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MDAC First Listen (part 00011110)

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ChrisPa

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John

Sounds a very wise suggestion. I'd love to wait for the full FPGA solution, but this suggestion allows for 'diversions and distractions' whilst having a real live product.

Your designs will always 'follow their nose' taking little side turnings on occasion.

So, an mdac2 in the hand is worth an FPGA mdac2 in the bush.
 
Hi John I think your proposal is good especially the potential to go to the tube stage later so I am in.
Modshop in Italy do a range of cases at sensible prices which may be suitable for the power supply I use them for my amps.
Geoff
 
GWM said:
Hi John I think your proposal is good especially the potential to go to the tube stage later so I am in.
Modshop in Italy do a range of cases at sensible prices which may be suitable for the power supply I use them for my amps.
Geoff
Click to expand...

+1.
 
The final digital hardware upgrade , what form will that be , card , small board ?

If the fitting of 2 pcbs and then a further digital "piece" is a simple enough task , then this undoubtably is the best way forward. Avoiding shipping costs and time without an MDAC is all positive in my view.

The idea of separating the digital from analogue board and adding galvanic isolation seems all very logical .

Edit .. In regards to all the digital pieces being reused in the Tdac , limits the expense on our behalf . When you first mentioned the cost of the Tdac it made me wonder if could afford it , but with these building blocks gives me time to save up.

Will be an interesting couple of months to see what the final outcome is in regards to the final design and choice of resistors etc... Oh and cost ;)

Btw John finally fired up the (Quattro) Quad :) just getting initial impressions right now.
First words that come to mind "warm and musical"
Top end is far more listenable. It's lost control a little in the lower register and on busy tracks some of the clarity is missing. I could certainly pick out and separate the instruments better with the audiolabs.
The sound is different , but a lot easier to listen :)

I'll swap out with the other 520 later in the week .
 
Oooh opto-couplers! Sounds good to me John. Although I've not been able to commit myself financially, I hope to sometime later this year. The very best of luck with this project!
 
John,
could the eventual TDAC be a two box unit? Keep the original MDAC casework for the digital and control electronics and then pass the signal to another box with the analogue stuff in it, splitting things at the point of the galvanic isolation. The second box could be simpler, as it doesn't have to be on show, so, hopefully cheaper to manufacture?

Also, if we keep to the current MDAC dimensions, I don't need to get a bigger rack!
 
Any chance the proposed TDAC upgrade would be available in the states? Looking forward to the next MDAC iteration!
 
JohnW said:
Ok, latest development is to added position for "headers" on the MDAC2 PCB which will allow us to add the Tube output stage at a later date. So owners of the MDAC2 can "Upgrade" to the Tube platform one its released (the MDAC2 will have to be returned to Czech Rep for Tube option).

Unfortunately, the difficulties with the "TDAC" is not so much the tube circuit itself, but we will need to rehouse the MDAC2 PCB + Tube section with its extra PSU into a new chassis - its this new chassis that adds the extra complexity. At this time, I'm not sure how we will handle this... Maybe Arek can help out the Mechanical work, I dread European pricing on Mechanical parts…

As I’ve now come to terms with the fact that the MDAC2 design will be based on 2 PCB’s – the logical step is to totally isolate the Digital and analogue stages – so one PCB contains the Dual ESS DAC’s, Clock, Analogue stage and PSU. While the second PCB (mounted above) – has the FPGA, USB and digital inputs etc.

We can add a galvanic isolation barrier between these 2 PCB’s so the critical “Analogue stage” is isolated from the “Noisy” digital sections, insuring the lowest analogue ground noise. While added complexity to the project in design time its has many advantages – not least that it’s really the correct method to do it:-

1. Should practically eliminate “Second order” digital processing effects on sound quality (Sound quality should not be effected by software routines etc).

2. Provides galvanic isolation from the digital section if the additional PSU is installed (an option).

3. Provides a future upgrade path (either the Digital or Analogue PCB can be upgraded in the future at reduced cost without scrapping the whole unit).

4. Allows as to pre-release a simpler interim Digital board very quickly (no FPGA and only supporting USB upto 24/96) – so basically the same functionality of MDAC but with the improved sound quality of the MDAC2 (Dual ESS + new output stage etc) with galavincally isolated USB etc. This allows those waiting for the MDAC2 to gain the improved sound quality ahead of the “official” release of the fully featured MDAC2, the extra MDAC2 “Digital” features can be added later with a simple board upgrade by the owner with the “fully featured” MDAC2 digital board.

This de-risks the project, allowing us to swiftly deliver the “basic” improved sound quality of MDAC2 while we continue the development work on the more advanced digital board with the promised features (DSD64, 128, 256, PCM 384fs + FPGA etc), so now a 2 stage process, but allowing us to deliver the MDAC2 "Sound quality" closer to the original target dates

MDAC2 audio performance will be further improved once we start introducing the more advanced FPGA firmware upgrades (upgraded via a software download) these will incorporate a more advanced digital filter etc…

The "Interim" Digital board will be sold at a nominal cost to cover its production and development (lets say around GBP150).

Comments? (Good idea or bad idea?)
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Just make sure to add a lead casing for the digital section (or the analog section), so that the radiation stays within the digital section and no coupling is taking place. :D Also, you can make it wireless, using lasers and photo-sensitive parts to transmit the data between the two boards. :) Now that would be cool.

Just kidding, thanks for the update, sounds interesting and would be great, but I guess it still depends on how far you want to go with the isolation. I mean - you can't easily decouple the digital section from the PSU without using transformers ..., but it makes sense to take advantage of the separate PCB somehow. Perhaps design it for 5V and a "USB power / internal power" switch? Would it be worth it / possible? Assuming the front panel is plugged to the digital PCB, it may pose a problem.

Just trying to be creative here. :)
 
John,

Generally I like the idea of a 2 PCB design. I'd be more than happy to pay for an interim digital board if we get a more sophisticated digital upgrade board in the end. Can the small case handle the heat with a 2 PCB solution? You mentioned an optional 2nd PSU for the digital board. Can you elaborate some more?

If the TDAC requires a new case after all wouldn't it make more sense so spin a new analogue board instead of reusing the MDAC2 board plus an extra tube addon? When I think "TDAC", I'm thinking "no compromises" and with the MDAC2 being a 2 PCB design you can use the same digital board.

Michael
 
hallo John

first, I like the idea of the 2 PCB (analogue / digital) solution.
But, I'm not sure if this mdac2 in small steps is a good idea.
everyone who is interested in mdac2 have at least a mdac. so, from this side no time pressure.
you expect the mdac2 at June 2014. so lets say July ;-). This is in front of the sommer holiday season. So, July or September is not that different.
I think most of the mdac2 user are interested in the final digital pcb. So the interim stage is a disposable article. Is that a good solution for our environment?

just my 2ct
F.S.
 
John, take you time, strive for the complete solution, most of us don't need some half way house we'll wait for the complete thing.
 
JohnW said:
As I love inflecting pain upon myself - I've upgraded your PCB to full toy + AV bypass, I'll charge you just for shipping + the Toy resistors... BTW, it appears it was the Crystal that failed (there was also a couple of capacitors in distressed which I don't understand the reason for - I can only presume QC issues).
Click to expand...
Yay! Thanks so much - just let me know how much and I'll get that sorted once I'm back home (I'm currently in a rather dilapidated cottage near Windermere, resplendent with Aga and a baby grand also. No music worth speaking about, though bizarrely the weather is being relatively kind to us!

Now I just need to find a defective MDAC so that come MDAC2 I can have L2 Toy for the second system and MDAC2 in the main system.... I don't suppose you know of any in the UK? ;)
 
sq225917 said:
John, take you time, strive for the complete solution, most of us don't need some half way house we'll wait for the complete thing.
Click to expand...

John I have to agree with this.

I would much, much prefer the finished job in one go. All done.

Then any software betterments can simply be downloaded to the FPGA.

A much tidier, more professional solution.
 
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