Digital Cable Length

[Jocko Homo]

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

[transducer]

Originally posted by Jocko Homo
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.

My understanding is that the jitter was measured at the receiving end of the s/pdif cable that was hooked up to a d/a (SFD2 MKII if I remember correctly).

RonS

[Cobra2]

If I designed one, would anyone buy it?????

I would!

Arne K

[Pjotr]

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.heijlige...tml/dactop.htm

[Guido Tent]

Originally posted by Pjotr


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.heijlige...tml/dactop.htm

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

[fmak]

Originally posted by Jocko Homo


Inside a player or a D/A box???

If I designed one, would anyone buy it?????

Jocko

----------------------------------------

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.

[fmak]

Originally posted by transducer


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

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D2D is too expensive and best on I2S connection. It is mno longer available. Come to think of it , an I2S13W unit for the receiving end of a DAC would be excellent

[Jocko Homo]

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

[mrfeedback]

"Do you have a feel for how close the average CDP is with respect to initial frequency accuracy? Just curious."

Pretty damm good I expect - the manufacturer figures for run of the mill gear says near to perfect.
Jitter figures of course are a whole different thing.

Eric.

[Guido Tent]

Originally posted by mrfeedback


Pretty damm good I expect - the manufacturer figures for run of the mill gear says near to perfect.
Jitter figures of course are a whole different thing.

Eric.

Hi

Jocko asked about CDP crystal acuracy, and Eric answered above.

My experience: I never saw one out of spec. The worst I sam was about +60 ppm, whereas +/- 100ppm is the redbook spec

best regards