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Review and Measurements of Okto DAC8 8Ch DAC & Amp

1234VICE

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@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.

Thanks, I have read the entire threat indeed. They mention that shorting the hot lead to the ground overloads the output stage causing distortion. I would hardly call this elaborate. They recommend a ~300 dollar Jensen solution that is unavailable in EU. Considering the serious limitations of transformer based isolators, and the mere recommendation by Oktoresearch, I felt it could be worthwhile to explore alternatives. I figured that more people would be interested in this.
 

g29

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Thanks, I have read the entire threat indeed. They mention that shorting the hot lead to the ground overloads the output stage causing distortion. I would hardly call this elaborate. They recommend a ~300 dollar Jensen solution that is unavailable in EU. Considering the serious limitations of transformer based isolators, and the mere recommendation by Oktoresearch, I felt it could be worthwhile to explore alternatives. I figured that more people would be interested in this.

Maybe I misread it, but my take was that by losing the differential outputs you are essentially polluting their clean signal and ground isolation model which defeats the performance gains that they engineered into their system design. Essentially asking the design to do exactly what it was designed not to do while maintaining the same stellar performance gains. Balanced amps are quite ubiquitous so their design choice is not out of the question. Coercing them to install isolation transformers would only unnecessarily drive up the cost of the unit for all customers (unless it was a modular option). For the price and performance range, I would assume customers have access to balanced amps for similar reasons.
 
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josh358

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Maybe I misread it, but my take was that by losing the differential outputs you are essentially polluting their clean signal and ground isolation model which defeats the performance gains that they engineered into their system design. Essentially asking the design to do exactly what it was designed not to do while maintaining the same stellar performance gains. Balanced amps are quite ubiquitous so their design choice is not out of the question. Coercing them to install isolation transformers would only unnecessarily drive up the cost of the unit for all customers (unless it was a modular option). For the price and performance range, I would assume customers have access to balanced amps for similar reasons.
This is always true of balanced vs. unbalanced. Someone with a limited budget or unbalanced gear may find that the performance degradation isn't significant enough to justify the cost of a transformer or buffer amp, both of which can themselves degrade the signal. If you've worked with balanced as opposed to unbalanced cables, you know that the latter are far more troublesome -- but ground lifters can work wonders. :) The benefits of a balanced cable really depend on your setup.
 

1234VICE

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I think you're elevating this into much more of an issue than it really is. Simply construct a cable with pin 3 floating or buy one. Job done.
https://benchmarkmedia.com/collecti...dapter-cable-pin-3-floating?variant=547761981

Dave.

Yes, this was my original question: can I simply leave the "-" disconnected (floating). As it seems to turn out that this indeed is the case, this is indeed a non-issue.

I suppose Oktoresearch recommends transformer based solutions, since this will avoid people from using incompatible cables. At the same time, this introduces another set of problems.
 

Twst

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Won't you loose half of the voltage when you leave half of the signal floating?
Depends on how much gain you need this might not be a problem.

With transformers you can even double up the gain if you need.
 

josh358

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OK, so I've spent several days now listening to the demo unit and thought I'd pass on my conclusions.

In a nutshell, this is a wonderful DAC at an amazing price, and I'm buying one. It almost equals the best DAC I have here, an Yggdrasil, which is twice the money for a quarter the channels and is frankly a hard act to follow, beating out even a $4000 DAC I had here. In fact, for the first half of my listening, I thought the Okto = would beat the Yggdrasil, and in the end, there were still some things it did better and some cuts as well.

All comparisons were level matched with a balanced A/B switch. I fed the Yggy from my Lynx E22 card, a slightly better source than my AES16e, and of course the demo version of the DAC8 is USB (but I'll be using it with the AES3 outputs of the AES16e, so hope they're as good as the USB one is). I usually triamp, but since my A/B switch has only two channels I went back to the passive crossover. I used my A21 rather than my AHB2 and the source was JRiver, using linked zones (damn, I wish JRiver would fix that feature) to feed the two DAC's.

The comparison was a challenging one, because there are so many filter options on the Okto. I had to familiarize myself with the sound of the filters first. That, though, was an interesting experience. I ended up preferring the linear phase apodizing filter, with the brick wall filter my least favorite -- which is curious, since they measure very similarly (in fact, it could be said that the apodizing filter measures worse since it has some probably inaudible ripple). Otherwise, overall, I found I preferred the linear phase filters, and the fast to the slow. It's hard to be absolutely sure, though, since you can only cycle through the choices, limiting A/B comparisons.

Anyone interested in how the various filters measure can check here:

http://archimago.blogspot.com/2019/02/measurements-look-at-hqplayer-325.html

A friend sent me that link after I'd listened and in retrospect, it seems I preferred the filters that had less high frequency garbage, and of course linear phase.

Once I'd settled on the apodizing filter, I used it for most of my comparisons. (Interestingly, piano was better on the Yggy with all filters but the apodizing filter, but better on the Okto with the apodizing filter.)

Anyway, overall, the main difference between the DAC's was in tonal balance. The Yggy had more midbass, and the Okto had more pronounced highs. I don't think that frequency response measurements account for this, since while the Yggdrasil has as I recall a downslope, it's very slight. (Though as I recall someone wrote a paper some years back claiming that such gradual slopes were responsible for perceived differences in the tonal balance of electronics.)

Unlike most of the other differences I noticed, this one was not subtle. As with every Sabre DAC I've listened to -- e.g., my Exasound e28 (ES9018), and the Exasound e38 Mk II that I had on trial here a few months ago (ES9038), the sound seemed hollowed out in the middle. It is a very light, bright, clean sound that's often exciting. However, at the top, it exhibits a high frequency emphasis, the infamous "Sabre glare." At its worst, violins and sopranos literally screeched (OK, screeched more than they usually do), and when that happened, switching to Yggdrasil was like running cold water over a burn.

That said, the Okto had its own virtues. It was cleaner on quiet passages (as was the Gungnir that I compared to the Yggy some months back), including chorus. It had more solid lateral imaging -- instruments were easier to pinpoint (I didn't notice much if any difference in depth). As I said, it was better on piano -- in general, the Okto had more pronounced attacks than the Yggy, perhaps because of the underdamped filters in ESS DAC's (which may be responsible too for the Sabre glare).

The Yggdrasil, on the other hand, was cleaner on orchestral climaxes. It had more and cleaner midbass, and of course less prominent highs. It also had more detail -- the Okto seemed to homogenize instrumental detail, so you'd hear the valve noise on an instrument through the Yggy but not on the same passage played through the Okto. (Based on experiments with HQPlayer, this may have to do with the closed form filter.) Curiously, it also had more reverberation than the Okto. I believe that I read a recording engineer say that when he tried a Benchmark (don't quote me on that) DAC in his studio, it stripped away the reverb. If so, there's an issue here.

The Okto sounded compressed and hard on massed strings -- not just violins, but violas as well. It had a slight layer of hardness overall.

I don't want to give the impression that these differences are huge. Except for the difference in the highs, which can be so pronounced you'd think someone had messed with tone controls, most were subtle. And I suspect that for many, the choice would be a matter of taste, other components, and the music you prefer.

Something that may not come through is that on some cuts, I prefered the Okto overall, and on others the Yggdrasil. I won't bore you with my nauseatingly exhaustive notes (will I ever even read them myself?), but I think some people would prefer one or the other on the basis of the music they listen to (I didn't listen to any rock but I did listen to some jazz and the Okto sounded great).

In the end, I preferred the Yggy for its rounder, glowing, more relaxed tone -- both because of subjective frequency balance and the lack of a slight hardness of the Okto. At essence, the music just sounded more real, and I found myself more and more inclined to keep that A/B switch on the Yggy side. So I'll be keeping the Yggy for the mid/tweet panels and using the Okto lower down. But hell, level matched A/B comparisons tend to show up things you'd never notice if you just sat down and listened -- the Okto is a wonderful DAC and if it weren't for the occasionally painful Sabre glare, I'd probably be selling the Yggy and vacationing in France. :)
 
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Snafu

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Thanks for the review. What speakers you have ?

Based on above Okto sounds better option for tube amps ?
 

MWC

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@josh358 Did you audition any DSD in the Okto. Were you testing with CD only or any Hi Res formats?
 
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Twst

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Isn't the Yggdrasil the one with SINAD of 86?

My DAC8 DSP does not sound compressed, having anything like a glare or a hardness.

Maybe the Schiit mask out some faults in playback :)
 

g29

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Isn't the Yggdrasil the one with SINAD of 86?

My DAC8 DSP does not sound compressed, having anything like a glare or a hardness.

Maybe the Schiit mask out some faults in playback :)

@Twst , what tweeters are you running ?
 

josh358

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Thanks for the review. What speakers you have ?

Based on above Okto sounds better option for tube amps ?
Tympani IVA's, modified with a new Neo 8 midrange. I think it's important because the Maggie true ribbon is on the bright side, and of course very revealing -- as are the Neo 8's. So it would tend to emphasize the Sabre glare. Whereas tubes might potentially have the opposite effect. But I don't know how to extrapolate -- there are so many variables here, not just your electronics but your speakers, the kind of music you listen to, your room, and even you. I'd say that if you want your system to sound brighter and more alive, the Okto will suit you perfectly, while if you want it to sound more "analog" or "tubey," a good ladder DAC like the Yggy or Gungnir would be better. But also that the Okto tended to be better on *simpler* music -- a few instruments or voices -- while the Yggy came into its own on large scale music like orchestra. So the kind of music you listen to also matters a lot.

Really, the only way to know for sure whether it suits you is to get it on loan and listen. This loan program is great.
 

Twst

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@Twst , what tweeters are you running ?

Usually B&C DE120 - but right now I am giving the Faital Pro HF108R a go in the STH100.

The Okto gives me whats in the recording without messing with the dynamics or anything else.
If one gets a hardness or glare, my guess it's coming from elsewhere in the playback/acoustics and not from the DAC.
This should in my opinion not be "resolved" with tube gear. One would be better off finding the cause in the first place.
 

josh358

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@josh358 Did you audition any DSD in the Okto. Where you testing with CD only or any Hi Res formats?
I tested mostly 44.1, since it's the hardest to reproduce. But I still have the unit. I disconnected the A/B switch and biamped it -- sounds amazing -- and I'm hoping to try more high res and DSD as well, which supposedly works very well on the Sabre DAC's. At least I'll try, because I'm doing the XO's in JRiver and you can't use the DSP with DSD, so I'd have to implement the XO's in Roon and put it through HQ Player for upsampling. I'll report back if I can get it done in time -- I told Pavel I was done on Friday, so when I hear back from him I'll have to pack it up.
 

josh358

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Isn't the Yggdrasil the one with SINAD of 86?

My DAC8 DSP does not sound compressed, having anything like a glare or a hardness.

Maybe the Schiit mask out some faults in playback :)
The Schiit is actually more transparent than the DAC8.

To hear most of these differences, you will have to do what I did -- level match the units and A/B switch them, listening to a wide variety of program material. As I said, most of the differences are subtle. Only the subjective tonal balance isn't. I was afraid when I wrote this that when people heard a word like "compressed," they would think in terms of something *obvious* rather than something *subtle* that one hears in a level-matched A/B session. If you heard the Okto on its own, you wouldn't think "compressed." In fact, overall, I find it has a very lively, exciting presentation. It sounds compressed and hard on massed strings.

The SINAD of 86 is interesting if you're concerned about things that a bat in the middle of Antarctica couldn't hear on a windless day, like 60 Hz hum at -120 dB. Most decent DAC's these days are very, very good, with noise and distortion below the threshold of hearing, so not infrequently, measurements compare the inaudible to the inaudible. Remember that at best we can hear something like -10 dB SPL in the midrange, and something like 10 dB into the room noise (which is a lot higher than 0 dB SPL). Something like hum at -120 dB is *way* below the threshold of what we can hear.

BTW, I definitely considered the possibility that the Schiit was too dead at the top and the ESS dacs are right. I have no way of knowing for sure, except the fact that ESS DAC's (and to a lesser extend any multibit delta-sigma DAC) have a general reputation for being bright and have sounded that way wherever I've heard them. If I had a good analog source, I could convert it and compare the analog to output of the Okto, but sadly, those days are passed, since it would be really interesting. What I can say is that the Schiit DAC sounds more natural in my system with the kind of recording I listen to, which is why I think you have to try various DAC's to know what works best for you.
 
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josh358

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You should take look at the numbers again making a statement like that :)

How did you level match the outputs?
You should take look at the numbers again making a statement like that :)

How did you level match the outputs?
Level matching was in JRiver, and I should have mentioned that, because it was an obvious shortcoming in my methodology -- the converters were working in a different part of their range, though not I think significantly so, since they're both spec'd at 4V maximum output. And of course the analog circuitry had the same levels.

Also, I didn't really stress the analog circuits as I have no multichannel analog preamp so full output would have been deafening!
 

Bliman

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OK, so I've spent several days now listening to the demo unit and thought I'd pass on my conclusions.

In a nutshell, this is a wonderful DAC at an amazing price, and I'm buying one. It almost equals the best DAC I have here, an Yggdrasil, which is twice the money for a quarter the channels and is frankly a hard act to follow, beating out even a $4000 DAC I had here. In fact, for the first half of my listening, I thought the Okto = would beat the Yggdrasil, and in the end, there were still some things it did better and some cuts as well.

All comparisons were level matched with a balanced A/B switch. I fed the Yggy from my Lynx E22 card, a slightly better source than my AES16e, and of course the demo version of the DAC8 is USB (but I'll be using it with the AES3 outputs of the AES16e, so hope they're as good as the USB one is). I usually triamp, but since my A/B switch has only two channels I went back to the passive crossover. I used my A21 rather than my AHB2 and the source was JRiver, using linked zones (damn, I wish JRiver would fix that feature) to feed the two DAC's.

The comparison was a challenging one, because there are so many filter options on the Okto. I had to familiarize myself with the sound of the filters first. That, though, was an interesting experience. I ended up preferring the linear phase apodizing filter, with the brick wall filter my least favorite -- which is curious, since they measure very similarly (in fact, it could be said that the apodizing filter measures worse since it has some probably inaudible ripple). Otherwise, overall, I found I preferred the linear phase filters, and the fast to the slow. It's hard to be absolutely sure, though, since you can only cycle through the choices, limiting A/B comparisons.

Anyone interested in how the various filters measure can check here:

http://archimago.blogspot.com/2019/02/measurements-look-at-hqplayer-325.html

A friend sent me that link after I'd listened and in retrospect, it seems I preferred the filters that had less high frequency garbage, and of course linear phase.

Once I'd settled on the apodizing filter, I used it for most of my comparisons. (Interestingly, piano was better on the Yggy with all filters but the apodizing filter, but better on the Okto with the apodizing filter.)

Anyway, overall, the main difference between the DAC's was in tonal balance. The Yggy had more midbass, and the Okto had more pronounced highs. I don't think that frequency response measurements account for this, since while the Yggdrasil has as I recall a downslope, it's very slight. (Though as I recall someone wrote a paper some years back claiming that such gradual slopes were responsible for perceived differences in the tonal balance of electronics.)

Unlike most of the other differences I noticed, this one was not subtle. As with every Sabre DAC I've listened to -- e.g., my Exasound e28 (ES9018), and the Exasound e38 Mk II that I had on trial here a few months ago (ES9038), the sound seemed hollowed out in the middle. It is a very light, bright, clean sound that's often exciting. However, at the top, it exhibits a high frequency emphasis, the infamous "Sabre glare." At its worst, violins and sopranos literally screeched (OK, screeched more than they usually do), and when that happened, switching to Yggdrasil was like running cold water over a burn.

That said, the Okto had its own virtues. It was cleaner on quiet passages (as was the Gungnir that I compared to the Yggy some months back), including chorus. It had more solid lateral imaging -- instruments were easier to pinpoint (I didn't notice much if any difference in depth). As I said, it was better on piano -- in general, the Okto had more pronounced attacks than the Yggy, perhaps because of the underdamped filters in ESS DAC's (which may be responsible too for the Sabre glare).

The Yggdrasil, on the other hand, was cleaner on orchestral climaxes. It had more and cleaner midbass, and of course less prominent highs. It also had more detail -- the Okto seemed to homogenize instrumental detail, so you'd hear the valve noise on an instrument through the Yggy but not on the same passage played through the Okto. (Based on experiments with HQPlayer, this may have to do with the closed form filter.) Curiously, it also had more reverberation than the Okto. I believe that I read a recording engineer say that when he tried a Benchmark (don't quote me on that) DAC in his studio, it stripped away the reverb. If so, there's an issue here.

The Okto sounded compressed and hard on massed strings -- not just violins, but violas as well. It had a slight layer of hardness overall.

I don't want to give the impression that these differences are huge. Except for the difference in the highs, which can be so pronounced you'd think someone had messed with tone controls, most were subtle. And I suspect that for many, the choice would be a matter of taste, other components, and the music you prefer.

Something that may not come through is that on some cuts, I prefered the Okto overall, and on others the Yggdrasil. I won't bore you with my nauseatingly exhaustive notes (will I ever even read them myself?), but I think some people would prefer one or the other on the basis of the music they listen to (I didn't listen to any rock but I did listen to some jazz and the Okto sounded great).

In the end, I preferred the Yggy for its rounder, glowing, more relaxed tone -- both because of subjective frequency balance and the lack of a slight hardness of the Okto. At essence, the music just sounded more real, and I found myself more and more inclined to keep that A/B switch on the Yggy side. So I'll be keeping the Yggy for the mid/tweet panels and using the Okto lower down. But hell, level matched A/B comparisons tend to show up things you'd never notice if you just sat down and listened -- the Okto is a wonderful DAC and if it weren't for the occasionally painful Sabre glare, I'd probably be selling the Yggy and vacationing in France. :)
Thanks for the review.
To me that seems pretty negative. I hate pronounced highs and glare and exhausting listening. That's why I sold my Unison Research Unico amplifier. And there were more negative things it seems. A bit sad to read this.
 

Twst

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DAC8 tour unit is 3.3V output, isn't it?
And the Schiit is specced at 4.2V - so I guess they wasn't level matched after all. :)
 

Bliman

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Usually B&C DE120 - but right now I am giving the Faital Pro HF108R a go in the STH100.

The Okto gives me whats in the recording without messing with the dynamics or anything else.
If one gets a hardness or glare, my guess it's coming from elsewhere in the playback/acoustics and not from the DAC.
This should in my opinion not be "resolved" with tube gear. One would be better off finding the cause in the first place.
Do you have clutter? Like things are not so good when the music gets complex? Because these for me are pretty negative points. Screeching sound, piercing highs and then clutter when music get's complex. To me that is critical because I listen to music that can get very complex.
 
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