Javin5 said:
Hi
A PLL in any DAC is an attenuator, hence less jitter in means less jitter out. The lower the jitter at the drive SPDIF output, the lower the jitter at the PLL output. Measurements have been published years and years ago at our site:
http://members.chello.nl/~m.heijligers/DAChtml/Measurements.htm
Yes, the DAC as master is better, but improving the clock in tradiional setups (drive - SPDIF - DAC) also works, as shown by the measurements (and the ears of thousands of my customers). No mystery at all......
The thing is in the standard. USB and HDMI are equally bad when it comes to jiter, so I have some work to do.
best
Guido
Guido Tent said:
Guido,
Are you saying that if the output of the transport has lower jitter, that it also results in less final jitter at the DAC even if the data is reclocked there?
Jan Didden
janneman said:
Hello Jan,
Yes.....
I have not yet heard any DAC that is fully intransparant to the drive. Even a Chord DAC, that uses a huge buffer, still is sensitive to the drive put in front.
best
Guido
If you properly re-clock the data (ie with fifo or a polyphase filter) then the amount of jitter on the input has no bearing at all on the output. In this case the only determining factor is the clock used to drive the DAC.
The design of CD players is dire, they are done all wrong.
The design of CD players is dire, they are done all wrong.
BlackCatSound said:
I don't agree with your first statement as you seem to ignore kinds of crosstalk caused by ground bounce (common impedance) and power supply crosstalk, for example. These are analog artefacts that play a role at implementation level, and are often ignored by conceptual thinkers.
I agree on the fact that the DAC clock is of high importance, and the fact that most CD players are done wrong.
best
Guido
BlackCatSound said:
Partly: Silicon has its' restrictions and Maxwell may be dead for a while but you can't ignore his laws: Groundbounce is not a cost issue.
best
Guido
Guido, thanks for your reply and for providing this interesting link, of which I wasn't aware. These measurements indicate indeed a significant improvement of the PLL-output when the input signal is improved. I knew that a clean input helps the PLL do its job, but didn't assume that there is that much transparency.
There seems to be agreement that most CD-players are done wrong, but it's still unclear why such a basic fault hasn't long been rectified. After all, this is a highly competitive market where suppliers are constantly looking for better performance and good reviews. And here is an opportunity for a significant competitive advantage at probably almost zero material cost increase.
I'm not sure if it's possible to provide an aftermarket kit to slave the drive to a DAC-master; it may involve too many changes which are all different for different players?
And again, is there any player we know of, that does it right? Such a player would get the maximum benefit from a good aftermarket master clock module and the jitter problem would be solved once and for all.
Kurt
There seems to be agreement that most CD-players are done wrong, but it's still unclear why such a basic fault hasn't long been rectified. After all, this is a highly competitive market where suppliers are constantly looking for better performance and good reviews. And here is an opportunity for a significant competitive advantage at probably almost zero material cost increase.
I'm not sure if it's possible to provide an aftermarket kit to slave the drive to a DAC-master; it may involve too many changes which are all different for different players?
And again, is there any player we know of, that does it right? Such a player would get the maximum benefit from a good aftermarket master clock module and the jitter problem would be solved once and for all.
Kurt
It would be possible to provide an after market FIFO device that would receive s/pdif and buffer it, and allow the output side to be slaved to a DAC clock. You could even have the output optically isolated if that would help with ground noise. Would only work if you could guarantee that your DAC clock was slightly slower than the incoming s/pdif stream.
Javin5 said:
Hi Kurt
Thanks for the feedback. Usually money is involved, or ignorance, or both. I have a set of modules in my program that allow master / slave combo and my own DIY CDP has some nice features in the jitter area.
best
The "very" old Linn Karik/Numerik transport and DAC used a DC voltage to slave the transport to the DAC. The DAC used a very good XO (maybe Guido Tent don't agree🙂 and I think a VCXO at the transport.
Still, the transport was VERY important for the final result. The price of the DAC and transport was almost the same (I think) But this is 15? years ago!
Nowdays Linn prefer to put the DAC in the transport (as in the stunning CD12) because of the problems of transporting digital signals between the transport and the DAC (or maybe it is cheaper).
Someone told me that any noisy electrical connection to the CD player makes the jitter higher. I think that's the reason why Naim CD-players usually do not have an electrical digital output and Linn CD-players nowdays use optical interface (to connect a PS2 or something)
Yeah, I hate it too! But jitter from digital signals is still a problem!!!
Still, the transport was VERY important for the final result. The price of the DAC and transport was almost the same (I think) But this is 15? years ago!
Nowdays Linn prefer to put the DAC in the transport (as in the stunning CD12) because of the problems of transporting digital signals between the transport and the DAC (or maybe it is cheaper).
Someone told me that any noisy electrical connection to the CD player makes the jitter higher. I think that's the reason why Naim CD-players usually do not have an electrical digital output and Linn CD-players nowdays use optical interface (to connect a PS2 or something)
Yeah, I hate it too! But jitter from digital signals is still a problem!!!
Dag said:
Hi
Yes, Linn knew their job. I have no clue about the oscillators they used that days. And yes, I prefer one-box solutions.....
cheers
You can isolate an electrical signal very easily. SPDIF should be isolated with a transformer (and should use 75ohm connectors/cable/tracks) but of course how many 'domestic' grade machines bother with this?
IMO if every CDP was designed correctly there would be no market for aftermarket addons, external DACs, expensive cables etc...
I know people who cannot accept that you could make a single box CDP. They think it HAS to have an external DAC. Good for the sellers profit, bad for their pocket. 😉
IMO of course! 🙂
IMO if every CDP was designed correctly there would be no market for aftermarket addons, external DACs, expensive cables etc...
I know people who cannot accept that you could make a single box CDP. They think it HAS to have an external DAC. Good for the sellers profit, bad for their pocket. 😉
IMO of course! 🙂
BlackCatSound said:
Tom,
I use transformers and take care of impedance matching. What I am talking about takes place on silicon, inside the DAC or whatever is in front of that (digital filters are very good jitter generators).
External DACs are indeed invented by marketeers. If done correctly (i.e. low jitter clock regeneration) they potentially are an improvement over the internal DAC in the CDP, but again, I prefer one box solutions (have seen commercial units using SPDIF as internal data protocol - yuck)
best
Posted by Daq:
"Someone told me that any noisy electrical connection to the CD player makes the jitter higher"
Does this mean that the average CD-player would benefit from a power line filter? Has anyone tried and found a significant improvement?
Kurt
"Someone told me that any noisy electrical connection to the CD player makes the jitter higher"
Does this mean that the average CD-player would benefit from a power line filter? Has anyone tried and found a significant improvement?
Kurt
Javin5 said:
Especially the interface should deserve attention. SPDIF Connectors need RF termination to both chassis, internal transformers are much prefered, and a coaxial cable with a low transfer impedance (i.e. very tight screen) should be used. In addition one may add ferrite wrapped around the cables. I am not much a fan of mains filters, these usually make the music a bit dull.
best
Guido, the transformer comment was aimed at Dig's comments.
I'm well versed in die ground bounce. There was ways to minimise it. Small drive currents, controled slew etc... Signals never need to be perfect square waves.
Javin5, if a mains filter changes anything it means the PSU design is flawed. In an ideal world the mains input should be totally isolated from the internal workings. However this is rarely the case.
I'm well versed in die ground bounce. There was ways to minimise it. Small drive currents, controled slew etc... Signals never need to be perfect square waves.
Javin5, if a mains filter changes anything it means the PSU design is flawed. In an ideal world the mains input should be totally isolated from the internal workings. However this is rarely the case.
BlackCatSound said:
Hi BlackCat,
There's indeed many ways of reducing groundbounce, but on-silicon there's little to do for the average customer :-(
faster switch can reduce groundbounce too by the way
cheers
Posted by Tom:
You can isolate an electrical signal very easily. SPDIF should be isolated with a transformer (and should use 75ohm connectors/cable/tracks) but of course how many 'domestic' grade machines bother with this?
-- Yes, you are right. That will prevent a direct dc path. But you will still have an unwanted connection through the trafo. The bandwith of the trafo could also cause problems because that will introduce distortion (I do not know if you can call it jitter??) to the digital data. I think both LF an HF is important. Maybe hysteresis and other things also can distort the digital data but I do not know. A clock will not have these problems since the signal (frequencies) is(are) constant.
Posted by Tom:
IMO if every CDP was designed correctly there would be no market for aftermarket addons, external DACs, expensive cables etc...
-- Yes! I think the performance of a CD player with an internal DAC is better than a transport/DAC combo for the same price.
Posted by Kurt:
Does this mean that the average CD-player would benefit from a power line filter? Has anyone tried and found a significant improvement?
-- Maybe, but usually not. Filters can acually introduce resonances that will make the performance worse. It is probably better to improve the power supply. Naim uses a separate powersupply with very low noise, connected to the CD-palyer with a high quality multi wire cabel and "military grade connectors" to prevent noise. Expensive but definitely an improvement!
Posted by Guido:
Especially the interface should deserve attention. SPDIF Connectors need RF termination to both chassis, internal transformers are much prefered, and a coaxial cable with a low transfer impedance (i.e. very tight screen) should be used. In addition one may add ferrite wrapped around the cables. I am not much a fan of mains filters, these usually make the music a bit dull.
-- Exactly! The SPDIF interface is much more problematic since you actually want signals to pass through it. For the power line you only want DC so you can use filters and regulators. But it is still important.
Bye
Dag
You can isolate an electrical signal very easily. SPDIF should be isolated with a transformer (and should use 75ohm connectors/cable/tracks) but of course how many 'domestic' grade machines bother with this?
-- Yes, you are right. That will prevent a direct dc path. But you will still have an unwanted connection through the trafo. The bandwith of the trafo could also cause problems because that will introduce distortion (I do not know if you can call it jitter??) to the digital data. I think both LF an HF is important. Maybe hysteresis and other things also can distort the digital data but I do not know. A clock will not have these problems since the signal (frequencies) is(are) constant.
Posted by Tom:
IMO if every CDP was designed correctly there would be no market for aftermarket addons, external DACs, expensive cables etc...
-- Yes! I think the performance of a CD player with an internal DAC is better than a transport/DAC combo for the same price.
Posted by Kurt:
Does this mean that the average CD-player would benefit from a power line filter? Has anyone tried and found a significant improvement?
-- Maybe, but usually not. Filters can acually introduce resonances that will make the performance worse. It is probably better to improve the power supply. Naim uses a separate powersupply with very low noise, connected to the CD-palyer with a high quality multi wire cabel and "military grade connectors" to prevent noise. Expensive but definitely an improvement!
Posted by Guido:
Especially the interface should deserve attention. SPDIF Connectors need RF termination to both chassis, internal transformers are much prefered, and a coaxial cable with a low transfer impedance (i.e. very tight screen) should be used. In addition one may add ferrite wrapped around the cables. I am not much a fan of mains filters, these usually make the music a bit dull.
-- Exactly! The SPDIF interface is much more problematic since you actually want signals to pass through it. For the power line you only want DC so you can use filters and regulators. But it is still important.
Bye
Dag
- Status
- Not open for further replies.