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MDAC First Listen (part 00100110)

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I decided yesterday evening, possibly foolishly, to try my MDAC without its case

Which was okay until I reassembled it

After reassembly, once powered up it sat there saying Unlocked on any input :-(

so I left it for a bit... ever hopeful...
...
...and with no change (unsurprising)...

...this evening I decided to check it out properly - pulled the PCBs out and connected it up to the front panel,
powered it up
and got - nothing
Check fuse
Grab multimeter with intention of checking PSU voltages
And then realised that if I waited until the end of The Wait of Doom - nothing for nearly a minute followed by no comms - that there was still some life in it
(John, can we speed up having something on the display with MDAC2 please, so it doesn't look like it's completely dead)

Anyway, after some removals and reinsertions of the ribbon (at both ends) between the mainboard and the front panel I got it to come to life and accept an SPDIF signal whilst still spread out on the table.

After reassembly it was back to no comms. :(

So some more dismantling, ribbon removal, checking the contacts were flat, and careful reinsertion, I got it working again. Having managed to get it working I left the front panel connected while reinserting the boards into the case

So a few questions please John:
- does it seem feasible that a dodgy connection in the ribbon might cause it to power up but decide it was "unlocked" or would there be some other reason for that particular fault mode?
- or is this likely to be a symptom of impending further doom (eg. motherboard crystal)?
- will you possibly have some spare ribbon cables available for the MDAC2?

Thanks

Oh yes - the reason for removing the case:
Did it sound better without the case? Possibly, probably
I didn't have the opportunity to swap backwards and forwards, and based on what happened I'm now not keen on the swapping process ;)

However whilst based on my very limited trial I think I did hear some differences, they're not the level of difference I'd be hoping for when comparing with the MDAC2
 
I was surprised when I took the boards out, just how much of the mainboard has circuit laid out on it but no components.

What was that for John?
(I suspect if I read back through the original Audiolab threads I'd find out, but is seemed easier to just ask you :))
 
ChrisPa said:
Does it seem feasible that a dodgy connection in the ribbon might cause it to power up but decide it was "unlocked" or would there be some other reason for that particular fault mode?
Click to expand...

Its 99% chance the problem was due to the incorrectly connected cable - or the FPC is not "cut" 100% correctly and it require several trials to insure its was correctly centred with the mating contacts.

ChrisPa said:
or is this likely to be a symptom of impending further doom (eg. motherboard crystal)?
Click to expand...

No, that fact you originally had a "No Lock" indication suggest that the Cable was not correctly fitted.

ChrisPa said:
Will you possibly have some spare ribbon cables available for the MDAC2?
Click to expand...

Yes, we will supply with a new FPC cable.
 
ChrisPa said:
I was surprised when I took the boards out, just how much of the mainboard has circuit laid out on it but no components.

What was that for John?
(I suspect if I read back through the original Audiolab threads I'd find out, but is seemed easier to just ask you :))
Click to expand...

For the originally planned "QDAC" which included the Analogue Pre-amplifier (the same design as the CDQ's Analogue pre-amplifier stage). However we could not afford the extra Heat dissipation due to the extra loading on the small regulator heatsinks.

The MDAC2 uses a "Heatbar" that runs the entire length of the Digital PCB just behind the front panel to increase thermal dissipation.
 
JohnW said:
Its 99% chance the problem was due to the incorrectly connected cable - or the FPC is not "cut" 100% correctly and it require several trials to insure its was correctly centred with the mating contacts.

No, that fact you originally had a "No Lock" indication suggest that the Cable was not correctly fitted.

Yes, we will supply with a new FPC cable.
Click to expand...

Thanks for the replies
 
JohnW said:
For the originally planned "QDAC" which included the Analogue Pre-amplifier (the same design as the CDQ's Analogue pre-amplifier stage). However we could not afford the extra Heat dissipation due to the extra loading on the small regulator heatsinks.

The MDAC2 uses a "Heatbar" that runs the entire length of the Digital PCB just behind the front panel to increase thermal dissipation.
Click to expand...

I wondered if it was the qdac
 
jamjar784 said:
H619uI9
http://imgur.com/H619uI9

Naked MDAC definitely sounds better to me, now clothed in pine wood. Plenty of ventilation holes so hopefully no heat problems :)

KaA2nGZ
http://imgur.com/KaA2nGZ
Click to expand...

Cool :)

Did you make some metal brackets to hold the front and rear panels in?.
 
Yeah it was real tricky to get everything to line up - lots of sanding until everything fitted just right. As you guys have pointed out if the power switch is sticky the box is not quite true, so I was quite amazed/chuffed it was OK. I made an aluminium bracket to mount the front and back panels onto the wood.
 
Hi JohnW,

How late does one need to commit if they're interested in some slave MDAC2s?

Might be tempted to go active crossovers, once I've switched to DIY speakers.

Ta
 
dtd said:
Hi JohnW,

How late does one need to commit if they're interested in some slave MDAC2s?

Might be tempted to go active crossovers, once I've switched to DIY speakers.

Ta
Click to expand...

dtd,

Anytime upto the time we start to order components / PCB's in bulk.

Also, once I start to work on the Digital PCB, then I'll have a better handle on how the slave combination will work - but it will be featured.

Over the past week, I've been working on getting a higher performance Phase noise measurement system installed to really be able to measure the MDAC2's Clock jitter levels - at the moment I'm limited by my test systems.

Its been pretty painful on the bank account :( but at the performance levels "expected" for the MDAC2 clock I've been pretty much working in the blind as its below what I can currently measure.

I just hope the systems performs well, as it has been recommend to me by an expert in the field of Ultra Low Phase noise measurements....

The complete system consists of many units controlled via dedicated PC:-

https://dl.dropboxusercontent.com/u/86116171/phasenoise.jpg

The large rack in the centre contains the phase noise measurement system (I'll be installing a similar system)...

I'll honestly be able to say that the MDAC2 will have been thoroughly engineered!
 
Well for what it's worth, it will translate if the rest of the chain can keep up. As you probably know I own an Auralic Vega which has an 'femto' clock, but what's really useful is the ability to adjust it from auto/coarse/fine/exact.

A few days ago, I tried a pair of kit speakers with the above DAC and Ncore amps. The Wilmslow Audio Prestiges to be exact. ATC midrange, ScanSpeak tweeter, 12" volt bass driver. Once the DAC had warmed up, switching from auto (course) to Exact created a big step up in performance in this case, something I'd not noticed prior - ever more accurate solid soundstaging, sharper imaging, more ambient detail, a real clear focus just got applied across the spectrum. I was rather shocked to hear the improvement jump, all be told. Even closer to 'performers in the room' experience. Eeerily close. Needless to say I'm buying that kit!

Long story short - chasing phase noise for the MDAC2's clock jitter will be worthwhile from what I heard.

As for your bank balance, once this is out of the door and gets recognition, is there no desire to commercialise it without being in China all the time? (poor Dom!)
 
I hope the cable on that rack are purest unobtainium John. Wouldn't do to have tens of thousands of pounds of test equipment wired up with just any old rubbish! ;-)
 
I've not actually ordered the cables yet, I'm waiting for the various units to arrive which will take a couple of weeks, once they are arranged and mounted in the rack then I'll worry about the cabling...

The system operates in may different configurations, so depending on how you want to perform the measure determines how the various units are interconnected to the main interface box.

Does anyone know how to ship a large "empty" 19inch cabinet from the US? - even if it arrives in the UK I can arrange transport via a van back here to Czech Rep. the 19inch cabinet dimensions are:-

23.5"L x 31.5"D x 63"H (before packing on a pallet or what have you).

I'm not sure what type of shipping company to contact - they would have to collect the empty cabinet from New Jersey in the US and deliver to Europe...

Its only an idea, but I'm really too busy to dedicate too much time to investigate - if there was any easy and affordable way then I'd go ahead, otherwise its not worth the distraction.

It would obviously be shipped by sea cargo... I've only shipped containers before and loaded them myself...
 
Hi all,
what is the best way to feed MDAC2 with a HDMI source? What kind of device I need? Any suggestion? Thanks.
 
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