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MDAC First Listen (part 00100000)

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jirij said:
Yeah, I wanted to do a write-up on boolean algebra, checksums (from the easy one used in TCP through CRC to SHA-2), lossless compression, that files in the digital domain can in fact retain bit-perfectness despite underlying analog technologies (and how), ... and also why emailing a file is very unlikely to modify it, but I'd just come across as an egoist trying to educate the world, which is not really what I want.
Short answer - strong mathematics and several layers of error protection or correction.

(just the digital part, any RF interference, time jitter, ..., can (= non-zero probability) of course affect the sound)
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Failing all that Buy a Samsung Win 8 laptop for £ 450.
though I'm sure there is something better down the line....:confused:
 
adamdea said:
John
Just thought I would let you know that I have now received an arcam delta 170.3 which is a very solid and quite handsome piece of kit. It seems to be working nicely and I have connected it by toslink clock in and clock out. It seems to work just fine with the clock output on the m-dac set at 64Fs which is the rate suggested in the service manual. It seems to work fine with 128 Fs but stutters every few seconds if set to 246 Fs. The m-dac will not connect if set to 96 Fs or 192Fs , display goers mental on output set to S/PDIF and makes no noise. Kind of as expected following our earlier discussion. I'm not altogether surprised the stuttering happens on 256 Fs -perhaps the receiver can't take the data rate. Ok, but weirdly it work just fine at 384Fs. Any idea why this might be?

Should I expect any particular report from the M-dac to show that clock lock has been properly achieved using the clock out (aside from the fact it works.). The sample rate reads a reassuring and stable 44,100 (whereas my SBT gives stable 44,094.) However, it does exactly the same when I disconnect the clock output from the M-dac. Which makes me slightly wonder whether the clock output is locking at 65, 128 and 384 or just not interfering with what the 170.3 was doing anyway.

I can't see anything on the 170.3 to indicate clock lock, whereas I can see from arcam's black box 5 and 500 manuals that they did indicate when lock lock was achieved between dac and CDT.
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With the MDAC1 there is no indication that the external sources is locked to the DAC - really the source should indicate that its looked to the DAC... I implemented a lock indicator on my transport designs for the Cambridge Audio / Pink triangle (and even a CD transport for Tube Technology)....

A DAC cannot reliably determine if the source is locked to its own clock - only indicate that its internal DAC is "switched" to operate from its own internal Master clock and hope that the source is Sync'ed to this... I believe this is all the BB 5 is doing.

On the MDAC as long as the Frequency is rock steady at 44.100KHz exactly then its looking good.

If it where not for yet another design bug in the ESS9018 then we could reliably read back the values from its ASRC rate estimator and insure the valves are "Fixed" which would be a sure indication of a locked source device.

Unfortunately a really really stupid design bug in the ESS9018 prevents us doing this...

On the MDAC2 not only will we be able to indicated a "Locked" external source - but we can also indicate the external jitter level by analysing the variance in the rate estimator values in real time - so as an option the MDAC2 can include a input jitter meter :)
 
misterdog said:
I find that the Bit Perfect Test can be misleading in so far as.

As have had had 2 laptops both of which passed the Bit Perfect Test, yet my newer Win 8 machine sounds clearly better.

So I conclude that the Bit Perfect Test does not show unwanted noise also being transmitted to the MDAC. Only that the music signal is complete.
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Yes, very possible - what you are hearing is what a refer to second order effect - basically external influences effecting the Analogue conversion - be it via Jitter, RF noise or system Ground loop.

Having bit perfect Data is the first primary requirement, if I'm to be blunt the audibility of these second order effects are an indication that the MDAC is not as resilient as I would have hoped.

The MDAC2 design offers additional counter-measures against these "second order" effects:-

1. Isolated USB port

2. Separated Digital and analogue PCB's

3. Isolation barrier between the Analogue and Digital domains

4. Improved HF / RF isolation of its PSU design

Hopefully the above steps will reduce (if not eliminate) the MDAC2's sensitivity to external "second order" effects.
 
PhilCTTE said:
John in regards to the visit , I'm in no rush , I'll wait for mdac2 , which was why I was asking when the bad weather starts in Czech. :D
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Lets hope the weather doesn't start to close in until the end of the year :p summers been pretty grim so far this year...
 
So in the MDAC2 it going to run on the Sabre chips? where does the FPGAs come in and what do they do?
I know somebody who has the Playback Designs MPS-5 SACD/CD player which i think uses FPGAs. My very brief impression of the Playback CD player is it seems to have a very open, grain-less, dynamic sound, while at the same time sounds relaxed and natural.
 
The FPGA on the MDAC2 will initially handle the Digital input decoding / (SPDIF / DSD etc) and then format this Data for Dual Mono operation - basically not much , however with later firmware software updates we will start to develop upon the power of the FPGA - first with digital filters, then ASRC and finally the modulator.

At each stage of FPGA advancement the sound quality of the MDAC2 will evolve... The MDAC2 will be like a Russian doll - constantly transforming itself by simply downloading the latest software.
 
Bob L said:
Adamdea pointed out that Chevron Audio may be able to provide a clock-locking CD system from Deltec, and this led me to follow up this name. It appears that Deltec were providing clock-locking back in the 90s or earlier, but they then disappeared for years. However they have reappeared with a new very expensive DAC, and this was reviewed by Hi-Fi Choice. Their conclusion was "Resistible", and included a comment that switching on the clock- locking made no difference!

Until I found this I was very interested in modifying my transport, but now I would very much like to hear from anybody with experience of using the Arcam or any other suitable transport with the MDAC. What sort of difference do you get?
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The clock locking system used by Deltec is called Deltran Locked and information can be found here http://deltecprecisionaudio.com/deltran/ On a good system the different is huge. It will transform a budget CD player into a super transport and it has been professionally designed to fit into a XLR size mounting hole. You would find similar results with other DAC systems.
 
JohnW said:
With the MDAC1 there is no indication that the external sources is locked to the DAC - really the source should indicate that its looked to the DAC... I implemented a lock indicator on my transport designs for the Cambridge Audio / Pink triangle (and even a CD transport for Tube Technology)....

A DAC cannot reliably determine if the source is locked to its own clock - only indicate that its internal DAC is "switched" to operate from its own internal Master clock and hope that the source is Sync'ed to this... I believe this is all the BB 5 is doing.

On the MDAC as long as the Frequency is rock steady at 44.100KHz exactly then its looking good.

If it where not for yet another design bug in the ESS9018 then we could reliably read back the values from its ASRC rate estimator and insure the valves are "Fixed" which would be a sure indication of a locked source device.

Unfortunately a really really stupid design bug in the ESS9018 prevents us doing this...

On the MDAC2 not only will we be able to indicated a "Locked" external source - but we can also indicate the external jitter level by analysing the variance in the rate estimator values in real time - so as an option the MDAC2 can include a input jitter meter :)
Click to expand...
Thanks for this John. It does seems to be 44,100- although it reads this without the clock out too. Perhaps the 170.3 just has a really well designed output. As a matter of interest which Cambridge transport did you design?

The jitter meter sounds like a great idea, I haven't heard of this feature anywhere else.
 
John

Out of interest (and off topic again)
Have you identified a quality slot load CD/DVD mech?
If so, what and why?

Thanks
 
ChrisPa said:
John

Out of interest (and off topic again)
Have you identified a quality slot load CD/DVD mech?
If so, what and why?

Thanks
Click to expand...

Yes, we used a Metal body car slot loader with our own servo PCB for our CD Player we designed for creek based on the loader we originally sourced for our own CD transport.

We chose the slot loader as the mechanism being designed for car applications is very rugged and not the plastic wonder that most CD tray loaders are these days. As the car loader is designed for harsh temperature and vibration environment - it should have a long life of bliss in the comforts of a domestic home setting :)

Also the Laser OPU is an all metal affair again designed to serve the stresses of a Vehicular environment...
 
JohnW said:
the stresses of a Vehicular environment...
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If it could survive the road surfaces in Sheffield then it would be bomb proof.

The term 3rd world has been applied , though personally I think this may be be an understatement.


We opted to fund the World Student Games in lieu of road maintenance.

The fireworks were excellent , though short lived. :D :confused:
 
Good logic

So that means it's a dedicated CD drive then rather than pc drives which are CD/DVD combos?

And it's not something that I (for example) could readily get hold of domestically?
 
ChrisPa said:
Good logic

So that means it's a dedicated CD drive then rather than pc drives which are CD/DVD combos?

And it's not something that I (for example) could readily get hold of domestically?
Click to expand...

If you drive a Merc. :eek: just rip one out.
 
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