Review and Measurements of Okto DAC8 8Ch DAC & Amp

[Bliman]

You don't understand me... Did you have 230v fuse ? I do not see any connection of the GND to the earth at IEC-230Vac. Mechanical switch on-off, fuse on live 230Vac and earthed signal ground are mandatory for CE regulation. The only one which is ok in Okto DAC is the chassis earthed. Take care with the CE regulation because it's not a joke.

I have spoken to Pavel. And he said they will have the CE label just like their other products.

 

[josh358]

So what is going on with the Domestic demo tour ?

There should be a couple more demo tour reports by now, but it has been radio silence.

Is the tour still active ?

Yep, I have it now, and while I still have more listening to do, I can tell you that I'm impressed! I've had $3000 DACs here that don't sound as good.

BTW, if anyone has the three missing screws, please let Pavel know.

 

[Zog]

BTW, if anyone has the three missing screws, please let Pavel know.

Have you been talking to my wife?

 

[josh358]

Have you been talking to my wife?

LOL

 

[Feyire]

Yep, I have it now, and while I still have more listening to do, I can tell you that I'm impressed! I've had $3000 DACs here that don't sound as good.

The Pro or Stereo?

If its the Stereo version, do you know of the additional extras and improvements Pavel talked about making to it before general release? I'm assuming that the current delay is partially due to this?

 

[Bliman]

I don't know if he would rather say it for himself here but Pavel told me that the first stereo dac units will be ready in a month. And that one would go on tour right away. I don't know anything about the extra features.

 

[josh358]

The Pro or Stereo?

If its the Stereo version, do you know of the additional extras and improvements Pavel talked about making to it before general release? I'm assuming that the current delay is partially due to this?

It was the pro version, so I only know about the coming improvements to that -- off the top of my head, AES/EBU inputs and a more robust cover.

 

[g29]

...

Jun 29, 2019

Well, not this month after all. But soon after the DAC8 PRO launch which is planned for 2-3 weeks from now.

....

@Okto Research

What is the latest ETA on the DAC8 PRO launch ?
When will production units be shipping ?

 

[1234VICE]

They both do the same - short one of the signal conductors to ground. This would overload the output stage and cause distortion.

I have been looking for a suitable transformer based signal isolator for XLR -> RCA, but I have been noticing a couple of issues with them in different magnitudes

1. They cause non-linear distortion
2. They are (really) expensive
3. They (easily) saturate (clipping)
4. They might be locally unavailable (Jensen in EU)
5. They cause linear distortion
6. There can be (EM shielding?) performance degradation with cable length (most manufacturers do not mention anything about this though)
7. In general is is unclear whether the XLR -> XLR type isolators support XLR -> RCA cables (I am not knowledgeable on electrical engineering, perhaps this is obvious)

For instance, I have noticed somebody recommending a neutrik offering, but this device does not seem to handle professional signal levels. You really get what you pay for; I would not recommend this device without a high pass filter.

In this context, I was wondering whether there are other solutions, specifically

1. Are there active circuits/units for this?
No clipping, and must be cheap considering that even some cheaper amplifiers feature balanced inputs. I have not been able to find anything yet online.

2. Could I simply make a XLR to RCA cable where I do not short circuit one of the hot leads to the ground?
I cannot find this easily on google why shorting is necessary (again; I have no clue about electrical engineering). Thus, wire; ground -> ground, "+" -> "+" (leave "-" unconnected).

Another question; how bad it would be to overload the output stage of the DAC8 to begin with? Will this affect all channels? How much distortion are we talking about, considering that a transformer based isolator will also raise THD by orders of magnitude?

I will be using XLR -> RCA for subwoofers, and my stance in this is that I don't want to worry about clipping (render it absolutely impossible). So the current outlook is to buy the highest input rated transformer based coupler [Volt Second], apply a very steep FIR high pass filter at 10 Hz, and take care of the rest by lowering the volume on these DAC channels. The downside is that too much volume reduction will require me to reduce volume on other channels as well, and I expect this filter to induce large time delay.

I am curious about your thoughts. My apologies for the lengthy message.

 

[nm4711]

1. Are there active circuits/units for this?
No clipping, and must be cheap considering that even some cheaper amplifiers feature balanced inputs. I have not been able to find anything yet online.

There are circuits. Look at the Balanced Line Receiver here:
https://sound-au.com/project87.htm
and here:
https://sound-au.com/project87.htm

2. Could I simply make a XLR to RCA cable where I do not short circuit one of the hot leads to the ground?
I cannot find this easily on google why shorting is necessary (again; I have no clue about electrical engineering). Thus, wire; ground -> ground, "+" -> "+" (leave "-" unconnected).

(This will not work. The potential difference is between + and -. The potential between + and gnd could be anything. I guess you wont get any sound when doing this.)
Edit: Thats only true for floating Outputs. My fault. For other balanced outputs it should work.

 

[Snafu]

Is there any problems with "numbers" pairing Octo DACstereo with Denafrips Hestia pre amp ? They would be paired to tube monoblocks & speakers. Hestia has XLR in and RCA (and XLR) out for monoblocks that have just RCA in.

Denafrips Hestia specs:
https://www.denafrips.com/specs-hestia-hyperion

Thanks & cheers

 

[1234VICE]

This will not work. The potential difference is between + and -. The potential between + and gnd could be anything. I guess you wont get any sound when doing this.

Thanks for the reply, I assumed that xlr +/- were defined versus the ground, thanks for clearifying this.

Another wild idea for wiring xlr to rca: leave the receiving end ungrounded, and connect xlr "+" to rca hot, and xlr "-" to rca ground. The reasoning here is that if the receiving end is ungrounded at the power grid, connecting the "-" to the rca jacket should not cause a short circuit.

Could this work? I suppose I should buy an impedance meter, to check the impedance of the rca jacket in this configuration.

 

[Deleted member 2944]

There are circuits. Look at the Balanced Line Receiver here:
https://sound-au.com/project87.htm
and here:
https://sound-au.com/project87.htm


This will not work. The potential difference is between + and -. The potential between + and gnd could be anything. I guess you wont get any sound when doing this.

That's just nonsense. That scheme most likely will work, in most cases.
Most gear is designed to tolerate the short-circuit placed on the "-" output if switching to an unbalanced interface, so it will probably work with either scheme. However, the output scheme of any piece of equipment should be checked first.
A lot of pro gear is, in fact, constructed to sense that "-" short circuit and adjust the other polarity upward in gain by 6db to compensate.

Dave.

 

[1234VICE]

Most gear is designed to tolerate the short-circuit placed on the "-" output if switching to an unbalanced interface.

I am really hoping that this will be one of the modifications to the latest iteration of the dac8. In an ideal world, every piece of equipment has balanced inputs. For now, the lack of proper compatibility with rca is a serious limitation for this prosumer device IMO.

 

[nm4711]

That's just nonsense. That scheme most likely will work, in most cases.
Most gear is designed to tolerate the short-circuit placed on the "-" output if switching to an unbalanced interface, so it will probably work with either scheme. However, the output scheme of any piece of equipment should be checked first.
A lot of pro gear is, in fact, constructed to sense that "-" short circuit and adjust the other polarity upward in gain by 6db to compensate.

Dave.

You are Right. Thanks for correcting me. I edited my post.

 

[nm4711]

Thanks for the reply, I assumed that xlr +/- were defined versus the ground, thanks for clearifying this.

I was wrong. My version is only true for floating outputs. For other outputs +/- are defined vs GND. Sorry for misinforming you.

 

[1234VICE]

I was wrong. My version is only true for floating outputs. For other outputs +/- are defined vs GND. Sorry for misinforming you.

This still makes me wonder why by default "-" and ground are shorted for xlr -> rca adapter. But based in this information, I will simply solder my own that only connect ground -> ground and "+" -> "+". This is a much better prospect than the transformer based isolators.

 

[Deleted member 2944]

This still makes me wonder why by default "-" and ground are shorted for xlr -> rca adapter. But based in this information, I will simply solder my own that only connect ground -> ground and "+" -> "+". This is a much better prospect than the transformer based isolators.

Because that's a wiring configuration that should work in all applications. If pin 3 was left floating and you hooked that cable to a transformer-coupled output you'd have a problem.
Also, if done correctly, the "-" shorting connection is pulled all the way back to the XLR (source) connector vice being tied locally at the RCA connector. Depending upon the type of cable used, that might be preferable. If using standard coax, that's not an issue, because it can't be wired that way.

A cable setup like this is not really a preferable configuration, regardless. With some gear you might lose channel-matching because of component tolerances in the analog output stages that come into play.

Dave.

 

[1234VICE]

A cable setup like this is not really a preferable configuration, regardless. With some gear you might lose channel-matching because of component tolerances in the analog output stages that come into play.

Dave.

Thank you for elaborating. It now indeed makes sense that "-" and ground are shorted from a general compatibility point of view.

As a layman, I find it challenging to follow this discussion on a technical level. Are you advising against the wiring scheme that I am proposing, for it might not work as intended? Specifically, it could cause channel imbalance? If "+" and "-" are defined with respect to the ground, I find it hard to imagine how.

I suppose I will await the release of the user manual, and as appropriate contact Oktoresearch directly. It has been a very interesting discussion though, all of this has been much appreciated.

 

[g29]

Thank you for elaborating. It now indeed makes sense that "-" and ground are shorted from a general compatibility point of view.

As a layman, I find it challenging to follow this discussion on a technical level. Are you advising against the wiring scheme that I am proposing, for it might not work as intended? Specifically, it could cause channel imbalance? If "+" and "-" are defined with respect to the ground, I find it hard to imagine how.

I suppose I will await the release of the user manual, and as appropriate contact Oktoresearch directly. It has been a very interesting discussion though, all of this has been much appreciated.

@1234VICE ,

If you read through this thread, you will see OKTO Research has addressed these questions multiple times already. They do NOT recommend single ended to XLR conversions unless transformer based adapters are used (they even recommend some models). They also explain the technical reasons for their decisions. Based on their public statements, doing something contrary to the manufacturer's recommendations puts the subsequent "results and ramifications" squarely on the user. If you haven't already read their responses posted in this thread, it might worth the time to answer your questions.