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Okto dac8 stereo DAC Review

amirm

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#1
This is a review and detailed measurements of the Okto dac8 stereo DAC. It was kindly sent to me by the company for review. It costs €1 089 from the company ($1,240 as of this writing). The version I have has the optional Raspberry Pi 4 module for streaming which costs an extra $89.

Last I tested a dac from Okto, it was their prototype 8-channel DAC. It set a new record in our measurements at the time, getting the highest "SINAD" score possible. While I loved many things about the hardware design, the case needed a new color and thicker sheet metal. Happy to report both of those have been managed producing a very professional and nice looking DAC:

Okto dac8 Stereo USB AES Balanced DAC Audio Review.jpg


As with the last model, the interface is a joy to use with large, bright text that changes lightning fast. An apple remote is provided for control which I used to good effect to navigate the menu system.

The back panel is quite unusual for a DAC:

Okto dac8 Stereo USB AES Balanced DAC back panel inputs Audio Review.jpg


For starters there are dual set of XLRs so that you can use them to connect to two sets of devices (active speakers and a pre-amp). We have two pairs of coax and toslink instead of usual one.

Streaming is provided by Raspberry Pi and while it is physically integrated into the unit, requires that you use the jumper to wire up the dac to its USB output. Fortunately you have another USB input so you don't have to take this in and out.

My unit came with a copy of Volumio software on the SD card which let me stream to it using Airplay. Sadly Airplay only supports 16 bits/44.1 kHz so severely impacted the performance. You can of course change that to another streamer software (e.g. DietPi) or install the Roon endpoint to get full 24-bit streaming at various sample rates.

So I would say the streaming functionality is less than perfectly integrated but as much as they could given the platform restrictions.

DAC Audio Measurements
Competition has gotten quite stiff since I tested the original okto DAC8. Can the new version unseat all the others considering that we are almost at the limit of what my analyzer can measure? Let's find out:

Okto dac8 Stereo USB AES Balanced DAC Audio Measurements.png


Darn it, it did it!

Best stereo dac usb review measurements.png


Best stereo dac usb review measurements zoomed.png


Yes, the output voltage is a tad high (4.2 vs 4.0) volts which probably helps a bit here. I dialed it down 0.5 dB and it essentially held its performance.

Note that actual performance is better than this as we are including the noise on the input of my analyzer in what the DAC is producing, hence my comment that there is not much more room left to get higher scores.

Speaking of noise, here is the dynamic range:

Okto dac8 Stereo USB AES Balanced DAC dynamic range Audio Measurements.png


Intermodulation distortion and noise is exceptionally low as one would guess:

Okto dac8 Stereo USB AES Balanced DAC IMD Audio Measurements.png


Multitone as a result is clean as well:
Okto dac8 Stereo USB AES Balanced DAC multitone Audio Measurements.png


And oh, in case you want to use the unit at lower output levels, here it is:
Okto dac8 Stereo USB AES Balanced DAC THD+N vs Level Audio Measurements.png


So the higher the better but even at just 0.8 volts, you have a SINAD of 110 dB.

Linearity is nailed showing superb accuracy:
Okto dac8 Stereo USB AES Balanced DAC linearity Audio Measurements.png


There are five filters with acronyms I did not try to decipher:

Okto dac8 Stereo USB AES Balanced DAC Reconstruction filter Audio Measurements.png


Extremely good attenuation for out of band spectrum helps with excellent THD+N versus frequency using 90 kHz bandwidth:

Okto dac8 Stereo USB AES Balanced DAC thd+n vs frequency Audio Measurements.png


Jitter over USB is extremely good:

Okto dac8 Stereo USB AES Balanced DAC Jitter Audio Measurements.png


For some reason though, there is some jitter with Coax but not with Toslink or AES/EBU:

Okto dac8 Stereo USB AES Balanced DAC Coax Jitter Audio Measurements.png


Headphone Amplifier Tests
I ran a couple of quick tests on the headphone amplifier and was pleased how good its performance is, no doubt helped with such a clean DAC upstream:

Okto dac8 Stereo USB AES Balanced DAC headphone out 300 ohm Audio Measurements.png


Okto dac8 Stereo USB AES Balanced DAC headphone output impedance Audio Measurements.png


There is good amount of power there but not enough to drive the most difficult headphones.

Edit: added streaming measurements.
Streaming Performance
The unit as supplied was running Volumio. I was pleasantly surprised that the Volumio UI has been enhanced to easily install extensions such as "Roon Bridge" which I used for the following tests:
Okto dac8 Stereo USB AES Balanced DAC Roon Bridge Streaming Audio Measurements.png


As we see performance is identical to USB which is great. Same is true of jitter test:

Okto dac8 Stereo USB AES Balanced DAC Streaming Jitter Audio Measurements.png


There is no degradation whatsoever when streaming instead of USB.

Conclusions
okto has done it again: producing state-of-the-art, class-leading, instrument-grade DAC. Not only that, the mechanicals and usability are a good match for it as well. When someone as picky as me can't find any faults, you can tell the job is well done. Very well done.

It is my pleasure to highly recommend the okto dac8 stereo DAC.

------------
As always, questions, comments, recommendations, etc. are welcome.

You would think after seeing such stellar measurements, I would be so happy to not demand more donations. No way. A man would not be a man if more money didn't make him happier. So please donate some money my way using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
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RichB

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#2
Nice review, I am seriously considering one of these.

When using Roon via the internal Pi4, can Roon control the volume of the DAC?

Using Volumio, I had to disable Airplay to get the full resolution 96/24 or greater via the USB port.
Roon kept using the Airplay connection.

- Rich
 

EchoChamber

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#3
Awesome!! I can’t wait for mine to get here. I do have a weakness for high performing audio gear...

Thank you for the review Amir!
 
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amirm

amirm

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Thread Starter #4
Nice review, I am seriously considering one of these.

When using Roon via the internal Pi4, can Roon control the volume of the DAC?

- Rich
It was with Volumio.
 

RichB

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#5
It was with Volumio.
Ideally, an integrated Roon endpoint (even from Volumio) allows Roon to let the device control the volume using DAC.
Otherwise, Roon has to attenuate and the DAC is at max volume.

- Rich
 

Racheski

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#10
Sadly Airplay only supports 16 bits/44.1 kHz so severely impacted the performance. You can of course change that to another streamer software (e.g. DietPi) or install the Roon endpoint to get full 24-bit streaming at various sample rates.
Why is playing audio at CD quality considered a severe impact to performance?
 

Veri

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#11
Why is playing audio at CD quality considered a severe impact to performance?
16/44 can only resolve up to 96 dB: 16-bit digital audio found on CDs has a theoretical SNR/DR limit of 96 dB, while professional 24-bit digital audio tops out at 144 dB (well, disregarding the practice of 16-bit dithering and noise shaping for a moment there :))
 
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amirm

amirm

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Thread Starter #16

EchoChamber

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#18
That external jumper to connect two internal systems is strange...
Feels a bit like a hack, doesn’t it? I thought the whole DAC integrated with the Pi like a “hat”. I think they might have run into issues integrating the Pi that way. Should work just as well though. Good thing there are 2 USB inputs.

Edit: Pi hat doesn’t do DSD and is jittery. I take back my comments.
 
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Tks

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#20
Feels like a bit like hack, doesn’t it? I thought the whole DAC integrated with the Pi like a “hat”. I think they might have run into issues integrating the Pi that way. Should work just as well though. Good thing there are 2 USB inputs.
Look at the price, I'm not seeing anything remotely close to what it offers. Small company, small output, and still within a "sane" pricepoint.
 

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