[Hantra]

This is where the Measurements Are Bullshit crowd suddenly does an about face and gets ultra objective and starts splitting hairs over connection procedure and other infinitesimal nonsense.

Nahh dude. . .  It IS measurable what you're doing by using a "Y" on a digital connection.  AND it's audible.  You can have it either way. . .

It's just a bad idea.  That's all I'm saying. . .

[Rob Babcock]

If using a Y on the digital harmed the sound, wouldn't it harm it equally and identically with both units?  If so, the result should still be relevant.  It may not be the ideal way to do it, but it probably is the neatest way.

[Hantra]

If using a Y on the digital harmed the sound, wouldn't it harm it equally and identically with both units? If so, the result should still be relevant.

Rob:

Sorry, but this is just plain silly.  Maybe the aCK had "synergy" with the "Y" cable.  aaaahahhahahah

I think you need to go back and re-read your statement again, and just repeat it to yourself, and ask yourself why you are HERE.

[Tyson]

Let's not let this get personal.  It's been civil so far, lets try to keep it that way.

[/facilitator]

[Hantra]

Let's not let this get personal. It's been civil so far, lets try to keep it that way.

Come on T.  You know this isn't personal.  There is nothing personal about anyone's comments here.  It is a very silly comment, and that says nothing about Rob.  It's easy to think like that, but when you really think about it, how can any of us say that, and still claim to be after the best sound?  

I mean, my down comforter thrown over my speakers would equally impact both the HDXV and the AU24 in the comparison I am doing right now of digital cables.  But. . . do I want to do that?  Can I tell which cable is better with that handicap?

[nathanm]

By changing the input switch he can compare the sound of the analog outs on the CD player to the analog out of the DAC.  The diagram shown is exactly how I demoed the dAck! on my own system, with the CD player on one input and the DAC on the other.  What is the problem with this?  I do not see any conflict with this scenario.  "Absolutely horrible?" Say what?  How else would you hook it up?

[Hantra]

How else would you hook it up?

I would never use a Y cable on a coaxial digital out.  That's measureably horrible.  Also, I wouldn't use a clock radio interconnect for one channel and a nice silver one for the OTHER channel.  I'd at least use another clock radio interconect and leave the silver one out of the equation.

But as I said before, it was an interestingly written review with nice pics.  I apreciate him taking the time to do it.  All I'm saying is that I'd be interested in results without the unfortunate connection issues. . .

[JoshK]

All I'm saying is that I'd be interested in results without the unfortunate connection issues. . .

You have those results.  It is what Mike reported.

[Carlman]

I'm trying to figure out what the deal is with the connection, Hantra's issue, who Tito is and whatnot....

What I see in the original post of how the original poster setup the test scenario for which the review is made.  What I see is this:
Both DAC's had both 'el cheapo' interconnect for one channel and one silver IC for the other.  So, one channel should've sounded better than the other.  

I agree that splitting a coax is not a good idea.  It would've been better to split a fiber optic output so the characteristics of the digital cable aren't compromised.  However, it appears the digital cables were equally compromised the way the Y adaptor was implemented.  So, I don't think that's a big issue.

The review is mainly about sound reproduction and not imaging.  Imaging would be the only thing that would be an invalid assesment in this review since there are 2 different IC's per DAC.... which should smear things a great deal.

Am I correct in this? The results of this review seem to me to be a good indication of the personalities of these DAC's.

The part I don't get is Tito.  Is it his system?  It doesn't matter where the test was done or on who's system to me.  It's the 'test system' is all I care.  If what was pictured is what was used to make the review, I think it's a level playing field for comparison of the DAC's personalities.

[csown]

Hola folks,

My, this thread has become a moving target.  I was planning on posting in reply to Tito's test methodology a couple days ago and now there's a lot more going on in this thread.  Anyway, about to head out but thought I'd real quick touch on some of these items (maybe I'll get to the others in another post):


1.  The dAck! inverts phase - it has an inverting transconductance amplifier in the circuit.  The validity of absolute phase is of course a questionable topic - while it is important to ensure similar phasing in tests, it makes no sense for everyday playback unless you are one of those people who knows the phase of your all recordings.

Incidentally, the phase response of many DACs is so poor (and add to that the myriad other amplifiers and filters down the chain) that one cannot expect absolute phase to be completely noticeable from setup to setup.  Case in point, simply applying an anti-sinc filter to a non-oversampling DAC (unless cleverly designed) results in almost unstable operation by 22KHz.  Read that folks: 180° out of phase by 22KHz.

Due to the group delay of the zero-order-hold, the phase error for any  DAC is unequivocally 90° by Nyquist.  For this reason, it is very dangerous to apply an anti-sinc filter to a non-oversampling reconstruction filter unless you specifically know all the transfer characteristics of the system.  An example is where you have phase error of a few dozen degrees in a power amplifier downstream.  Assuming you have phase-corrected loudspeakers, with a sinc-corrected DAC, you would essentially be inverting your tweeter.  (In contrast, oversampling has vastly better phase response intrinsically; however, engineers are so obsessed with applying post-filters that the phase response is hopelessly mucked up in  most cases anyway).


2.  Using different interconnects for the two channels will be extremely damaging to soundstage performance.  The transfer functions for the two channels become vastly modified, you probably end up with slightly different levels in each channel, and you have little hope of setting up a wide and accurate soundstage with clear image localization.


3.  Splitting the digital signal passively works poorly at best unless one of them is loaded down while the other is active.  Even then, the transfer characteristics become unpredictable and are certainly not optimal.  When dealing with transmission of RF signals, you are trying to avoid waveform reflections sourced at the terminations that sum with varying phase with the initial waveform and essentially blur the leading edge.


The consequence of using a simple Y-splitter in the transmission line is soundstage collapse, some loss of resolution, and a blurring of midrange detail.  The upper midrange is where it's at with the dAck!, and it's critical not to lose that.

A way to do digital signal-splitting properly is to put the signal into FIFO's and re-buffer it out to multiple outputs.  This is how things are done in your PC.  You can also do it with analog electronics, but you cannot do it passively unless you are very tricky about it.  It's not something you do in an afternoon; I don't even have anything like this myself in my test setup.  I do it the old-fashioned way, by switching out cables for A/B testing, sometimes blind, usually not.

-Chris

[arthur]

Lets not forget the importance of synergy and taste differences.

With the TubeDak+ i thought that it did sound great with Classical, Jazz, Blues, etc, but a bit slow when it came to more dynamic music when i was using a Creek OBH12 passive pre. Ever since i replaced the Creek with the Odyssey Tempest, the sound has become much more involving even on the most dynamic discs.

But even here, by "dynamic music" i mean bands like Sentenced, Cradle Of Filth, and Bolt Thrower. So obviously this is not something relevant to most (any?) audiophiles. Also, I’m used to listening to my Legacy Classics, which are very dynamic speakers, so there is another bias.

That's why I would never dismiss just about any claims about how a piece of gear sounds to someone. But after having the pleasure of listening to the TubeDak+ and dealing with such a GREAT guy like Scott, i do understand Hantra's sensitivity when it comes to this topic.
Yes I did think that the first review was a bit questionable in it’s setup, but the second setup appears to have been just fine (if they gave enough time for both units to warm up).

One thing that did turn me off about D/A’s like dAck! and ArtDIo was the additional care that these units require. ArtDio has syncing problems with some DVD players (I use a Sony 7000, so i wasn't sure if it would work for me). And, dAck! should only be listened to 4 hours at a time, and then you have to replace the battery when it goes out. True the TubeDak+ does have a tube which will at some point expire, but it is VERY inexpensive... you wouldn't believe how inexpensive... but i'll let Scott tell you exactly how much  
So after reading these reviews I am very tempted to hear an ArtDio and dAck! in my system, but I doubt if I would keep them EVEN if they did sound better in my system (which I do doubt)… especially, also considering differences in cost. With the dAck! the cost difference only matters if you are planning on keeping the unit for many years… mostly I just don’t like the hassle of having to deal with batteries… but again, “hassle” this is matter of preference – with my video projector, I enjoy putting it away every time and then spending 20 minutes every time to set it back up every time I want to watch a movie.

PS. Last time I called Scott Nixon, he told me that he is thinking about installing a filter bypass switch on the TubeDak+ which would turn it into a TubeDak but with better components, thereby, giving us an instant choice of sound. I hope Scott does not hate me now for giving away too much... but i figure if he told me - just another one of his customers, then it's probably not a big secret.

[Jay S]

My $0.02 is that you don't really know what you are hearing if you use lower quality cables to audition good components.... are you hearing the component or the cable.  The reason I value this comment at $0.02 is that some people don't think the differences in cables are meaningful.   C'est la vie.  I do, much to the detriment of my bank account, but also much to my personal satisfaction.

Back to dacs, I do agree that the TubeDac (at least my TubeDac with a Siemens 7308 tube with a Bolder bybee'd power supply) is not the last word in dynamics.  My Mensa Plus clearly beats it.  The TubeDac does seem to have a purer more natural midrange than the modded DI/O.  Muhammad Ali vs George Foreman - different styles but both heavyweight champions.  

I'd be curious about the dACK! but I'm a bit wary about batteries....  

That said, my current thinking is to mod a hires player to the max.  There are SACDs that I want to listen to and I've recently discovered concert DVDs, which are way cool...

[Danny Richie]

And, dAck! should only be listened to 4 hours at a time, and then you have to replace the battery when it goes out.

We used the dAck at the VSAC show and played it for 8 to 10 hours straight with no problems. I play it 6 to 8 hours straight here at my home some times too.

I'd be curious about the dACK! but I'm a bit wary about batteries....

I thought the same thing until I tried it.

They are actually trouble free.

You just leave it plugged into the charger all the time.

When you turn it on, it automatically disconnects the charger from the system.

When you turn it off it automatically starts charging back up.

You just turn it on and off just like any other component, and never even give it a second thought.

[duff138]

would someone mind explaining this to me?  I'm not familar with this and don't understand what it would require me to do?  "this dac does invert phase"

 from scott nixon site:
  "Since there is no 'analog stage'  this dac does invert phase.  If you're comparing other digital gear, at least swap the speaker phase when using DacKit or TubeDac. Since most recordings are phase random it's not imperative to swap phase.  I mention it mostly in regard to direct comparison to other digital source"

  thanks

[Hantra]

would someone mind explaining this to me? I'm not familar with this and don't understand what it would require me to do? "this dac does invert phase"

Duff:

From what I know about the Ack, it does NOT invert phase.  Despite what Chris said, I know people with the Ack, and they tell me it does not invert phase absolutely.  

Anyhow, to answer your question, all DAC chips invert phase.  It requires an analog stage to revert phase back to original phase.  In a DAC like the Nixon DAC, there is no analog stage, so one must invert absolute phase.  One can accomplish this by simply swapping the speaker leads red to black, and vice-versa.  

HTH,

B

[duff138]

Duff:

From what I know about the Ack, it does NOT invert phase.  Despite what Chris said, I know people with the Ack, and they tell me it does not invert phase absolutely.  

Anyhow, to answer your question, all DAC chips invert phase.  It requires an analog stage to revert phase back to original phase.  In a DAC like the Nixon DAC, there is no analog stage, so one must invert absolute phase.  One can accomplish this by simply swapping the speaker leads red to black, and vice-versa.  

HTH,

B

O.K., so if it did that would mean that when switching from using the dac to another source like my turntable, I would then have to go to the amp and switch the leads back.

[Hantra]

O.K., so if it did that would mean that when switching from using the dac to another source like my turntable, I would then have to go to the amp and switch the leads back.

Well technically, yea.  

But what you ought to do is swap the leads on your cartridge.  If you wire your cartridge out of phase, then all will be well.  That's what I did when I had my TT.

B

[csown]

Hantra, you are correct .  The dAck! has the same phase as what is encoded on the CD (this may or may not be correct absolute phase).  

What I wanted to convey in my post is that the dAck! inverts the phase of the DAC chip output.  In other words, inverted with respect to Nixon's basic DAC's output (the one with passive I/V).  I don't know the TubeDAC or TubeDAC+ circuits, but it appears from Hantra's above post that Nixon's tube follower does not invert phase.  I had always thought that his follower was a single inverting gain stage, which would result in same phasing as the dAck!, but this is apparently incorrect.

So the concensus (Scott or Hantra correct me if I'm wrong on the Nixon stuff), with respect to absolute phase:

dAck! - phase correct
basic Nixon - invert
TubeDAC(+) - invert


I want to reiterate that it is important to ensure that comparisons between two units should have provisions for identical phasing, which has been discussed in this thread already.  However, for day-to-day playback, phasing in most cases it is of limited noticeablilty, but more compellingly it is just not practical.  There is a good chance that one of the boxes downstream inverts phase, and who knows what has happened to the signal prior to storage on the disc?  As far as I'm concerned, you practically cannot know if a recording is phased absolutely unless the recording actually indicates it (just saying a recording "sounds better" with a particular phase setting does not qualify correct phase for me).  The ear is a good phase-difference detector, but really not that good of an absolute phase detector.

-Chris

[csown]

But what you ought to do is swap the leads on your cartridge. If you wire your cartridge out of phase, then all will be well. That's what I did when I had my TT.

Careful about this one... (assumption that you have an absolute phase-inverting digital source like the Nixon units) ...do this only if you know you have an even number of inverting stages in your phonostage.  Your TT phase could possibly have been the same as your DAC all along, and switching the cartridge leads would then give you the wrong phase.

-Chris

[viggen]

I use the Dackit and do not invert phase.  Somehow, when I first got the Dackit, I inverted phase, and this sounded out of phase.  So, in other words, the phase issue isn't an issue with my system.