Review and Measurements of Okto DAC8 8Ch DAC & Amp

[March Audio]

On the previous picture, I just noticed something interesting on the PCB: pin 1 of XLR output connector is mentioned to be "not connected to the PCB". Thinking about the different possible causes of "ESS IMD hump" discussed on other topics, I'm wondering if this unconnected ground is not "improving" in some ways the sensitivity or impact of common mode disturbances (i.e. including a kind of correlated noise that would appear as a THD/IMD) generated by ESS DACs on the differential outputs. If you don't connect the ground between your 2 devices (DAC and AudioPrecision in the case of Amirm testings) you are floating and it adds a non negligible common mode rejection to the system. Of course, we all know that we wouldn't be totally floating because of different parasitic impedances, and I know this is not the best way to proceed in pure terms of EMC, but be sure that the guys at Okto are well aware about EMC, they know how to work, and if they decide not to connect pin 1, they have good reasons...

An easy way to validate/eliminate this root cause would be to perform a test on an isolated (i.e. on PSU and inputs) DAC with the well known "ESS IMD hump", and to check if the hump is affected when connected using a cable with pin 1 left unconnected.

P.S: Sorry for my poor english skills...

It should be connected to the case at entry, if so they are doing the right thing.This wont affect the ESS hump.

 

[Medul]

Hi Pos And thanks for letting me know about this website!

 

[Medul]

It should be connected to the case at entry, if so they are doing the right thing.

Probably and I hope so, because that should lower EMC trade-off of pin 1 not connected to ground by forming a Faraday cage with both enclosures and cable shield. But still, even in that case it's not clear that analog ground is connected to the case, and we would be back to the floating signals...

I would add that if analog ground is connected to the chassis, as you expect it to be, then it will be clear that pin 1 left unconnected has nothing to do with hump, but only ground loop optimisation, connection between the case and the pcb being a starpoint.

This wont affect the ESS hump.

Please, did you performed some tests, or do you have the clear explanation of the phenomenon and know why we can find it or not with the same chip depending on the design?

 

[Okto Research]

The XLR ground (i.e. shield + pin 1) should never be connected to a PCB with sensitive analog circuitry, but directly to a chassis instead. It doesn't mean they can't share the same potential - they do in our case, but the PCB is grounded elsewhere. The key is to divert the cable interference currents directly to the mains Protective Earth conductor and disallow them to wander through the PCB and create a voltage drop (which would inject them into the analog signals including the feedback paths).
http://pin1problem.com/
https://www.rane.com/note165.html

This is no design secret and any sane manufacturer should do it like that, since it is the only way to avoid ground loop problems for good. The pursuit to avoid hum issues with inherently flawed RCA single-ended connections even led to unsafe hi-fi equipment with Protective Earth conductor disconnected from a metal chassis in order to break the ground loop. This is why we only endorse balanced analog connections that allow for a grounded enclosure without hum issues.

So I'm afraid it has nothing to do with the ESS hump .

 

[Medul]

@Okto Research Thank you very much for this answer It confirms what @March Audio expected and what I added to my previous post:

I would add that if analog ground is connected to the chassis, as you expect it to be, then it will be clear that pin 1 left unconnected has nothing to do with hump, but only ground loop optimisation, connection between the case and the pcb being a starpoint.

But unfortunately killed my hypothesis about the vanished hump!

Thank you once again for your answer

 

[Neddy]

That Pin1 thing was also 'discovered' by the theater lighting industry, when the DMX (RS-422/485) control protocol was introduced, and mile long cable runs to 3 phase 800A dimmers (not always co-located) led to ground loops that frequently launched the 422 chips right off the pcbs. One smart mfgr even included spare driver chips in 'empty' sockets on the PCBs. The show must go on, after all.

 

[rickyhgarcia]

Because I have not read all 16 pages of this thread, only Amir´s test report, I do not know if anyone have asked these questions and gotten an answer. I have sent these questions to Okto, but still no answer.

I guess most of this forum readers would be US buyers, so...

"As with all electronics components, it is most likely that some units may malfunction eventually, due to abusive use or a manufacturing defect. Since your company is just launching and in Europe, how RMA´s would be handled? Will you have a repair shop in the US? How long is the warranty period? Will you service units after the warranty period? Have you estimated a cost of such service? If not a US repair shop, must all units be sent back to Prague for repair?"

And, would units shipping outside of Europe would undertake a more rigorous pre-shipping test to verify its functionality and operability?

@Okto Research

 

[chriskilbourn]

Please stay tuned for the final reveal. We are going to add something extra on top of the specifications on our website.

First DAC8 DSPs about to be delivered. More will follow soon.
View attachment 25021

Waiting anxiously

 

[JohnYang1997]

Hi. Recently I had been investigated imd hump. And it doesn't seem to happen only with low signal level. So in short, there are two tests that I am comfortable with can show some modulation distortion when the signal level is still high.

First is 30hz + 1000hz 1:4 spectrum. Not the IMD number but the frequency spectrum.

Second is pink spectrum no interharmonic distortion multitone. Pink spectrum means -20db/decade. No interharmonic means all signals are prime number.And these numbers are not spaced evenly. 10 sines are good enough.

Would love to see the measurements with these two signals.

File:
https://drive.google.com/open?id=1ikONePQwsxNCQ5WTufwRw0qXNloll9DP

 

[Okto Research]

Because I have not read all 16 pages of this thread, only Amir´s test report, I do not know if anyone have asked these questions and gotten an answer. I have sent these questions to Okto, but still no answer.
@Okto Research

We are currently late in replying to e-mails due to amount of messages we receive, so sorry for that.

I guess most of this forum readers would be US buyers, so...

"As with all electronics components, it is most likely that some units may malfunction eventually, due to abusive use or a manufacturing defect. Since your company is just launching and in Europe, how RMA´s would be handled? Will you have a repair shop in the US? How long is the warranty period? Will you service units after the warranty period? Have you estimated a cost of such service? If not a US repair shop, must all units be sent back to Prague for repair?"

And, would units shipping outside of Europe would undertake a more rigorous pre-shipping test to verify its functionality and operability?

@Okto Research

We build our products in-house and each one of them is rigorously tested before shipping. Our warranty period is 2 years and in case of a spontaneous malfunction, we are going to cover both the service and shipping cost. In case of a defect due to abusive use, the customer is going to cover both and the price will be negotiated individually in advance. We do not have a service or repair shop in the US at the moment, but we would like to establish one within several months.

 

[pos]

@Okto Research, any info you can share about the new functionalities you are implementing into the DAC8 PRO?

 

[rickyhgarcia]

We are currently late in replying to e-mails due to amount of messages we receive, so sorry for that.



We build our products in-house and each one of them is rigorously tested before shipping. Our warranty period is 2 years and in case of a spontaneous malfunction, we are going to cover both the service and shipping cost. In case of a defect due to abusive use, the customer is going to cover both and the price will be negotiated individually in advance. We do not have a service or repair shop in the US at the moment, but we would like to establish one within several months.

Thanks!!

 

[Swaroop]

Does this support DSD?

 

[Bliman]

It seems so quite in the thread. Has more people heard it by now and can they give their impression?
Also Okto Research, do you have a more precise time when the tour will start in Europe?
And is the Stereo Dac totally completed and is there anything different in the finalized form?
I am also curious if there will be more information on your site in the future?

 

[Okto Research]

It seems so quite in the thread. Has more people heard it by now and can they give their impression?
Also Okto Research, do you have a more precise time when the tour will start in Europe?
And is the Stereo Dac totally completed and is there anything different in the finalized form?
I am also curious if there will be more information on your site in the future?

We are working hard on DAC8 DSP deliveries, preparing the DAC8 PRO launch and designing DAC8 Stereo. I am unable to tell the timeline for DAC8 Stereo European tour at the moment, the PRO tour will take place before that.

Thank you for your patience.

Does this support DSD?

Yes.

@Okto Research, any info you can share about the new functionalities you are implementing into the DAC8 PRO?

You've got a PM.

 

[jtwrace]

You've got a PM.

How about you post here if there's new info?

 

[Bliman]

We are working hard on DAC8 DSP deliveries, preparing the DAC8 PRO launch and designing DAC8 Stereo. I am unable to tell the timeline for DAC8 Stereo European tour at the moment, the PRO tour will take place before that.

Thank you for your patience.


Yes.


You've got a PM.

First thanks for the answer. That's to bad because I have no preamplifier/dac in my system for a time now. I had hoped that the tour would start in May.
But now it seems that it must come first to Europe and the Dac8 Pro will be first, so that means a very long time waiting.
So you are still designing the Stereo Dac, what work must still be done?
I also see that the DSP is already unavailable on the website. Will there will be more information on the website about the products? Because you see we still have questions.

 

[Veri]

I also see that the DSP is already unavailable on the website. Will there will be more information on the website about the products? Because you see we still have questions.

Stereo is also unavailable, already went through pre-order availability. They are too busy with finalising their products and are getting a lot of attention online (surely in part due to Amir's rave review too).

You'll have to exert some patience Bliman!

 

[rickyhgarcia]

@Okto Research Any idea when the DAC8 Stereo be available for buy? Will this happen within this year?

 

[Veri]

@Okto Research Any idea when the DAC8 Stereo be available for buy? Will this happen within this year?

They told me this:

We expect to open pre-orders for DAC8 Stereo in about a month, which should be shortly before the product launch.
Thank you for your understanding,