Why aren't we pushing for more 4-8 channel DACS for a quality Stereo setup

[MCH]

Given the cost of wide bandwidth (read with low frequencies at high volume - otherwise not audible - and low distortion) loudspeakers, and my enjoyment of woodworking, I have tried passive x-overs, analog active, and digital active solutions. I am a BIG fan of the latter. I have tried Behringer (more than adequate for most things), an onkyo/integra recveiver from few years back (my favorite inexpensive solution, it has internal 2-way digital x-over, plus sub filtering, audyssey xt32 and multiple power amps - all you need is some drive units and boxes, all for <$400 used (onkyo 818 receiver)).
I was looking into a miniDSP 2x8 solution plus Octo DAC, but in one review here of a miniDSP x-over, the attenuation was only in the high 40dB range - this is inadequate with stiff cones having breakups as much as 30dB above nominal output.
My solution, for now, is to use Hypex plate amps, and I am very happy with those. A simple box to house them, and you have a competent, cost effective solution.

Once you have the okto dac, you can have a look at @mdsimon2 's tutorial for camilladsp in this forum

 

[mdsimon2]

Given the cost of wide bandwidth (read with low frequencies at high volume - otherwise not audible - and low distortion) loudspeakers, and my enjoyment of woodworking, I have tried passive x-overs, analog active, and digital active solutions. I am a BIG fan of the latter. I have tried Behringer (more than adequate for most things), an onkyo/integra recveiver from few years back (my favorite inexpensive solution, it has internal 2-way digital x-over, plus sub filtering, audyssey xt32 and multiple power amps - all you need is some drive units and boxes, all for <$400 used (onkyo 818 receiver)).
I was looking into a miniDSP 2x8 solution plus Octo DAC, but in one review here of a miniDSP x-over, the attenuation was only in the high 40dB range - this is inadequate with stiff cones having breakups as much as 30dB above nominal output.
My solution, for now, is to use Hypex plate amps, and I am very happy with those. A simple box to house them, and you have a competent, cost effective solution.

Those measurements of the DDRC-88A crossover looked very odd to me and do not seem correct based on measurements of other miniDSP products. I do not a DDRC-88A but I do have (and have measured) a miniDSP 2x4HD, miniSHARC (same base DSP as DDRC-88A) and SHD Studio and all have no issue attenuating down to the noise floor.

That being said if you are using an Okto I would not use a miniDSP. At least on firmware 1.42 the Okto will not work with a nanodigi (also not available new any more). I hear that a DDRC-88D will work but that is $900. When I first got my Okto I DIYed a solution with a miniSHARC -> https://www.minidsp.com/forum/hardware-support/18550-minisharc-8-channel-digital-output, but that is also expensive and the FIFO adds variable delay which is not good for A/V applications.

As mentioned by @MarcosCh I highly recommend using a RPi4 running CamillaDSP with the Okto (see link in my signature). It is much cheaper than any miniDSP option and much more powerful. Of course the Hypex plate amps are also a very good option in lieu of the Okto.

Michael

 

[mdsimon2]

Would something like this work ? https://www.audiosavings.com/audioc...ZvAFB3O2mPmeTWr5GrlkDp_gpld9A-AcaAoqrEALw_wcB

It has 5 line outputs though

That is something that has an internal DSP and is more similar to a miniDSP. It definitely could be used to create active speakers but spec'd performance is not good compared to a standalone DAC.

A lot of what was being discussed in this thread was using a USB DAC with DSP done a computer, this allows you to use a very high performance DAC and leverage the processing power of the computer. The computer can be as inexpensive as a Raspberry Pi 4 and still offers much more processing power than a traditional DSP solution.

Michael

 

[dearchap]

@mdsimon2 In case of the rpi4 being used as a DSP where is the input coming from ? Streaming ? I dont know the state of freeDSP but this looks like it would do the job

freeDSP-aurora/GettingStarted.pdf at release/0.9.0 · freeDSP/freeDSP-aurora

freeDSP ADAU1452 with 8 analog input, 8 analog outputs, S/P-DIF I/O, ADAT I/O, USB Audio Class2, WiFi, Bluetooth - freeDSP-aurora/GettingStarted.pdf at release/0.9.0 · freeDSP/freeDSP-aurora

github.com

 

[mdsimon2]

@mdsimon2 In case of the rpi4 being used as a DSP where is the input coming from ? Streaming ? I dont know the state of freeDSP but this looks like it would do the job

freeDSP-aurora/GettingStarted.pdf at release/0.9.0 · freeDSP/freeDSP-aurora

freeDSP ADAU1452 with 8 analog input, 8 analog outputs, S/P-DIF I/O, ADAT I/O, USB Audio Class2, WiFi, Bluetooth - freeDSP-aurora/GettingStarted.pdf at release/0.9.0 · freeDSP/freeDSP-aurora

github.com

There are many options. On the Okto it can be the AES inputs or USB input from the RPi4 (squeezelite, shairport-sync, roon bridge, etc).

For AES the signal flow looks something like this: AES input -> Okto -> USB to RPi4 -> CamillaDSP processing on RPi4 -> USB to Okto -> Okto analog outputs.

For USB inputs anything that can play to an ALSA loopback works: ALSA loopback -> CamillaDSP processing on RPi4 -> USB to Okto -> Okto analog outputs.

In general audio interfaces are similar with even more I/O functionality.

Michael

 

[somebodyelse]

@mdsimon2 In case of the rpi4 being used as a DSP where is the input coming from ? Streaming ? I dont know the state of freeDSP but this looks like it would do the job

freeDSP-aurora/GettingStarted.pdf at release/0.9.0 · freeDSP/freeDSP-aurora

freeDSP ADAU1452 with 8 analog input, 8 analog outputs, S/P-DIF I/O, ADAT I/O, USB Audio Class2, WiFi, Bluetooth - freeDSP-aurora/GettingStarted.pdf at release/0.9.0 · freeDSP/freeDSP-aurora

github.com

We're in danger of repeating the threads that spawned this one, where hardware DSP options including freeDSP (Aurora and others) were also discussed. The ASR open source streamer project thread is perhaps the main one covering the options for active crossovers.

 

[dearchap]

But the Okto has only 2 analog outputs correct ? Couldnt you use the rpi+camillaDsp + 4 Schiit Modi to get 8 analog outs ? CamillaDSP does output sync on all channels right ?

 

[dearchap]

We're in danger of repeating the threads that spawned this one, where hardware DSP options including freeDSP (Aurora and others) were also discussed. The ASR open source streamer project thread is perhaps the main one covering the options for active crossovers.

Sorry I've been living under a rock(audio) for many years now.

 

[mdsimon2]

But the Okto has only 2 analog outputs correct ? Couldnt you use the rpi+camillaDsp + 4 Schiit Modi to get 8 analog outs ? CamillaDSP does output sync on all channels right ?

I agree that a lot of this has been covered and it might be a good idea to do some quick searches for "DSP", "Camilla", "CamillaDSP" to see some of the past discussions.

A few quick points. PRO version of the Okto dac8 has 8 channels of output. In order to use multiple stereo DACs like the Modi you need some way to sync them, miniDSP U-DIO8 is one way of doing it.

Michael

 

[dearchap]

I did some basic searching around this site but no one seems to have mentioned this

SigmaDSP Evaluation Boards | Design Center | Analog Devices

www.analog.com

EVAL-AD1940AZ (PDF) has 4 stereo outputs(8 channels) and the EVAL-ADAU1442EBZ (PDF) as 8 stereo outputs(16 channels).

 

[mdsimon2]

I did some basic searching around this site but no one seems to have mentioned this

SigmaDSP Evaluation Boards | Design Center | Analog Devices

www.analog.com

EVAL-AD1940AZ (PDF) has 4 stereo outputs(8 channels) and the EVAL-ADAU1442EBZ (PDF) as 8 stereo outputs(16 channels).

I've looked at the AD evaluation boards in the past and in general I do not think they are that attractive.

A big motivation behind using software DSP with USB DAC is better analog performance then you can get from something like a miniDSP. The AD boards you linked are spec'd with significantly worse analog performance than evening the worst performing miniDSPs and are a long way off from high performance DACs. For example both AD board use AD1938/1939 DACs which have THD+N of -86 dB when all 8 channels are used, something like the Okto is around -118 dB.

Michael

 

[dc655321]

The AD boards you linked are spec'd with significantly worse analog performance than evening the worst performing miniDSPs and are a long way off from high performance DACs.

And this is not even considering the difference in DSP capabilities versus using a general purpose computing platform (eg: rpi4, nuc, etc)...
For audio reproduction, a CPU and external N-channel DAC is the way to go (imo).

 

[dearchap]

@mdsimon2 When you connect the Oct8 to rpi via USB does it appear as 8 different DACs to the rpi ?

 

[mdsimon2]

@mdsimon2 When you connect the Oct8 to rpi via USB does it appear as 8 different DACs to the rpi ?

It looks like an 8 channel DAC, see output below from cat /proc/asound/DAC8PRO/stream0. See thread linked in my signature for more details about setup with CamillaDSP and the RPi.

michael4@raspberrypi4:~$ cat /proc/asound/DAC8PRO/stream0
OKTO RESEARCH DAC8PRO at usb-0000:01:00.0-1.4, high speed : USB Audio
Playback:
  Status: Running
    Interface = 1
    Altset = 1
    Packet Size = 576
    Momentary freq = 96013 Hz (0xc.0068)
    Feedback Format = 16.16
  Interface 1
    Altset 1
    Format: S32_LE
    Channels: 8
    Endpoint: 0x01 (1 OUT) (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 24
    Channel map: FL FR FC LFE RL RR FLC FRC
    Sync Endpoint: 0x81 (1 IN)
    Sync EP Interface: 1
    Sync EP Altset: 1
    Implicit Feedback Mode: No
  Interface 1
    Altset 2
    Format: S16_LE
    Channels: 8
    Endpoint: 0x01 (1 OUT) (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 16
    Channel map: FL FR FC LFE RL RR FLC FRC
    Sync Endpoint: 0x81 (1 IN)
    Sync EP Interface: 1
    Sync EP Altset: 2
    Implicit Feedback Mode: No
  Interface 1
    Altset 3
    Format: S32_LE
    Channels: 8
    Endpoint: 0x01 (1 OUT) (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 32
    Channel map: FL FR FC LFE RL RR FLC FRC
    Sync Endpoint: 0x81 (1 IN)
    Sync EP Interface: 1
    Sync EP Altset: 3
    Implicit Feedback Mode: No
  Interface 1
    Altset 4
    Format: SPECIAL DSD_U32_BE
    Channels: 8
    Endpoint: 0x01 (1 OUT) (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 32
    DSD raw: DOP=0, bitrev=0
    Channel map: FL FR FC LFE RL RR FLC FRC
    Sync Endpoint: 0x81 (1 IN)
    Sync EP Interface: 1
    Sync EP Altset: 4
    Implicit Feedback Mode: No
Capture:
  Status: Running
    Interface = 2
    Altset = 1
    Packet Size = 576
    Momentary freq = 96000 Hz (0xc.0000)
  Interface 2
    Altset 1
    Format: S32_LE
    Channels: 8
    Endpoint: 0x82 (2 IN) (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 24
    Channel map: FL FR FC LFE RL RR FLC FRC
  Interface 2
    Altset 2
    Format: S16_LE
    Channels: 8
    Endpoint: 0x82 (2 IN) (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 16
    Channel map: FL FR FC LFE RL RR FLC FRC
  Interface 2
    Altset 3
    Format: S32_LE
    Channels: 8
    Endpoint: 0x82 (2 IN) (ASYNC)
    Rates: 44100, 48000, 88200, 96000, 176400, 192000
    Data packet interval: 125 us
    Bits: 32
    Channel map: FL FR FC LFE RL RR FLC FRC

Michael

 

[dearchap]

Fantastic thanks.

 

[Sal1950]

Ok so I've read almost half of this thread and don't have a clue of what the OP is trying to achieve. Why are 6/8 channel output DACs necessary in the first place(for stereo) ? I can understand 4 outputs in case you have 2 speakers and 2 subs. Where does CamillaDSP come into the picture here ?

More tweakability for the tweaker

 

[B&WTube]

I agree that a lot of this has been covered and it might be a good idea to do some quick searches for "DSP", "Camilla", "CamillaDSP" to see some of the past discussions.

A few quick points. PRO version of the Okto dac8 has 8 channels of output. In order to use multiple stereo DACs like the Modi you need some way to sync them, miniDSP U-DIO8 is one way of doing it.

Michael

The Okto dac8 pro has been out of stock, ever since I started this thread. Have you seen it for sale, or heard that it is coming back?

 

[mdsimon2]

The Okto dac8 pro has been out of stock, ever since I started this thread. Have you seen it for sale, or heard that it is coming back?

It has been back for sale at least twice since this thread started. This is the latest -> https://mailchi.mp/9e8acc78eedf/dac8-stereo-launch-10711016?e=384d3a4c6f.

Michael

 

[B&WTube]

We're in danger of repeating the threads that spawned this one, where hardware DSP options including freeDSP (Aurora and others) were also discussed. The ASR open source streamer project thread is perhaps the main one covering the options for active crossovers.

The big problem with that is that I searched all the titles, before I started this thread, and guess what- it doesn’t show up if you are searching anything along the lines of DAC’s or Multichannel (not everyone building active speakers cares about streaming).
I am glad to be made aware of this thread, but people are going to search titles. I can’t imagine how many places ‘multichannel’ and ‘DAC’ are found within threads on here. Perhaps someone should pull the multichannel stuff out of that thread and post it somewhere with a ‘Multichannel DAC’ title.

 

[B&WTube]

It has been back for sale at least twice since this thread started. This is the latest -> https://mailchi.mp/9e8acc78eedf/dac8-stereo-launch-10711016?e=384d3a4c6f.

Michael

Thanks. I must have just had bad timing. Any idea if they are using their old stockpile of AKM’s, or did they go ESS, like the D90?

It still looks like a great way to go. I do wonder if MINI DSP is going to do a 6 or 8 out version of the newer Flex https://www.minidsp.com/products/minidsp-in-a-box/flex .