Can I use multiple stereo DACs instead of one multichannel DAC?

[goldistan]

Assume the input is 4xSPDIF like this unit:
https://www.minidsp.com/products/minidsp-in-a-box/nanodigi-2x8-b

The different channels go to an 8-ch power amp connected to stereo 4-way speakers, so the phase matters (at crossover point).
Would there be phase/clock sync issues with multiple DACs fed from the same SPDIF source?

 

[maverickronin]

The S/PDIF signal contains it's own clock so you might be OK as long as you used DACs without asynchronous sample rate conversion.

 

[AnalogSteph]

I'd even say you'd be OK regardless, but the DACs for all channels should be identical or at least as close as it gets (same DAC chip or at least digital filter, same output polarity, same ASRC if any).

 

[waynel]

Assume the input is 4xSPDIF like this unit:
https://www.minidsp.com/products/minidsp-in-a-box/nanodigi-2x8-b

The different channels go to an 8-ch power amp connected to stereo 4-way speakers, so the phase matters (at crossover point).
Would there be phase/clock sync issues with multiple DACs fed from the same SPDIF source?

I do both, In my main system I use and Okto Dac8 pro 8-channel dac, in my living room system I use a nanodigi feeding two identical dacs.
The main issue with multiple dacs is you need volume control upstream of the nanodigi (you might be able to use the nanodigi for volume control with the remote but there is no display ) I prefer a volume knob for safety and quick adjustment.

 

[goldistan]

I do both, In my main system I use and Okto Dac8 pro 8-channel dac, in my living room system I use a nanodigi feeding two identical dacs.
The main issue with multiple dacs is you need volume control upstream of the nanodigi (you might be able to use the nanodigi for volume control with the remote but there is no display ) I prefer a volume knob for safety and quick adjustment.

Yes volume control is such a pain I'm considering an 8-ch mechanical or relay potentiometer from this guy:
https://khozmo.com/
OR just get the Okto DAC8.
Problem is: both are in Europe. I'd get them myself when I visit but they also take 8-12 weeks lead time.

 

[waynel]

Yes volume control is such a pain I'm considering an 8-ch mechanical or relay potentiometer from this guy:
https://khozmo.com/
OR just get the Okto DAC8.
Problem is: both are in Europe. I'd get them myself when I visit but they also take 8-12 weeks lead time.

I’d do the volume control upstream of the dac in the digital domain (I use a Yamaha wxc-50 for this). Also , do you really need 8 channels? If 4 is enough the minidsp SHD is a good solution.

 

[phoenixdogfan]

I’d do the volume control upstream of the dac in the digital domain (I use a Yamaha wxc-50 for this). Also , do you really need 8 channels? If 4 is enough the minidsp SHD is a good solution.

Lotta other good options. Something like a Motu M4 has 4 high quality DAC channels for $240 with a master volume control. They have another which has 20 channel output unit for around $650. They're both labelled interfaces, so you also get high quality A to D conversion, microphone inputs, balanced outs (via TRS), a headphone amp, and lots of recording software if you do music production/mixing. Not a conventional solution, but does everything a conventional solution does and more.

Seems like a bargain to me.

 

[dualazmak]

Synchronization, as well as the master volume and relative gain control, is always one of the main issues in multichannel system.

I also mainly use the most upstream digital domain, JRiver MC 28, as the "master" volume control in my multichannel multi-driver (multi-way) multi-amplifier system, stereo 5-way (10-channel) system, using OKTO DAC8PRO. Just for your reference, the most updated volume/gain configuration in my system can be found here. In this configuration, I may also use DAC8PRO's pre-amp master gain dial (which I always keep at -4 dB) as the system's master volume controller, though...

 

[Dichotome]

@dualazmak: Interesting as I have plans to do something similar using room correction and crossover filters derived from Audiolense. Re your comment in the blue box about volume controls on the amps, presumably once you have used the individual volume controls to get the right balance between the different drivers you leave those controls alone and just use the master volume control in JRiver?

 

[dualazmak]

@dualazmak: Interesting as I have plans to do something similar using room correction and crossover filters derived from Audiolense. Re your comment in the blue box about volume controls on the amps, presumably once you have used the individual volume controls to get the right balance between the different drivers you leave those controls alone and just use the master volume control in JRiver?

Thank you for your interests on my project. My general answer is "Yes", and, furtheremore, I also use "the individual volume controls" of the "integrated" amplifiers for fine tuning of the total sound.

If you would have your relaxing occasion, please read carefully throughout my project; I actually took intesive and long journey of amplifier exploration around here to here.

As I wrote here, "throughout my amplifier exploration, I well experienced and learnt that we should never exclude high quality Hi-Fi "integrated amplifiers" to be possibly implemented in this type of multichannel multi-amplifier project."

 

[Plcamp]

I’d do the volume control upstream of the dac in the digital domain (I use a Yamaha wxc-50 for this). Also , do you really need 8 channels? If 4 is enough the minidsp SHD is a good solution.

I want 8 channels for diy 4 way open baffle.

If you have an upstream dsp with volume control solving that problem, is it true that multiple two channel DACs would have varying latency that makes them unusable in a crossover?

 

[mdsimon2]

I want 8 channels for diy 4 way open baffle.

If you have an upstream dsp with volume control solving that problem, is it true that multiple two channel DACs would have varying latency that makes them unusable in a crossover?

If they are the same DAC I wouldn't imagine there being an issue. Even if you had different DACs as long as the latency difference was a fixed value you should be able to compensate in DSP. All of this assumes SPDIF in/out, if you are using multiple USB DACs with free running clocks that is definitely an issue.

Michael

 

[Dichotome]

If you use the same type of DAC then latency should be similar. However I believe the main problem is that the clocks would not be synchronised and so that could create small timing differences.

 

[mdsimon2]

If you use the same type of DAC then latency should be similar. However I believe the main problem is that the clocks would not be synchronised and so that could create small timing differences.

If using SPDIF the DACs will be synced to that SPDIF signal. Even if you are using DACs with an ASRC and a free running local clock the DAC DPLL will lock to that SPDIF signal and there should be no issues. See below for a really good thread on how ASRC / DPLL function.

https://www.diyaudio.com/forums/digital-source/28814-asynchronous-sample-rate-conversion.html

Michael

 

[Plcamp]

In products such as DACs which take usb in and produce both analog out and SPDIF out, would there be any latency added at the SPDIF?

 

[mdsimon2]

In products such as DACs which take usb in and produce both analog out and SPDIF out, would there be any latency added at the SPDIF?

I would guess there would be a slight latency difference (if only for latency differences from the second DAC) but this would be easy enough to measure. I have such a DAC (MOTU Ultralite Mk5), I can make some measurements with an external DAC and post the results.

When attempting a multichannel active DSP system like this it is a really good idea to have the ability to make some basic measurements. Heck, even the Okto dac8 pro has slight latency differences between analog output channels when using AES inputs.

Michael

 

[Dichotome]

@mdsimon2: how do you like your MOTU? If I can’t get my hands on an Okto I might have to resort to one of those.

 

[mdsimon2]

I really like the MOTU, I feel like a shill because I've been recommending it so much. There is some more info in the review thread about my experience with it but as I also have an Okto it might be appropriate to make a few comments comparing the two.

The MOTU output (8.6 V) is hotter than the Okto (4.2 V), as my NC252MP amplifiers have normal input sensitivity (1.7 V) line level attenuators are probably warranted especially if using volume control upstream of the DSP.

The Okto is just a bit quieter than the MOTU but neither have any audible noise once you get a foot away from the speaker.

10 channel output from the MOTU is really nice and would be perfect for a 4 way + sub or a 3 way + sub where you are bridging a Hypex amplifier for the sub and want a + / - output to the sub amp.

The biggest differences are price and usability. The Okto is great in that it has 5 V trigger output, bigger volume knob, bigger display and IR receiver for remote control. You can definitely work around these issues with the MOTU but it definitely adds cost / complexity.

I have found that a Bobwire DAT1 can be used to add a trigger output as the MOTU does have a TOSLINK output. I really like that the MOTU has TOSLINK and SPDIF inputs as these are obviously much more prevalent in consumer gear than the Okto AES inputs. MOTU works great with a RPi4 running Ubuntu Server / CamillaDSP.

I really wish the MOTU had an IR receiver for volume control which is probably my biggest compliant. You can get around this if you use upstream volume control, there are plenty of DIY solutions for this especially if you are using a RPi / CamillaDSP but that adds complexity and is not for everyone especially if you want a "finished" looking solution. I am currently using a SHD Studio with the MOTU as it provides good input switching functionality and volume control although it is super expensive for just that functionality. Would love to find something much lower cost that has decent input functionality, a nice display, IR receiver and digital volume control to use upstream of the MOTU. All that being said the Okto is quite a bit more expensive (and unavailable) so it somewhat offsets. Looking at my setup with the Okto which uses a DIY miniSHARC with 8 channels of AES output the total cost is upwards of $2K so if you compare to a SHD Studio ($900) + MOTU ($600) + RPi4 w/ PSU ($70) + Bobwire DAT1 ($70) you end up at just over $1600 total and have more input functionality, more outputs and Dirac.

I mentioned it a bit but the Okto has non-deterministic delay between channels (between 1 and 2 samples) when using the AES inputs which is super annoying. This can be accounted for in DSP but if you power cycle the DSP, power cycle the Okto or switch the Okto from Pure AES to Pure USB back to Pure AES these delays can change. Fortunately it is super easy to measure these delays with just the Okto itself. I haven't actually done the same testing with the MOTU yet so it will be interesting to see if it has any issues in that regard, especially given that it uses two DAC chips.

Michael

 

[Dichotome]

Thank you Michael. If I could get an Okto I’d use the USB input, the source being an audio PC running JRiver and filters derived from Audiolense.

 

[goldistan]

I really like the MOTU, I feel like a shill because I've been recommending it so much. There is some more info in the review thread about my experience with it but as I also have an Okto it might be appropriate to make a few comments comparing the two.

The MOTU output (8.6 V) is hotter than the Okto (4.2 V), as my NC252MP amplifiers have normal input sensitivity (1.7 V) line level attenuators are probably warranted especially if using volume control upstream of the DSP.

The Okto is just a bit quieter than the MOTU but neither have any audible noise once you get a foot away from the speaker.

10 channel output from the MOTU is really nice and would be perfect for a 4 way + sub or a 3 way + sub where you are bridging a Hypex amplifier for the sub and want a + / - output to the sub amp.

The biggest differences are price and usability. The Okto is great in that it has 5 V trigger output, bigger volume knob, bigger display and IR receiver for remote control. You can definitely work around these issues with the MOTU but it definitely adds cost / complexity.

I have found that a Bobwire DAT1 can be used to add a trigger output as the MOTU does have a TOSLINK output. I really like that the MOTU has TOSLINK and SPDIF inputs as these are obviously much more prevalent in consumer gear than the Okto AES inputs. MOTU works great with a RPi4 running Ubuntu Server / CamillaDSP.

I really wish the MOTU had an IR receiver for volume control which is probably my biggest compliant. You can get around this if you use upstream volume control, there are plenty of DIY solutions for this especially if you are using a RPi / CamillaDSP but that adds complexity and is not for everyone especially if you want a "finished" looking solution. I am currently using a SHD Studio with the MOTU as it provides good input switching functionality and volume control although it is super expensive for just that functionality. Would love to find something much lower cost that has decent input functionality, a nice display, IR receiver and digital volume control to use upstream of the MOTU. All that being said the Okto is quite a bit more expensive (and unavailable) so it somewhat offsets. Looking at my setup with the Okto which uses a DIY miniSHARC with 8 channels of AES output the total cost is upwards of $2K so if you compare to a SHD Studio ($900) + MOTU ($600) + RPi4 w/ PSU ($70) + Bobwire DAT1 ($70) you end up at just over $1600 total and have more input functionality, more outputs and Dirac.

I mentioned it a bit but the Okto has non-deterministic delay between channels (between 1 and 2 samples) when using the AES inputs which is super annoying. This can be accounted for in DSP but if you power cycle the DSP, power cycle the Okto or switch the Okto from Pure AES to Pure USB back to Pure AES these delays can change. Fortunately it is super easy to measure these delays with just the Okto itself. I haven't actually done the same testing with the MOTU yet so it will be interesting to see if it has any issues in that regard, especially given that it uses two DAC chips.

Michael

MOTUs don't have per-stereo-pair digital inputs (4x SPDIF or 4x AES), instead they use ADAT. as far as I know Okto is the only DAC that takes such weird inputs.
This means I cannot use a nanoDIGI 2x8 as input.
This means the DSP will have to be performed in software (deal breaker for me, I don't trust windows with 3000W of amplification), or in the MOTU itself, which would be great.
However in order to determine that I'll need to read the entire manual for the MOTU and its software, every word, and again for every model I'm considering. so unless I can find someone who runs a LX521 from a MOTU, it's too much research work.