[FRANKe]

I'm trying to wrap my head around something, so I was wondering if someone could put this into terms I can understand. (Forgive me if this has already been covered - I did not find the information in past posts)

I was reading a website of a company who claims to have a better DAC solution than the Benchmark DAC1 and one of the reasons is because of the clock. They say the best solution is to have the DAC operate in MASTER mode (which is set via jumper) and the source as SLAVE. This synchronization is accomplished through a WordClock or SuperClock input on the source.

I am very interested in the USB Off-Ramp Turbo, and when asking this DAC company how this would work with their DAC, they said:

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"All of the USB-->S/PDIF chips we have ever seen use 27 MHz frequency or similar clock. From this frequency, they use PLL's to arrive at the audio sampling frequencies needed. If you're looking for top quality it will be by making sure that there are no PLL loops in your clock generation and by making sure that the digital source is SLAVED "
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So my question is - does the USB Off-Ramp Turbo use a 27MHz frequency? or PLL? And would it be possible to slave the Off-Ramp?

Any clarification on clock frequencies or the MASTER/SLAVE relationship would be much appreciated.

Thanks!
-FRANKe

[PLMONROE]

Marketing Hype --  (ours is better)?

[audioengr]

So my question is - does the USB Off-Ramp Turbo use a 27MHz frequency? or PLL? And would it be possible to slave the Off-Ramp?

None of the USB converters use 27MHz.  I dont know where they get this nonsense.  ALL of them use 12MHz or derivatives of this.

The Off-Ramp uses a TI chip, the TAS 1020A, which has a phase-locked loop to balance the flow-rate difference between the computer and the converter.

As for slaving, only the Creative Audigy 2 NX actually drives the computer with it's master clock, instead of the other way around.  This is the only way to eliminate the PLL in the converter, not by sourcing the clock in the DAC.  Many DAC's do not upsample, so they do not have a clock.  They depend on the clock that arrives with the data stream.  Putting the clock in the DAC serves no purpose and is not superior to having it in the converter, assuming that there is a discrete clock signal running between the converter and DAC.

What they do not understand is that the very best way to do this is to use a circuit like the Creative Audigy 2 NX, with the clock in the converter clocking everything downstream.  This can be accomplished with an I2S interface to the DAC.

I have modeled the I2S interface, but using an Off-Ramp, and it is better than a S/PDIF Off-Ramp Turbo when driving the P-3A DAC.  I will be showing this at RMAF in October.

[FRANKe]

Thanks for the information!

Well, FWIW, in case you are curious, the DAC is a LessLoss DAC 2004.
http://www.lessloss.com/
They say the frequencies they operate in are 33.8688, 16.9344 or 11.2896 MHz.  And they recommend using the Lynx 22 soundcard which has a clock sync input capable of "256 Word". (This would achieve the soundcard SLAVE / DAC MASTER relationship - running a sync cable from the DAC "output" to the source "input")

But if you feel like reading through the website, they have a lot of the same principles as Wadia.  (Using the 27ix DAC with the 270 CD Transport). Here is a quote from the Wadia website of their version:

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ClockLink™
This provides the most stable possible clock, when the 27ix is paired with a Wadia 270 CD Transport, by positioning the master oscillator adjacent to the DAC chips rather than in the transport. It results in lower jitter and better sonic performance than is possible in conventionally clocked systems.
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Anyway, I'd like to hear more about why you think a clock in the DAC serves no purpose. (This is still a little over my head, but I'm learning)

Also, I look forward to hearing more about using the Off-Ramp with the I2S interface. Sounds exciting!

Thanks again for taking the time to educate me.
-FRANKe

[art]

Wadia is not an example of how to do things right. A bunch of engineers, operating out of their field, spending $$$$$$ like it isn't theirs (surprise! it isn't), running loose like a bunch of children without adult supervision, and turning out some of the most over-priced and over-hyped stuff around.

Don't ask me how I know.............

Lessloss seems to be a reasonable outfit. I wish them well.

Pat

[audioengr]

Anyway, I'd like to hear more about why you think a clock in the DAC serves no purpose. (This is still a little over my head, but I'm learning)

The clock can be put in the DAC or the converter.  The advantage of putting it in the DAC is that any jitter introduced by the buffers from the converter to the DAC is eliminated.  That's it.

Steve N.