Apogee AD16x: how clocking effects a DAW?
wm_b
Thread Starter
#1
30th August 2004
Old 30th August 2004
  #1
Gear addict
 

Thread Starter
Apogee AD16x: how clocking effects a DAW?

I got hold of an AD16x for the weekend and l have made up my mind that I will get one. The little bit of testing I was able to do was enough to clearly hear the improvement. It also has given me questions about clocking and tracking.

My test was to track drums and guitar through my pre's into the Apogee and then repeat through the converters in my Tascam DM24. I clocked the Apogee test with the Apogee and the DM24 test with the DM24. The apogee was much more clear and the stereo image was much more defined.

How does clocking effect tracking? If I track with a good clock and play back with a lesser clock it there a difference to the sound than if I did everything with the lesser clock? If I track something at my studio with the Apogee clock and my friend takes it back to play it at his place with a MAUDIO sound card would it playback differently than if I used the clock in the DM24? Is clocking something that goes INTO the tracks or is it only involved in how it's played back?

This was quite a day getting all of this to work in the small window of time I had to test. I'm glad wasn't trying to actually get something done.

Cheers. Wm.
Max
#2
30th August 2004
Old 30th August 2004
  #2
Max
Lives for gear
 

Wm,

You have hit on one of the biggest factors that set Apogee apart from most of the other converters out there.

As you might know from the information about the AD-16X, the clock inside is actually the same as our breakthrough clock box Big Ben. Not only does Big Ben have an extremely low jitter spec, but it is able to adjust to and clean-up any incoming clock signal.

It is well documented that a jittery clock source during A/D will permanently alter a recorded signal. An unstable clock will essentially be encoded in the converted signal since the manner in which audio is sampled is based upon the clock. Even the most stable and accurate clock source after the fact (monitoring back during D/A, for instance) cannot change that as the unstable clock is still embedded (recorded) in the audio signal, and manifested, for example, in the form of anomalies in stereo imaging and other compromises to the sound quality. Therefore, a stable clock source on the A/D is the first and most important place where proper clocking is essential.

It is a common misconception, however, that clocking is only important during the initial A/D conversion. Maintaining a similarly stable clock is just as important when listening back from a DAW. A jittery clock on the D/A side of things will skew playback and the resulting deficiencies in the output will cause the mix engineer to overcompensate for them in the final mix. This is one reason why we emphasize the dual-stage clocking present in, for instance, the Mini-DAC. The Mini-DAC is able to clock to any digital source, jittery or otherwise, and sufficiently clean-up the clock to deliver a full and accurate signal. We therefore recommend using the most stable clock available on both your inputs and outputs in order to maintain highest fidelity at all points in the process.
wm_b
Thread Starter
#3
30th August 2004
Old 30th August 2004
  #3
Gear addict
 

Thread Starter
Max,

Thanks for the info.

Does the length of the 75 ohm clocking cable make a difference. I know coaxial cable has some limitations regarding length and radius of turns, is 10 feet too long?

I have to decide exactly how I'm going to integrate this unit into my system and I don't even know where to begin describing it. I currently use outbaord pre's into the converters on a Tascam DM24. The DM24 is connected to my computer with a MOTU 2408 Mk3 via TDIF.

Last night I connected the AD 16x to the DM24 via lightpipe (The DM24 has one ADAT IN/OUT). I could assign this so that I could hear the input from the AD16x as if it were the normal input channels. The trouble is that the board is unable to send this out via TDIF to the MOTU. This prevented actually recording into my DAW software. I tried many things and I am pretty sure that it's impossible to do it this way (shucks).

Finally I connected the AD16x to the MOTU with Lightpipe and used the MOTU mixer application to send input from the AD16x to my DM24. This allowed me to work more or less the way I always do. This will have to change though (shucks again).

I was only using 8 channels in my test and going to 16 will mean I will have to figure out a way to track and mix a little differently than before. I used to use 1-16 to track and 17-32 for mixing. I usually start setting up a mix on the fly. Now I will have to find an alternative unless I there is some kind of box that will split lightpipe into two identical streams, or get another 2408 mk3.

Thanks again for the clocking information.

Cheers, wm
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