[mcbroomf]

My first post!

  I set up my stereo system about 11 years ago, and at the time worked on reducing upper-mid glare, the "key" as I recall was to replace a Classe 5L pre with a high quality passive attenuator that was custom made with discrete resistors (I don't recall what make).  As I listen to a lot of female vocal music this was important to me and the glare was pretty evident at medium-high volumes.
  For years the system has geven me great pleasure, and over time I have found myself listening at more moderate levels.  I have also included a CD changer to add more convenience.  I did some (perhaps casual) listening at the time I bought the changer and concluded there was no real difference to my transport.  My DAC can take 2 inputs and I still find that to be true in simple A/B listening.
  Just recently my interest in listening more critically to music at higher volumes has been tweaked (possibly since finding this and the AVS forum), and I've found the glaring upper-mids are back.  I have read many posts about current DACs and digital amplifiers and I'm interested in evaluating a dAck which has recieved many positive reviews.
  I emailed Chris and he mentioned that I should be careful about paring the dAck with cheaper transports as it employs no jitter correction.  He specifically mentioned a case where it was paired with a Rotel and sounded bad.  I have a Cal Delta and he suggested it would sound OK but not spectacular.  I've searched for posts in the dAck and seen a number of recommendations that suggest paring it with cheaper CD or DVD players to yield a great front end.
  So, to get to my questions..

  Does anyone have any experience with a cheap CD/DVD/transport and the dAck?

  For my specific problem of glaring upper-mid/female vocals, do you see anything in my system other then the front end that might be my problem? (for example I've been thinking of trying a Carver ZR1000 to see if my Classe/Thiel combo might be the problem)

  Is there a possibility that, over years playing at lower volumes, that my system needs to be broken in again?

Sorry for the long post, I figured that some background might help with the questions I'm trying to get answered.

Thanks,

Mike

CAL Delta transport
Adcom GCD 600 changer
Theta Pro Mk III DAC
Passive volume control
Classe 15
Thiel 2.2
XLO interconnects
XLO type 5 speaker cables

[mcrespo71]

Well, I'd try it with your CAL Delta, as that is a respectable transport.  I use a Parasound Belt Drive Transport, which sounds absolutely stunning with the dAck.  You can find them used for $500-$600.  At one time, my friend, Tito (another dAck owner), was using a pro audio sony Cd recorder into the dAck.  It sounded better with the dAck, but nothing like I heard with the Parasound transport.  You could try using the Cal into a Monachy DIP to kill jitter before it travels into the dAck.  Good luck.

[audioengr]

I believe that Marbles has tried the ack with a Sony DVP-S7700.

[Marbles]

I did try the Emprical Audio modded Sony DVP-S7700, but I have a 10 Kohm input impedance amps and a TVC (Bent) pre....the system was very mismatched NOT in the favor of the ACK!

In my system the ACK! was not to my liking.

Steve, just curious, what is the output voltage of your S7700/P3a DAC combo?  It must be at least 2.0v and I'm guessing higher because it really drives the Bent pre and amps well.

[Hantra]

I emailed Chris and he mentioned that I should be careful about paring the dAck with cheaper transports as it employs no jitter correction.

You don't need to be concerned with jitter in a non-oversampling DAC.  The level of tolerable jitter is exponentially higher when you go non-oversampling.  Oversampling DAC's are very sensitive to jitter, but not non-oversamplers.  

That said, I recommend the 7700 also as a transport for any DAC.  Unless you can go remoteless, at which point I would use a nice CD-ROM drive like the NEC.

[mcbroomf]

Thanks for the reponses.  It sounds like I should try my Delta and plan to get hold of an alternative transport, the Sony looks like a good value, if I don't hear any improvement.  I should have time given Chris's evaluation period.

Mike

[csown]

mcbroomf wrote: I emailed Chris and he mentioned that I should be careful about paring the dAck with cheaper transports as it employs no jitter correction.

The dAck! actually does have a jitter filter in it.  It uses a PLL to recover the clock, which is the same way that 99% of outboard DACs do it.  This technique is just not very sophisticated, but it is the industry standard.  Hantra is right in saying that non-OS is less sensitive to jitter than OS DACs in theory.  Because of this, non-OS DACs rarely sound bad.  However, the difference in performance between a good transport and a poor transport driving the dAck! is quite huge, and this is the cause for my warning.

When comparing between a monolithic CDP and CDP-driving-outboard-DAC, you have to be careful.  The CDP has an internal master clock that is used to tell everything inside what to do - the transport needs to read samples, the filters inside need to process them, and the D/A to output samples.  This is advantageous because the master clock is right inside, near the D/A chip, and is not subject to external fluctuations.

Contrast this to an external DAC, which must recover the clock from the S/PDIF stream.  This stream is passed through several devices which can contribute jitter - the S/PDIF packager inside the CDP, the digital output buffer in the CDP, the cable, its terminations, and finally the PLL which recovers the clock.  These components contribute jitter and contribute it in different ways (sometimes additive, sometimes subtractive (PLL), often nonlinear).

So when comparing a CDP to a DAC connected to the CDP, remember that the DAC is *always* disadvantaged in terms of the clock signal quality it has to work with.  It may be the best DAC in the world, but if there is something very wrong along the chain, the quality will suffer.  Most CDP manufacturers pay very little attention to the aftermarket expansion capabilities - they sell a feature, not performance - so the S/PDIF outs are very poor in most cases, especially with sub-$1K players.  Dedicated transports almost always have much better jitter specifications because they had better or else they would be a useless product.  It's kind of ironic - you're supposed to have expansion capabilities on your S/PDIF-capable redbook player but unfortunately, the manufacturer crippled it by slapping on a cheap output buffer.  It's like selling a monster truck with 15-inch tires.  It'll get you around, but you're not going to be mudding or crushing cars in something like that.

A nice article by Robert Harley about the practical consequences of jitter can be found here:
http://www.stereophile.com/reference/368/index.html

-Chris

P.S. - There are some very sophisticated ways of recovering the clock nearly jitter-free, but they tend to be very expensive and very complicated.

[audioengr]

Steve, just curious, what is the output voltage of your S7700/P3a DAC combo? It must be at least 2.0v and I'm guessing higher because it really drives the Bent pre and amps well.

The output voltage is higher than most CDP's.  I recently tried it at a friends house where he had a home-grown passive attenuator.  Even at high attenuation settings it clipped the amp, so we could not use it.

[eico1]

Of cource upsampling dacs use a sample-rate convertor at the input which will reduced the incoming jitter quite a bit. The clock internal to the upsampling dac is what determines the jitter at its output for the most part, but you have the addition of the digital filter.


steve