jwb said:
Seems to me that we should eliminate as many of these connections as possible, and solder the cable directly to the pins of the transmitter and receiver chips.
What do you think of the Apogee Wide Eye S/PDIF cable? I have a 126cm length of it that I never did anything with, the one before they started to mark "direction" on it.
RonS
What do you think of the Apogee Wide Eye S/PDIF cable? I have a 126cm length of it that I never did anything with, the one before they started to mark "direction" on it.
RonS [/B][/QUOTE]
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Not as much as it is made out to be. I have several. spdif, bnc and aes/ebu in different lengths. They all ring more than better cables (illuminati etc) and sound ok but not spectacular in a wide range of systems. The best cable I have come across is the Illuminti D60 with the old version better than the new.
RonS [/B][/QUOTE]
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Not as much as it is made out to be. I have several. spdif, bnc and aes/ebu in different lengths. They all ring more than better cables (illuminati etc) and sound ok but not spectacular in a wide range of systems. The best cable I have come across is the Illuminti D60 with the old version better than the new.
Re: Size matters
Hi Fred,
Does this imply that al the internal wiring of a DAC c.q. CD-player carrying clock signals and digital data signals (I2S, SPDIF etc.) must be at least 1m long
Come on Fred, a proper terminated HF cable ….? Longer cables are more susceptible to EMI (e.g. from mains cables) and as such can introduce more jitter due to varying threshold levels such EMI can cause at the receiver end.
Oh and the mismatch due to the 2 cm long cinch plugs is so small that you can safely ignore it concerning overshoot/undershoot at the receiving end.
For those who want to change to BNC connectors, be careful to use the 75 ohms ones then and not the 50 ohms ones. The 50 ohms ones are much more common.
Fred Dieckmann said:
Hi Fred,
Does this imply that al the internal wiring of a DAC c.q. CD-player carrying clock signals and digital data signals (I2S, SPDIF etc.) must be at least 1m long
Come on Fred, a proper terminated HF cable ….? Longer cables are more susceptible to EMI (e.g. from mains cables) and as such can introduce more jitter due to varying threshold levels such EMI can cause at the receiver end.
Oh and the mismatch due to the 2 cm long cinch plugs is so small that you can safely ignore it concerning overshoot/undershoot at the receiving end.
For those who want to change to BNC connectors, be careful to use the 75 ohms ones then and not the 50 ohms ones. The 50 ohms ones are much more common.
fmak said:
In my main system I use an Illuminati, I think it's the D30, I'd have to check. It's pretty stiff and yellowish in colour. Much better than the Van Den Hul cable I used before. I bought the apogee wideeye when I was picking up some mic cable, figured I could use it one day. I think I'll use it between my DVD players digital output and my home theatre receiver.
RonS
Re: Re: Size matters
Let's distinguish between a transmission line like the S/PDIF link and shorter traces. Reflections aren't a problem if the length of the trace is sufficiently short with respect to the rise time of the signal.
Pjotr said:
Does this imply that al the internal wiring of a DAC c.q. CD-player carrying clock signals and digital data signals (I2S, SPDIF etc.) must be at least 1m long
Let's distinguish between a transmission line like the S/PDIF link and shorter traces. Reflections aren't a problem if the length of the trace is sufficiently short with respect to the rise time of the signal.
Jitter Causes Everywhere
I think it is Jocko who has made mention in the past of lousy reciever stages spitting data (noise) back up the line.
This I expect is one of the first things to sort out, and then optimum cable lengths and Phreds termination networks.
Of course all need to be done to gain max performance, and then maybe a line driver that does not react to incoming (backfeed) junk.
Interestingly one of my trick cables works wonders on digital data coax feeds too.
Eric.
I think it is Jocko who has made mention in the past of lousy reciever stages spitting data (noise) back up the line.
This I expect is one of the first things to sort out, and then optimum cable lengths and Phreds termination networks.
Of course all need to be done to gain max performance, and then maybe a line driver that does not react to incoming (backfeed) junk.
Interestingly one of my trick cables works wonders on digital data coax feeds too.
Eric.
Jocko Homo said:
How about like the Assemblage D2D, as a stand alone unit? Although I'm uncertain that I need one. I'm using a Sonic Frontiers SFT1 transport, which is supposed to have extremely low jitter. It was designed by UltraAnalog for SF. The d/a is an Assemblage Dac2 ( I know your opinion of SF digital gear Jocko
)RonS
It may have low jitter, but I suspect that they are refering to jitter coming off of the disc. Two diferent beasts to deal with.
The methods to reduce sensitivty to jitter on the TX end of the cable is similar to those on the RX side. Not hard, but no one pays attention to it.
Speaking of which......a famous audio designer once built a D/A box with a 100 ohm resistor on the input. When I asked him why not 75 ohms, he replied:
"Hey, it is a lot closer than no load at all. Which is what most everyone else does. 100 ohms is what we had that day."
Or even worse.......a 5-pole LPF.
As for internal stuff.......it is possible to build a good clock that is phase locked to the recovered clock with a long time constant. I would expect that such a circuit would need the incoming signal to be within +/- 500 ppm, as it would be hard to pull a decent crystal very far without degrading performance.
Jocko
The methods to reduce sensitivty to jitter on the TX end of the cable is similar to those on the RX side. Not hard, but no one pays attention to it.
Speaking of which......a famous audio designer once built a D/A box with a 100 ohm resistor on the input. When I asked him why not 75 ohms, he replied:
"Hey, it is a lot closer than no load at all. Which is what most everyone else does. 100 ohms is what we had that day."
Or even worse.......a 5-pole LPF.
As for internal stuff.......it is possible to build a good clock that is phase locked to the recovered clock with a long time constant. I would expect that such a circuit would need the incoming signal to be within +/- 500 ppm, as it would be hard to pull a decent crystal very far without degrading performance.
Jocko
Hi Jocko and others,
A pull range of 500ppm is not feasible, unless you have a very cheap crystal with a low Q or degrade the Q with a small series inductance. It is the very small series resonant capacitance together with the parasitic case capacitance that limits the pull range. Crystals for VXCO’s are therefore usually packed in a glass envelope, ± 100ppm is a more realistic pull range. But ±100ppm is sufficient, the clock of the SPDIF signal coming out of the transport is usually no more than 10 ppm off.
For some inspiration read the work of Guido Tent, he already did build a VXCO based PLL clock circuit for a DAC:
http://members.chello.nl/~m.heijligers/DAChtml/dactop.htm
Pjotr said:
Hello Pjotr, others
Thanks for refering to our design. And yes, you are right, a pull range of +/- 100 ppm is sufficient, assumed the redbook is followed. We measured nearly always 2.3 - 2.7V at the control pin of the VCXO within the DAC (wehere 0,5 to 4,5 was possible)
For those interested, I have designed a module that contains a phase comperator, a slow (1 Hz) PLL and a neat, low jitter VCXO.
Jittery clock in, clean clock out !
This module can be used to upgrade external DACs
all the best
----------------------------------------Jocko Homo said:
Absolutely, if it is universal (in and out formats) and lo jitter. Inside a player is best but I know of no DIY system that has both (player and receiving end of DAC). This will be excellent.
There are expensive players (TEAC and Krell) that have lousy digital outputs.
Ooops.......
I meant 50 ppm, my brain was stuck on a figure around 500 Hz for an 11 MHz crystal.
As for Krell having lousy digital outputs.......yeah, I would believe that.
Guido:
Do you have a feel for how close the average CDP is with respect to initial frequency accuracy? Just curious.
Jocko
I meant 50 ppm, my brain was stuck on a figure around 500 Hz for an 11 MHz crystal.
As for Krell having lousy digital outputs.......yeah, I would believe that.
Guido:
Do you have a feel for how close the average CDP is with respect to initial frequency accuracy? Just curious.
Jocko
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