Low End Gear High End Clock...

[thebighandster]

I own a Tascam FW1884 (for those not fimilar its a FireWire controll surface with 8 onboard preamps and AD/DA conversion). I was wondering has anybody ever tried to use a high end clocking device on some low end converter and preamps. Does it improve the sound. If i put the FW1884 as a slave and clocked it to an Apogee MiniMe will it improve the sound of the converters on the console? Essentially creating a cleaner signal and bringing out more nuance in the onboard preamps? I could really use some imput im totally lost...

[tINY]

Repeat after me:

"external clocks do not improve jitter when using one converter"

"When I have extra money to spend - I will buy more good microphones"



Thank you.



-tINY

[jwantuch]

An external wordclock will, in fact, make a difference assuming it's of a higher quality than the internal clock. I remember comparing the internal clock of a Soundtracks Virtua (digital console built for broadcast) to an Apogee AD-8000 used exclusively as a word clock and you could definitely hear a difference, albeit subtle. The MiniMe is probably not your est choice since it doesn't have a wordclock output. If you're looking for a high-end clock at a considerable price, check out Black Lion Audio. Matt specializes in modding gear (mostly converters) for better sound and now sells his own master clock for only $385. I have only heard great things about his work from colleges of mine. Economically speaking, the difference will be subtle, and you would probably be better off upgrading the analog circuitry of your Tascam with some better op amps. If you feel faint about modding your Tascam for lack of soldering skills (it's probably all SMT) a good technician should have no problem doing the mod for you (be aware that this will void any warranty).
Back to the question of wordclocks, I vaguely remember hearing that an upgrade to an internal wordclock is even better than an external. I cannot verify this whatsoever, but if you are dealing with limited digital gear, it may not be a bad idea. It will definitely simplify your rig a bit. But to answer your question, a good wordclock is priceless.

Best of luck.

[rainbobryte4]

Originally Posted by jwantuch

a good wordclock is priceless.

well said :)

[tINY]

Remember that the external wordclock signal has to go through more distribution before it gets to the PLL inside the converter - and it uses the same PLL.

Good crystal clock references are cheap - there is nobody who uses a bad one inside a converter that costs anything over $49.99. It's the distribution, power supply decoupling, PLL design and other things inside the converter that make clocks marginal at the conversion sampler.

I should go into business selling blingy external clocks - they're cheap to build and the marketing is already done.....

....I'll cringe all the way to the bank, but I've done less scrupulous things for money before.



-tINY

[Tomer1]

Im with tiny on this,
Before buying anything see if you can first demo the unit and then see for your self it does make any difference to your ears.

[jbuehler]

Originally Posted by Tomer1

Im with tiny on this,
Before buying anything see if you can first demo the unit and then see for your self it does make any difference to your ears.

Otherwise buy better gear!!! My buddy who owns a shitty multitrack and amazing mics, pres, and has a great room makes incredible recordings all 16bit all 44kHz. All without an external clock.

[WuTangChan]

gonna have to agree with tiny on this one. i am no expert, but know enough that in clocking your converter externally you risk introducing more problems than you are trying to take care of; rather than relying on the crystal oscillator of your converter, you would be relying on the quality of the PLL of the converter and its interaction with the external clock. you also risk problems with interference and degradation of the external signal through AES/EBU, WC, or whatever other connections you would be using.

although i am unfamiliar with that sepcific piece of gear, being that it is much easier to implement a stable crystal clock than it is a good PLL, it is likely you would be better off to either upgrade your AD/DA converter, or find someone who knows what they're doing to mod the clock within your FW1814. if you do decide to clock externally and notice improvements in your sound, that should say something about the quality of the converter you are using, and not the external clock you are connected to.

[1monkey1]

i guess this is a fairly heated topic.
not just in this thread.

my questions is: why do the same converters sound better (deeper sound stage and smoother overall feel) when i hook the converters to an external clock? btw, this is not a 5% difference.

i understand when you say that adding an external clock introduces other issues, but it would appear to alot of people on this forum that a rig can sound better with a higher quality external clock. i don't want to argue the technical aspects of wordclocking, but i also don't want someone to tell me there's no difference when i hear a difference.

steven walcott
Engine Studios

[tINY]

You probably like the sound of more jitter in your converter. Or maybe it's the distribution of the jitter...

Nobody can argue with what you like.


There is a lot of squishiness in the perception of sound. If you can really hear a difference, instead of just feeling better about your system because you spent more money on it, then you should be able to pick the better system in a blind A/B test.... consistantly. I haven't see the studies to support that small changes in jitter are readily perceptable.



-tINY

[WuTangChan]

Again, I am no expert. As tINY suggested, are you AB-ing these things blind? If you really do feel it sounds better then I can't argue with that. Could be one of those issues where the oscillator in your converter is poorly designed and the PLL in the converter is of a very good design.

In general though that shouldn't be the case. The PLL has to both function as a jitter filter and an oscillator, and theoretically for the designer of the piece of equipment, it should be both easier and cheaper to build a stable crystal oscillator than a PLL which outperforms it. If I am off on this assumption, feel free chime in.

[moon_unit]

Originally Posted by thebighandster

Low end gear + high end clock ...

= complete waste.

[AudioGaff]

I'll add my 2-cents as I have some recent direct experience in this area. It is not a clear case of one way always being better than another. Using an external clock may or may not improve the sound and/or jitter performance. It depends on a few variables and the overall design of the A2D/PLL/clock circuit of the device being clocked. Many times, jitter performance is worse using a external clock of any kind. Looking at the specs of some devices, you clearly tell that external clocking is not going to improve jitter performance. As to one way sounding better than another, that is much harder to measure and is much more subjective to each person.

Like all things that invlove audio engineering, you just need to try it and come to your own conclusions.

[jwantuch]

A typical oscillating crystal that you can readily find in audio gear from CD players to high res interfaces from big industry players runs at a high multiple of the sampling frequency (like 256 x 44.1khz). These crystals are not designed specifically for digital audio. They are designed for digital computing circuits, timers, microcontrollers, etc. It's not uncommon for these devices to have a jitter upwards of 250ps. For $100 you can get a clock module that boasts around 5-10ps. For $500+ you can get that number down below 2ps. How little jitter can you afford. Keep in mind that these are not word clocks, these are oscillators that are set to a single frequency. So if you want to upgrade your interface, you'll need one for 44.1(88.2, 176.4) and another for 48(96, 192). Or just pick the sampling rate that you prefer and never use the other one unless you desperately need to. Add one of each of the $100 variety, a power supply ($10-50), a nice painted chassis($20-100) and other components and you're easily close to $300 if not way over. Open any high end word clock and I doubt you'll find the same crystal that I can buy from Digikey for $1.60. I think the numbers speak for themselves. 250ps vs 10ps of jitter. I remember looking at a converter at an AES convention that boasted 6ps of jitter. It sounded pretty good. Yes, there are more complications when dealing with external clocks. That is why some people are big proponents of upgrading the internal clock rather than using an external. I have never personally compared a end low-jitter oscillator internally installed to the same one in an external enclosure so I will not comment on this issue. Jitter error has not, until recently, received the attention that it deserves. For years, there was a constant battle between tube amp builders and transistor amp builders. Tube amp builders claimed that their amps sounded more musical. Solid state builders claimed THD in the hundredths or thousandths of 1%. A little research in psychoacoustics and we find that tube distortion is all 2nd and 3rd order which we have a hard time hearing at moderate levels. Solid state devices have higher harmonic distortion which we are MUCH more acute to, even at extremely low levels. Eventually, the people who claimed to hear a difference found the science to back up their claim. It's only a matter of time before more people start to accept low-jitter clocks for what they really are.

[amd]

Originally Posted by thebighandster

I own a Tascam FW1884 (for those not fimilar its a FireWire controll surface with 8 onboard preamps and AD/DA conversion). I was wondering has anybody ever tried to use a high end clocking device on some low end converter and preamps. Does it improve the sound. If i put the FW1884 as a slave and clocked it to an Apogee MiniMe will it improve the sound of the converters on the console? Essentially creating a cleaner signal and bringing out more nuance in the onboard preamps? I could really use some imput im totally lost...

I used an R 800 to clock a Motu 896 just to see what would occure and the sound was improved dramaticaly. That being said, I would suggest you take the plung and save up for some new converters instead of using an expensive clock to improve the sound of cheap converters!

[tINY]

Originally Posted by jwantuch

It's not uncommon for these devices to have a jitter upwards of 250ps. For $100 you can get a clock module that boasts around 5-10ps. For $500+ you can get that number down below 2ps..

With the advent of high speed busses in PC's, there are lots of clocks available with RMS Jitter < 10pS measured with a 1.5MHz BW.

But you have to design the PLL to get the word clock frequency from the 100MHz reference......



-tINY

[jwantuch]

Originally Posted by tINY

But you have to design the PLL to get the word clock frequency from the 100MHz reference......

Sorry if I was unclear. For $100, I'm talking about a complete PCB package that will give you 33.8688Mhz that you can run right into your converter. Take a look at some spec sheets for some converters and this is the range of frequency that it will accept as a reference. There are other acceptable frequencies as well. Generally x128, x192, x256, x384, x512, x768 the sampling frequency will work. There are some exceptions when dealing with the higher multiples of higher sampling rates (eg. 768 x 192Khz.) But that's 100 dollars and all of your PLL problems and jitter problems are out of the way. Of course you need 33.8688Mhz for 44.1 and 36.864Mhz for 48. Forgive me if I'm missing something but it seems like this would be really easy to integrate into just about any piece of digital gear. I must admit that I have limited knowledge of word clock distribution systems (exact frequency, etc.) And I will also admit that distribution amplifiers seem to hint at possible disaster. But I have seen good results from external clocks, as have many others, and such low jitter seems like a good improvement. If you'd like to argue about quality of clock references, a crystal with 2 capacitors on the side doesn't seem to me like a very good reference. If you'd like to argue about distribution systems, arguments could be made either way. Using an external clock reference, I can claim to have heard an improvement. If you want to argue that the clock distribution amplifier is actually creating jitter, I would be more than willing to entertain such arguments, but I find it difficult to accept. If you do happen to have further evidence, I would honestly love to see it. As I said in my first post, there are people who seem to, above all other solutions, advocate upgrading the internal clock in a system. I am not in a position to comment on this specifically and so I will not attempt to.

[jslevin]

Originally Posted by tINY

Repeat after me:

"external clocks do not improve jitter when using one converter"

"When I have extra money to spend - I will buy more good microphones"

I agree with the general thrust and emphasis, but you are hewing religiously to one small element of the theory on this. Jitter quantitatively does not absolutely equal sonic fidelity. Lots and lots of mediocre converters will be improved noticeably by locking them to a better clock, and his idea is probably a good one.

You will note that a Mini-Me in particular will also add two high-quality preamps and two AD converter channels to his system, which makes it a more cost-efficient upgrade.

JSL

[johnnyjellybean]

FWIW I own a Tascam FW1884 with the FE-8 extension and I tried clocking it with my Apogee rosetta. I can't hear any difference between clocking with the Apogee or clocking with the Tascam. I AB'd them quite extensively. The clocking of the Tascam is not so bad and neither are the pres in that unit.

[D K]

Originally Posted by johnnyjellybean

FWIW I own a Tascam FW1884 with the FE-8 extension and I tried clocking it with my Apogee rosetta. I can't hear any difference between clocking with the Apogee or clocking with the Tascam. I AB'd them quite extensively. The clocking of the Tascam is not so bad and neither are the pres in that unit.

+1 - Was going to say exactly the same thing - The 1884 has some issues

Pres and AD converters are not among them (DA is a different story) - A quick search here will confirm that and your ears should do the same.

Certainly not trying to be a jerk here but the 1884 would be as good as any mid priced interface out there and if you can't get a decent sound out of it my guess would be it's not the equipment - and trust me here I use one everyday and while I love the hardware I am definitely no Tascam Fan-boy ( The Customer service absolutely sucks) but the hardware is more than decent and capable of delivering very acceptable results

[D K]

..also wanted to add that if you are not happy with the sound/robustness of the pres - There are mods available on the unit

Check out the Tascam forums for more info

[theblue1]

Providing an external clock source to a modern AD converter does not -- repeat not -- remove the converter's own clock from the picture or improve that clock's internal accuracy.

The timing of the converter is still driven by its own clock.

Only now the converter's internal clock must use a phase locked loop to continually attempt to synchronize to the incoming clock.

This in actuality will almost always tend to decrease interstitial sample timing accuracy -- meaning that the time between samples will vary more (than it would as its own master) as the device continually tries to "correct itself" to the incoming clock.

They call that interstitial timing error jitter.


Even Apogee will admit that external clocking increases jitter in a given device. It's simply the way the technology works.

As Apogee marketing guy Max Gutnik said in this GS thread:

[snip]... Read carefully. Anytime Apogee says performs better, sounds more accurate, etc. We are referring to how it sounds, not how it measures... [snip] ... We never said Big Ben produces less jitter than a converter using its internal PLL. The only jitter claims we make with Big Ben are in reference to it's own clock or when its a slave to a jittery source. Everything else is about how it sounds.

For those interested in a 10 page article that covers most major aspects of clocking multiple devices, the August 2007 Electronic Musician has just that. If you can wait it out, it'll probably be availabe free on their site in a couple months. It's worth reading. They're walking on egg-shells, considering that Apogee is one of their main advertisers (of course Digi is another -- but I'm sure they need them both; Lavry is mentioned in passing * ), but I think they do a fair job of covering the issues and -- as long as you read carefully and thoroughly -- you will have enough info to see through some particularly egregious marketing BS.

* For those who don't know what I'm referencing it was an epic -- debate's not quite the right word, ultimately -- brouhaha might be a better one, that involved converter design legend Dan Lavry, some folks from Apogee, and a whole sidecast of jokesters, fantabulists, and genuinely knowledgeable bystanders and participants. It eventually seemed to spill over into a white paper on clocking technology and basic science from Digidesign that was seen to support the Lavry "side." You can find the archived thread here. (And that thread almost bookended Dan Lavry's old PSW forum. It was a fascinating, heady place, while it lasted.)

__________________

UPDATE: You know, I was looking, once again, at Max (from Apogee's) quoted statement above...

Now I'm certainly I'm no digital design engineer -- but I'm thinking that a standalone converter doesn't use PLL for anything, right? Phase locked loops are used (in converters) for synchronizing clock signals, as far as I know and as far as I can tell from my reading... so a standalone converter may well have a PLL circuit for synchronizing to an external signal -- but I don't think that PLL comes into play unless it's attempting to sync to an external clock source... right?

Can we get a knowledgeable yea or nay on that?

[tINY]

Originally Posted by jslevin

Jitter quantitatively does not absolutely equal sonic fidelity. Lots and lots of mediocre converters will be improved noticeably by locking them to a better clock, and his idea is probably a good one.

You will note that a Mini-Me in particular will also add two high-quality preamps and two AD converter channels to his system, which makes it a more cost-efficient upgrade.

What is "fidelity", then? Any jitter adds/changes the signal.... You might like the sound better, but it's less true to the source.

Yes, the pre-amps in the minime are likely to be a boon to his set-up, but they won't make the jitter on the Tascam converters less.



-tINY

[tINY]

Originally Posted by theblue1

Now I'm certainly I'm no digital design engineer -- but I'm thinking that a standalone converter doesn't use PLL for anything, right? Phase locked loops are used (in converters) for synchronizing clock signals, as far as I know and as far as I can tell from my reading... so a standalone converter may well have a PLL circuit for synchronizing to an external signal -- but I don't think that PLL comes into play unless it's attempting to sync to an external clock source... right?

Can we get a knowledgeable yea or nay on that?

Did you notice that most converters will run at different sample rates? The easiest (and probably the best) way to do this is to use PLLs. Often there is more than one PLL in the clock circuit to take an accurate crystal (which only operates at one frequency) and get the sample frequency from it. Usually, the external clock source is applied somewhere within this PLL circuit.


So, wrong, the PLL is being used in stand-alone mode. There may be some designs out there that don't use a PLL in the stand alone mode, but I'm not sure how you'd accoplish that.....


-tINY

[theblue1]

Thanks for getting that straightened out for me, there, tINY!

[peeder]

There's a pervasive interest in keeping these as black boxes and preventing any knowledge of their workings or objective assessments from seeping out into the customer dialogue. Mr. Lavry is openly vilified by manufacturers and dealers alike for breaking this code of omerta, but I am very grateful and urge others to break away.

If you are secure in the value you are offering, educating the customer, arming them with the complete truth and means of its verification, will justly bring you the market you deserve.

[ddageek]

from personal experience a clock may or may not help as with most things in audio design there are no hard rules but one heck of a lot of theory ! If you can try to use another clock and you may find an improvement! OF ciurse it may be that you it sounds better and to your ears jitter sounds better, but hey its you music so who are we to argue!

[fxs]

My tascam MX2424 DA s sounds much better if clocked from my fireface 800 via wordclock than from its internal clock, I don't know tha technical reasons, but to my ears they just sound better.

Francisco

[jslevin]

Originally Posted by theblue1

Providing an external clock source to a modern AD converter does not -- repeat not -- remove the converter's own clock from the picture or improve that clock's internal accuracy.

Only now the converter's internal clock must use a phase locked loop to continually attempt to synchronize to the incoming clock.

Even Apogee will admit that external clocking increases jitter in a given device. It's simply the way the technology works.

I know you are well intentioned on this, but I think frankly that your reach has exceeded your grasp on this subject. You have most of the basics right, but the nuances are escaping you.

1. The effects of jitter cannot be summed up as "Kids, jitter's bad, m'kay?" Jitter is not a single-value variable to be increased or reduced, and its effects on converter accuracy are not as straightforward as you imply.
   
2. To say that increasing jitter must decrease the accuracy also implies that the rest of the conversion system is perfectly linear in its performance, which of course if far from the case. There are cases where jitter is measurably higher but the end result is more accurate -- not just subjectively, but objectively as well.
   
3. A converter may in fact end up with a better clock reference by reclocking an external reference than by using its own internal reference. This does not apply to very high-quality converters with very good internal clocks, but it certainly does apply where there is a significant gap between the quality of the clocks and the slave device has a reasonably well implemented PLL design -- and some would say even when it doesn't, as with the Digi 002.

I will say this -- if the 1884's converters sound as good as some have suggested here, then it is unlikely that anything but a high-end clock is going to help them.

Beyond the science, our own ears tell us that sometimes it helps noticeably, other times not at all. I defy you to pick up an old MOTU 2408, try it on its own, then clock it to an Apogee AD8000, and tell me you can't hear the difference, and tell me you don't think it's more accurate "despite" the external clocking.

I am a proponent, by the way, of setups where the "lead AD converter" is also the master clock -- and our monitoring DAC is one that markets itself based specifically on its advanced RE-clocking technology. But for smaller and low-end systems, an external clock sometimes offers the best conversion on the dollar.

JSL