This is a review and detailed measurements of the minidsp U-DIO8 8-channel USB to and from AES/EBU digital converter. It is kindly sent in by a member. The U-DIO8 costs US $325 from the company. It is a very cool device in that it lets you stream 8 channels of audio to multiple independent devices. Or capture data form them in reverse. There is also a S/PDIF version.
The box is small which is a bit of a drawback as they used a 25-pin DB connector with a thick dongle to get the inputs and outs:
The connectors feel a bit cheap and I had a hard time inserting and removing my XLR cables from them. Not a big deal though in operation.
You need a 5 volt input adapter which I did not get. So I tested it using my lab power supply.
Digital Audio Measurements
I have been struggling to get good template for measuring digital output devices and I think I have finally found it. I play the J-test signal (12 kHz @ 48 kHz sampling) and then capture its jitter thusly:
The red curve is minidsp U-DIO8. Blue is the cheap little Topping D10 which in addition to being a DAC also acts as USB to S/PDIF converter. Finally in green (and barely visible) is the Audio Precision APx555 measuring itself using the same XLR cable as I used with minidsp.
Sadly the U-DIO8 has much more jitter components than topping. They are a regular pattern which means bleeding from digital signal into the AES clock.
To get a better handle of what we are talking about all up, here is the same thing but shown in time domain, i.e. amplitude instead of frequency:
We see peak to peak jitter of about 800 picoseconds. From what I recall, 500 picoseconds is the worst you can have (for a sinusoidal) jitter to preserve 16 bits.
Audibly though, I doubt that you can hear this effect. I tried to test it but realized that the couple of DACs I used perform much better with USB than AES input. And that I have no assurance of their S/PDIF being the same as AES. So I am not posting it. As a reference though, the Matrix MQA DAC got a SINAD of 115 dB with minidsp DIO8 which is shy of its best performance. But again, this may just be due to AES input not being as good as USB, not because of minidsp.
Conclusions
The minidsap U-DIO8 is a very useful type of device. It doesn't cost a lot for its functionality if you are trying to build an 8-channel device (hoping that the clock is shared between all the outputs). It has higher jitter as it should be audibly I am not concerned about it. Get it because you need it, rather than wanting to brag about the purity of its interface.
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As always, questions, comments, recommendations, etc. are welcome.
We got a few inches of snow so I asked the panthers to help shovel it. Imagine my surprise when they demanded pink snow shovels! Apparently they make some but I don't have the money for it. So please donate what you can using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The box is small which is a bit of a drawback as they used a 25-pin DB connector with a thick dongle to get the inputs and outs:
The connectors feel a bit cheap and I had a hard time inserting and removing my XLR cables from them. Not a big deal though in operation.
You need a 5 volt input adapter which I did not get. So I tested it using my lab power supply.
Digital Audio Measurements
I have been struggling to get good template for measuring digital output devices and I think I have finally found it. I play the J-test signal (12 kHz @ 48 kHz sampling) and then capture its jitter thusly:
The red curve is minidsp U-DIO8. Blue is the cheap little Topping D10 which in addition to being a DAC also acts as USB to S/PDIF converter. Finally in green (and barely visible) is the Audio Precision APx555 measuring itself using the same XLR cable as I used with minidsp.
Sadly the U-DIO8 has much more jitter components than topping. They are a regular pattern which means bleeding from digital signal into the AES clock.
To get a better handle of what we are talking about all up, here is the same thing but shown in time domain, i.e. amplitude instead of frequency:
We see peak to peak jitter of about 800 picoseconds. From what I recall, 500 picoseconds is the worst you can have (for a sinusoidal) jitter to preserve 16 bits.
Audibly though, I doubt that you can hear this effect. I tried to test it but realized that the couple of DACs I used perform much better with USB than AES input. And that I have no assurance of their S/PDIF being the same as AES. So I am not posting it. As a reference though, the Matrix MQA DAC got a SINAD of 115 dB with minidsp DIO8 which is shy of its best performance. But again, this may just be due to AES input not being as good as USB, not because of minidsp.
Conclusions
The minidsap U-DIO8 is a very useful type of device. It doesn't cost a lot for its functionality if you are trying to build an 8-channel device (hoping that the clock is shared between all the outputs). It has higher jitter as it should be audibly I am not concerned about it. Get it because you need it, rather than wanting to brag about the purity of its interface.
------------
As always, questions, comments, recommendations, etc. are welcome.
We got a few inches of snow so I asked the panthers to help shovel it. Imagine my surprise when they demanded pink snow shovels! Apparently they make some but I don't have the money for it. So please donate what you can using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
