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Review and Measurements of Okto DAC8 8Ch DAC & Amp

Snafu

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I would change, if until is possible, the placement of the ventilation grill away from the audio electronics. And already put, better that they were small round holes.
could you please stop spamming / spreading disinformation like this ?
 

maty

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That the holes are small and circular is always recommended. The problem is in the boxes available in the market.

If you want, open another thread and discuss it, but not here.
 
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@Okto Research

Question: would the trigger output of the DAC8 be able to power a relay? Something like this [link]? I cannot find the trigger voltage on your website, but in case of 5V the max specified current is 190mA.

Is the trigger output fully isolated from the rest of the unit? I am curious whether this scheme could introduce noise inside the unit.
 

maty

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Antennas science says:

A slot behaves like an equivalent dipole with polarization. Opening efficiency = function of maximum length.

If you want to open a new thread and I will participate in it.
 

NQR

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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
Thank you Pavel,for these explanations,any chance of some images of the back panel and inside of the DAC8 stereo
 
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I would agree with you/although I just read this report, and there may be something in what is suggested.
If one is not interested in reading the whole report,just skip to the conclusion
https://asatid.tabrizu.ac.ir/PDF/104_f28974dc-cc6e-4ae1-9960-a688ea35f350.pdf
Cheers
This report is about heat transfer, not EMC.
I have to admit that I just read the conclusions, and didn't find mention of the shape of the holes, neither that the holes had to be as far as possible from the heat source. ;)
 
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Dec 4, 2018
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dac8pro_front.jpg

Hello everyone, here is the long-awaited launch of our 8-channel D/A converter, the DAC8 PRO!

After the ASR review, we received a lot of questions, feedback and suggestions and so we thought it would be a big shame to miss the chance to implement some of them into the production version. In the end, it took much more time than planned so thanks everyone for the patience, continuing support and interest in our products.

Let’s dive into the feature list, starting with the most noticeable one:

More compact enclosure
The difference visible at the first sight is the more compact enclosure (448x183x50mm excl. feet), made from AW6082 aluminium alloy. This change only applies to the DAC8 PRO, not the upcoming DAC8 Stereo.

Dust-proof and spill-proof design with conductive cooling
Speaking of enclosure… we thought what other improvements could we make to increase the durability of the product. We wanted to get rid of the vents that allow dust to get trapped inside and pile up, eventually causing overheating and possibly even killing the electronics, not to mention an accidental spill of your favorite beverage. But our DAC module produce an amount of heat that needs to be taken care of. So instead of relying on convection, we have implemented a conductive cooling using a CNC-machined aluminium heatsink that transfers heat away from the DAC module to the enclosure. Additionally, the DAC8 PRO does monitor the temperature on the DAC module and will shut down in case of overheating.

heatsink.jpg


Now for the electronic sweetness inside:
dac8pro_inside.jpg

Our own XMOS implementation
No 3rd party modules in the DAC8 PRO! Our own XMOS-based board controlling the USB input and AES/EBU inputs is a result of our work for the last few months. It allows for a low-latency transfer, direct control over the data flow and is tightly integrated with the user interface and the DAC board. Based on a 16-core XU216 MCU, it gives us a solid foundation for future products. Huge thanks to our software team!

4xAES/EBU inputs routed to DAC and DAW + 1 AES/EBU output
In addition to the USB connectivity, 4 XLR AES/EBU connectors provide another 8 input channels. The data flow can also be routed to the DAW USB host for additional processing before looping back to the DAC. The AES frame clock is recovered by a precise receiver and the ESS’s time-domain jitter eliminator does remove any remaining jitter. The first pair of channels is available as an AES/EBU output on a dedicated connector.

All incoming AES/EBU signals are expected to come from a single source domain. The DAC8PRO is not a quad stereo DAC, but an 8-channel DAC without any ASRC. The 8 AES/EBU dataflow is reassembled bit-perfectly by the XMOS processor and passed to the Sabre chip.

Next-generation DAC board
DAC8 PRO has received a next generation of our DAC board optimized for the task, including improved power supplies and shorter signal paths. As our other products, DAC8 PRO is designed to directly drive balanced amplifier inputs.

Ability to receive firmware updates
To add new features or fix bugs, DAC8 PRO is able to receive software updates through USB using a standard DFU protocol and an utility available for Windows, Linux and MacOS.

New functions
A powerful 8x8 routing matrix is available separately for USB and AES inputs. Individual volume can be assigned to each output channel using a 32-bit Sabre volume control

Rack mounting brackets
Our custom-designed 2U rack mounting brackets come with every unit. They are equipped with a soft lining so you don't scratch your DAC8 PRO when mounting them.

Designed for reliability, handmade in Prague
With a relay-free design and just 3 large electrolytic capacitors in the power supply, DAC8 PRO is designed for a lifetime of 10+ years. The intention during the design process was also to streamline the production and allow us to make the product in more significant numbers. But we continue to handmade all the units for you in Prague.

We are looking forward to your feedback!
 

jtwrace

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Will this work with a USB Streamer and Roon for MCH?
 

amirm

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I'd add that, as I said, Amirm didn't measure what seems to be a cause of the sonic difference between these DAC's, the overshoot in the feedback loop of the Sabres, which the folks at ESS themselves say makes a difference to the sound and which I suspect is the source of the commonly-perceived difference in the highs.
Audible? No way. An impulse response has infinite bandwidth. It is a single that goes from zero to maximum amplitude instantly. You would need infinite spectrum to describe it. No way it represents what you hear, nor what exists in music signals. This is math. Not conjecture. Here is the wiki on it: https://en.wikipedia.org/wiki/Impulse_response

1565561683260.png


If someone doesn't understand the above, run, run away from them.

Audio signals are limited to what we hear which is about 20 kHz. That is far cry from infinite bandwidth of an impulse.

As to what ESS claims, let's have them put that in writing and present it to Audio Engineering Society. They won't of course because they don't have any reliable listening test to back it.

Just because a company knows how to design a chip, doesn't give them a pass on ignoring everything about psychoacoustics, proper way to run listening tests, math and signal processing.
 

Bliman

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View attachment 31129
Hello everyone, here is the long-awaited launch of our 8-channel D/A converter, the DAC8 PRO!

After the ASR review, we received a lot of questions, feedback and suggestions and so we thought it would be a big shame to miss the chance to implement some of them into the production version. In the end, it took much more time than planned so thanks everyone for the patience, continuing support and interest in our products.

Let’s dive into the feature list, starting with the most noticeable one:

More compact enclosure
The difference visible at the first sight is the more compact enclosure (448x183x50mm excl. feet), made from AW6082 aluminium alloy. This change only applies to the DAC8 PRO, not the upcoming DAC8 Stereo.

Dust-proof and spill-proof design with conductive cooling
Speaking of enclosure… we thought what other improvements could we make to increase the durability of the product. We wanted to get rid of the vents that allow dust to get trapped inside and pile up, eventually causing overheating and possibly even killing the electronics, not to mention an accidental spill of your favorite beverage. But our DAC module produce an amount of heat that needs to be taken care of. So instead of relying on convection, we have implemented a conductive cooling using a CNC-machined aluminium heatsink that transfers heat away from the DAC module to the enclosure. Additionally, the DAC8 PRO does monitor the temperature on the DAC module and will shut down in case of overheating.

View attachment 31138

Now for the electronic sweetness inside:
View attachment 31130
Our own XMOS implementation
No 3rd party modules in the DAC8 PRO! Our own XMOS-based board controlling the USB input and AES/EBU inputs is a result of our work for the last few months. It allows for a low-latency transfer, direct control over the data flow and is tightly integrated with the user interface and the DAC board. Based on a 16-core XU216 MCU, it gives us a solid foundation for future products. Huge thanks to our software team!

4xAES/EBU inputs routed to DAC and DAW + 1 AES/EBU output
In addition to the USB connectivity, 4 XLR AES/EBU connectors provide another 8 input channels. The data flow can also be routed to the DAW USB host for additional processing before looping back to the DAC. The AES frame clock is recovered by a precise receiver and the ESS’s time-domain jitter eliminator does remove any remaining jitter. The first pair of channels is available as an AES/EBU output on a dedicated connector.

All incoming AES/EBU signals are expected to come from a single source domain. The DAC8PRO is not a quad stereo DAC, but an 8-channel DAC without any ASRC. The 8 AES/EBU dataflow is reassembled bit-perfectly by the XMOS processor and passed to the Sabre chip.

Next-generation DAC board
DAC8 PRO has received a next generation of our DAC board optimized for the task, including improved power supplies and shorter signal paths. As our other products, DAC8 PRO is designed to directly drive balanced amplifier inputs.

Ability to receive firmware updates
To add new features or fix bugs, DAC8 PRO is able to receive software updates through USB using a standard DFU protocol and an utility available for Windows, Linux and MacOS.

New functions
A powerful 8x8 routing matrix is available separately for USB and AES inputs. Individual volume can be assigned to each output channel using a 32-bit Sabre volume control

Rack mounting brackets
Our custom-designed 2U rack mounting brackets come with every unit. They are equipped with a soft lining so you don't scratch your DAC8 PRO when mounting them.

Designed for reliability, handmade in Prague
With a relay-free design and just 3 large electrolytic capacitors in the power supply, DAC8 PRO is designed for a lifetime of 10+ years. The intention during the design process was also to streamline the production and allow us to make the product in more significant numbers. But we continue to handmade all the units for you in Prague.

We are looking forward to your feedback!
First a big congratulations. It looks very nice.
Has the knob changed in the stereo one? Because when I enlarged this one it still has one with those ribbles that reminds me of a lemonade knob.
I hope to see the info of the stereo one very soon.
 

amirm

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Hello everyone, here is the long-awaited launch of our 8-channel D/A converter, the DAC8 PRO!
Looking sharp! Great to hear about the improvements.
 
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Audible? No way. An impulse response has infinite bandwidth. It is a single that goes from zero to maximum amplitude instantly. You would need infinite spectrum to describe it. No way it represents what you hear, nor what exists in music signals. This is math. Not conjecture. Here is the wiki on it: https://en.wikipedia.org/wiki/Impulse_response

View attachment 31144

If someone doesn't understand the above, run, run away from them.

Audio signals are limited to what we hear which is about 20 kHz. That is far cry from infinite bandwidth of an impulse.
No offense, Amir, but that's something every EE knows from the time he's in diapers. So why is the impulse response one of the most used audio test signals? Because we're interested in the frequencies that we can hear, and those affect the impulse response, which is after all the Fourier transform of the frequency response; have one and you have the other.
 

amirm

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No offense, Amir, but that's something every EE knows from the time he's in diapers. So why is the impulse response one of the most used audio test signals?
Who says it is one of the most used audio test signals? A 1 kHz tone fits that definition far, far more than an impulse signal.

An impulse signal is highly useful in characterizing a black box system due to its finite spectrum. That analysis has little to do with what is or is not audible.

Because we're interested in the frequencies that we can hear, and those affect the impulse response, which is after all the Fourier transform of the frequency response; have one and you have the other.
What?
 

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