Ext Word Clocks - No point unless syncing other digital gear

[James Steele]

Remember though, I am clocking several pieces of digital equipment here and that could be a big difference for me. Where you or someone else may only be using one or two pieces of gear. Each person will have to use what sounds best to them, whether it be an external clock or not. Main thing is we all just want to record great sounding audio, we may all get there different ways, but in the end, it's all about the sound.

If you are clocking several pieces of equipment, as I alluded to in the title of this thread, you have no choice about using an external clock and using one, according to the article I mentioned, if it is a good clock, will not perceptibly change the audio. What he was addressing was the belief that an audio interface with a decent internal clock to start with will perform BETTER (according to scientific measurements) when clocked by an external clock via a wordclock connection.

[James Steele]

When we are actually cutting thru A/D's here, the A/d being used always becomes the house clock - via the Antelope distribution, unless we are cutting thru 'multiple' brand interfaces (A/D's), then they all get locked to house clock. For D/A and mix etc, everything is then locked to external.

Right. So when you are tracking through A/Ds you are using the A/D's internal clock and just distributing that clock. (Except in the case you mentioned).

[stephen1212b]

It seems that the assumption still exists that the clocking circuit in a MOTU interface is of the quality and type that can not be improved by the application of an external clock. This is not the case. Below is a quote from the Black Lion site referring to MOTU interfaces.

"A second weak spot is definitely the clock. It's based around Texas Instruments TLC2933, which is a VCO and PLL all in one. Jitter is high in comparison to good converter clocks-the datasheet claims at least 120 picoseconds, although I suspect it's much higher than that because of power supply noise."

The data sheet I looked at listed 100 picoseconds depending on layout and suggests that the part not be considered for new designs.

The fact as pointed out in the article, that a good quality XO or better TCXO properly implemented local clock circuit can only be degraded from a jitter perspective by having to slave to an external word clock is moot without the decent local XO clock. MOTU interfaces can be improved by a good external word clock and further improved by battery operation. Replacement of the internal VCO clock could provide an even better solution, but that is beyond the discussion at hand.

[labman]

Right. So when you are tracking through A/Ds you are using the A/D's internal clock and just distributing that clock. (Except in the case you mentioned).

Exactly.

[Shooshie]

I don't think I've seen anyone mention yet that the article in SOS showed the effects of using improper cabling (ie, regular microphone cables) instead of word clock cables. The signal was very noticeably degraded due to jitter when using the lesser cables.

It was an interesting article, especially given their measured results. I was expecting another gear-affirming article so typical of magazines who must please their advertisers. I expected it to conclude "you really haven't lived until you have installed an Aardvark on your system. Of course, if you want Nirvana, you'll need to go with a Big Ben, and then for the big budget Orgasmatron you'll need…", so I was genuinely surprised with a basic "keep whatcha got. If ya getcha self more gear, then at least use a good cable."

That's the only article I've read in this issue of SOS to date, but I knew when I saw it that there would be some discussion here about it. Nice to see that it's drawn some heavy-hitters into the discussion. Gotta love something that does that. It's nice to know there are things we still don't know, or that we disagree on. The jury is still out on things like this, and for me that's always reassuring in an odd way. I mean, where would the fun be if the data were all in, we were all aboard, and there was nothing left to say except "buy the book, kid. It'll tell you everything."

Shooshie

[tomeaton]

Well, you can't use mic cables instead of wordclock cables... you can (but shouldn't) use mic cables instead of AES/EBU cables... which is probably what you meant. Many folks are using AES cable for facility wiring for ALL signals, analog and digital. The tighter tolerances for AES cable can really only help common mode rejection in an analog balanced connection.

Word clock cables don't carry audio... every standard digital audio cable can carry clocking info, but using a proper BNC 75ohm word clock cable (when possible) in addition to your digital audio connection is preferred!

t

[Shooshie]

You are indeed correct. This is a subject about which I'm pretty ignorant, not having an external clock, and having learned "studio" before the digital era. Sorry for the error.

Shoosh

[labman]

We just use great true 75ohm cables and connectors and all is well. (Usually from markertek)

[willheim]

house sync has always been a mysterious area. I have been resolved to house sync since day one, since I am a scoring guy and the post guys always wanted to know if I was resolved to house sync and so over the years I have always been so. I remember having a different horita for Pal projects and having to change them out. Now I have the Antelope Isochrone - I also run adat lightpipe out from five different computer sources and they need to grab master resolved clock or they tic and pop.

I have always been a nut about making sure my scores totally conform and don't drift and have high resolution

I want to get that SOS issue I can't believe I missed it!

[James Steele]

Somebody post a link to Ethan Winer's "Audio Myths Workshop"

http://www.youtube.com/watch?v=BYTlN6wjcvQ" onclick="window.open(this.href);return false;

Pretty interesting stuff if you have time.

[bongo_x]

Somebody post a link to Ethan Winer's "Audio Myths Workshop"

http://www.youtube.com/watch?v=BYTlN6wjcvQ" onclick="window.open(this.href);return false;

Pretty interesting stuff if you have time.

Everyone should make time. That is a pretty great demonstration. It's amazing how much people just don't want to hear this though. I think it's partly because it suggests to the viewer that the problem with your recordings is you, and your recording skills, and buying another piece of gear isn't the quick answer you'd hoped for.

bb

[stephen1212b]

Although I agree with much of what is in the video, and delight in recognizing how identified and misled by my beliefs I can be, I still must mention that listening with Sony 7506 headphones from a mostly stock 2408 Mk 3 I correctly identified every example up to the phase demonstration where it was unclear what was being demonstrated and the controls were changing all the time. As is pointed out this is not statistically significant but 100% even with the compressed audio track.

Lastly remember that bit identical null tests are useful to verify the proper functioning of code related processes but do not apply to listening unless there is a re-digitizing of the analog signal at at least 5X the sample rate of playback. Read your digital oscilloscope manuals. It is not just the right bits, it is also the right time and to quantize time to the same resolution as the source hides the potential audible differences. Bits are bits doesn't mean sound = sound. Don't believe me take tis simple test. Play back a few seconds of a track while rerecording it to another track. Play the same track again recording to another track but pause DP in the middle of the process and then resume. Everyone will agree that the continuous playback sounds different from the paused playback yet the two re recorded tracks will null. It is important to recognize the assumptions being made when testing. Double blind is useful but triple blind is well kind of like the blind leading the blind in the dark.

[bongo_x]

No.

[James Steele]

I see that this thread comes perilously close to violating the policy on this board about discussing "religion." Whatever makes you happy. I can't remember the audio examples now but I think some of them were fairly clear in making a plausible case that those who claim they can hear for example one sort of dither over the other may only "think" they can and that you do have to objectively do these blind tests, otherwise the brain is very powerful and can make us hear what we want to hear.

[tomeaton]

It is also possible that all this stuff is audible and matters.

I spent most of a week mixing an acoustic guitar record. Tracked at 96 and brought down to 44.1 before assembly. 24 bit until the very last step, at which point I used SampleManager and iZotope's mBit+ dither and brought it down to 16 bit. I listened to the files and they were distinctly dark. The air I had worked SO hard to get in an ITB project was gone. I was bummed. Just for kicks I re-ran the process with SampleManager and the flat Type II dither. Well, there was the air. I pulled the two examples into Nuendo (where I do my two-track work) and went back and forth to make sure I was not crazy...and I wasn't. It sounded like the mBit+ had a lo-pass filter engaged. They tout it as sounding "analog"... so maybe that's by design. It was not the right choice for the project i was working on.

I would be happy to take a 24 bit file and process it with both dither flavors somewhere... you'd certainly hear the difference.

So... dither is quite audible on the right sources. I've had another acoustic guitarist choose very specifically the dither that was used on his project... and yes, we were clearly hearing differences to the PROGRAM while listening to different dithers at a maybe slightly elevated level... but not loud. The Oxford limiter is really pretty great for examining how dither changes your program, by the way. It allows you to listen and blend flavors of noise-shaped and flat dithers on the fly.

Is this stuff a BIG DEAL? No. Does it change what your music sounds like? Absolutely.

tom