Stacked Stereo DACs for Multichannel

[cmarin]

But two channel only correct? I am interested in MCH.

thanks

 

Yes correct, only two channel.

 

 

Sent from my iPhone using Computer Audiophile

[Kal Rubinson]

Thanks Kal, I didn't know about that equipment. Good call.

Have you by any chance written about either the DirectStream and/or the Manhattan/Brooklyn and/or an I2S/USB implementation?

Thanks.

I am expecting to play with and report on both the PD and Mytek setups shortly. AFAIK, the DS setup requires a PF board on the server and I do not have a slot for one at this time.

[Kal Rubinson]

Looking closer at the USB-XIII manual, it appears that the device may support any other branded DAC playback on two channel only, not MCH. MCH may only be available through the PLINK system.

That is my understanding.

[Keith_W]

Jitter isn't the problem here, long-term accuracy is. Looking at the Mytek Brooklyn, it uses an Abracon ABLNO-V 100 MHz crystal oscillator with a specified frequency stability of 18 ppm. Over an hour, that amounts to 65 milliseconds. Worst case, two DACs using this oscillator would exhibit a drift of 130 ms per hour. Listening to that would be intolerable.

 

Thank you for your response. I am trying to follow through your maths here to see how you arrived at your figures.

 

18ppm frequency stability at 100MHz

- 1MHz = 10^8

- 18ppm = 18 / 10^6

- Error per second = 1MHz * 18ppm = 10^8 * 18/10^6 = +/-1800Hz

--> Therefore in 1 second, the timing may vary by 1/1800 seconds, or 0.555 ms

--> Therefore in 1 hour, the timing may vary by (0.555 * 60 * 60) = 2000 ms

(that is, assuming that the 18ppm jitter consistently results in a +0.555ms timing error?)

 

Clearly my calculations are a couple of orders of magnitude incorrect relative to yours. My math skills are rather poor, or I might be misunderstanding these definitions. I would like to know how you arrived at your figures.

As one DAC maker famously said, it's what comes after the DAC chip(s) that really tells the story on how it will sound....

Can you expand on "what comes AFTER the DAC chip(s)"? You are talking about the output stage of the DAC? Anything else?

 

I thought that what comes BEFORE the DAC is also quite important - the power supply, design of the PLL, quality of the clock, etc.

[bmoura]

I am expecting to play with and report on both the PD and Mytek setups shortly. AFAIK, the DS setup requires a PF board on the server and I do not have a slot for one at this time.

Ted Smith, the developer of the DirectStream DAC offers some thoughts on linking DirectStream DACs for Multichannel playback at the PS Audio forum. Worth a read. Ted says, in part:

 

"In a brief internet search I couldn’t find any information on a “PinkFaun I2S Multichannel Bridge card”, but they list PS Audio as one of the compatible DACs for their stereo I2S bridge card so I’d expect that if they have a MC card it would work with PS Audio DAC’s as well.

 

From PS Audio’s side, tho the DS wasn’t designed to sync multiple units together for multichannel one of the previous software updates helps them track well enough for MC. (I and a few other members of this forum have three DSs in a multichannel setup.) The NuWave will definitely have different delays than the DS and the DS Jr, they may even add up to perhaps a 10′ difference in speaker placement so I wouldn’t use a NuWave along with the DSs unless you have some kind of delay compensation in your system (which would probably convert DSD to PCM.)

 

The DS and the DS Jr share the same source and FPGA hardware. I see no reason that I’d ever significantly change the delays in one without changing both. You might need to use the same software release in both (i.e. use Yale in both or Torreys in both…) when I do make an overall change in processing – which I expect to do in the next release."

 

 

 

 

Multi Channel SACD Files | DirectStream DAC | ForumsPS Audio

[mansr]

Thank you for your response. I am trying to follow through your maths here to see how you arrived at your figures.

 

18ppm frequency stability at 100MHz

- 1MHz = 10^8

- 18ppm = 18 / 10^6

- Error per second = 1MHz * 18ppm = 10^8 * 18/10^6 = +/-1800Hz

--> Therefore in 1 second, the timing may vary by 1/1800 seconds, or 0.555 ms

--> Therefore in 1 hour, the timing may vary by (0.555 * 60 * 60) = 2000 ms

(that is, assuming that the 18ppm jitter consistently results in a +0.555ms timing error?)

 

Clearly my calculations are a couple of orders of magnitude incorrect relative to yours. My math skills are rather poor, or I might be misunderstanding these definitions. I would like to know how you arrived at your figures.

 

The absolute frequency of the clock is unimportant, the tolerance being a relative measure. A clock having a tolerance of 18 ppm means the number of cycles it goes through over a duration if time may differ from the ideal number such that abs((actual - ideal) / ideal) ≤ 18e-6. Put differently, a duration of time as measured by the clock might differ from the true value by a factor of 18e-6. This means that what the clock calls an hour might be off by as much as 3600 * 18e-6 = 64.8e-3 or roughly 65 ms.

 

With two DACs, it is possible that one is fast and the other slow, both by the maximum specified amount. The relative drift between the two is therefore twice the error of a single clock.

 

Hope this helps.

[jjkale]

Ted Smith, the developer of the DirectStream DAC offers some thoughts on linking DirectStream DACs for Multichannel playback at the PS Audio forum. Worth a read. Ted says, in part:

 

 

 

 

 

Multi Channel SACD Files | DirectStream DAC | ForumsPS Audio

 

Yes, Ted S. replied in answer to my query (ref. Tim Meadows "The Ladies Man").

So here is the question: since the Ted said he was unaware of the MCH PinkFaun card, how do the PS Audio boys synch their multi machines?

[Keith_W]

The absolute frequency of the clock is unimportant, the tolerance being a relative measure. A clock having a tolerance of 18 ppm means the number of cycles it goes through over a duration if time may differ from the ideal number such that abs((actual - ideal) / ideal) ≤ 18e-6. Put differently, a duration of time as measured by the clock might differ from the true value by a factor of 18e-6. This means that what the clock calls an hour might be off by as much as 3600 * 18e-6 = 64.8e-3 or roughly 65 ms.

 

With two DACs, it is possible that one is fast and the other slow, both by the maximum specified amount. The relative drift between the two is therefore twice the error of a single clock.

 

Hope this helps.

 

Thank you. That answers my question.

[Kal Rubinson]

Yes, Ted S. replied in answer to my query (ref. Tim Meadows "The Ladies Man").

So here is the question: since the Ted said he was unaware of the MCH PinkFaun card, how do the PS Audio boys synch their multi machines?

He said "From PS Audio’s side, tho the DS wasn’t designed to sync multiple units together for multichannel one of the previous software updates helps them track well enough for MC."

 

To me, that implies no synch and the rest of his statement seems to deal with latency, rather than synch.

[jjkale]

He said "From PS Audio’s side, tho the DS wasn’t designed to sync multiple units together for multichannel one of the previous software updates helps them track well enough for MC."

 

To me, that implies no synch and the rest of his statement seems to deal with latency, rather than synch.

 

Yes, but he also said this: "(I and a few other members of this forum have three DSs in a multichannel setup.)"

I've been trying to get further clarification from PS Audio about exactly how they implement their multichannel system.

Thanks

[Kal Rubinson]

Yes, but he also said this: "(I and a few other members of this forum have three DSs in a multichannel setup.)"

Sure. It works well enough.

[Iansr]

 

You also need software that is going to specifically start the stream to all the DACs at exactly the same time, most audio systems do not guarantee

 

John S.

Regarding this specific point and ignoring the clock sync issue, is this a problem if you simply split a SPDIF signal from a digital source and send the resulting 2 signals to your 2 DACs ? (ASsuming the split signals are strong enough for the DACs to lock onto.)