Review and Measurements of Okto DAC8 8Ch DAC & Amp

[rickyhgarcia]

Hi everyone,

hopefully I'll be able to shed some light on the previously discussed XLR-RCA interfacing.

The main reason why two wires aren't enough for a high-performance audio interconnect is that no matter what you do, there will be current caused by a different ground potentials and/or a real-world interference flowing through the shield conductor. Since the shield conductor has a non-zero impedance, this current will produce a voltage and in case the shield conductor also doubles as a signal conductor, this voltage will be mixed straight into your audio.

To quote Bruno Putzeys:


If the receiver is made differential, i.e. it only cares about the difference between the two signal conductors (XLR pins 2 and 3 or hot and cold), the "dirty work" is offloaded to shield (or XLR pin1) conductor. As long as those are not connected to the PCB on either transmitter or receiver side (which causes so called Pin1 problem) but rather diverted to the Protective Earth mains conductor, this makes for a hum-free connection.

When interfacing XLR outputs to RCA inputs, you have these options:

1) The best one from a technical standpoint: retrofitting a XLR differential input to a legacy equipment
It might be either built inside or made as an outside box with separate power. The XLR shield and pin1 would need to be grounded to the chassis on the receiving side or the whole thing might be bolted to it. A company called THAT Corporation makes very good receiver chips that would fit this task and a module using those has even been a commercially available product at some point .
https://www.neurochrome.com/that-receiver-rev-1-0/

2) A drop-in solution if you don't mind some distortion: tranformers
The transformer-based approach (like with Neutrik NA2F-DOB-TX or much more expensive Jensen transformers) will work and avoid ground loop issues. Transformers also have higher common-mode rejection ratio than what can be achieved with semiconductors. The distortion might not matter for use with tube amplifiers that already have a transformer in the signal path or with subwoofers.

3) Off the shelf XLR-RCA cables
As mentioned, these short XLR pin 3 (cold) to pin 1 (ground). That makes them work both with direct-coupled and transformer-coupled XLR inputs/outputs, but the direct-coupled ones might not be happy about the short. While the outputs of DAC8 PRO are short-circuit proof, operational amplifiers do not like huge loading and will respond with increased distortion (by several orders of magnitude).

4) Cable with floating pin3 (cold)
Using just one of the signals from the XLR side to interface with RCA is a dirty and cheap solution. We cannot guarantee this will be hum-free (depends on circumstances) or that DAC8's output will be pop-free on turn on/off in this configuration, but it is certainly a better way than the previous one. There will still be an increased distortion compared to interfacing a regular XLR input since you will be picking up the common-mode distortion products that would otherwise be rejected. Because you are only taking half of the signal, you will lose 6dB. If you still want to go that way and don't have pliers, Benchmark already makes cables like that: https://benchmarkmedia.com/collecti...dapter-cable-pin-3-floating?variant=547761981



They don't specify the input voltage nor the gain, but given the fact that their output works with the same voltage as DAC8 (4V RMS), I don't expect any issues.



DAC8 PRO launch coming up in the following days! Shipping will start shortly after that. Stay tuned for the news.

Pavel, Okto Research

This post from Okto offer a few options for connecting the DAC8 Stereo to legacy preamps/amps (i.e. only RCA inputs), and in the order of preference by Okto. Since this is exactly what I am planning to do (Okto DAC to my legacy Audio Research preamp), I do not intend to go beyond option two (2) for the hook up. Besides, it is clear that doing XLR and RCA on the same cable is not recommended by Okto ("RCA should be banned by law")...

As to the options:

1)This is the preferred solution for Okto. But, this is what´s available for option one:

Nice board if one has the skills to put it in a box, with external connectors and a power supply. There is no finish product for this board, it is offered as a DIY project. Does anyone in the forum worked a solution with this board?? The board alone is $139 for two channels.

2)Transformers that may introduce noise to the signal. The noise may be inconsequential for tube electronics since they "have a transformer in the signal path" already. My Audio Research preamp is a tube unit. These are the options:

Jensen ( https://www.jensen-transformers.com/product/pc-2xr/ )

Neutrik ( https://www.neutrik.com/en/product/na2f-d0b-tx )

The Jensen unit is $299 for two channels, while the Neutrik can be found for $30 for one channel. I am not sure if the Jensen unit above is the correct unit recommended by Pavel, since its application is for PRO Electronics (i.e. studio console) to a home stereo.

Any thoughts or suggestions?

 

[Veri]

This post from Okto offer a few options for connecting the DAC8 Stereo to legacy preamps/amps (i.e. only RCA inputs), and in the order of preference by Okto. Since this is exactly what I am planning to do (Okto DAC to my legacy Audio Research preamp), I do not intend to go beyond option two (2) for the hook up. Besides, it is clear that doing XLR and RCA on the same cable is not recommended by Okto ("RCA should be banned by law")...

As to the options:

1)This is the preferred solution for Okto. But, this is what´s available for option one:
View attachment 55294
Nice board if one has the skills to put it in a box, with external connectors and a power supply. There is no finish product for this board, it is offered as a DIY project. Does anyone in the forum worked a solution with this board?? The board alone is $139 for two channels.

2)Transformers that may introduce noise to the signal. The noise may be inconsequential for tube electronics since they "have a transformer in the signal path" already. My Audio Research preamp is a tube unit. These are the options:

Jensen ( https://www.jensen-transformers.com/product/pc-2xr/ )
View attachment 55295

Neutrik ( https://www.neutrik.com/en/product/na2f-d0b-tx )
View attachment 55297
The Jensen unit is $299 for two channels, while the Neutrik can be found for $30 for one channel. I am not sure if the Jensen unit above is the correct unit recommended by Pavel, since its application is for PRO Electronics (i.e. studio console) to a home stereo.

Any thoughts or suggestions?

DON'T go for that Neutrik one its specs for a normal line level conversion are nothing to write home about. The Jensen one is much better!
But honestly, transformers are kind of a last resort. As you say, probably not an audible concern though, given your final amplification.

 

[maverickronin]

Please define exactly what you mean by "more stable".

Pure anecdotal but I've seen people having drop-outs or issues on USB 3.0 ports that are fixed by using a spare 2.0 port.
Of course if something is USB3 you should use that, but otherwise I would just use USB2. is what I meant.

All kinds of reasons. It can be drivers depending on your OS and the chipset running the ports, but also electrical.

USB 3.0 devices run at higher speeds and tend to be very noisy.

On one of my machines, if I plug in 3.0 thumb drive next to the receiver for my Logitec wireless mouse it becomes completely unusable while reading/writing to the drive.

 

[wineds]

This post from Okto offer a few options for connecting the DAC8 Stereo to legacy preamps/amps (i.e. only RCA inputs), and in the order of preference by Okto. Since this is exactly what I am planning to do (Okto DAC to my legacy Audio Research preamp), I do not intend to go beyond option two (2) for the hook up. Besides, it is clear that doing XLR and RCA on the same cable is not recommended by Okto ("RCA should be banned by law")...

As to the options:

1)This is the preferred solution for Okto. But, this is what´s available for option one:
View attachment 55294
Nice board if one has the skills to put it in a box, with external connectors and a power supply. There is no finish product for this board, it is offered as a DIY project. Does anyone in the forum worked a solution with this board?? The board alone is $139 for two channels.

2)Transformers that may introduce noise to the signal. The noise may be inconsequential for tube electronics since they "have a transformer in the signal path" already. My Audio Research preamp is a tube unit. These are the options:

Jensen ( https://www.jensen-transformers.com/product/pc-2xr/ )
View attachment 55295

Neutrik ( https://www.neutrik.com/en/product/na2f-d0b-tx )
View attachment 55297
The Jensen unit is $299 for two channels, while the Neutrik can be found for $30 for one channel. I am not sure if the Jensen unit above is the correct unit recommended by Pavel, since its application is for PRO Electronics (i.e. studio console) to a home stereo.

Any thoughts or suggestions?

Option 4 worked fine for me when using single ended input amps. Very little hum with ear next to speaker even less if you use outputs 3,4 insad of 1,2.

 

[dualazmak]

I am still waiting for arrival of my DAC8PRO (order #106) which is on "Processing" at OKTO's facility in Prague. I understand that COVID-19 pandemic in Europe (and all over the planet) would somewhat affect and disturb the delivery logistics in Europe and Japan; I am happy to wait for another one month or two, or three.

As I am carefully considering candidate 4 stereo or 8 monaural amplifiers to build my stereo 5-way 10-channel multi-amplifiers system with software crossover EKIO and DAC8PRO, the discussion on "XLR or RCA" and "XLR to RCA" is very much valuable and informative for me.

By the way, my active sub-woofers, two YAMAHA YST-SW1000, have unbalance RCA line level input to be directly connected from another DAC (in my case OPPO SONICA DAC) which will only handle 15 - 50 Hz super-low signal from EKIO. DAC8PRO, of course, will be used in stereo 4-way 8-channel mode.

As for "XLR or RCA", I decided to use fully XLR capable pre-main amplifiers: I assume many people here would like to know the reasons for using good quality pre-main amplifiers, especially with high quality attenuator/volume, in multi-amplifiers system.

My policy and strategy are;

"line level output from DACs should be in flat FQ response allover 15 - 25,000 Hz in high gain",
and
"fine tuning of relative gain/volume for sub-woofers (SW), woofers (WO), squawkers (SQ), tweeters (TW) and super-tweeters (ST) should be controlled by each amplifiers".

I know, of course, that EKIO on PC can act as master volume controller for all of the 5-way 10-channel.

During the past three months, in one of the audio-enthu web sites in Japan in Japanese, I could have very nice and intensive discussion on the use of pre-main amps in multi-amp system, and I finally decided to use pre-main amps in my coming muti-amp system.

I have already done my in-depth "simulation" of 5-way 10-channel crossover with EKIO by directing all the 10-channels into one DAC, i.e., OPPO SONICA DAC, and I could find some best-fit 10-channel EKIO crossover configurations for my speaker units, even though currently still through outer LC network box and three attenuators for SQ, TW and ST.

Just for example;

Using a sound measurement microphone ECM8000, I measured FQ-responses with pink noise, white noise and sine sweep, and also measured/optimized group delay by using REW (Room Equalization Wizard) and its Wavelet spectrum analysis. The details of such measurements, including FQ response curves and several Wavelet spectrum images, can be show here upon requests. REW-Wavelet is really nice and sensitive enough for EKIO's crossover configurations, and EKIO's group delay function is just accurate as confirmed by REW-Wavelet.

I am now using ACCUPHASE E-460 (XLR input capable) and OPPO SONICA DAC (XLR out capable) in my audio system, and I will continue to use E-460 to drive woofers (XLR from DAC8PRO), and as mentioned above OPPO SONICA DAC will be used for sub-woofers (unbalanced RCA cabling).

Consequently, I need 3 new fully XLR capable pre-main amplifiers with high quality attenuator/volume to drive squawkers (SQ), tweeters (TW) and super-tweeters (ST).

My current candidates, also in consideration of my budget, are;

ACCUPHASE E-270 (for SQ?)
SONY TA-A1ES (for SQ and/or TW?)
TEAC AX-505 (8Ohm 70Wx2)
NMODE X-PM7 MKII (one bit digital 8Ohm 20Wx2, XLR for mono, so maybe for TW and/or ST)
SOULNOTE A-0 (8Ohm 10Wx2, so for TW and/or ST)

Your comments and/or suggestions for the selection of XLR capable amplifiers will be highly appreciated.

 

[tomchr]

When interfacing XLR outputs to RCA inputs, you have these options:

1) The best one from a technical standpoint: retrofitting a XLR differential input to a legacy equipment
It might be either built inside or made as an outside box with separate power. The XLR shield and pin1 would need to be grounded to the chassis on the receiving side or the whole thing might be bolted to it. A company called THAT Corporation makes very good receiver chips that would fit this task and a module using those has even been a commercially available product at some point .
https://www.neurochrome.com/that-receiver-rev-1-0/

Thank you for the nod. I appreciate it. Unfortunately, I discontinued the THAT Receiver and replaced it (and the THAT Driver) with the Universal Buffer.

I've been nudged a couple of times to develop a differential/XLR to single-ended/RCA converter retail product. I would lean heavily on the Universal Buffer, so that should give you a clue about the performance. You can have a look at my HPA-1 headphone amp for an idea of what the aesthetics of the design would be.

The big question is: Would you be interested in such a product if I could make it at a price point of, say, $399 for a stereo version?

I don't want to hijack the thread, so feel free to respond by PM to me directly.

Tom

 

[John1959]

I am still waiting for arrival of my DAC8PRO (order #106) which is on "Processing" at OKTO's facility in Prague. I understand that COVID-19 pandemic in Europe (and all over the planet) would somewhat affect and disturb the delivery logistics in Europe and Japan; I am happy to wait for another one month or two, or three.

Hi,
Just to inform you. I ordered the DAC8 PRO (silver) about a week ago (order #116, status = processing). I was told that the DAC probably will be ready within about 8 weeks after I placed the order. Fortunately, courier shipping seems - in general - not much affected by COVID-19 in Europe . All my packages from various destinations in Europe arrive on scheduled time as before the crisis.

John.

 

[dualazmak]

Hi,
Just to inform you. I ordered the DAC8 PRO (silver) about a week ago (order #116, status = processing). I was told that the DAC probably will be ready within about 8 weeks after I placed the order. Fortunately, courier shipping seems - in general - not much affected by COVID-19 in Europe . All my packages from various destinations in Europe arrive on scheduled time as before the crisis.

John.

Hello John,
Thanks a lot for the nice information, even though I am sincerely joining all the people's prayers for early shutdown of COVID-19 pandemic in Europe and allover the planet. My order# is 106 to Japan, and we may expect to receive our DAC8PROs almost at the same time, I hope.

 

[dualazmak]

Consequently, I need 3 new fully XLR capable pre-main amplifiers with high quality attenuator/volume to drive squawkers (SQ), tweeters (TW) and super-tweeters (ST).

My current candidates, also in consideration of my budget, are;

ACCUPHASE E-270 (for SQ?)
SONY TA-A1ES (for SQ and/or TW?)
TEAC AX-505 (8Ohm 70Wx2)
NMODE X-PM7 MKII (one bit digital 8Ohm 20Wx2, XLR for mono, so maybe for TW and/or ST)
SOULNOTE A-0 (8Ohm 10Wx2, so for TW and/or ST)

Your comments and/or suggestions for the selection of XLR capable amplifiers will be highly appreciated.

Just to test/check the stereo 4-way 8-channel multi-amplifiers with DAC8PRO, one another possible candidate would be two of YAMAHA XM4080;
https://usa.yamaha.com/products/proaudio/power_amps/xm_series/index.html
https://usa.yamaha.com/files/download/other_assets/5/334565/xm4180_en_om_e0.pdf

Dose anyone here have experiences using XM4080 in home audio system?

 

[dualazmak]

The specs of XM4080 looks fine and acceptable, but it should be better to change the fan or to add fan-speed controller....
https://www.thomann.de/gb/yamaha_xm_4080.htm#bewertung
So far, I could find only this quick review on XM4080.

 

[dualazmak]

Just for your quick notice and understanding, what I am planning with DAC8PRO is shown in this draft scheme.
Does anyone here have similar idea? Did anyone here already build similar system with DAC8PRO?

 

[Porcari]

This is a review and detailed measurements of the Okto Research DAC8 8-channel DAC and headphone amplifier. I was sent a prototype unit for measurements. From my understanding, the company has been producing the internal DAC module for a while for the DIY market. But now are building complete systems. So what makes this an early production unit is not the DAC module but the integrated version with input and other features. The version I have has the Okto DAC8 module plus an off-the-shelf UBS Input. My understanding is that the final units in production in April will also have their own USB input implementation plus 4xAES/EBU. It will cost 989 EUR in this configuration (about $1,120 as of this writing). This version will be known as DAC8 Pro. I will just be calling it DAC8 from here on.

There will be two other versions, one with DSP and the other in stereo configuration where four channels are folded into one to get better performance. See: https://www.oktoresearch.com/index.htm

Due to large number of outputs, the unit comes in "rack mount" 1U size (at least I think it complies with that spec). But through out any impression of dull, industrial look out of the window. The DAC8 employs two beautiful and highly legible OLED displays flanking its rotary control, giving it an exquisite look:

View attachment 23760​

From what I have read, they have done the mechanical design (and production?) themselves too. The metallic part of the front panel looks a bit cold to me so if there is an option in black would be nice. Any misgivings on that part goes away the moment you interact with the unit. Display changes are instantaneous, giving you a very solid feel that you are making changes. I love all the key information nicely visible including the sample rate, input, volume, etc. Love it!

I had no trouble navigating the unit with the rotary control. The DAC8 though is able to learn the remote control of your choice or you can get it with an Apple Remote.

One minor thing is the top: it has screws on each side but none in the middle. This allows the top or flex a bit. I suggest putting a single additional screw in the back middle to remedy this.

The back panel on my unit is not fully populated per intro:

View attachment 23761​

I am too lazy to usually show you all the menus but I thought I make an exception here. Pushing the rotary control changes the left side to:

View attachment 23762

A second click changes the right side to this for volume. The menu will scroll down to let you lower the levels in all 8 channels:
View attachment 23763

I turned on the 18 dB boost and it produced severe clipping at anything above -19 dB. I am not sure of its use other than for digital input that is at very low level. I hope @Okto Research can explain what they think this is useful for.

System menu is such:
View attachment 23764

Display shows the usual stuff:
View attachment 23765

And finally the ESS Sabre DAC settings which I left alone:
View attachment 23766

Okto Research advertises superlative specs for this product -- numbers which we have not seen in our reviews. Is it the usual marketing games or real? Let's find out.

DAC Measurements
As usual, we start with our dashboard view:

View attachment 23767

Wow! What a way to impress. Distortion+noise of just 0.000127%? And with such excellent channel matching? This places the SINAD at 118 which is a new record:

View attachment 23785

Yes, a new SINAD king has been crowned!

In honesty though, there is an unfair advantage here. Can you spot it? The output voltage is 3.3 volt, not the usual 4 volt we like to see. Okto says they can program this to any level one wants. Usually distortion sets in when levels are increased so I expect some performance will be lost if this were boosted to 4 volts. Fortunately in use you are not going to need more voltage since you have a volume control in DAC8 so will be driving an amp below these levels anyway.

As if to deliver a one-two punch, the DAC8 delivers exemplary stable and noise-free linearity results sailing to -120 dB (20 bits of resolution):

View attachment 23769

Dynamic range pushes the limits of my analyzer so likely the actual DNR is better than reported:

View attachment 23770

With threshold of hearing being -116 dB, this is one silent DAC!

Jitter shows tiniest imperfection made more visible by very low noise floor:

View attachment 23771

I had to remove audiosciencereview.com sticker at the bottom of the graph since the noise floor slid under it!

DAC8 is using ESS DAC chip so for sure we will see our famous "ESS THD IMD," yes?

View attachment 23772

There is a tiniest hint of that -- maybe -- around -32 dB or so. Or then again it could just be the variations we see throughout the graph. Whatever, it bests my reference DX3 Pro DAC I use for this test.

Distortion and noise relative to frequency shows flat response which indicates plenty of bandwidth/gain:
View attachment 23773

With some 30 dB lower distortion at 20 kHz, you do get something for paying more than $99 for your DAC (read: Khadas Tone Board).

For multi-tone test, I switched to a new method as the one I was using was too finicky and would generate garbage results if the delay through the DAC was not what it was expecting. So don't quite compare this to previous measurements:

View attachment 23774

The accumulation of distortion products stops around -150 dB. Our tones are around -20 dB meaning there is almost 130 dB of distance between the peak and distortion products!

Folks, we have to stop here. I can't find any holes in this design. Surely we find a fertile in the headphone amp though. It has to be a throw-away feature made to fill the spec sheet....

Headphone Amplifier Measurements
Let's jump right into our power versus distortion+noise:

View attachment 23775

From distortion and noise point of view, the DAC8 easy bests my DX3 Pro reference even in its low-gain mode. Alas, power is highly limited due to maximum of 1.6 volt output. So we don't even make it to 10 milliwatts. Those of you who have the DX3 Pro and operate it in low gain mode would have almost the same amount of power here.

Switching to 33 Ohm load gives us more power as expected but still not as much as we like:

View attachment 23776

Again, power output is near what DX3 Pro produces in low gain mode.

No, the 18 dB boost doesn't help here. Again, it just makes the clipping point -18 dB on the volume control.

Output impedance is excellent at 1 ohm which is close to limit of how low I can measure with my fixture:
View attachment 23777

Headphone Listening Tests
I plugged in my HD-650 into DAC8 and was greeted by what you see in the measurements: there is no hint of distortion to max 0 dB volume level. Due to limited power, there is no sensation of "subwoofer in your ear" as I like to see. What was there though is likely sufficient for many though. I was able to listen at levels between -9 to 0 dB.

The situation was a bit better with Hifiman HE-400i. A very pleasant experience but no chance of rattling off the screws on the drivers.

If you are interested in this product for headphone listening, I would start with what is there and see if it is enough. If not, then a pairing with Massdrop THX AAA 789 would be in order.

Conclusions
Let me confess that I had a few down moments prior to testing the Okto DAC8. There is such a large backlog of gear to review and it seems I am jumping from one measurement to another. Nothing cured that better though than putting the Okto Research's DAC8 on the bench. The DAC8 Pro is superbly engineered and delivers on objective measurements like there is no tomorrow. Heck, I got tired of putting exclamation marks in my review above. Could we have predicted this? To some extent yes: despite being a small company, they used the major competitor to my Audio Precision analyzer from Rohde and Schwarz. Time and time again we have seen that companies that measure their designs, product superb products. You have to verify what you build folks.

And this is not just some 2-channel DAC. You have 8 channels of output that should satisfy anyone who needs that many channels now or in the future. It is remarkable that Okto achieved such excellent results without combining four or 8 channels together as other companies do.

Then we have highly responsive, well design and clear displays. And excellent connectivity in the final version with more inputs to let you tailor this with your favorite DSP upstream.

The only miss is lack of infinite amount of power in its headphone stage for anyone wanting to use it that way. But what is there is high performance and distortion and noise-free.

As you can surmise, the Okto Research DAC8 is an incredibly well designed and featured product. It is my absolute pleasure to recommend the DAC8.

I am also so happy to find a device designed and manufactured in Europe (Prague). I always feel bad giving high marks to US built devices that wind up being very expensive to import into EU.

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

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upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).

This is a review and detailed measurements of the Okto Research DAC8 8-channel DAC and headphone amplifier. I was sent a prototype unit for measurements. From my understanding, the company has been producing the internal DAC module for a while for the DIY market. But now are building complete systems. So what makes this an early production unit is not the DAC module but the integrated version with input and other features. The version I have has the Okto DAC8 module plus an off-the-shelf UBS Input. My understanding is that the final units in production in April will also have their own USB input implementation plus 4xAES/EBU. It will cost 989 EUR in this configuration (about $1,120 as of this writing). This version will be known as DAC8 Pro. I will just be calling it DAC8 from here on.

There will be two other versions, one with DSP and the other in stereo configuration where four channels are folded into one to get better performance. See: https://www.oktoresearch.com/index.htm

Due to large number of outputs, the unit comes in "rack mount" 1U size (at least I think it complies with that spec). But through out any impression of dull, industrial look out of the window. The DAC8 employs two beautiful and highly legible OLED displays flanking its rotary control, giving it an exquisite look:

View attachment 23760​

From what I have read, they have done the mechanical design (and production?) themselves too. The metallic part of the front panel looks a bit cold to me so if there is an option in black would be nice. Any misgivings on that part goes away the moment you interact with the unit. Display changes are instantaneous, giving you a very solid feel that you are making changes. I love all the key information nicely visible including the sample rate, input, volume, etc. Love it!

I had no trouble navigating the unit with the rotary control. The DAC8 though is able to learn the remote control of your choice or you can get it with an Apple Remote.

One minor thing is the top: it has screws on each side but none in the middle. This allows the top or flex a bit. I suggest putting a single additional screw in the back middle to remedy this.

The back panel on my unit is not fully populated per intro:

View attachment 23761​

I am too lazy to usually show you all the menus but I thought I make an exception here. Pushing the rotary control changes the left side to:

View attachment 23762

A second click changes the right side to this for volume. The menu will scroll down to let you lower the levels in all 8 channels:
View attachment 23763

I turned on the 18 dB boost and it produced severe clipping at anything above -19 dB. I am not sure of its use other than for digital input that is at very low level. I hope @Okto Research can explain what they think this is useful for.

System menu is such:
View attachment 23764

Display shows the usual stuff:
View attachment 23765

And finally the ESS Sabre DAC settings which I left alone:
View attachment 23766

Okto Research advertises superlative specs for this product -- numbers which we have not seen in our reviews. Is it the usual marketing games or real? Let's find out.

DAC Measurements
As usual, we start with our dashboard view:

View attachment 23767

Wow! What a way to impress. Distortion+noise of just 0.000127%? And with such excellent channel matching? This places the SINAD at 118 which is a new record:

View attachment 23785

Yes, a new SINAD king has been crowned!

In honesty though, there is an unfair advantage here. Can you spot it? The output voltage is 3.3 volt, not the usual 4 volt we like to see. Okto says they can program this to any level one wants. Usually distortion sets in when levels are increased so I expect some performance will be lost if this were boosted to 4 volts. Fortunately in use you are not going to need more voltage since you have a volume control in DAC8 so will be driving an amp below these levels anyway.

As if to deliver a one-two punch, the DAC8 delivers exemplary stable and noise-free linearity results sailing to -120 dB (20 bits of resolution):

View attachment 23769

Dynamic range pushes the limits of my analyzer so likely the actual DNR is better than reported:

View attachment 23770

With threshold of hearing being -116 dB, this is one silent DAC!

Jitter shows tiniest imperfection made more visible by very low noise floor:

View attachment 23771

I had to remove audiosciencereview.com sticker at the bottom of the graph since the noise floor slid under it!

DAC8 is using ESS DAC chip so for sure we will see our famous "ESS THD IMD," yes?

View attachment 23772

There is a tiniest hint of that -- maybe -- around -32 dB or so. Or then again it could just be the variations we see throughout the graph. Whatever, it bests my reference DX3 Pro DAC I use for this test.

Distortion and noise relative to frequency shows flat response which indicates plenty of bandwidth/gain:
View attachment 23773

With some 30 dB lower distortion at 20 kHz, you do get something for paying more than $99 for your DAC (read: Khadas Tone Board).

For multi-tone test, I switched to a new method as the one I was using was too finicky and would generate garbage results if the delay through the DAC was not what it was expecting. So don't quite compare this to previous measurements:

View attachment 23774

The accumulation of distortion products stops around -150 dB. Our tones are around -20 dB meaning there is almost 130 dB of distance between the peak and distortion products!

Folks, we have to stop here. I can't find any holes in this design. Surely we find a fertile in the headphone amp though. It has to be a throw-away feature made to fill the spec sheet....

Headphone Amplifier Measurements
Let's jump right into our power versus distortion+noise:

View attachment 23775

From distortion and noise point of view, the DAC8 easy bests my DX3 Pro reference even in its low-gain mode. Alas, power is highly limited due to maximum of 1.6 volt output. So we don't even make it to 10 milliwatts. Those of you who have the DX3 Pro and operate it in low gain mode would have almost the same amount of power here.

Switching to 33 Ohm load gives us more power as expected but still not as much as we like:

View attachment 23776

Again, power output is near what DX3 Pro produces in low gain mode.

No, the 18 dB boost doesn't help here. Again, it just makes the clipping point -18 dB on the volume control.

Output impedance is excellent at 1 ohm which is close to limit of how low I can measure with my fixture:
View attachment 23777

Headphone Listening Tests
I plugged in my HD-650 into DAC8 and was greeted by what you see in the measurements: there is no hint of distortion to max 0 dB volume level. Due to limited power, there is no sensation of "subwoofer in your ear" as I like to see. What was there though is likely sufficient for many though. I was able to listen at levels between -9 to 0 dB.

The situation was a bit better with Hifiman HE-400i. A very pleasant experience but no chance of rattling off the screws on the drivers.

If you are interested in this product for headphone listening, I would start with what is there and see if it is enough. If not, then a pairing with Massdrop THX AAA 789 would be in order.

Conclusions
Let me confess that I had a few down moments prior to testing the Okto DAC8. There is such a large backlog of gear to review and it seems I am jumping from one measurement to another. Nothing cured that better though than putting the Okto Research's DAC8 on the bench. The DAC8 Pro is superbly engineered and delivers on objective measurements like there is no tomorrow. Heck, I got tired of putting exclamation marks in my review above. Could we have predicted this? To some extent yes: despite being a small company, they used the major competitor to my Audio Precision analyzer from Rohde and Schwarz. Time and time again we have seen that companies that measure their designs, product superb products. You have to verify what you build folks.

And this is not just some 2-channel DAC. You have 8 channels of output that should satisfy anyone who needs that many channels now or in the future. It is remarkable that Okto achieved such excellent results without combining four or 8 channels together as other companies do.

Then we have highly responsive, well design and clear displays. And excellent connectivity in the final version with more inputs to let you tailor this with your favorite DSP upstream.

The only miss is lack of infinite amount of power in its headphone stage for anyone wanting to use it that way. But what is there is high performance and distortion and noise-free.

As you can surmise, the Okto Research DAC8 is an incredibly well designed and featured product. It is my absolute pleasure to recommend the DAC8.

I am also so happy to find a device designed and manufactured in Europe (Prague). I always feel bad giving high marks to US built devices that wind up being very expensive to import into EU.

------------
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Hi Amirm,
I am new here and you are doing terrific reviews,well done.

I want to buy a good,decent dac and my picks are the Matrix X Sabre Pro and the Okto 8 dac (stereo version). You had reviewed the Pro version.
Which one will you advise,they are both very good?

Thanks and Regards.

 

[mk1classic]

Just for your quick notice and understanding, what I am planning with DAC8PRO is shown in this draft scheme.
Does anyone here have similar idea? Did anyone here already build similar system with DAC8PRO?

View attachment 56460

The digital setup with the subwoofers controlled by two USB based DACs will not work. The USB DACs are asynchronous i.e. you don't have control over the timed signal going from the PC to the OKTO and the Subwoofer DAC. If you use the AES/EBU output to a AEB/EBU DAC then you can have controlled signal to both the OKTO and a Subwoofer DAC.

 

[dualazmak]

The digital setup with the subwoofers controlled by two USB based DACs will not work. The USB DACs are asynchronous i.e. you don't have control over the timed signal going from the PC to the OKTO and the Subwoofer DAC. If you use the AES/EBU output to a AEB/EBU DAC then you can have controlled signal to both the OKTO and a Subwoofer DAC.

Thank you for your comment. I knew/know and understood/understand your point.

Theoretically, your point would be correct, I believe. I assume, however, especially for the very low subwoofers Fq region of ca. below 60 Hz, the "exact" timing synchronization would not be essential in real audio/music listening, and I, therefore, would direct the lowest Fq region, channel-1 and channel-2, into another DAC, and all of other higher Fq channels would be directed into DAC8PRO.

Using EKIO and two DACs, I have carefully tested/simulated this idea by sending the subwoofers (SWs) singal, i.e., below ca. 50 Hz, into one DAC = ONKYO DAC-1000S and its unbalanced RCA lines were conneted to SWs, L and R YST-SW1000. All of the other higher Fq stereo 4-way 8-channel were sent into OPPO Sonica DAC --> ACCUPHASE E-460 --> LC-network -->woofers, squawkers, tweeters and super-tweeters. In this simulation, all sounds quite nicely. I hope and believe this would also work nicely with DAC8PRO.

The following several photos will show my trials and results;

Please note in and after the below info# 12, the super low signal channel-1 and channel-2 went into one DAC = ONKYO DAC-1000S, and other higher 8 channels, i.e. channel-3 through channel-10, went into another DAC = OPPO SONICA DAC, for real total sound measurements.

(to be continued to next post)

 

[dualazmak]

Sorry for the above multiple images/photos; I hope these would be somewhat useful for your review and understandings on my plan and simulation trials.

 

[somebodyelse]

Theoretically, your point would be correct, I believe. I assume, however, especially for the very low subwoofers Fq region of ca. below 60 Hz, the "exact" timing synchronization would not be essential in real audio/music listening, and I, therefore, would direct the lowest Fq region, channel-1 and channel-2, into another DAC, and all of other higher Fq channels would be directed into DAC8PRO.

The problem is that the clocks will drift further out of sync the longer you leave it running. Whether this is a problem will depend partly on what the difference in clock speed is, what the length of tracks or albums is, and on exactly how EKIO works. If EKIO stops at the end of a track then restarts then it'll bring them back into sync at each track change and you might be ok. If it just keeps running then sooner or later things will get too far out of sync unless you luck into matching clocks. I'm guessing you were testing over short periods, not the length of an album.

 

[John1959]

Just for your quick notice and understanding, what I am planning with DAC8PRO is shown in this draft scheme.
Does anyone here have similar idea? Did anyone here already build similar system with DAC8PRO?

View attachment 56460

That's quite an impressive system! I am looking into a much more modest 3-way system LXMini Studio (see: https://www.linkwitzlab.com/LXmini/LXstudio.htm ). Probably with a relatively affordable Hypex based 6-channel amp (4x500W/4ohm + 2x 100W/4 ohm (for the tweeters), see https://www.apollonaudio.com/multichannel-amplifiers/#3way ). And of course a multichannel DAC, the Okto DAC8 Pro where I am patiently waiting for. I have learned from this thread that a hardware solution like the miniDSP nanoDIGI module, which I already purchased, is not necessary for programming the Xover because that can be done in the small NUC with the Ekio software. I am grateful for that information. The NUC doubles as a Roon core.

BTW, I choose the Okto DAC mainly because I don't like the idea of too many boxes (another 3 separate DAC's) and there are not many alternatives. And I like the balanced outputs. Second, the unit looks good (optically and technically).

John.

 

[dualazmak]

The problem is that the clocks will drift further out of sync the longer you leave it running. Whether this is a problem will depend partly on what the difference in clock speed is, what the length of tracks or albums is, and on exactly how EKIO works. If EKIO stops at the end of a track then restarts then it'll bring them back into sync at each track change and you might be ok. If it just keeps running then sooner or later things will get too far out of sync unless you luck into matching clocks. I'm guessing you were testing over short periods, not the length of an album.

Hello, thanks a lot for your very important points.

I am also aware of your point, and tested/confirmed several times on this. I kept EKIO running for ca. 3 hours without any interruption, and measured the relative delay of the channels by REW-Wavelet at the start time and 3 hr after. Just fortunately, in my simulation with DAC-1000S and SONICA DAC, I could confirm little negligible drift of synchronization. I agree with you, however, I should restart EKIO rather frequently during my intensive audio listening session.

I have one another option....
My SWs, two YST-SW1000, also have speaker level input terminals with large resister into internal low-dedicated amplifier. We can, therefore, branch from the woofers SP terminals with SP cables to go into SWs. In this case, the EKIO crossover should be configured as stereo 4-way 8-channel, and the lowest Fq region should be 0 Hz - 600 Hz to be covered by subwoofers and woofers. YST-SW1000 has its own variable hi-cut filter (-24 dB/Oct, any Fq at 30 - 130 Hz), volume controller, phase inversion switch, and mute switch, all can be controlled by IR remote controller. So, the volume and phase matching between SWs and WOs are easily achieved using one remote controller which is active for both SWs while I sit at the listening position. A minor feature of this option is that WOs would also receive super-low Fq below ca. 50 Hz which I would like to be taken care of by SWs only. In this case the relative delay between SWs and WOs, if any, cannot be corrected by EKIO, of course. I already have the branching SP cables from WO into SW, and I will certainly test this option after having DAP8PRO.

The best and ideal solution would be.....
I would have one more DAC8PRO or DAC8 STEREO, and fully utilize AES/EBU sync for real 5-way 10-channel in complete sync.

Do you have any suggestion on possible AES/EBU sync capable reasonable stereo DAC which I may use for SWs and in sync with DAC8PRO?

 

[Kal Rubinson]

I've used multiple Mytek stereo DACs with one as master and the others with their clocks slaved and daisy-chained. The signal is USB from JRiver via a USB hub and the output is formatted for a virtual multichannel device by MacOS. In theory, any DACs with clock in/outs could work.

 

[dualazmak]

That's quite an impressive system! I am looking into a much more modest 3-way system LXMini Studio (see: https://www.linkwitzlab.com/LXmini/LXstudio.htm ). Probably with a relatively affordable Hypex based 6-channel amp (4x500W/4ohm + 2x 100W/4 ohm (for the tweeters), see https://www.apollonaudio.com/multichannel-amplifiers/#3way ). And of course a multichannel DAC, the Okto DAC8 Pro where I am patiently waiting for. I have learned from this thread that a hardware solution like the miniDSP nanoDIGI module, which I already purchased, is not necessary for programming the Xover because that can be done in the small NUC with the Ekio software. I am grateful for that information. The NUC doubles as a Roon core.

BTW, I choose the Okto DAC mainly because I don't like the idea of too many boxes (another 3 separate DAC's) and there are not many alternatives. And I like the balanced outputs. Second, the unit looks good (optically and technically).

John.

Hi John, thank you for your nice info on 6-channel amp. I am also considering this type PA multi amp, especially YAMAHA XM4080, XLR capable and with volume/gain controller. My plan is to build stereo 4-way 8-channel with DAC8PRO, and therefore two of XM4080 should be the best fit in terms of channel numbers. The specs also seem to be acceptable;
https://usa.yamaha.com/products/proaudio/power_amps/xm_series/index.html
https://usa.yamaha.com/files/download/other_assets/5/334565/xm4180_en_om_e0.pdf