Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems S/P-DIF format

This is confusing to me! Meridian offer S/P-DIF outputs to connect (for exsample) 800/861 or 596/568. Refering to an artical it is meansioned that the S/P-DIF outputs are rather bad.

Quote:
Duncan emphasized that upsampling could not create new information. Instead, he said that it alters the jitter characteristics of the digital receiver (eg. the DAC) in a favorable way because the S/P-DIF format was so bad. Duncan didn't mention that this was predicted by Malcolm Hawksford in a paper written years earlier. I expressed surprise at this reason given that Meridian goes through great lengths to suppress jitter, and he expressed his disappointment in the S/P-DIF format in his one-word response,"unfortunately".

What does this mean for those sources without upsampling like the 596? The ultra low digital jitter is useless because the weakest point of the chain is the S/P-DIF format?

Hmmm, any comments on this issue?

Speedy,

S/P-DIF is the physical and electrical interface, you have to connect to something.

There is nothing wrong with this as an interface except that you find on it cheap as well as expensive devices. It's all about implementation.

On the 596 it is implemented really well using expensive components etc.

What is important about the connector is that it maintains 75 ohm's with no attenuation, a properly constructed cable is all that is required to go from the transport to the processor.

Martin.

So actually they should have reported that upsampling alters the jitter characteristics in a favorable way compared to 44.1kHz sources?! This would be a better understanding for me.

I mean the background is the structure of the
SPDIF (SonyPhilipsDigitalInterface)signal itself.Because the clock and the data are
"combined" and if jitter appears somewhere,
with INCORRECT upsampling its even jitter more.If the SPDIF didnt have "combined" data and clock signals, the data could be better
"extracted" or "decoted" and and wouldnt have
jitter at all.
Maybe the MHR encrypted interface have a different structure?

I don't understand the comment about upsampling doing nothing but improving jitter. Upsampling does not necessarily improve jitter at all...depending on the implementation, it could even make it worse. What upsampling does provide is an interpolation between sample points. This allows for a better estimate of the signal between sample points vs. using the analog-filtered output of the A/D.

Hi,

As the writer of the passage quoted, I think I should clarify what I said. As one poster mentioned, a clearer way of stating it is that upsampling may alter jitter characteristics in a favorable way relative to 44.1kHz. However, like anything else, it can also degrade the signal, and it all depends on the particular details of the implementation.

For example, many DACs these days use a Sample-Rate Converter (SRC) to do their upsampling. The architecture of the SRC affects its response to jitter. The Analog Devices AD1862 SRC popular a few years ago would convert jitter into a higher noise floor rather than FM-modulated components, leading, theoretically, to a more benign, less audible response to a jittery signal. Incidentally, tests done on the Meridian 518 indicates that it does something similar to that, though I don't think it uses an SRC.

As for the SPDIF architecture being inherently flawed, I think, while that may be possible, that is but one component of a device's performance in the real world. Other things that can affect it as well, which some jitter boxes fixe inadvertently also fix are:

1. Resistance to common-mode RF noise, both airborne and conducted. Many jitter boxes actually improve this because they commonly have some kind of pulse transformer at their digial inputs and outputs. The Z-Systems RDP-1 and RDQ-1 digital preamps and EQs do this quite well because their SPDIF interfaces are exceedingly well-designed with respect to this. Things that may help in this category include:

a. good shielded cabling

b. good interface to the chassis, which is properly grounded. A BNC plug with a circumferential bypass cap to ground and circumferential termination of the ground to chassis is a good start.

c. input and output transformers with appropriate filtering: low inductance, low reactance at the appropriate frequencies.

d. good conductive chassis with screws no further apart or openings not larger than 1/4 of the wavelength of the highest frequency your circuit will react to.

2. Good internal circuit design:

a. surface-mount components throughout, especially bypass caps for high-frequency components (all digital chips, high opne-loop bandwidth op-amps, etc.). The components must be of low-inductance and low-reactivity, ideally resistive up to the upper limits of their working frequency range.

b. multi-layer board of at least 4 layers with complete ground planes, and good layout. This includes routing high-frequency currents on the ground plane correctly, mounting of chips directly to the board with appropriate shielding on the board and perhaps around the chip, and taking into account the high-frequency impedance of traces when transmitting signals.

3. Good handling of the analog interface, which means only correctly balanced I/O, with analog shields circumferentially attached to chassis only, and balanced operation up to upper limits of analog working frequencies (meaning upper end of open-loop bandwidth of amps in the analog section). To get balanced signals, an output transformer is best, but a passive balancer (matching impedance to ground of pins 1 and 2 with resistors, inductors, capacitors) is fine, too.

I don't think I've seen any one component with all of these things, except perhaps for the Z-Systems stuff. The TAG McLaren AV32R is very good in many of these respects. Meridian's pretty good too.

--Andre

Andre,

thanks for your greate comments but it was a bit much for me to understand. I am not familier with all those issues on circuit layout, shielding etc. etc. but I'm willing to learn For my part as a consumer I would just have to pay attension to a good S/P-DIF connection ( gee what else could I do ).

Do you think the TAG McLaren AV32R is a notch better then the Meridian 596? I'm just curious.

Speedy,

The AV32R is a surround processor, not a CD/DVD player, so it's not comparable to the 596. Meridian makes good stuff, and I wouldn't worry too much about their electrical interfaces.

--Andre

Ups, I mixed up the AV32R with the DVD32R.

Speedy

Speedy,

The DVD32R looks cooler than the 596, and that's all I can say about it. I saw and played with one at TAG McLaren's display at this past CES, but I can't tell you much more beyond that. It is quite a piece of engineering, with TAG McLaren doing basically almost everything from the ground up, including the disc reading and navigation. I don't think it decodes MP3.

--Andre

I have to say looking cool and sounding and playing DVD's are two different things.

Right it has this funky blue light and draw that has some radom way of shutting, uses a clamp with a magnet, cost almost twice as much as a 596 and does not sound as good.

If you are into style over substance then the tag CD/DVD player might me for your, but we are here because we KNOW Meridan is not just better, but it a way way better, maybe I am just bias?

Forget value for money, the 596 is just simply better, period or full stop as we say in the UK.

Martin.

Martin,

I've never heard the saying "period or full stop" and I have some difficulty in understanding.

Does it mean; "flash it(down the toilet) or stop go for it" ?

Hmmm, english can be so interessting