Using miniDSP 2 x 4 HD's usb port as output.

[phoenixdogfan]

I have a miniDSP 2 x 4 HD and I've just learned that the micro usb port on the front can be used as both and input and an output. My question regards what limitations it has as an output. I plan (hope) I can use the spidf input for a 24/96 digital signal, then use the device's digital xover, PEQ, and Dirac Live, and then output a four channel processed digital stream over USB to an Octo 8. Is this possible, or does the device simply work as a resampler of the spidf stream, bypass the remaining DSP and DAC, and then output that stream to USB? For that matter when using the digital input via Spidf and out via usb does it do a D/A conversion with its DAC and then do an A to D conversion prior the output of the digital stream? Obviously, my entire purpose here is to use the 2 x 4 HD as strictly a digital processor and avoid the cheap and poorly performing ADC/DAC in the unit, so it would be nice to know if this is possible without further surgery on it.

Anyone have any experience using the USB port as a digital output who might be able to answer this question?

 

[JustJones]

Not sure if this answers your question it's under section 4.3. It looks like it can with a computer I would think it would send the 4 channel to a DAC.

Connect the USB (Type B mini) port of the miniDSP 2x4 HD to a free USB 2.0 port on your computer using the
supplied cable. The USB is used for:
• Configuration and real-time control of the miniDSP 2x4 HD,
• Streaming audio from a computer or other device such as a music streamer, at up to 192 kHz, and
• Streaming the processed audio (four output channels) from the miniDSP 2x4 HD to the computer.

 

[mdsimon2]

At least on a Mac it treats the 4 channels as sound card inputs to your computer. You can use these even when you are using another input (SPDIF) and any processing done in the miniDSP is maintained. Everything remains completely digital with no DAC. I've attached a few measurements of SPDIF in -> USB out for reference.

It seems like you would need additional software to take that USB audio from the 2X4HD and route it as an output to the Okto. Maybe some sort of pro audio / studio software?

Michael

 

[phoenixdogfan]

At least on a Mac it treats the 4 channels as sound card inputs to your computer. You can use these even when you are using another input (SPDIF) and any processing done in the miniDSP is maintained. Everything remains completely digital with no DAC. I've attached a few measurements of SPDIF in -> USB out for reference.

It seems like you would need additional software to take that USB audio from the 2X4HD and route it as an output to the Okto. Maybe some sort of pro audio / studio software?

Michael

Not sure why I would need additional software, isn't it an LPCM digital data stream? Is some sort of USB driver needed by the Octo? BTW, am I seeing a huge fall off in FR at higher frequencies on the 2nd graph? Am I reading that right?

 

[mdsimon2]

Not sure why I would need additional software, isn't it an LPCM digital data stream? Is some sort of USB driver needed by the Octo? BTW, am I seeing a huge fall off in FR at higher frequencies on the 2nd graph? Am I reading that right?

I am not a USB audio expert but my understanding is that asynchronous USB is bi-directional and always requires a connection to the host, it cannot simply send a signal. To use USB on the Okto a driver is required (see manual).

The second graph was meant to show that the processing in the 2x4HD is maintained when using the USB audio output. That example is a woofer from an active speaker hence the drop off in high frequencies.

Michael

 

[phoenixdogfan]

I am not a USB audio expert but my understanding is that asynchronous USB is bi-directional and always requires a connection to the host, it cannot simply send a signal. To use USB on the Okto a driver is required (see manual).

The second graph was meant to show that the processing in the 2x4HD is maintained when using the USB audio output. That example is a woofer from an active speaker hence the drop off in high frequencies.

Michael

Would my PC employing J River work?

 

[mattf]

Would my PC employing J River work?

You'd have to route the sound somehow... the 4 channels of the DSP would look like microphones to your PC; you could route them via ANOTHER USB connection to another DAC.

 

[beren777]

Keep in mind if you upgrade the HD to Dirac you will lose USB-out without making hardware modifications.

 

[abdo123]

Keep in mind if you upgrade the HD to Dirac you will lose USB-out without making hardware modifications.

Really? I just did the upgrade and i still have the device as output. I haven’t actually tried it yet since.

 

[abdo123]

Also you’re better off with the Motu M4 instead of the Okto, since it has 4 channels.

 

[ck42]

Even if it could send audio OUT the mini-USB interface, I would think that this would be disabled after the Dirac conversion. I have the same thing (2x4HD converted to DDRC-24) and learned that the internal header, that was recently enabled for i2s output on the 2x4 HD, gets disabled on Dirac units/conversions (licensing thing with Dirac they say). My understanding is that the only way to accomplish all-digital flow on Dirac versions of the 2x4 HD is to solder wires that bypass the header pins. (which then requires an i2s-to-SPDIF converter).
So point being that if they disabled the digital stream on the headers of the Dirac versions, I would assume that they would also disable the output over USB. If they didn't, it would seem to be an oversight by miniDSP.

 

[mdsimon2]

Keep in mind if you upgrade the HD to Dirac you will lose USB-out without making hardware modifications.

This is not true. A very typical use of the bi-directional USB is to measure the boost being applied by Dirac.

It is true that the I2S header is disabled when you upgrade to Dirac but that is a different issue.

Michael

 

[Neddy]

Just FYI, (this is a fascinating use of the 2x4HD), I used the Motu Pre8 USB (ADC) as an input to my JRiver PC (to get streaming and/or analog inputs over to the Okto8), and it recognizes it as a multi-channel input directly.
I went down the path of thinking I needed to have mixer software in there at first, and attempted that mess, but when I removed it all, and just plugged the thing in directly, it worked, and could be seen by Jriver as an 8 channel USB input, no fancy drivers or software required.
So I'm thinking this would work. Anybody try it yet?

 

[mdsimon2]

Just FYI, (this is a fascinating use of the 2x4HD), I used the Motu Pre8 USB (ADC) as an input to my JRiver PC (to get streaming and/or analog inputs over to the Okto8), and it recognizes it as a multi-channel input directly.
I went down the path of thinking I needed to have mixer software in there at first, and attempted that mess, but when I removed it all, and just plugged the thing in directly, it worked, and could be seen by Jriver as an 8 channel USB input, no fancy drivers or software required.
So I'm thinking this would work. Anybody try it yet?

I downloaded Jriver tonight to give this a try but it seems like the Mac version does not have the "Open Live" feature that Windows does.

I agree that this should work though. Definitely an interesting option as for $400 you can get a stereo Dirac setup with TOSLINK and analog inputs. Add your choice of high performance USB DAC and you would be well under the price of a SHD, although the PC adds to the cost and I would still be tempted to use Dirac on the PC instead. It would be interesting to know what the latency looks like with such a setup.

Michael

 

[joebloggs335]

Really? I just did the upgrade and i still have the device as output. I haven’t actually tried it yet since.

Very interesting. For me, USB output disappeared after Dirac upgrade. Could you please post a screenshot so I can confirm I’m not missing something obvious? Thanks in advance.

 

[mdsimon2]

Very interesting. For me, USB output disappeared after Dirac upgrade. Could you please post a screenshot so I can confirm I’m not missing something obvious? Thanks in advance.

See attached, at least in Mac you still have access to all 4 outputs. I tested with REW and confirmed that USB input / output still work.

Michael

 

[joebloggs335]

Thanks so much! I’ll give it a spin and update soon

 

[voodooless]

Both devices are USB slave devices. You cannot connect them together. You’ll need a device that acts as a host. Even then you’ll need sample rate conversion to convert from the miniDSP to the octo clock domain.

 

[mattf]

Both devices are USB slave devices. You cannot connect them together. You’ll need a device that acts as a host. Even then you’ll need sample rate conversion to convert from the miniDSP to the octo clock domain.

A Raspberry Pi could do this easily. But not everyone wants to "go there".

 

[abdo123]

A Raspberry Pi could do this easily. But not everyone wants to "go there".

Camila DSP in moode can do it easily actually.