irgendjemand said:Finney,
I am sure that Herb will response ... meanwhile I can tell you that at least in 2 major points, you might have well missed his all work.
First of all, Herb wrote on this thread (Post #161): "I do NOT use a VCXO with PLL or so. I route the clock signal in my cd-player directly to the DAC.....". Then, in Post #176 he wrote: “For all certainty: VCXO's always produce more noise/jitter than XO's? He is taking the XO from the Transport - see also his “DAC Principia 4? He is telling us all this since long.
And: The RMS/Jitter of his Rutgers Oscillator is 0.4060 ps. ... Just read his mails.
The other point you missed ?just like you wrote here, Herb implies that it is all about moving mass & momentum? In other words, this perfectly corresponds with his explanation for his using of the Philips CD 624 ?as he explained - because of the low-mass laser-head, etc. ?
As for the PCM63’s LATCH: As much as I understood from Herb, the all problem arise also because there is no ideal isolation of the LATCH from its data and other clock signals - inside the PCM63 (!!!!!). Therefore, the idea of the "DAC Principia 4" is the re-clocking of the data and the clock to the DAC as well. Well, this can’t be so bad.
I am sure many here whould be happy to have the mentioned 3ps!
Greetings,
IJ
1. Ok, my mistake. I thought most were using Tent VCXO here. Wait, when was the talk switched to fixed frequency XO? I thought we were still talking about PLL loop?
2. There's still a big quality difference between 0.18ps and 0.40ps XO.
3. Even with a 0.40ps VCXO, a 3ps jitter simple PLL loop will be a big stretch with common discrete components and basic PCB. Not even mention the PIC-DAC-VCXO thing.
4. Again, as I have said, dont expect the filtering of PLL loop can do much for you, or the circuit will not work 100% of the time.
5. Now, werent we talking about reclocking, PLL, etc, solutions in DAC? When did it come inside the CD player? Fixed XO? CD main XO?
You know, if you keep moving the targets, definitely I will miss the target! Hehehe 6. CD disc shakes like hell. To get good tracking, you want the laser unit to be as light as possible, the servo as nimble as possible. This is more about reading miss/dont miss, OK? You are comparing oranges to apples. Moving miss doesnt matter? Then why Teac VRDS would use an alloy disc to clamp down the CD, Pioneer would put CD on a heavy platter? How about those CD clamps?
7. What? Philips 624? You must be kidding! Hahahahaha
About PCM63:
1. Nope, the *latch* is not the first thing to get the signal. There's one more thing called "I/O pad" This thing would give you extra jitter already.
2. You really should not call it a latch. After I2S comes in, the data goes to a shift register. Then the word mark will move the data at the right time to registers. From there, the value will be splitted to various groups to drive several complicated switch networks through delay lines, probably DEM (cant recall whether PCM63 has DEM. Dont expect you find the info from the datasheet though.
TDA1541 has DEM) then you have this output charging/discharging thing. All of these mean lots of extra jitters.3. PCM63 datasheet states that the *typical* output settling time is 200ns! How much extra jitter is included in this *typical* 200ns? A 3ps or 50ps clock jitter? What big difference will that make? Yes, a few hundred pico seconds of clock jitter does matter yet 50ps, 3ps, or even 0.18ps will not make any difference. You look the system performance as a whole, not just the number of single component, ok?
PA0SU said:
Well, I knew that you had fallen into the trap when I saw your 10us!
So you saw that the timing between DPG pulse and the end of first period of RF track signal was 650us +- 15us. You took that 15us, gave it a 30% discount then came out the 10us, right? After I showed you the math, you simply dropped the 10us to 10ns, right?
The fact is that this +-15us is really not the jitter. It's all about the track synchronization. The whole track data may have the +-15us shift but the individual bit data inside one track still has very low jitter, the timing distance between the bit data and the track head is pretty much fixed.
This is like a long line of train. The train may arrive the station a few minutes early or late; however, the position of each cart to the head of the train pretty much stays fixed. So as far as you can remove the timing problem of train arrival time, each cart's timing will be perfectly aligned. This is exactly what happens in DAT. A FIFO can easily remove the +-15us shift to get low jitter bit data. This is also why the 10us will not have the big impact. And this is very similar to what Lavry has been trying to achive. This is the beauty of DAT.
Can one agree?
Finney,
Let's do it a bit more simple & straight:
The subject here is indeed Transport and DAC (no CD Player).
The idea discussed here is to take an XO from the transport, to bypass the receiver in the DAC and to connect it to the DF, etc.
There was no talk about second PLL, also not about VCXO - for the moment as they are “noisy”. The idea was - to find some other direction to go - and Herb suggested here his "DACPrincipia4" (please see the attachment).
I am not against what you wrote here: Even if there is quality differences between 0.18ps and 0.40ps XO, the target should be somewhere around the 50ps by the PCMs. Less would be even better.. May be you could please take a look into the attachment and see, if the 3ps target is OK for you.
CD disc shakes like hell and the Philips 624 might be a joke; however, you surely heard yourself some TEAC VRDS CD Players that sound like you know what, Pioneer with CD clamps etc. etc . - - the same. I had at home Audiomeca "Mephisto II" for a try - it turned to be very short try indeed.
I am sure that we will agree that the moving laser better be light as possible, the servo nimble... but, I (and I am sure that You as well) also heard Transports that play excellent, even though they have some crazily-shaking CDM 4.19 or whatever (one of them is my modified Marantz CD-10). So the technology by itself is not definitely wrong. These Transports can play terrific.
We surely agree that one had better look at the system performance as a whole, not just the number of single component. Good to hear this from someone so knowledgeable like you! As long as one see the large picture, it will not go wrong.
I am sure that I am not the only one here who appreciates your deep knowledge concerning the “inner life” and functionality of the PCM63
.
Last yet important: Why shell one not use the Tent XO3.2. ? Isn’t it more then good enough? You are saying yourself, that the all system-performance counts, and that you think that we can be OK even with 200ps at the PCM's Out ?
Greetings,
IJ
Finney,
Let's do it a bit more simple & straight:
The subject here is indeed Transport and DAC (no CD Player).
The idea discussed here is to take an XO from the transport, to bypass the receiver in the DAC and to connect it to the DF, etc.
There was no talk about second PLL, also not about VCXO - for the moment as they are “noisy”. The idea was - to find some other direction to go - and Herb suggested here his "DACPrincipia4" (please see the attachment).
I am not against what you wrote here: Even if there is quality differences between 0.18ps and 0.40ps XO, the target should be somewhere around the 50ps by the PCMs. Less would be even better.. May be you could please take a look into the attachment and see, if the 3ps target is OK for you.
CD disc shakes like hell and the Philips 624 might be a joke; however, you surely heard yourself some TEAC VRDS CD Players that sound like you know what, Pioneer with CD clamps etc. etc . - - the same. I had at home Audiomeca "Mephisto II" for a try - it turned to be very short try indeed.
I am sure that we will agree that the moving laser better be light as possible, the servo nimble... but, I (and I am sure that You as well) also heard Transports that play excellent, even though they have some crazily-shaking CDM 4.19 or whatever (one of them is my modified Marantz CD-10). So the technology by itself is not definitely wrong. These Transports can play terrific.
We surely agree that one had better look at the system performance as a whole, not just the number of single component. Good to hear this from someone so knowledgeable like you! As long as one see the large picture, it will not go wrong.
I am sure that I am not the only one here who appreciates your deep knowledge concerning the “inner life” and functionality of the PCM63
.Last yet important: Why shell one not use the Tent XO3.2. ? Isn’t it more then good enough? You are saying yourself, that the all system-performance counts, and that you think that we can be OK even with 200ps at the PCM's Out ?
Greetings,
IJ
Finney,
I had been looking at DIR9001. Given that it's a normal analog PLL structure, with charge pump and fixed external loop filter values, [no VCXO in there, and no spact], furthermore, it locks in 100 msecs -
May I ask what is the PLL filter corner frequency? 5Khz? 10KHz? It's carefully avoided in the data sheet.. In the crystal data sheets - [which might be older, but still are based exactly on the same principles] they are honestly stating 20kHz..
In my setup I'm having it below 0.1 Hz, fixed, not moving when locked.. Now THAT is a difference [You asked for the difference]
Ciao, George
I had been looking at DIR9001. Given that it's a normal analog PLL structure, with charge pump and fixed external loop filter values, [no VCXO in there, and no spact], furthermore, it locks in 100 msecs -
May I ask what is the PLL filter corner frequency? 5Khz? 10KHz? It's carefully avoided in the data sheet.. In the crystal data sheets - [which might be older, but still are based exactly on the same principles] they are honestly stating 20kHz..
In my setup I'm having it below 0.1 Hz, fixed, not moving when locked.. Now THAT is a difference [You asked for the difference]
Ciao, George
Re: Can one agree?
Well, whatever you are saying here just confuses me even more. Are you sure we are talking about the same thing? I was focusing on a DAC design itself, assumed that you could not do anything with the transport. Then you simply jumped to the scenario that you could do extra with the transport. Without a common ground, the discussion would just confuse everyone.
Ok, if I can build a system which contains both transport and DAC, I will even not use Herd's idea. Why bother with SPDIF at all?
As for the moving mass thing, you missed my point as well. I was trying to compare DAT with CD. In the world of CD transport, some people may try to increase moving mass to improve the performance yet fall short on other aspects. Some may do other things right yet the disc shakes like hell. So what? You are comparing products with engineering errors here and there. But when you switch to DAT, that will be a totally different league. This is the key point.
Again the light laser head, nimble servo is more about tracking, not much about jitter. Bad tracking definitely will give you lots of jitters, or more precisely, erros, yet good tracking does not guarantee you will have good jitter spec, see the point? I will never call ligt laser head/nimble servo means low jitter. This is extremely misleading.
About Tent XO, I call it medicore but at the same time I am also saying that you may not gain much by using better XO, right? The main problem with XO is that most cheap XOs have QC poorly done. You never know a 50ppm XO you buy is really 50ppm. I assume Tent XO has much better QC here. Whether its price is right or not, that's not something we should discuss here.
Sure, if you start to use DDS then definitely you need very good XO.
irgendjemand said:Finney,
Let's do it a bit more simple & straight:
The subject here is indeed Transport and DAC (no CD Player).
The idea discussed here is to take an XO from the transport, to bypass the receiver in the DAC and to connect it to the DF, etc.
There was no talk about second PLL, also not about VCXO - for the moment as they are “noisy? The idea was - to find some other direction to go - and Herb suggested here his "DACPrincipia4" (please see the attachment).
I am not against what you wrote here: Even if there is quality differences between 0.18ps and 0.40ps XO, the target should be somewhere around the 50ps by the PCMs. Less would be even better.. May be you could please take a look into the attachment and see, if the 3ps target is OK for you.
CD disc shakes like hell and the Philips 624 might be a joke; however, you surely heard yourself some TEAC VRDS CD Players that sound like you know what, Pioneer with CD clamps etc. etc . - - the same. I had at home Audiomeca "Mephisto II" for a try - it turned to be very short try indeed.
I am sure that we will agree that the moving laser better be light as possible, the servo nimble... but, I (and I am sure that You as well) also heard Transports that play excellent, even though they have some crazily-shaking CDM 4.19 or whatever (one of them is my modified Marantz CD-10). So the technology by itself is not definitely wrong. These Transports can play terrific.
We surely agree that one had better look at the system performance as a whole, not just the number of single component. Good to hear this from someone so knowledgeable like you! As long as one see the large picture, it will not go wrong.
I am sure that I am not the only one here who appreciates your deep knowledge concerning the “inner life?and functionality of the PCM63
Last yet important: Why shell one not use the Tent XO3.2. ? Isn’t it more then good enough? You are saying yourself, that the all system-performance counts, and that you think that we can be OK even with 200ps at the PCM's Out ?
Greetings,
IJ
Well, whatever you are saying here just confuses me even more. Are you sure we are talking about the same thing? I was focusing on a DAC design itself, assumed that you could not do anything with the transport. Then you simply jumped to the scenario that you could do extra with the transport. Without a common ground, the discussion would just confuse everyone.
Ok, if I can build a system which contains both transport and DAC, I will even not use Herd's idea. Why bother with SPDIF at all?
As for the moving mass thing, you missed my point as well. I was trying to compare DAT with CD. In the world of CD transport, some people may try to increase moving mass to improve the performance yet fall short on other aspects. Some may do other things right yet the disc shakes like hell. So what? You are comparing products with engineering errors here and there. But when you switch to DAT, that will be a totally different league. This is the key point.
Again the light laser head, nimble servo is more about tracking, not much about jitter. Bad tracking definitely will give you lots of jitters, or more precisely, erros, yet good tracking does not guarantee you will have good jitter spec, see the point? I will never call ligt laser head/nimble servo means low jitter. This is extremely misleading.
About Tent XO, I call it medicore but at the same time I am also saying that you may not gain much by using better XO, right? The main problem with XO is that most cheap XOs have QC poorly done. You never know a 50ppm XO you buy is really 50ppm. I assume Tent XO has much better QC here. Whether its price is right or not, that's not something we should discuss here.
Sure, if you start to use DDS then definitely you need very good XO.
Joseph K said:
Hi George
Never expect the diagram will tell you much. There's a VCO, right? Remember that the major role of DIR9001 is to follow the input. It's not intended to remove jitter through filtering. If you look at DIR1703's diagram, you will see that the loop actually has an adaptive stepper inside. The end result is extra 50ps jitter and I am ok with that.
Corner frequency? Never expect TI to publish the number either. This has a lot to do with their new silicon processing technolgies.
Greetings,
IJ
No big deal, but please don't use the symbol. It is reserved for moderators to show when they are talking seriously as a moderator, and that they aren't just expressing an opinion. Hmmmm , Maybe we should post that in a FAQ or something....
Except for me. Being Chief Mod I get my own symbol!
Variac
IJ
No big deal, but please don't use the
symbol. It is reserved for moderators to show when they are talking seriously as a moderator, and that they aren't just expressing an opinion. Hmmmm , Maybe we should post that in a FAQ or something....Except for me. Being Chief Mod I get my own symbol!
Variac
sorry...
Sure Captain!
Indeed, I was not at all safe about using the above by myself..., but now it is good to know that we are not so much left alone here (at least not as we thought...).
You know, we have great egos here, and there have been some heavy "ongoing" at the past...
It seems that not everybody is so perfect,
However, mostly there are great people here 
You might still need something like this
at the coming future (I can't tell: just to be ready).
Greetings and all best wishes!
IJ.
Variac said:Greetings,
IJ
No big deal, but please don't use the
Except for me. Being Chief Mod I get my own symbol!
Variac
Sure Captain!
Indeed, I was not at all safe about using the above by myself...
, but now it is good to know that we are not so much left alone here (at least not as we thought...). You know, we have great egos here, and there have been some heavy "ongoing" at the past...
It seems that not everybody is so perfect,
However, mostly there are great people here You might still need something like this
at the coming future (I can't tell: just to be ready). Greetings and all best wishes!
IJ.
tritosine said:I have a question to finneybear, if you know a DAT machine with more obscure adc, like 2* 8bit Flash +r2r , or less obscure SAR converters? (can also pm me)
Flash + R2R? Not in DAT as far as I know. 8bit table is still a bit too big to count for 48KHz sampling. SAR type is quite common in first generation machines, for instance, Sony DTC-1000ES, PCM-2500, etc. They use the Sony CX20018. After those, Sony switched to Crystal chip.
SAR ADC is sensitive to aliasing hence a LPF is must have. One important thing about SAR ADC is the quality of LPF is crucial. One common mod for PCM-2500 is to replace the stock LPF with an Apogee, shown in one of my posts.
Again, dont expect me to sell you the Apogee!
"[8/9/92] Sony PCM-2500: pro, old model. Two box set. Bulky, troublesome [sk] Doorstop [dg] First Sony "pro" DAT which is the DTC-1000ES painted grey on top, with all i/o and some input and output buffers and error lights in a second box underneath. Records digital or analog at 44.1 or 48. Pre-SCMS. Bulky and troublesome due to the two box arrangement but IMO not a doorstop. Mods available to allow top unit to function alone. Some Nashville studios think that this deck, with Apogee input filters replacing the Soshin filters in the A/D, sounds better than any of the current crop (see comments above about sample-to-sample variability of the DTC-1000 which is the same as the 2500). (I don't agree) Both of these decks are fixable by mortals, especially with the Sony theory book. [J]"
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