cards into a PC and expect it to make an 8-channel system.

Artlav 10y ago
It's not between the microphones on a cell, but between the cells themselves - i screwed up on the sync logic somewhere.
visakanv 10y ago
> This is also why you can't just plug four stereo cards into a PC and expect it to make an 8-channel system. Huh, I always sorta wondered about this. Thanks for clearing it up!
morsch 10y ago
You can't? I'm sure I tried multi-channel via separate sound cards and it sounded fine to me. Maybe I was lucky with the timing, or the audio subsystem somehow accounted for it?
- radiowave 10y ago
  Depending upon what you're using it for, you might well get away with it, but for some purposes the accumulated sample rate clock drift eventually gets too bad. You could make a long multitrack recording this way, and so long as you played it back from the start on the same hardware (i.e. so the soundcards would drift relative to one another more-or-less consistently with how they drifted during the recording), the playback might be ok. But if you begin playback half way through the recording, then the timing between channels might be out, as your software has no idea how much drift each channel ought to have accumulated by that point in the recording. Mind, it's been at least 15 years since I actually put any of this stuff to the test. Tolerances on modern soundcards might be really tight.
radiowave 10y ago
Strictly, multiple ADCs are fine, but what matters is that they are all locked to the same sample rate clock, connected to each card either via a digital audio input (e.g. SPDIF) or a dedicated clock input (e.g. word clock).
- extrapickles 10y ago
  Most of these digital mems microphones take a clock input, so you can synchronize the internal ADCs (normally used for doing stereo).

Artlav 10y ago

It's not between the microphones on a cell, but between the cells themselves - i screwed up on the sync logic somewhere.

visakanv 10y ago

> This is also why you can't just plug four stereo cards into a PC and expect it to make an 8-channel system. Huh, I always sorta wondered about this. Thanks for clearing it up!

morsch 10y ago

You can't? I'm sure I tried multi-channel via separate sound cards and it sounded fine to me. Maybe I was lucky with the timing, or the audio subsystem somehow accounted for it?

radiowave 10y ago
Depending upon what you're using it for, you might well get away with it, but for some purposes the accumulated sample rate clock drift eventually gets too bad. You could make a long multitrack recording this way, and so long as you played it back from the start on the same hardware (i.e. so the soundcards would drift relative to one another more-or-less consistently with how they drifted during the recording), the playback might be ok. But if you begin playback half way through the recording, then the timing between channels might be out, as your software has no idea how much drift each channel ought to have accumulated by that point in the recording. Mind, it's been at least 15 years since I actually put any of this stuff to the test. Tolerances on modern soundcards might be really tight.

radiowave 10y ago

Strictly, multiple ADCs are fine, but what matters is that they are all locked to the same sample rate clock, connected to each card either via a digital audio input (e.g. SPDIF) or a dedicated clock input (e.g. word clock).

extrapickles 10y ago
Most of these digital mems microphones take a clock input, so you can synchronize the internal ADCs (normally used for doing stereo).