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Squeezing out extra perfomance: Reclockers

I am in the process of moving out of CD land and into a mac driven iTunes environment for all of my music (well, except for the vinyl:).

The setup I am using centers around a DEQX box. I like the DEQX because it just means less junk in the system - this thing has a VERY good DAC, preamp and the amazing active crossover/room correction ability. I figure it gets me about 90-95% of the way to what a dCS stack can do. Speakers are a homebrew that is pretty similar to the Emerald Physics CS-1 (no, not the 2. I am using 8 eminence drivers, but it was still inexpensive and pretty easy to build, and sounds INCREDIBLE with the DEQX). Files are going to be FLAC only, via xACT and Fluke, and Apple Lossless (at least until iTunes suppots FLAC natively, or somebody comes up with a better hack).

I have already decided I don't want to go the way of a Transporter, or a squeezebox, or a sonos. All are nice products, and have their thing going on, but I want to use a mac because I just dig the iTunes interface and at the end of the day, I want to control the head from my iPhone. Narrow minded, I know.

But Macs have a lot of jitter. They just are not precision audio devices. So the question is: how to reduce it?

It seems like in the reclocker market, there are the following options, priced from high to low:

Antelope Isochrone 10M - like $6k?
Esoteric...i forget the model, but its like 3K
Empirical Audio Pacecar - about $1200-1400 i think?
Apogee big ben - used around $1k

I'd be very interested in anyone's experience with any of the above reclockers/word clocks/masterclocks in the context of the Mac. Or, if you are aware of a product I should look at.

I really am open to suggestions, and, for sound quality, if I have to abandon the Mac as a front end I will, but it would be a bummer.
portypop
15 responses Add your response
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drubin
3,274 posts
 
Keep us posted, Portypop. There are many among us in the same boat as you.
portypop OP
6 posts
 
Steve -

Excellent and concise explanation - I thank you! Part of the difficulty of reading about this stuff is that it seems that many of the authors don't have such great command over the technology themselves, and terms have a regrettable tendency to be used interchangeably when they are actually not.

So really Jitter reduction is about bit clocks and master clock. Word clocks are incrementally beneficial in comparison.

Now I have some direction to try some things out!

Thank you all!
audioengr
3,282 posts
 
Portypop - I'll try a second time:

I2S is the bus most commonly used to drive modern D/A chips.

I2S is comprised of:

Master clock or MCLK - 256fs
Bit clock or SCLK - 64fs
Word Clock or sync - fs
Serial Data

Fs, or sample rate frequency is generally 44.1kHz for ripped CD files and 96kHz for master tapes.

In older DAC's, the Word Clock was used to clock the D/A conversion, but most modern DAC's use bit-clock. Master clock is generally used for digital filtering.

Word clock is the lowest frequency, so it is more easily used to synchronize the various digital devices in a recording studio.

For reducing jitter, reducing word-clock jitter is not that interesting. It may have a small improvement in some systems, but the bit-clock and master clocks are the ones that affect the D/A chip most.

Steve N.
Empirical Audio
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Post removed 
portypop OP
6 posts
 
Anybody want to pick this up and expand upon it? I'm really trying to learn here!
portypop OP
6 posts
 
According to Wikipedia, the Word Clock is not a device; it is a clock signal generated by the master clock device.

http://en.wikipedia.org/wiki/Word_clock

In this context, it seems to me that the Antelope serves the role of the Master Clock, sending out a synchronization signal to all devices, aligning their time and thereby reducing jitter? Is this an accurate understanding of the functionality?
portypop OP
6 posts
 
Hey Kurt,

I'm interested too in why this works. I've been trying to find an intelligible(!) article on clocks and jitter reduction, but without a lot of success. There are a number of good articles out there that explain Jitter, but they don't go deeply into the cure. At least, not so a non-engineer non-math geek can understand it!

Audioengr, you seem to have a great grasp of this - I know you produce the Pace Car, which a lot of people like a lot. Are there really so many clocks involved? Could you please define them for us, and their different roles? It would certainly broaden my understanding of this jitter problem we area all looking to solve!
glide3
402 posts
 
Portypop,
I bought mine off ebay new

Audioengr,
I really can;t answer your questions as I don't understand any of this from a technical perspective. I followed the advice of Stepehen Balliet at Reflection Audio and have been very leased with the results.
I attempt to get an answer to your question from Stephen and post

Regards,
Kurt
audioengr
3,282 posts
 
The Isochrones are word clock generators. How does this improve jitter at the D/A? Most modern D/A chips need low jitter on the master and bit clocks, not the word clock.
portypop OP
6 posts
 
Glide3 - where did you get your Antelope Isocrone?
glide3
402 posts
 
I am running my mac via firewire into an RME fireface ($1000) and then to an antelope isocrone ($1400) and then into a reflection audio modified benchmark dac 1....I have been very happy with this after owning Meitner seperates and one box as well as some other top line conventional digital.
portypop OP
6 posts
 
I found one other reclocker, but I am guessing the parts are junk:

Behringer ULTRAMATCH PRO SRC2496 for $129.00!

Now, just cause it is cheap, does that mean it does not do a good job of passing the data thru to the dac while keeping extremely accurate time? After all, its well known that as timekeepers go, a $10 timex does a better job than a $100,000 patek.

Has anyone used this?
audioengr
3,282 posts
 
You could use the AirPort Express or Apple TV with a reclocker. This way you can still use iTunes and do it wirelessly. There is no audio quality hit with using WiFi if you use a reclocker.

Steve N.
Empirical Audio
usblues
1,217 posts
 
Keep the Mac,find the other piece of the puzzle,its around,your almost there.Try computeraudiophile.com for more info.Chris will know of something I bet,good luck,Bob
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