24 Channel Playback via Linux/Rpi?

[jonathan_david]

Hi,
I am working on an installation that takes from a website I created 24 channel output (24 single, mono sine frequencies). I wish to play them back independently though 24 small speakers.
I am still planning the hardware, and am looking for a simple way to output 24 channels from linux. My first thought was to aggregate three 7.1 usb DACs via alsa etc', and route that to the different amplifier+speaker configuration.Because it is a DIY installation, I was thinking to build the speaker+amp setup *24, using simple 3" speaker sand TPA3116D2 ampswith volume knobs.
I'd love to hear ideas / references, or solutions that might be better. Again, it is a prototype so still trying to make it cost-effective but keep on decent playback.
Thanks for the help and the forum!

 

[rp86]

What level of synchronisation does there need to be between channels? Aggregated devices generally don't have deterministic latency for each device in the aggregate, ie it's not recommended to use for a speaker crossover for example. If you do need precise/deterministic synchronisation between channels than the cheapest option for >10 channels I've found in my research so far is the RME Digiface USB + 3x 8 channel DACs connected via toslink.

 

[Redacted]

Is this an attempt at early 70's experimental music from Germany?

 

[john61ct]

USB interface with solid Linux driver support (or none needed)

Some have their own onboard analog ports - 24 is rare but MOTU 24ao is one nice example all dedicated to output only.

RME Digiface USB has none, just use 3x ADAT expansion to secondary 8-port converter / DACs, no need for those to also be primary interfaces themselves.

MADI and AVB will work but expensive, intended for bigger pro systems.

Ideally for timing / phase precision (no clock drift between DACs) look for converters that allow for connecting BNC Word Clock cabling, one as Master the others as Slave. The RME primary does not need that.

Behringer gear is super cheap, but depending on the SQ specs your use case requires perhaps good enough.

Multichannel audio on a Pi will get a whole lot easier and cheaper!

which DA converter would you use for a 100% active speaker home cinema with 42 channel ? :) the smls su2 is not really an option for that amount

www.audiosciencereview.com

 

[john61ct]

relevant

ADAT interface hosts, high SQ but cheaper than RME Digiface USB?

I am looking for an interface "hub" based on multiple ADAT, clean and transparent. I'm not recording / mixing, just for recreational home DSP - crossovers timing delays / phase alignment tuning Happy to buy secondhand to save money, vintage discontinued no problem. 24-bit, 44.1 / 48kHz is...

www.audiosciencereview.com

 

[jonathan_david]

Thanks everyone for the responses! so much great knowledge in this forum!The installation should play specific sounds up to 1 minute at a time, which makes me think it doesn't need such high precision. I thought to aggregate USB 7.1 External audio adapters such as the Vantec- would love your opinions on this cheapy solution. Again - its for a prototype and cannot afford an RME adapter for this matter.

 

[john61ct]

This is an 8-ch DAC

Are you thinking 3x USB out from one RPi?

Beside limited SQ, there is no way to keep the DAC chip clocks in sync, during a given playback session there will be drift accumulating over time. This is likely to create phase alignment / timing issues

Are all those speakers playing the EXACT SAME mono signal? No splitting / routing / crossovers?

 

[rp86]

Thanks everyone for the responses! so much great knowledge in this forum!The installation should play specific sounds up to 1 minute at a time, which makes me think it doesn't need such high precision. I thought to aggregate USB 7.1 External audio adapters such as the Vantec- would love your opinions on this cheapy solution. Again - its for a prototype and cannot afford an RME adapter for this matter.

This should probably work ok then. To be safe you could do a quick trial aggregating 1 USB adapter with the built in RPi audio device before buying the other 2 adapters.

Pipewire is the default audio server for most recent Linux distributions and is how I would attempt the aggregation rather than Alsa.

 

[LTig]

3 Behringer UMC 1820?

Behringer UMC1820

USB Audio Interface USB 2.0 audio interface, 18 x 20, Up to 24-bit / 96 kHz, 18 Inputs and 20 outputs: 8x XLR / 6.3 mm jack combo microphone / instrument / line input, switchable, MIDAS designed preamp, 2 ADAT / SPDIF optical inputs and outputs...

www.thomann.de

 

[90sNintendoKid]

3 Behringer UMC 1820?

Behringer UMC1820

USB Audio Interface USB 2.0 audio interface, 18 x 20, Up to 24-bit / 96 kHz, 18 Inputs and 20 outputs: 8x XLR / 6.3 mm jack combo microphone / instrument / line input, switchable, MIDAS designed preamp, 2 ADAT / SPDIF optical inputs and outputs...

www.thomann.de

I've ordered 3 Behringer ADA 8200s and a RME Digiface USB and I think this will also work.

 

[jonathan_david]

3 Behringer UMC 1820?

Behringer UMC1820

USB Audio Interface USB 2.0 audio interface, 18 x 20, Up to 24-bit / 96 kHz, 18 Inputs and 20 outputs: 8x XLR / 6.3 mm jack combo microphone / instrument / line input, switchable, MIDAS designed preamp, 2 ADAT / SPDIF optical inputs and outputs...

www.thomann.de

Nice! Not a bad idea for a future iteration.

 

[jonathan_david]

This should probably work ok then. To be safe you could do a quick trial aggregating 1 USB adapter with the built in RPi audio device before buying the other 2 adapters.

Pipewire is the default audio server for most recent Linux distributions and is how I would attempt the aggregation rather than Alsa.

Sounds like a plan, thank you so much!
I will get into pipewire for that, the way I was thinking was is to auto-open a web browser that I created that outputs 24 channels. Do you think pipewire can get its input live? (tested on audacity on my mac)

 

[jonathan_david]

Is this an attempt at early 70's experimental music from Germany?

Haha, basically, synthesizing a sound and outputting its 24 strongest frequencies, so you can experience fourier IRL.

 

[90sNintendoKid]

3 Behringer UMC 1820?

Behringer UMC1820

USB Audio Interface USB 2.0 audio interface, 18 x 20, Up to 24-bit / 96 kHz, 18 Inputs and 20 outputs: 8x XLR / 6.3 mm jack combo microphone / instrument / line input, switchable, MIDAS designed preamp, 2 ADAT / SPDIF optical inputs and outputs...

www.thomann.de

How would you chain 3 of these together?

I thought this only had one adat input and one adat output. I believe this would only allow 2 to be chained to produce 16 channel inputs and 18 outputs.

 

[john61ct]

You can't. Even in separate USB, no BNC clock sync.

If phase is relevant for the use case

 

[90sNintendoKid]

You can't. Even in separate USB, no BNC clock sync.

If phase is relevant for the use case

I thought so I think the maximum is 2 Behringer UMC1820 with one acting as a slave.

 

[mpw]

Get 24 track mixer along with 24 track interface.

 

[john61ct]

I thought so I think the maximum is 2 Behringer UMC1820 with one acting as a slave.

yes the ADAT receiver, via signal sync'ing.

Best to use BNC when phase is important

 

[LTig]

Nice! Not a bad idea for a future iteration.

But not for longer playback. 1 minute as required should be OK.

 

[LTig]

How would you chain 3 of these together?

I thought this only had one adat input and one adat output. I believe this would only allow 2 to be chained to produce 16 channel inputs and 18 outputs.

You don't. Run them in parallel, snyc should be OK for 1 minute as required. Of course the solution posted in #10 should be better.