[art]

Well, yes!

Look, we all have the same problem. Even the guys who make the crystals/clocks.

There is no way to do it cheaply. Everyone wants a clock that is "lights out", but only costs $1. It can't be done.

Likewise, for the folks who make these parts............

A lot of them have the capacity to "grow their own rocks", but the bosses say it is too expensive. "Just go buy some blanks, from China, and we'll grind 'em." They only grow their own, for the specialty parts. Sometimes, the bosses say to just buy the complete part, and we will put our name on them. All of this is viewed as nothing more than a commodity, so it has to be done as cheaply as possible.

This will help to segue into something I am planning to bring up. I do work, in an unofficial way, with one or more companies that build these parts. They know that I have the equipment, knowledge, and more importantly, the time, to look into some of these subjects more deeply than they do. One in particular measures their parts at 10 Hz offset. They routinely send me samples to measure, since I do so at 1 Hz offset. I send the samples and the data back to them, so they can try to correlate what I find with their internal measurements. Sometimes they go as far to grind the top off of the parts, and probe them to see what they can find. (Seems like more work to me, but if that is how they do it, well, it is their business.) I have a hunch that one of these ventures led to a part that is available, that is shown in the data sheet of a certain DAC part. (So I have been told. All I know is that the part is available, but only if you know the p/n and can buy them buy the reel.) (And that is the other problem. Even if you know the p/n, like the NDKs, you have to buy an entire reel. Who is going to do that, other than a large company? Or some goofball consultants, who think they can make money selling sorted ones.)

More later............

[art]

Well.................had a reply to your question, and between ATT "DUH-verse" and the power company................it is gone!

It is one of those days. When I calm back down, I'll try to reconstruct it. Of course, it will be something totally different, but you won't know that!

(And speaking of DUH-verse, which goes down all the time, when it is up, I can not connect to any of my sites. Mail, ftp, website, you name it...............nada. If only I was in charge of that what ISP we use.) (Who am I kidding. The alternative is probably just as bad. Maybe worse.)

[wushuliu]

Great thread, Pat, which pretty much convinces me that the standard DIY approach of ordering a couple of clocks off of the worldwide web and replacing existing ones in a DAC or USB interface is a complete crapshoot.

On a positive note, it means I can just use the vacuum cleaner to pick up the ultra-tiny NDK clocks that have disappeared somewhere on the floor near my work area. 

Lol. Same here.

And thanks for the thread, Pat.

[art]

OK, here is condensed version of the first part of the reply I was working on.

What do we do?

Well, not much! There is no way to get the level of performance, that allows digital audio to reach its maximum potential, without a fair amount of effort and expense.

And it is not only us who are in this situation. The folks who make the crystals and/or clocks that can be used are facing the same issues. While most of them have the facilities to "grow their own rocks", the bosses are not interested in that. "Just go and buy some blanks, from China, and we will grind 'em ourselves. On second thought, no, forget that. Just buy the whole dang part, from China, and we will put our name on it." They only go the full route of grinding their own blanks (still probably sourced from China) for their top-of-the-line products. It simply costs too much to do anything else.

The reality is all of these parts are viewed as a commodity. Translation: cheap. Dumbed down specs. Jitter at frequency >1 kHz. Noise floor. Looks good on the spec sheet. Industry is used to that spec. The purchasing guys think they are buying a quality product, and everyone is happy.

Except us.

Some of us, through arduous trial and error, have found that jitter matters, and the jitter that matters is not the jitter on the spec sheet.

And what is wrong with any of that? We all have several digital audio products, with generic $1 clocks. Which is why they pretty much all sound the same. But, maybe 20 years ago, those of use who had a background in this stuff started to discuss the possibility that jitter at 10 Hz was important. There was no doubt, among us, that only measuring the noise floor was useless. But, measuring at 10 Hz offset was something that took some effort.

(As you can see in the most recent post, going by even 100 Hz numbers miss the mark.)

Eventually, the 10 Hz idea started to gain traction. I know of one of the "big boys" that measures their batches at 10 Hz offset. (I know this, because they frequently send me samples, to look at, since they know I have the time, equipment, and more importantly, the desire to look more closely. When I return the samples, they usually grind the top off of some of the parts, and probe the unit, to see if there is any correlation to their internal data, and the results I come up with.)

But, some of us were still not happy, and that is why we started looking at 1 Hz data. Eventually, for reasons I will gloss over, we found that it was necessary to go down to 0.1 Hz.

Which brings us up to now.

(Going in a slightly different direction, from the original twilight zone ether of the 'Net. So, new post for that.)

[art]

"Why does it cost so much to buy something that you have tested and sorted, that only cost you $1?"

Well, for starters.................we do not make as much as we should, to make it viable. We can only buy the parts we need, for our internal use, if we buy an entire reel. (Either 1000 or 2000, depends who we buy them from. Some places want 3000. Like we can ever use or sell that many.)

So, since we a lot of these parts to unload, what to do?

First, we have to sort them, to get a rough idea of the potential yield. OK, maybe we only have to do a fraction of the reel to get a good idea, but that takes a lot of time. We now know how many we are going to get from a reel.

I am not going to give the exact number, but the yield percentage is single digits. Which means if we buy a reel of 1000, then at least 900 are of no use to us. So, right off the bat, a $1 part is now at least a $10 part.

Use your imagination, and you can probably guess why we sell the really good ones for $30. Not counting the time to do it.........................the cost of the equipment................and what-not, but..............

If we sold then for what they realistically cost to test, sort, etc., then we should probably charge $50. Which may or may not leave much of a profit margin.

Kinda pricey, eh? YEAH!

Would I pay $50 for something that good?

Maybe not. I would probably shell out another $25-30 and buy an SC-cut crystal that would be much better. If you are going to spend that kind of money, it better be good.

At $30.........................well, you can buy a part from Digikey or Mouser that is probably decent. I wouldn't use them, because I know they are not good enough. But, if you need something better than the bog standard $1 special, what alternative do you have?

None. Unless you spend at least $75 or $80. Oh, did I mention that is if you buy several of them. I know of one company (they used to make crystals for microwave oscillators we used back when I had a real job), that have an odd policy of "Well, tell us what you need, and how good, etc. and how many, and we will get back to you and let you know if we are interested." (Yes, I am dead serious! That is how they operate!) Other outfits will say it costs x, and take y weeks, but since they do work for the military...........................well, ha! Never on time. Never on budget. It is a way of life with them. Yes, you get what you wanted. Just takes forever and costs a lot more than promised.

So, here we are. Back at Square One.

As an aside, yes, we sell sorted parts. And they cost a lot. We probably should charge more, but since there is another popular part that costs around $30, that kinda sorta limits how high we can go.

And what about all of the ones we deem are not good enough?

Good question!

We could sell ones that are not up to our standards, but are probably better than aforementioned $30 part, for maybe $20, and pick up some money. But, unless you are a manufacturer, and you only need one (or maybe 2) pairs, is it worth saving a few bucks to buy "almost as good"?

No, probably not.

Eventually, we are going to have a massive "mix and match" sale, where we put all of the ones that we don't want, mix them in with the "almost as good", and probably some "you really don't want to use these dogs", and blow them out, in large batches (say 25 or 50 pieces). At that point you guys decide for yourself how much do clocks REALLY sound different!

Some will get lucky. Will be a darn good bargain. Some not so lucky. But, it won't cost you and arm and a leg. Remember, those parts that we buy? Yeah, you can't buy just one. Except for some outfits that somehow got their hands on some, and sell them one at a time. (For more than $1, I might point out.)

OK, enough of that "behind the scenes" stuff. Next post will be some interesting parts, that will show what can be done, for a buck or so.

Sort of!

[art]

OK, here are some parts that show what can be done, at decent price.

I do not believe these parts are still in production. Even though they are a SM part, they are a bit on the big side (3x5 mm), and are just a crystal. Most manufacturers do not want to mess with crystals. You have to design the oscillator. And make sure it reliably starts under a wide range of conditions. Takes more parts, which means more cost and "real estate". IOW, easier to buy a clock chip, and leave the oscillator design to dorks like me.

The bigger problem is the cell phone market is driving this industry. Small size, low cost, and all that entails. While there is a movement to better audio, their idea of better is far from our idea of better. Even for companies like ESS, our segment of the market is pretty darn small, and not worth much effort.

Having said all of that...................



As you can see, these guys do a very good job of repeatability. Darn near all of their products that I have looked at exhibit these qualities. Yes, there have been some that have a larger spread. I have reason to believe they take my data, and examine it, to see if there is a certain "knob that needs to be tweaked", in the manufacturing process. In truth, it is not that simple. But, these guys seem to be willing to give it a try. (I suspect they want to surpass the company ahead of them, in terms of global sales. We are talking hundreds of millions, annually, so it is encouraging they are looking for any edge, to move up.)

Anyway, these are a roughly $1 part. It can be done. Not easy, but it can be done.

In terms of how they would stack up, to what we consider to be "yeah, you need this level of performance", I would rate these as very good. (Ok, too bad they are not an audio sampling frequency multiple. But, if you are using an ESS DAC, in an async mode, these would be something I would look at. If you can find them...........)

To put it another way, if you were to reference these parts to 45/49 MHz, and looked at the 10 Hz numbers, they would be a tad better than the aforementioned $30 specials. Actually, I would rate them better. We have other metrics we use to evaluate clock performance. Unfortunately, we consider it to be proprietary, and even if I did share it....................let's just say unless you work with this stuff, all day long, it would be a lot of gibberish. You'll just have to trust me on this last part.

OK, at this point someone will want to ask "Well, you ever do is talk about phase noise numbers, and this, that, or some other offset frequency. Now you want to tell us that it isn't important, and that you have the functional equivalent of some secret Masonic handshake?"

Well, no. But, phase noise is an easy number to understand and grasp. Just takes time to measure below 1 Hz offset. But, there are other properties that are important. While I have stated that drift is not important (it isn't), there are short-term "funnies" that clocks do, and finding out which ones are important, which ones are not, and what level of the important ones took a lot of work. And, honestly, isn't easy to explain.

Ok.................next up.....................stuff that will really make me more unpopular than I already am! (How can that be possible? Just wait.)

[art]

OK, here is a bog standard $1 clock, a 5 x 7 4-pin package, that you can buy at any number of places. Don't know who made it. Have a pretty good idea, looking at the number on the case. But, it isn't about them. It is about what you find in 99.99% of your typical audio product.



Yeah, not so hot. Ok, not dreadful, but let's just say this is why digital audio sounds like digital audio, and not what we call "audio".

Now, if you believe that clocks are spec'ed by "jitter" numbers, you know, the ones that start at 1 kHz and go up to 100 kHz (or wherever), well it says 170 fSec. Ok, big deal. Couldn't pay me to use this part. Ok, maybe in my ham radio, if I still did ham radio. (No, probably not, because I probably have a 100 or so parts around the shop much better than this one. And there is a reason they are just "sitting around the shop".)

But, what if you decide to be brave and extend the jitter frequency down to 100 Hz? Some folks are that brave!



Hey, how 'bout that: it doesn't change! So, maybe those folks aren't really that brave, after all.

Let's get braver....................10 Hz!



Oh, my..................the jitter doubles. No way we can put that in the data sheet!

But, what if you get really, really, really brave, and go down to 1 Hz? (Heresy!)

Uh...............saving that for later. You'll see why. (Heh, heh, heh!)

[art]

OK, everyone still here? Everyone ready to see how many people in the industry I can get to hate me? (Assumes they don't already. Most probably do, so what is a few more?)

First off, I can see ABSOLUTELY NO REASON to use this next part. Yet, it is really popular. (Just goes to show how advertising in trade journals pay off.)

If you look at the datasheet, us skeptics just shake our head and say "WHY?" Why go to all the bother? OK, I get it. Put a nice rock, in a chip, and phase lock it to some oscillator. This way, we can put all of our efforts into a really good rock, and benefit from it. And not have to grind dozens of different frequencies.

So, here is the data sheet:

https://www.silabs.com/documents/public/data-sheets/si530.pdf

And the diagram of what goes on inside:



So....................let's say you are one of the guys who thinks that all jitter comes from all the junk that is created by muxes, dividers, etc., etc., etc. So why in the world would you use a clock that is full of that crap?

(Ok, not saying any of that is not a problem. It just isn't the biggest problem, when it comes to digital audio. Yet, a lot of folks pick a clock source that has those problems already built in. So, you are behind the 8-ball, before you even start.)

So................drum roll......................here is this marvel of modern design. Overlaid with our bog standard $1 special. And what is possible, from the right vendor. For roughly that same buck.



Oh my goodness....................that is truly awful! Yes, much worse than what you can buy for $1! So why do so many of you use these things? (You should see some of the hate mail I receive, from manufacturers, who take strong exception to my measurements. Of course, their main retort is "your measurements are crap, and you have no idea what you are talking about.................you are the world's biggest know-nothing idiot.............these parts have really good measurements, so stick it in your ear and don't ever bother me again, got it?")

Ok, got it!


I can hear the howls of derision already..................

"We use one that is selected for low jitter'. So, there!"

OK, maybe you do. It might get rid of all that crap around 1 kHz. (Some of you may recall what happens when I stick an extra divider in the measurement chain, to get the frequency down to where our equipment can measure it. It is in that area where you will see those effects.)

But....................if you look at the 49 MHz sample.....................

It also runs through that "extra divider", and we can see how it stacks up to the marvel of technology. (Actually, our extra divider adds crap in around 100 Hz. So, how do you explain all the crap from 1 kHz  to 10 kHz? Only one explanation! Who can guess what it is?)

So, using our standard, of jitter from 1 Hz to 1 kHz, this is what we get. It is over 10 pSec. While the other 2 parts are in single digits.

OK, maybe I am being too picky, and not fair enough. Maybe if we look at jitter from 100 Hz up, and not the stuff down around 1 Hz, the area under the curve will be less. And let's see if the nasty crap above 1 kHz will be mitigated.

OK.................here it is:



Oh, ok! We are back to close to that magical femtosecond range! (Remember, in the previous post we saw the 1 kHz and 100 Hz numbers were pretty much the same.)

"See, I told you that you were an idiot!"

Yeah, whatever..................

So, in the sake of fairness, let's assume someone is brave and goes down to 10 Hz!

(Isn't this exciting?)

"Hell, no!"



OK, now that we are looking at more of the true jitter, and not the silly noise floor, the divergence starts to show up. (The reason why the 3rd sample, in the second plot is a bit higher than the 2nd sample, which is clearly not as good, is the effects of that divider, and having the s/w manipulate the data. The latter skews the noise floor. You can see it if  you look closely.)

So, now we get a better picture of the relative values. The 3rd sample pretty much stays the same, and the crud added by the extra divider (which is also in sample 1, remember) is not significant. Sample 2 is about double its previous, and sample 1 also is roughly double. Any wonder no one publishes jitter below 1 kHz? Any wonder now why it means pretty much nothing?

(I had planned to show jitter from just 1 kHz, to 100 kHz, but it somehow did not make it to the thumb drive I thought it was on. Oh, well. If you really want to see it, let me know. But, haven't we seen enough? Do I need to get more manufacturers mad at me!)

Well, at this point, best to wrap things up for a while. You guys have a lot to think about.

"Are you going to share with us any of the new hate mail that you get?"

No, probably not. If folks know I am dying to show how many of the emperors are buck nekkid, they may keep their pie holes shut. Think of the entertainment us dorks in Texas will be depriving ourselves of!

(I think I just ended a sentence with a preposition. Better stop before the resident English teacher sees it, and raps the back of my hand with a metal-edged ruler!)

Enjoy.................

[art]

Guess what.....................found the "spec sheet" for the NDK NZ2520 parts.



Yeah, some will perform that well. But a lot will not.

What do you want for $1?

[mike gergen]

Pat

3 questions from an idiot;

1 Temp
Knowing that temp variations affect jitter, how does it affect jitter. Is it he variation over a short period of time? Like have the furnace or AC turning on and off and the clock is not covered well. Or is it the base temp, like having the house at 68F in winter and 72F in summer. Do we care about the base temp once the temp has stabilized?

2 Power
A clean supply to the clock is crucial, we know this. How does this translate? Is there a PSRR number , or similar, for clocks based on frequency? Assuming we don't want to use a 3 pin regulator is it because the high frequency stinks or is it because the output voltage can drift vs temp?

3 Oscillator
At another forum there is much talk about buying good crystals and they are using the crystals in different oscillators. Being 30+ years since I've used my FCC license or looked at RF oscillators, can you explain some the whats, whys, and the don't do this unless you're a huge idiot....

Mike

[art]

Pat

3 questions from an idiot;

You are not an idiot. You are not posting this on that hobbyist forum!

1 Temp
Knowing that temp variations affect jitter, how does it affect jitter. Is it he variation over a short period of time? Like have the furnace or AC turning on and off and the clock is not covered well. Or is it the base temp, like having the house at 68F in winter and 72F in summer. Do we care about the base temp once the temp has stabilized?

It doesn't affect jitter. It affects stability, which is too slow to be considered as jitter.

The thing that is more important is that you keep the oscillator powered up and actually oscillating. Figure that it takes 10-20 minutes for most crystals to settle in, once they are powered up. The enable pin, on dang near every commercial part, turns everything off. This is to save power. Which, in our applications, isn't a concern. Some will argue that having two clocks oscillating, even if they are well isolated, is a no-no.

OK, let's say it is. You need to find a better way to isolate them, so that both are on and oscillating.

2 Power
A clean supply to the clock is crucial, we know this. How does this translate? Is there a PSRR number , or similar, for clocks based on frequency? Assuming we don't want to use a 3 pin regulator is it because the high frequency stinks or is it because the output voltage can drift vs temp?

The guys who make oscillators keep their regulator circuits a closely-guarded secret. This is because they only measure the jitter above some frequency, usually 1 kHz. So, if that is how you measure jitter, then yes, it makes a big difference.

But, since you asked........................

Here are two of our crappy products, that are mainly different in that one is powered by a wall wart, with a 5-legged $1 gizmo for the clock reg. The more expensive one has a traditional "leen-yer" power supply, and a discrete reg that we cooked up.



If you look in the range from around 100 Hz to 1 kHz, you can see about 2 dB of difference. You will have to trust me, and believe me when I state that is the difference in the regs.

One of our dealers would kvetch that not only could he hear the differences, in the regs, he would insist he could hear the difference in the caps we used on the regs.

OK, let's say he can. We can not measure it, so we tend to say it is insignificant, if the difference does exist.

Of course, he claims our test equipment is not sufficient to do its job.

Ok.......................

As for reg drift.................

Someone that you probably know built some regs that used a mish-mash (color-wise), of different color LEDs, to get the right voltage for the clock. I think we were able to determine we could see drift, wrt temperature.

Maybe.

We would see more drift when the A/C cut on and off. Which is why the new building has a storage area that doubles as the "environmental chamber". Which means it is tucked away in a remote corner, where there is no HVAC system.

3 Oscillator
At another forum there is much talk about buying good crystals and they are using the crystals in different oscillators. Being 30+ years since I've used my FCC license or looked at RF oscillators, can you explain some the whats, whys, and the don't do this unless you're a huge idiot....

Mike

Well, let's say they are the idiots, but for other reasons.

First, you need to have the right crystal. A lot goes into that. And sometimes, just maybe sometimes, you can find some sub-$1 POC crystal that will surprise you. But, you have to be lucky, and then some. And it sometimes it takes more than luck.

The sub-$1 POC crystals we used to build our clocks with were able, on occasion, to yield great results. But, they were not an ideal configuration. It made things tricky. You had to operate on the right part of the impedance curve. You had to have the drive just right. And, believe it or not, the Q had to be just right. Too low................yeah, forget it. No way it was going to work. Too high, and it would never work. (It was at that point I decided we needed to find a better alternative.)

So, if you have the wrong crystal, you either have no chance, or you get really lucky.

If you really do have the right crystal, they are a lot more forgiving. You can do most anything to them, and they seem to work fine.

Of course, knowing that the idiots are spec'ing these crystals, and they don't really know what is good, well, all bets are off.

(I can say this because I am 99.9999% certain none of the "idiots" have the background that I do, and since they are the first ones to tell me that I am the one who is really the idiot........................well, I did design oscillators, for a living, at one time. And not some computer/innerwebs related tasks. 'Nuf said.) (Ok, probably too much, but some of those folks have seen fit to malign me, when I am not around.)

At this point, I will point out that the place I worked at built a 6 GHz SSB microwave network. (No, I did not design the master oscillator. That was done by some place in Austin, that probably had ties to Charles Wentzel's outfit.) Anyway, the point is this system had to hold 1 Hz stability, coast-to-coast. And this was at 6 GHz.

Not an easy task. (Ok, somehow it was phase-locked to the 100 kHz LORAN-C network.)

Anyway......................when we were packing up to move, I found the phase noise plot of the system. This was measured at the 6 GHz clock, so that we could use the "90 degree phase shift method", of measuring phase noise.

That clock put most audio clocks to shame.

OK, granted, I think we paid $40k, for the master clock, at each repeater. So, for that price, it better be good.

But, it was 6 GHz.

Not 24.576 MHz.

Anything else?

[THROWBACK]

So, what might this mean for the average audiophile like me? Let’s take just one example. My very best digital recording is a Mercury SACD of Rachmaninoff’s 3rd Piano Concerto played by Byron Janis. The original recording was made in 1960.
 
But I also have the same recording on vinyl. I had a group listening session a couple of weeks ago in which I played both versions. The result: everyone preferred the vinyl version.

“Lot’s more involved here other than just digital vs. vinyl” you might say, and you would be right, of course. And the differences were not huge, but overall consistent with my daily experience. When I want to really listen to music, I find myself reaching for my digital only when I do not have the same piece of music in my record collection.

Are you saying that I could (maybe) get a lot closer if I upgraded the clock in my DAC?

[art]

In theory, yes.

The problem with the theory is that it is not easy to implement.

1.) Some frequencies are a lot harder to make quality clocks than other frequencies.

2.) It isn't cheap, to make a good clock.

3.) It isn't practical for most manufacturers to spend the money to get a really good clock. At least not if they want to hold the price down. Everyone only wants to spend $1, for a clock. It isn't going to happen. (Unless you are as stupid as we are, and buy some gizmo to measure an entire reel of $1 parts. Assuming you have >$10k to buy the gizmo. And know what to do with it. Which is another story. I know of one crystal manufacturer that has the $33k one that ours is based on. They have never figured out how to make it work. I know, because they told me so. But, they did not want to invest the time or money to pay me to show up and show them how to use it.)

4.) Some designs are harder to fix than others. Ones that use a DAC chip that does everything async has its own issues, when it comes to sound quality. Yes, some of those can sound very good. There are some folks who can not stand how they sound. Possibly due to their personal prejudice, based on their understanding of how they operate. Another one of those "well, in theory...................blah blah blah" things.

5.) And the big one..........................

99% of the industry (maybe more) has no idea what a good clock really is. You can read any number of forums, and see any number of threads, all discussing x pSec (or x fSec) of jitter. None of which mean diddly-squat. Unfortunately, the manufacturers are of the same mind set. Some are clueless that things can sound better. Some are convinced they are already at the pinnacle of performance. Some just don't want to hear about it.

Some tell me to shut up and go away.

Most of them just are not interested. Either because they know it will cost more money, they are unaware how much better they can make their products, or they flat-out just don't care.

Look...................there is one company, that makes fairly decent part, that most companies can buy for around $20, in the quantities they would use them in. (I haven't checked the price lately, so it may even be a bit less than that.) But, how many use them? Not many that I have seen.

But, even if they do.........................

How can I put this in a way that will not get various parties upset....................?

When these parts were introduced, a manufacturer that we know bought several pairs, and had us measure them. Around 3/4 of them met spec. From what I recall, the total number of units we measured for them was around 2/3 of which we would consider as "decent". IOW, sticking one of them into a product would give a level of performance that would set them apart from the competition. But, would still leave something to be desired. (What those same parts would measure today, I can not say. Your guess is as good as mine whether or not they got better, stayed the same, or the folks in China who supply the crystals are dumping whatever they can on them, and get away with it.)

So, there is a starting point. If you want to attempt to make your DAC sound better, you can try one. Assuming it will fit, they come in the right frequency, and someone can help you if you can not perform that task yourself. You will only be out around $30 to try one. (In theory!)

A lot of folks have gone back to vinyl. I understand why.

[THROWBACK]

Art, thanks for your reply.

Looks like I have some digging to do.

1. Does my Ayre QB-9 use a DAC chip that does everything async?
2. What clock is in there now?
3. How hard would it be to replace?
4. Where does one find the magic $30 replacement?

[HAL]

There is an external clock system that M2Tech made many years ago to drive their XMOS USB to S/PDIF, I2S, AES/EBU interface box.   

There was an external switch that selected the clock family that was to be used for what you were playing.  A bit more manual than most probably like.  It used a 50 Ohm coaxial connector output with RF cable between the two units. 

I have one here.  Is there a way to measure the unit for a possible upgrade? 

[art]

Art, thanks for your reply.

Looks like I have some digging to do.

1. Does my Ayre QB-9 use a DAC chip that does everything async?

Don't know........................Charlie is no longer with us, and I haven't talked to them much since then.

2. What clock is in there now?

See above. I do know Charlie paid a lot of attention to the clocks, as everything else.

3. How hard would it be to replace?

See above.

4. Where does one find the magic $30 replacement?

Nothing magic about it.

Mouser...................Digikey....... ........others...................

http://www.crystek.com/crystal/spec-sheets/clock/CCHD-957.pdf

[art]

There is an external clock system that M2Tech made many years ago to drive their XMOS USB to S/PDIF, I2S, AES/EBU interface box.   

Oh..................those guys...................(if it is who I am thinking of)

How can I say this diplomatically?

One of our dealers sent us his USB-SPDIF converter, made by those guys, when he signed on with us.

"Well, did you measure it? What can you do to fix it?"

"Uh, yes...............and nothing. Do you want me to throw it away for you?"

There was an external switch that selected the clock family that was to be used for what you were playing.  A bit more manual than most probably like.  It used a 50 Ohm coaxial connector output with RF cable between the two units. 

I have one here.  Is there a way to measure the unit for a possible upgrade?

Of course! The question is do you really want to spend the money for us to measure it? Since you are not a manufacturer, I guess we could give you a break, on the price. But, if it is what I suspect that it is, I would not feel great about taking your money.

Let's put it this way.......................you can probably buy what is inside it for around $30, from Mouser or Digikey. (Translation: if you can take the lid off, you will know for certain. And that won't cost anything!)

[HAL]

Ok, I will take the panels off and look what is inside. 

[audioengr]

Nothing magic about it.

Mouser...................Digikey....... ........others...................

http://www.crystek.com/crystal/spec-sheets/clock/CCHD-957.pdf

This is a decent oscillator at 45 and 49MHz, but not at 24 or 22MHz.

Try this one instead:

https://www.mouser.com/datasheet/2/94/CCHD-575-18036.pdf

Steve N.

[audioengr]

Art, thanks for your reply.

Looks like I have some digging to do.

1. Does my Ayre QB-9 use a DAC chip that does everything async?

It's not the DAC chip that is asynch, it's the USB interface circuit.  This was the old asynch technology from Gordon Rankin, using a TAS1020B chip, called Streamlength.  I have used the TAS1020B in earlier products, the Off-Ramp 3 with my firmware coming from another company.  The newer technology of my Off-Ramps 4-6  sounds better, however I did go back a upgrade the decoupling caps and clock in the Off-Ramp 3 for several customers and it is quite good now.  I don't do mods to other companies products anymore.

The latest version is XMOS-based and supports DSD.  It seems to use two CCHD957 oscillators at 49 and 45MHz.  You will be hard-pressed to find better than these off-the-shelf.

They also changed DAC chip from the Burr-Brown DSD1796 to the ES9016S at some point.

Read more at https://www.audiostream.com/content/ayre-qb-9-dsd-dac#8osL6QBPDSSmsA1j.99

2. What clock is in there now?

I think you may have to open it up and examine it to see what is used for the clock.  I believe I used 12MHz in the Off-Ramp 3.  For XMOS, you will find two oscillators, at 24.576MHz and 22.5792MHz or 49.152MHz and 45.1584MHz.

3. How hard would it be to replace?

Any good technician can do this if he knows SMT rework.

4. Where does one find the magic $30 replacement?

Mouser.com, Digikey.com