MDAC First Listen (part 00100110)

[JohnW]

Thanks for the update. Sorry to hear about all the hassle you are facing. I find drinking a good Scotch and an hour or two of good music often helps in these situations.

Here's to when you have it all working... Cheers!

Jadidih,

Well nothing too serious, just the extra stress of "wasted" time, and the extra costs hurts alittle.

Hey - Cheers! I was planning to have a few drinks once I'd issued the MDAC2 analogue PCB, in the end the drinks never happened but maybe once the analogue stage is debugged and tested (or once I've issued the VFET output stage PCB design)

 

[Nick1881]

Back from the Lab after installing the replacement display for the analyser - its now up and working once again

Today the HDMI Audio extractor arrived, the PCB is surprisingly well designed.

Tomorrow I'm make some quick measurements of its clock jitter just for kicks... this will give me an idea of what we are dealing with. I don't expect too much.

Seeing the positive interest I'll work towards adding the slot loader as an option to the full sized Chassis.

Also, I'll add a second internal digital expansion connector so that we have the option to add HDMI (etc) at a later date to the full sized chassis. I'm thinking of a blanking plate on the rear of the full sized chassis where the user can upgrade there unit as options become available - this way we can add the latest and greatest digital interface 5 years down the line at little extra cost....

John, you are amazing <3

Hope the build all goes to plan.

 

[vincey103]

would also go for slot loader option if becomes available.

 

[Steven Toy]

When the MDAC2 board is ready,,,,,,

I'd like to fly over with my MDAC and Rega Apollo R in bubble wrap, get the former's boards swapped, the latter clock locked and pay in cash if that's possible. If not I will give the cash to Tasha and she can pay you via paytwat or bank transfer.

Flight to Prague plus train to Olomouc and back the next day could be an option for me.

 

[Clerenlas]

A bit late to the party - but I would be interested in a CD transport in an MDAC2 wide chassis.

Currently I use my 1996-vintage Meridian 508 as CD transport into the MDAC. I imagine that it would not be possible to clock-lock this to the MDAC2.

I'd be interested to hear any views on the quality of the 508 transport. I'm not really in a position to test any comparisons.

 

[Steven Toy]

At a later date I'd either like the CD transport and MDAC2 integrated into a wide chassis or an MTRN in a separate box.

The former would be preferable.

 

[davidjt]

A bit late to the party - but I would be interested in a CD transport in an MDAC2 wide chassis.

Currently I use my 1996-vintage Meridian 508 as CD transport into the MDAC. I imagine that it would not be possible to clock-lock this to the MDAC2.

I'd be interested to hear any views on the quality of the 508 transport. I'm not really in a position to test any comparisons.

I'm in the same boat: a long shot I know, but if you have any views on or knowledge of clock-lock-ability of the Bel Canto CD1, John, it would be really helpful. Also, the player has an AES/EBU (?) XLR balanced digital output and I can't remember whether this will be accommodated on MDAC2?
Thanks.

 

[Vinz]

I'm in the same boat: a long shot I know, but if you have any views on or knowledge of clock-lock-ability of the Bel Canto CD1, John, it would be really helpful. Also, the player has an AES/EBU (?) XLR balanced digital output and I can't remember whether this will be accommodated on MDAC2?
Thanks.

Some SPDIF receivers are also compatible with AES. So using a passive AES -> SPDIF adapter might be an option.

 

[davidjt]

Thanks for that: there's an optical output, an RCA and a BNC marked 'SPDIF' and an XLR marked AES/EBU. According to Wiki, the latter is a 'balanced SPDIF', so to make it worth using it there would have to be a balanced DAC input. I think.
(I would just flog it and go for the built-in option, but suspect it's current value would be a nasty shock. )

 

[Vinz]

Thanks for that: there's an optical output, an RCA and a BNC marked 'SPDIF' and an XLR marked AES/EBU. According to Wiki, the latter is a 'balanced SPDIF', so to make it worth using it there would have to be a balanced DAC input. I think.
(I would just flog it and go for the built-in option, but suspect it's current value would be a nasty shock. )

I meant the MDAC(2) as the receiver. I wouldn't put too much trust on 'balanced SPDIF'. Anyway, why not using the coaxial or optical outputs? They are already used, perhaps?

 

[JohnW]

As promised measurements of the HDMI Audio extractor.

https://dl.dropboxusercontent.com/u/86116171/HDMI Converter.jpg

I was not expect much from the jitter results - whopping 29.88nS of Jitter!

https://dl.dropboxusercontent.com/u/86116171/HDMI Extractor Audio MCLK.jpg

The phase noise is around a million times higher then the MDAC2's reference clock at 1KHz offset (-44dBc, verses about -150dBc to -160dBc of the MDAC2's clock).

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

The test set-up, and Bobby guarding the lab

https://dl.dropboxusercontent.com/u/86116171/IMG_6651.JPG

https://dl.dropboxusercontent.com/u/86116171/IMG_6652.JPG

Interesting results - just goes to show that HDMI is not really geared towards HiFi audio applications. There is no reason it cannot be (just like USB) but the design of the HDMI transceivers leave a lot to be desired.

The biggest problem is that the peak jitter is very low rate at 1.1689Hz making it very hard to attenuate.

In fact the jitter level was so high I had to read the analysers manual for the first time to understand how to configure some settings on the analyser so that it could cope with the extreme Jitter levels.

 

[JohnW]

Thanks for that: there's an optical output, an RCA and a BNC marked 'SPDIF' and an XLR marked AES/EBU. According to Wiki, the latter is a 'balanced SPDIF', so to make it worth using it there would have to be a balanced DAC input. I think.
(I would just flog it and go for the built-in option, but suspect it's current value would be a nasty shock. )

The MDAC 1 & 2 have balanced digital SPDIF inputs (despite the RCA connector ) as they are transformer coupled.

Once a CD transport is clock locked, then optical connect becomes the best to isolate RF / Ground loops etc.

Any transport can be modified to be clock-locked to the MDAC1/2 but its a question of time.

Once the VFET / MDAC2 are cleared out the way then I can consider designing a small Clock-lock card that can be retrofitted to CD players / transports - but the slot loader option for the full sized chassis will be around GBP300 extra so does it justify my time? maybe if I need quick buck

 

[ChrisPa]

As promised measurements of the HDMI Audio extractor.

The phase noise is around a million times higher then the MDAC2's reference clock at 1KHz offset (-44dBc, verses about -150dBc to -160dBc of the MDAC2's clock).

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

I can't work out what the scales are on that plot

The test set-up, and Bobby guarding the lab

https://dl.dropboxusercontent.com/u/86116171/IMG_6651.JPG

Now that I'm impressed by. You're properly in the lab and using it
Congratulations!

Does this mean you've now reclaimed the room you were previously using in your house?

In fact the jitter level was so high I had to read the analysers manual for the first time to understand how to configure some settings on the analyser so that it could cope with the extreme Jitter levels.

The old engineering mantra.
If all else fails, RTFM

 

[misterdog]

Lab looking good there John.

I especially like the rack mount, pullout chopping board.

Is this so you can prepare snacks without leaving the bench ?

 

[Sibbers]

Ha! In some way John I'd like to hear your statement midi music centre just to see what you'd end up with. Anyway just checking in to see how things are coming on doff the proverbial cap in your general direction. I think I know what my benchmark music will be already

Take care!
Martyn.

 

[JohnW]

I can't work out what the scales are on that plot

Sorry about that, I have no control over the saved output from the analyser - even I get lost looking at the graph. The trick is to note the Marker (0) on the plot (I set it at 1KHz offset) its "only" -44dBc down, then you can workout the graph scaling etc - it makes sense then, until you look at the graph later and need to re-establish your barrings once again...

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

Left corners 100Hz, Right 100KHz offset

Top is 0dBc with 10dB Div.

Find the "0" Curser on the curve plot to reference 1KHz at about -44dBC

Its really poor performance - the PLL corner frequency is around 1.6KHz (and notice the peaking)... the PLL wiil be OK to extract Video data, but for Audio its just HORRID!

 

[JohnW]

Ha! In some way John I'd like to hear your statement midi music centre just to see what you'd end up with. Anyway just checking in to see how things are coming on doff the proverbial cap in your general direction. I think I know what my benchmark music will be already

Take care!
Martyn.

Martyn,

Loosing hair, getting older & still working on the MDAC2 / VFET designs so no change here!

 

[JohnW]

Lab looking good there John.

I especially like the rack mount, pullout chopping board.

Is this so you can prepare snacks without leaving the bench ?

Well I did say I purchased a whole stock pile of Oak a good few years back eventually we plan to build our house in the mountains, but I used a little for the lab as I'll be here for 5 years or so until Renata completes her studies!

Hey, I have a built-in Microwave and fridge under the staircase, but I bought a 20 Litre Ultra sonic cleaner (larger enough for the VFET PCB's) - its dominated the vast majority of the "kitchen's" worktop space!

 

[JohnW]

Now that I'm impressed by. You're properly in the lab and using it
Congratulations!

Does this mean you've now reclaimed the room you were previously using in your house?

Sadly no, I still have the PCB CAD design system in the house, the Pups are not happy in the lab yet so I work on the PCB designs during the day, and can retreat to the lab once Renata returns.

Its also a question of time, items are slowly moving to the lab as needed, but I just get too stressed with time do it in one go! there is now space to walk around the apartment without bruising ones knee cap on the corners of test equipment - rather nice to see the room corners and the floor once again!

 

[JohnW]

I'm in the same boat: a long shot I know, but if you have any views on or knowledge of clock-lock-ability of the Bel Canto CD1, John, it would be really helpful. Also, the player has an AES/EBU (?) XLR balanced digital output and I can't remember whether this will be accommodated on MDAC2?
Thanks.

David,

The MDAC2 will have transformers on it digital inputs so offers Balanced inputs even though the RCA connector is used.

Its possible to add XLR Balanced digital inputs on the Full sized chassis - but due to space limitations not on the standard chassis.

To be quite honest, I don't see any advantage to XLR balanced Digital inputs in a domestic environment - the input Transformers already provide the additional Common mode rejection.