Okto 8 Owner’s Thread

[Zooqu1ko]

The following actions do NOT trigger a change in delay:

-Soft powering down Okto with remote (I believe this is more of standby mode as Okto remains visible to a computer)
-Changing DSP configuration
-Changing DSP inputs

Have you contacted Pavel with those findings?

I have also been doing a bit of experimenting with a nanoDIGI as it is a low cost option with 8 channels of digital output. Unfortunately it only has coaxial SPDIF outputs so it will not interface directly with the Okto's AES inputs. At first I tried using 6 ft long RCA to XLR cables from monoprice. This worked well for up to 4 channels of output from the nanoDIGI but if more channels of output are used there is significant noise / crackling. I also tried using 1.5 ft RCA to BNC cables to Neutrik NADITBNC-M transformers to 3 ft AES cables. In this configuration I could use up to 6 channels of output with no issue but if I tried to use all 8 channels I would get noise / crackling. I did not have any shorter cables to try and I wonder if I could use all 8 channels with shorter cables. In any event for applications that require 6 channels of output the nanoDIGI is a great low cost option for the Okto.l

The number of channels used should not impact the signal quality. Your cable lengths should be perfectly fine; AES should work reliably over 360m. SP/DIF on the other hand is "officialy" designed for just 1m, but I haven't encountered any problems with 5m cables. Are you using proper 75 Ohm cables on the SP/DIF side?

How frequent is the noise/crackling? Does it occur on all channels? The Okto DAC's manual states that it requires the inputs to be mutually synchronized and carry signals with matching sampling rates. Does the nanoDIGI guarantee that? Do you have any 8 channel SP/DIF sources other than the nanoDIGI?

I've bought Canare bcj-xp-trb transformers specifically so that I can avoid the extra AES cable(s), but I haven's tested more than 2 channels at the same time yet.

 

[mdsimon2]

Have you contacted Pavel with those findings?

Yes. 2 weeks ago, no response. To be fair to Pavel I did not threaten to return the unit because I was able to work around the delays but did ask if he had seen the issue before and if a firmware update could fix it (or at least make the delays consistent).

The number of channels used should not impact the signal quality.

I agree with this in principal but clearly there is something occurring with the nanoDIGI + Okto combination. Feels to me that it is impedance mismatch related as the transformers improve performance.

Are you using proper 75 Ohm cables on the SP/DIF side?

There is no such thing as a RCA plug with 75 ohm characteristic impedance. That being said I am using a RG6 cable which has a characteristic impedance of 75 ohms and a 75 ohm BNC connector. The exact cables I am using are linked below.

https://www.bhphotovideo.com/c/product/1053971-REG/kopul_vrbc_401_bnc_male_to_rca.html

How frequent is the noise/crackling? Does it occur on all channels? The Okto DAC's manual states that it requires the inputs to be mutually synchronized and carry signals with matching sampling rates. Does the nanoDIGI guarantee that? Do you have any 8 channel SP/DIF sources other than the nanoDIGI?

The noise is a popping / crackling that occurs every few seconds. It never occurs on Okto channels 1-2 but occurs on all other channels. I've tried routing different channels from the nanoDIGI to the Okto but the results are the same, whatever is routed to channel 1-2 of the Okto is fine and the other channels have noise. That being said there is definitely some interaction with the DSP here. With everything set to flat the crackling does not occur as often as when crossovers / EQ are applied.

The nanoDIGI operates at a constant 96 kHz sample rate (ASRC on input). I do not have any other 8 channel SPDIF sources besides the nanoDIGI. As I mentioned the nanoDIGI was not intended to be my primary DSP (I prefer the SHARC as it has much more power and 3 inputs with the DIGI-FP) and am really just trying this out as an experiment.

Tonight I will try routing channels 1-4 to the Okto and channels 5-8 to other DACs, will be interesting to see what happens. Prior to this I had never used all 8 channels of the nanoDIGI, it certainly is possible that the nanoDIGI is defective.

I am very interested if anyone has successfully used 8 channels of output from a nanoDIGI with the Okto dac8 pro.

I've attached some measurements to add to the discussion. The frequency response sweep shows the difference in noise when no DSP is applied (brown) and when DSP is applied (green), both cases have 8 channels of output from the nanoDIGI. Clearly DSP has an adverse effect. I've also attached 1 kHz FFTs showing 6 channels vs 8 channels of output with no DSP applied. There is clearly a huge step change in noise when adding those 2 extra channels.

Michael

 

[Zooqu1ko]

There is no such thing as a RCA plug with 75 ohm characteristic impedance. That being said I am using a RG6 cable which has a characteristic impedance of 75 ohms and a 75 ohm BNC connector. The exact cables I am using are linked below.

https://www.bhphotovideo.com/c/product/1053971-REG/kopul_vrbc_401_bnc_male_to_rca.html

That should certainly be good enough for short runs.

The noise is a popping / crackling that occurs every few seconds. It never occurs on Okto channels 1-2 but occurs on all other channels. I've tried routing different channels from the nanoDIGI to the Okto but the results are the same, whatever is routed to channel 1-2 of the Okto is fine and the other channels have noise. That being said there is definitely some interaction with the DSP here. With everything set to flat the crackling does not occur as often as when crossovers / EQ are applied.

I would conclude from that that the Okto derives its clock from channel 1-2, and the signal that arrives on the other channels isn't "good enough" when decoded with that exact clock. If you have a multichannel oscilloscope, you could try to check the timing yourself.

Tonight I will try routing channels 1-4 to the Okto and channels 5-8 to other DACs, will be interesting to see what happens. Prior to this I had never used all 8 channels of the nanoDIGI, it certainly is possible that the nanoDIGI is defective.

It could be defective, or just not compatible with the requirements of the Dac8. If you have enough BNC T pieces (and cables), you could try connecting to all 4 AES/EBU inputs of the Okto to a single output of the nanoDIGI. That should result in pretty crappy signal quality, but essentially identical signal timing on all ports. If that works without crackling, that would point to the nanoDIGI as the cause of your problems.

Have you considered @fabriceo's alternative firmware for the Okto? He might also be interested in the the 1 sample offset problem.
https://www.audiosciencereview.com/...kto-dac8-8ch-dac-amp.7064/page-89#post-536652

 

[mdsimon2]

That should certainly be good enough for short runs.

I would conclude from that that the Okto derives its clock from channel 1-2, and the signal that arrives on the other channels isn't "good enough" when decoded with that exact clock. If you have a multichannel oscilloscope, you could try to check the timing yourself.

Yes, Pavel confirmed that all clocks are synced off of the first AES input in the thread below.

https://www.diyaudio.com/forums/vendor-s-bazaar/331847-okto-research-dac8-pro-dac8-stereo-3.html

Did a bit more experimenting tonight. First tried to route channels 1-4 from the nanoDIGI to the Okto and then routed channels 5-8 from the nanoDIGI to other DACs. In this configuration there was no noise on any channel. I also tried channels 1-6 on the Okto and channels 7-8 on another DAC, again no noise issues.

I also tried your suggestion of using a single nanodigi output split 4 ways in to the Okto. I did not have any BNC tees so I attempted this with RCA splitters in to RCA to BNC adapters. Again if I only used 6 channels of output this was fine but if I used all 8 channels I got noise.

Not sure of what to make of all this other than it seems like the Okto and the nanoDIGI do not play nice with 8 channels of output, if anyone has a different experience please let us know!

At this point I am switching back to the miniSHARC and moving on from the nanoDIGI.

Michael

 

[jtwrace]

Does anyone know if the dac8 Pro will work with a RPi4 running RoPieeeXL? Or even any other USB Bridge for Roon? Okto doesn't respond to emails still.

 

[Machismo]

I hope the problem with the nanodigi is fixed by the time I get mine. I could buy something else too, if I would know what would have 8 channels and similar functions? Even if the price would be high.

 

[mdsimon2]

I hope the problem with the nanodigi is fixed by the time I get mine. I could buy something else too, if I would know what would have 8 channels and similar functions? Even if the price would be high.

I purchased some cheap 75 ohm to 110 ohm BNC/AES transformers with male XLR outputs to see if I can get the nanodigi to work with short RCA to BNC cables (no AES cables). They should be here this weekend and I will report back.

I get the impression not many people are using the AES inputs on this DAC and most are using USB. As far as DSP options that are known to work:

1) DDRC-88D (have not personally tested this but it has AES outputs and was recommended by Pavel)
2) DIY miniSHARC + 4x AES out (this definitely works as I have tested it)
3) Software DSP in a computer using Pure USB mode

I am curious if anyone else has experience with 8 channel hardware DSP. I imagine there are some pro audio pieces that would work but I am not very familiar with that world.

Michael

 

[Burning Sounds]

I purchased some cheap 75 ohm to 110 ohm BNC/AES transformers with male XLR outputs to see if I can get the nanodigi to work with short RCA to BNC cables (no AES cables). They should be here this weekend and I will report back.

I get the impression not many people are using the AES inputs on this DAC and most are using USB. As far as DSP options that are known to work:

1) DDRC-88D (have not personally tested this but it has AES outputs and was recommended by Pavel)
2) DIY miniSHARC + 4x AES out (this definitely works as I have tested it)
3) Software DSP in a computer using Pure USB mode

I am curious if anyone else has experience with 8 channel hardware DSP. I imagine there are some pro audio pieces that would work but I am not very familiar with that world.

Michael

I tried my Nanodigi briefly with my Okto DAC8 PRO using Neutrik 75/110 ohm transformers and can't remember hearing anything untoward. I'll dig it out and give it another go and let you know what I find.

 

[mdsimon2]

I tried my Nanodigi briefly with my Okto DAC8 PRO using Neutrik 75/110 ohm transformers and can't remember hearing anything untoward. I'll dig it out and give it another go and let you know what I find.

Thanks, that would be great. What I am experiencing is very audible / measurable but again only occurs when all 8 channels are in use.

Which Neutrik transformers are you using, NADITBNC-MX or NADITBNC-M? What cables are you using and what length?

Michael

 

[Matt 5fe1]

Thanks, that would be great. What I am experiencing is very audible / measurable but again only occurs when all 8 channels are in use.

Which Neutrik transformers are you using, NADITBNC-MX or NADITBNC-M? What cables are you using and what length?

Michael

Michael,

In response to your AES input point...This might not be much help as I'm a newb and the DAC's still in the post (order #259) - but I do have a Xilica XD4080 dsp/xo and plan to feed 8xAES channels into the DAC8.

I have been using a rpi4B with an AES hat into the Xilica with outs set to analogue into to 2 subs and 3way mains.

So, this may not be relevant but I got a nasty crack (like a whip) changing tracks on the Pi - to do with zero voltage rather than an empty signal which gives a voltage spike when the signal restarts. Various things made it better or worse like resampling, or keeping the player output high and the dsp volume low etc. I managed to fry the hat, so use the HDMI out into a £16 Amazon basics SPDIF converter into the Xilica AES through a made up 110 ohm AES lead. I didn't want to spend anything on a USB decoder given the DAC will arrive any minute now (hint Pavel and the cheapest decoder was the HDMI. The cracking seems to have gone so I'm hoping it wont be there on the USB either.

My intention is to feed RPi USB into the DAC8 in hybrid mode, and the 2xAES outs into the dsp and output 8x AES back into the DAC8. I have been told that the AES out in hybrid is cleaner than the USB feed, but also read elsewhere the noise or jitter doesnt affect a dsp, only a DAC.

I don't know if it makes any difference but I used one lead for 2 AES input channels - it might be worth trying that if you are using one lead per channel (if that's even possible).

Once I get the Okto I'll update

 

[Burning Sounds]

Well, this is interesting - I'm now getting the same problem as you described. Long or short cables makes no difference (as it shouldn't).

I tried my Nanodigi with Okto DAC8 PRO just after I first got it - probably about February last year and it was fine on all 8 channels as I have 4-way actives. Here's what I posted some time later in response to a question about using the Nanodigi and the Okto:

https://www.audiosciencereview.com/...kto-dac8-8ch-dac-amp.7064/page-70#post-382567

So, something has changed on my unit and the only thing that comes to mind that would cause this is a firmware update from a few months ago.

What firmware are you on?

 

[mdsimon2]

Well, this is interesting - I'm now getting the same problem as you described. Long or short cables makes no difference (as it shouldn't).

I tried my Nanodigi with Okto DAC8 PRO just after I first got it - probably about February last year and it was fine on all 8 channels as I have 4-way actives. Here's what I posted some time later in response to a question about using the Nanodigi and the Okto:

https://www.audiosciencereview.com/...kto-dac8-8ch-dac-amp.7064/page-70#post-382567

So, something has changed on my unit and the only thing that comes to mind that would cause this is a firmware update from a few months ago.

What firmware are you on?

1.42 on the Okto and 2.04 on the nanoDIGI.

Michael

 

[Burning Sounds]

Yes, I'm on 1.42 also. I think when I tested it before I was on 1.32.

Looking through the original Okto DAC8 thread there were a few people using the AES inputs from different devices and I can't see any reported problems. They would have been on an earlier firmware too.

 

[DWPress]

I got the call from US customs this morning! Order #222 for a DAC8PRO could be here tomorrow!

 

[mdsimon2]

I purchased some cheap 75 ohm to 110 ohm BNC/AES transformers with male XLR outputs to see if I can get the nanodigi to work with short RCA to BNC cables (no AES cables). They should be here this weekend and I will report back.

The Canare BCJ-XP-TRB transformers I purchased arrived yesterday. Unlike the Neutrik NADITBNC-M transformers I used previously these can be used directly in to the Okto's AES inputs with no AES cable. Performance with the nanoDIGI was improved compared to the Neutrik transformers but there was still the occasional pop when using all 8 channels.

It is interesting that previous firmware versions seemed to not have this problem. I am definitely out of my area of expertise but in Amir's original review of the DAC8 it looks like you could change the DPLL bandwidth, I wonder if the recent firmware updates default to a lower bandwidth that doesn't play nice with the nanoDIGI. Any thoughts @Okto Research , @fabriceo?

Michael

 

[Mashuri]

I got the call from US customs this morning! Order #222 for a DAC8PRO could be here tomorrow!

Did you get your Dac8? Mine is order #223 and it's still shown as "Processing"

 

[DWPress]

Did you get your Dac8? Mine is order #223 and it's still shown as "Processing"

I received mine last Friday after it languished in customs for 2 days. I got a call from customs asking what it was - mostly to clarify that there were no wooden components strangely enough. Once I explained what a DAC was and there was probably one in their pocket I received it 2 days later via FedEx.

To be clear, mine was a DAC8PRO and not a stereo version. Hope your delivery resolves itself quickly!

 

[phoenixdogfan]

I received mine last Friday after it languished in customs for 2 days. I got a call from customs asking what it was - mostly to clarify that there were no wooden components strangely enough. Once I explained what a DAC was and there was probably one in their pocket I received it 2 days later via FedEx.

To be clear, mine was a DAC8PRO and not a stereo version. Hope your delivery resolves itself quickly!

Did you have to pay any Duty or Brokerage fees and the like?

 

[DWPress]

Did you have to pay any Duty or Brokerage fees and the like?

No extra fees involved.

 

[dualazmak]

In my case when I received DAC8PRO in Japan in May 2020, FedEx send me an invoice of Custom Handling Charge (Jpn Yen 1,000) plus Local Consumption/Sales Tax (Jpn Yen 6,700) two months later, and I paid it by my credit card... The total amount was Jpn Yen 7,700, ca. USD 71. Of course, these charges vary country to country.