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Author Topic: Proper word clock implementation  (Read 161528 times)

danlavry

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Re: Proper word clock implementation
« Reply #135 on: December 17, 2004, 09:15:21 PM »

Lucas van der Mee wrote on Fri, 17 December 2004 02:08

Dan ,
You think it is ok to down our products without knowing how they work , spec out and/or perform. You use your platform for pure marketing against us, while you claim in the same response that is not on topic.

The reason why people prefer the Big Ben over Aardvark is very simple. We perform better specs wise, we offer more features and our box is better value.
You have yet to design a product that can beat the Big Ben, so I understand your frustration. But I do not understand your abuse of the PSW platform to release this anger. I consider that to be a sign of very low quality.


Lucas van der Mee,
Sr. Design Engineer
Apogee Electronics




Lucas,
First, I did not intend to restart this argument. In fact, I deleted Nika’s attempt to re-stir the pot. Nika insisted I comment. He complained to the people running the PSN about my deleting his message. Perhaps I should not have replied to his comments, but now that you are here……..well here we go again!

These are 2 of the questions asked previously on  11 6 2004. They are still not answered.

“THE BOTTOM LINE:”

I.  QUESTION:  WHICH SOLUTION PROVIDES LESS JITTER AT THE AD LOCATION?

1.   A REASONABLE FIXED CRYSTAL
2.   BIG BEN DRIVING A CLOCK INTO A CHASSIS EQUIPPED WITH A PLL VIA A 10 FOOT CABLE?

II.  QUESTION: CAN ONE EVER CANCEL OR REDUCE A RANDOM NOISE AT ONE END OF A CABLE WITHOUT KNOWING WHAT KIND OF JITTER ACTIVITY IS OCCURRING AT THE OTHER END?
(can one cancel, remove or reduce the receiver and PLL noise, some of it unknown, some totally random, by driving it with a clean low jitter clock? Driving it with any clock?)


So now you are back once more still without technical input.  You say:

“You think it is ok to down our products without knowing how they work, spec our and/or perform.”

I also know you cannot fly by waving your arms, which is equivalent to the claim that you can have better jitter performance by driving an AD externally.  And yes, lets stay technical:  YOU SAID SPEC OUT:  Thanks for reminding us all. What are the JITTER SPECS?  We are particularly interested in data supporting the claim regarding reduction of the jitter inside the AD when Big Ben is hooked as external source.

“You use your platform for pure marketing against us, while you claim in the same response that is not on topic.”

First, you guys came in here displeased with my general statements that internal clock is a preferred method.  I guess it went against your marketing propaganda, and you tried to intimidate with “your engineering of the 21st century” and the rest of the bull.  You are claiming it was started as pure marketing against you EVEN AFTER BEING SET STRAIGHT by some people on the thread. (Selective memory?)

Second, as you said, I do not make a crock, uh clock, so I am not in competition with you on that product. I feel clean. Do you?

“The reason people prefer the Big Ben over Aardvark is very simple.  We perform better specs wise, we offer more features and our box is better value.”

Hopefully you will desist from spinning “value and features” and talk like an engineer.  Please remember this thread had nothing to do with values and features. The subject we are talking about is JITTER.  

But now that you are here lets get into the engineering. Many people bought into your claims that driving their AD with Big Ben will reduce their AD clock jitter. We are not talking about whether people like what they hear when they use your clock. We are speaking as engineers about actual physical engineering principles that are SOLID. Your claims go against those SOLID ENGINEERING PRINCIPLES.

One of the visitors previously on this threat asked if you were going to offer an official apology to people around the world who believed the misinformation spewed about this product and purchased it.

“You have yet to design a product that can beat the Big Ben, so I understand your frustration.”

My dear boy trying to insult me is silly especially since I was the one who designed the first Apogee “low jitter clock” and created the concept. I may design another one in the future. Thanks for the idea.

“But I do not understand your abuse of the PSW platform to release this anger. I consider that to be a sign of very low quality.”

No technical comments? Only more personal attacks?

  ------------------------------------------------------------ ---------------------------------------------------------
Let us see your “high quality” comments in the form of a technical defense of your design.

We begin with the following questions:

Question:  Does an average AD operating with reasonable internal crystal clock have less jitter when driven by Big Ben? YES OR NO

If you say NO, the group will need to determine what steps your company should take to remedy the wrong that was done.

If you say YES, Then:

LETS HAVE YOUR TECHNICAL COMMENTS ANSWERING MY TECHNICAL COMMENTS (I and II above) (Marketing and personal attacks qualify as “low quality” responses. If you choose to disappear as you did last time without answering, well that is certainly your choice).

One can discuss concepts and principles without divulging what you call your “secrets”.  I can help you along with the following comments in the form of general principles.

EXAMPLE:(Box A) cannot correct for jitter in another (Box B) without knowing what takes place at (Box B) is as universal and general as gravity! This is no secret.

EXAMPLE: An ideal clock with least jitter is based on having all cycles identical, thus there is no room for ANY modulation of the clock. This is another universal and general principle.

I look forward to hearing a professional design engineer’s response from you Lucas.

Dan Lavry


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bobkatz

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Re: Proper word clock implementation
« Reply #136 on: December 18, 2004, 08:37:40 AM »

Level wrote on Thu, 16 December 2004 22:10

That would be a nice one to put to bed Bob. Implementation of the clock, you could give the perspective. I use my internal clock and I just don't get all these clock issues, although I would love to be proven wrong, if my internal is giving problems I do not hear, nor anyone else has noticed to date.


Another way to look at this is "the battle of the marketing against the science", or "can $1800 (retail) of external components really beat $40 of internal"?

For (in a particular test) if an external clock really beats an internal one, then the manufacturer of the converter under test must really have cut some cheap corners, OR at the time of manufacture, his technical chops were not as good as they oughta!It takes a tremendous amount of knowledge of analog, digital, RF and systems design to make a great-performing converter. Which is why my personal list of "great" converters is very small, indeed.

I know a converter designer who is modest and does know what he is doing. He also knows the limitations of his design expertise. So he freely admits that to design a great PLL would take far more time and money and consulting work than he could afford, so instead, he made sure that he had a well-performing internal clock in his converter, and exploit that as an advantage. I thoroughly agree to that philosophy.

I also know another converter designer who built a converter with "no compromise" in mind. It took one man-year to design the clocking circuits, both internal and the superior PLL. How long do you think it will take for them to make up their R&D costs?

Additionally, BOTH of these converter manufacturers have been entirely honest in their marketing statements of the capabilities and limitations of their gear.

BK
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Nika Aldrich

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Re: Proper word clock implementation
« Reply #137 on: December 22, 2004, 12:50:18 AM »

Sorry guys, I've been on vacation - still am.  I'll have to chime in when I get some time.

Cheers!
Nika
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doug hazelrigg

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Re: Proper word clock implementation
« Reply #138 on: December 22, 2004, 04:54:59 PM »

My I/O gear: Apogee 200 via SPDIF into M-Audio Audiophile 192. My question is: should I always be using the Apogee as the clock source even after A/D conversion and tracking is done, in other words, when mixing? Or should I switch to the card's internal clock. I ask because I had assumed the clock from the Apogee was "better" than whatever the soundcard used

Thanks for allowing me to but in the long and informative thread
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Eliott James

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Re: Proper word clock implementation
« Reply #139 on: December 22, 2004, 05:15:20 PM »

Please forgive my non technical observation but it does address the financial constraints placed on the designers of more comman converters, and the $ constraints of the recordist. They go hand in hand.

Many smaller studio, and yes, the project guys, don't use the best converters. They can't afford multiple channels of ins and outs of great converters. When you can clock these less expensive converters to a better clock, the whole rig sounds better. I have done this myself clocking a MOTU rig with a Mytek 2 channel AD converter. It does sound better that way. I think that is what Apogee is addressing in their marketing.

I don't think anyone is fooled into thinking the MOTU (or any other lessor brand) rigs of the world have great converters, and you could even say they are "defective" in that their clock and analog stages are not the best, but I think "defective" is a strong word. Lessor quality, yes. Less expensive, yes.

If I could I would have nothing but the best. Buy I can't. Is it wrong for Apogee to offer a better clock to make the whole system sound better? I don't think so. This is real world, not the world of absolute best.

BTW, I don't use and am not affiliated with Apogee, and I've never thought much of their equipment personally, but then I've not heard their stuff lately. Maybe it's improved. I like the Mytek gear. Good stuff.
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bobkatz

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Re: Proper word clock implementation
« Reply #140 on: December 22, 2004, 07:08:53 PM »

Eliott James wrote on Wed, 22 December 2004 17:15



Many smaller studio, and yes, the project guys, don't use the best converters. They can't afford multiple channels of ins and outs of great converters. When you can clock these less expensive converters to a better clock, the whole rig sounds better. I have done this myself clocking a MOTU rig with a Mytek 2 channel AD converter. It does sound better that way. I think that is what Apogee is addressing in their marketing.




I agree. Though from the claims expressed in these threads, you'd think that the Big Ben can improve any converter on earth. Apogee backed down a hair from that claim by revising their statement in saying that D/A converters with ASRC circuits built in cannot be improved by Big Ben.

We can extrapolate from that, since ASRCs consist of a VERY good DIGITAL PLL coupled with variable low pass filters----that any converter with a real good PLL would not benefit from the Big Ben.

What are the economics of the MOTU converters versus the Big Ben addon, anyway? To me it seems expensive enough to warrant an upgrade to a better set of converters anyway. By the way, I'm not knocking MOTU, I think they offer great value for the money. But at some point you have to look at the economics; would you put a Cadillac engine in a Yugo? How much do you have to spend in bandaids before it would have been better to upgrade the converter in the first place? What are the dollars we're talking about here?
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Eliott James

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Re: Proper word clock implementation
« Reply #141 on: December 22, 2004, 09:42:39 PM »

Well, 8 in of Mytek is $2500, 8 out is $2500, plus computer firewire interface. You're at $5500 to $6000.

8 in of Lavry Blue is $4300, 8 out is $3850. Plus firewire computer interface. Your're at $8650 to $9250.

MOTU 828 MKIII (8 in and out) is about $950. Add Big Ben at, what, $1400. Firewire interface is on the MOTU.  You're at $2350.

MOTU 828 MKIII is about $950. Clock to Mytek 2 channel AD at $975. Firewire interface is on the MOTU.  You're at $1925.

$1925 for pretty good sound with MOTU/Mytek clock, plus many other options in/out on the MOTU, plus have two extra very good converters with the Mytek.
$2350 for pretty good sound (presumed) with MOTU/Big Ben, plus many other options in/out on the MOTU.
$6000 for very good sound with Mytek.
$9250 for presumed great sound (I haven't heard them personally) for Lavry Blue.

Those extra thousands (around $4075) between the MOTU/Mytek rig and the 8 in/out Mytek setup goes to better mics, mic pres, monitors or whatever the small studio needs that will probably have a greater impact on the final sound they're after than the clarity of the converters, depending of course on the type of music they're recording.

This is the choice many have to make.

*Prices are based on an online retailer. YMMV.
My experience is a MOTU rig clocked to a Mytek 2 channel AD will noticably improve the sound of the MOTU converters, but they will not sound quite as clear and defined as the Mytek converters themselves. Can't vouch for the Big Ben.
I don't use the MOTU unit now, but did at one time.
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Level

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Re: Proper word clock implementation
« Reply #142 on: December 22, 2004, 11:38:30 PM »

Great point Eliott!

Some cats are just rolling in the dough, have 200K in outboards of different kinds and still will not pay an acoustic engineer a meager sum of 3000.00 to come in and provide proper sound control for the rooms.

It IS a situation of priorities. Throwing dollars at issues has never been the best remedy. Room/Monitors/calibration and clean signal path is the one half. Knowing proper useage and judgement is the other.

I had a 3 million dollar facility I was the Chief engineer of 10 years ago, what I have now smokes it all and little of what I have now is truly from a technological development.
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danlavry

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Re: Proper word clock implementation
« Reply #143 on: December 23, 2004, 06:53:46 PM »

Eliott James wrote on Thu, 23 December 2004 02:42

Well, 8 in of Mytek is $2500, 8 out is $2500, plus computer firewire interface. You're at...$1925 for pretty good sound with....This is the choice many have to make....



There are many ways to configure your studio, and yes mics are important and so are AD’s and speakers. Different people balance it differently. Personally, I subscribe to the notion of having very good tools, for a carpenter, mechanic, EE, for mastering, recording… There is a lot of range between spending a 1 million dollar for one mixing counsel and a few grand… What should investment priorities be? This is not the place to argue specifics while referring to specific gear and prices.

But I agree with you that one should spend their money wisely. One way to prioritize is to understand the technical facts, not just react to hype, advertisements, specific unit recommendations.

This thread is about clocks and jitter is an important clock issue. So IF you decide you need external clock, what then? Let’s isolate the clock as a STAND ALONE decision.

What do you want from an external clock? Say you need a few frequencies (such as 44.1KHz, 48KH, 88.2KHz and 96KHz) as a steady low jitter source. What is better than a box with 4 (or more) good crystal oscillators and some line drivers (cable drivers?). It is a cheap, good solution based on the right technology, and it is the cheapest way to go.

Big Ben claims some wonderful secret jitter filtering. You do not get to filter a good crystal based clock. You can receive a jittery clock and filter out the jitter, then send it as a clock. Is that what you need? A jitter filtering box, acting as a slave PLL to a poor clock? Or do you need a steady stand alone low jitter clock box. It is an important distinction to make. In most cases, a house sync is a stand alone master clock.

A few people said that the external clock improved their poor AD’s. I am not at all convinced of it, accept in very rare cases. As a rule, MOST of the jitter problem is ahead of the external clock (cable, receiver, PLL…). Say you have a real bad internal clock, say 1nesc (1000psec). But the same designer put in a 50psec random jitter PLL circuit for external lock (including cable, receiver…). If you drive that circuit with external 1psec jitter, the combined jitter outcome is 50.01psec. If your external clock jitter is 10psec, the combined outcome is 50.99psec – less than 1psec difference. If the external clock jitter is 25psec, the outcome is 55.9psec – less than 6psec difference! As long as the external clock is less than 1/2  the internal jitter, you are almost completely limited by the internal PLL, not the external clock.

Do you need to receive a dirty clock and clean it? Or do you need a fixed clock (a few known frequencies). The statement “we filter jitter” is too general. The question is where do you filter it. Filtering it at the INPUT (received jittery clock) does not matter to most house sync applications where you do not need to start with a jittery clock. One way or another, you are looking for say a word clock with repeated 01 cycle pattern where each cycle is identical to each other cycle. That means steady voltages, fast rise and fall times and low jitter. The same holds for AES but with a different pattern. No one is sending secret messages forward. I would not call it a marketing hype if they pointed out clearly that the jitter applies when the box operates as an intermediary PLL, trying to “look like” a stand alone crystal while tracking yet another clock. But they got carried away claiming that their clock as a stand alone box, has some magic ability to impact what is ahead.

I am amazed at how much talk and focus has been given lately to clocks. Yes, you may need an external clock, but it is not the “next step in improving conversion” like so many people were convinced of. Conversion is complex and has many aspects to it. A clock is only one such aspect, and my 50psec PLL jitter example shows that an external clock need only be two or three times better than the PLL, and you are at the point of diminishing returns.

Regards
Dan Lavry
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bobkatz

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Re: Proper word clock implementation
« Reply #144 on: December 23, 2004, 10:46:26 PM »

Thanks, Elliot, for the dollars to donuts comparison.

I'd spend the root money on great converters first. If your car doesn't have a good motor, it doesn't matter how much premium gas you put in the tank, the performance will suck. I disagree that great mikes and preamps still sound good through mediocre converters. Some people have actually gotten used to that "hazy" sound, but when they hear the transparency improvement with a great converter, it changes their whole day.

A client changed his analog mixdown from direct into a Masterlink using its converters to a high end external converter running at 2496. The sound quality of his mixes went up tremendously. I say, don't scrimp on converters!

BK
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Eliott James

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Re: Proper word clock implementation
« Reply #145 on: December 24, 2004, 02:37:33 PM »

I agree with you, Bob. If you can find the $, it makes sense to go for the best.

On a whole different level though, it's like you wrote about the Lavry Gold DA. When you've got those $ in your budget.....
Smile
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Lucas van der Mee

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Re: Proper word clock implementation
« Reply #146 on: December 27, 2004, 01:40:41 PM »

Bob and Dan,

You are both “interpreting” our words and saying that we claim things we don’t. So let’s get it straight one more time.
We do CLAIM:
1.   The Big Ben is an excellent low jitter solution if you need a master clock
2.   If you have to clock to a very jittery source, you’ll get better results most of the time by having the Big Ben cleaning it up first.
We haven’t claimed anything else.

We did REPORT that users feel that their converters sound better when they clock to the Big Ben. These reports are multiple and consistent. That is where you guys become all upset about, because it seems to be against all we know about conversion, etc.
So was I, when I got the first reports, but unlike Dan I do not say: “that cannot be”. I do trust the critical thinking and listening of my customers and investigated the results. The fact is, through our own investigations we have discovered that there is indeed an audible improvement in most cases when using Big Ben as a master clock. We have not CLAIMED that this is due to an external clock lowering the jitter. This is your own presumption and it is wrong.

Bob,
With regards to your comments about ASRC based clocking: In contrast to your claims, SRC based converters usually do NOT have a great PLL. That is the whole purpose of using the SRC. You can use a cheap chip-based PLL on the input side of the SRC and a crystal on the output side which also clocks the DA chip. Simple, but it means that the SRC is ALWAYS in the audio path. So you never get the original data and always get the SRC artifacts at the DA converter chip.

Lucas van der Mee
Sr. Design Engineer
Apogee Electronics
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Lucas van der Mee
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Apogee Electronics

bobkatz

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Re: Proper word clock implementation
« Reply #147 on: December 27, 2004, 07:18:34 PM »

Lucas van der Mee wrote on Mon, 27 December 2004 13:40

Bob and Dan,

You are both ?interpreting? our words and saying that we claim things we don?t. So let?s get it straight one more time.
We do CLAIM:
1.   The Big Ben is an excellent low jitter solution if you need a master clock
2.   If you have to clock to a very jittery source, you?ll get better results most of the time by having the Big Ben cleaning it up first.
We haven?t claimed anything else.




Aww gee! You took all the fun out of it, Lucas! Well, regardless, it doesn't matter how much water has gone under the, dam, let's just limit the claims to that and test for that. Words are slippery and I personally believe that Apogee's printed advertisements and some previous statements by Apogee employees in this thread have gone somewhat beyond those claims.

Quote:



Bob,
With regards to your comments about ASRC based clocking: In contrast to your claims, SRC based converters usually do NOT have a great PLL.




Did I claim that? Not to my knowledge. Of course you are right. The analog PLL in an ASRC-based converter can be anything from a shitty to an ordinary to an extraordinary model. Perhaps you got the idea that I was claiming otherwise from my statement describing the ASRC as containing a superb Digital PLL, which of course both the Analog Devices and TI chips contain. However, it is the dual stage reduction of a great front end (analog) PLL combined with the Digital PLL (and good power supply, grounding, and layout, of course!) that makes an ASRC-based DAC sound as good as it does. I have NEVER claimed otherwise, unless someone has misinterpreted my words or taken them out of context.

Quote:



That is the whole purpose of using the SRC. You can use a cheap chip-based PLL on the input side of the SRC and a crystal on the output side which also clocks the DA chip. Simple, but it means that the SRC is ALWAYS in the audio path. So you never get the original data and always get the SRC artifacts at the DA converter chip.




Absolutely, you can't get something for nothing. The AD 1896's predecessor did not have sufficient resolution to be considered "super hi-fi", but things have changed drastically. The distortion products produced by the 1896 and the TI equivalent are orders of magnitude lower and the SRC artifacts are all-but inaudible.

Well-designed ASRC-based D/A converters employing the latest ASRC chips have raised the quality bar so much that it requires a very-expensive, well-made design, in my opinion, to top them sonically.

BK
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Nika Aldrich

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Re: Proper word clock implementation
« Reply #148 on: December 31, 2004, 11:45:33 AM »

Guys,

I've been on vacation for the past 10 days and have intentionally avoided the internet for that time.  I have no idea of all that may have transpired, but have read through the last several posts and am relieved that it seems we're finally coming to some conclusions and agreement on some matters.  Moreso, it appears we are clearing up a lot of miscommunication and opportunity for further miscommunication.  Because it appears that this forum is going to be turned off in the next 24 hours I am not going to go any further into reading everything and trying to respond as that seems like it would be wasted effort.

Thanks to all that participated and thanks to all that worked to encourage cooler heads to prevail.

Nika
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danlavry

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Re: Proper word clock implementation
« Reply #149 on: December 31, 2004, 04:24:37 PM »

Nika Aldrich wrote on Fri, 31 December 2004 16:45

Guys,
.... it appears we are clearing up a lot of miscommunication and opportunity for further miscommunication.  Because it appears that this forum is going to be turned off in the next 24 hours...Thanks to all that participated and thanks to all that worked to encourage cooler heads to prevail.
Nika


Nika,

I am sorry to see that you are back disseminating misinformation again. Due to an outpouring of an amazing number of intelligent people, I will be a permanent moderator on this site.

Dan Lavry
http://www.lavryengineering.com
“In a time of deceit, telling the truth is a revolutionary act.”
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