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MDAC First Listen (part 00110001)

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JohnW,

You have said the other day "Would not a tent lashed up in the back garden with a merry little fire with marsh mellows on a stick not suffice?" regarding to my holiday plans over buying MBs... I have to say I probably should have done what you have proposed... as Lowcostholiday Ive booked holiday with have gone bankrupt! Potentially Ive been ripped off for £700! Likely flights are paid, need to repay for accommodation, travel insurance and some other services! Yupi! Lets hope my bank can help and charge them back :(
 
DANOFDANGER said:
The circuitry looks very familiar to the mdac, seems that room has been made for a better internal power supply. I wonder if thats the main improvement. Output stage looks remarkebly similar.
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Yes, in fact the DAC and Analogue stage is an EXACT "Copy and Paste" of the MDAC's - they tried to design there own analogue stage with the QDAC and we know how that turned out - so for MDAC+ I can suppose / believe that the designers would have been directed to "just modify" the now proven MDAC design by adding internal PSU & the XMOS USB 2.0 PCB.

A few weeks ago, I reach a token finical agreement with IAG selling them the complete rights to the MDAC Analogue stage design etc. (as they quite clearly reused the design for the MDAC+). No real loss as the FDAC (and MDAC superior update) is so far in advance of the now 5 year old MDAC design.

I kinda feel sorry that they did not contact me first before they coped the PCB design as there is a PCB error around the output stage protection transistors where I'd accidental swapped the Base and Emitter connections on the current sense transistors (I designed this at the time of my fathers death so my mind was was very distracted) lucky, the CROSS (Current Regulated Output Stage Solution) limits the overload current under fault conditions.
 
I'm very surprised IAG didn't involve you in the MDAC+ John .... as a consultant, at the very least. As far as I can discern the MDAC+ is being very well received in the UK press and forums and is probably a successful product for IAG.

Is there anything to be learnt/said on how they improved the PSU which I guess is now giving this the edge over the original MDAC....Is it 6-independent rails (or 8?).
 
timola said:
I'm very surprised IAG didn't involve you in the MDAC+ John .... as a consultant, at the very least. As far as I can discern the MDAC+ is being very well received in the UK press and forums and is probably a successful product for IAG.

Is there anything to be learnt/said on how they improved the PSU which I guess is now giving this the edge over the original MDAC....Is it 6-independent rails (or 8?).
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Is it an improvement on the MDac? What exactly have they done to the psu beyond putting the transformer in the same case? Genuine question.
The MDac is a really good dac. Which means that unless someone actually compared the MDac + with it side by side and level matched, they probably couldn't tell whether the MDac plus was an improvement or not.
 
"Der erste Eindruck des originalen DA-Wandlers ist überraschend anders als der M-DAC, denn es klingt bedeutend "heller", aber auch erheblich "kühler" und bei Stimmen tendenziell "nervig". Wenn Sie dem Gerät eine ausreichend lange Einspielzeit zugestehen, wird es zwar ausgewogener, aber selbst nach 10 Tagen klingt es längst nicht so "entspannt" wie beim M-DAC." (hoer-wege.de)

The MDAC+ sounds "colder" and more sibilant, voices sounds a little bit "stressed".
 
adamdea said:
Is it an improvement on the MDac? What exactly have they done to the psu beyond putting the transformer in the same case? Genuine question.
The MDac is a really good dac. Which means that unless someone actually compared the MDac + with it side by side and level matched, they probably couldn't tell whether the MDac plus was an improvement or not.
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Well its hard to say whether its better, but there are definite differences. To start the transformer is torroidal where i believe the mdacs wall wart was probably not.
Looking at the board it seems theres actually been some sacrifice ? Certain number of components have been shaved in favor for possibly more expensive components.
I vote that there would most definitly be a difference, better or worse however i'm unsure.
 
DANOFDANGER said:
Well its hard to say whether its better, but there are definite differences. To start the transformer is torroidal where i believe the mdacs wall wart was probably not.
Looking at the board it seems theres actually been some sacrifice ? Certain number of components have been shaved in favor for possibly more expensive components.
I vote that there would most definitly be a difference, better or worse however i'm unsure.
Click to expand...
I'm not sure I would call the MDac transformer a wall wart. It's a big heavy hunkl. And I'm not sure why it would be better to have it in the box.
I'm sure John will be able to help. MDac + USB input section has to be able to cope with dsd.
 
@JohnW,

sold my MDAC when you decided to abandon the upgrade of the MDAC in favour of FDAC, which was fine, in retrospect (see Superiour MDAC) I feel a bit cheated.

Anyway, there's a couple of questions from me (see previous post from me) and a new one below.

I know you have/had a stash of MDAC's awaiting repair as slave MDAC's, any plans to have them available as Superiour MDAC's for us?

/Lars
 
adamdea said:
I'm not sure I would call the MDac transformer a wall wart. It's a big heavy hunkl. And I'm not sure why it would be better to have it in the box.
I'm sure John will be able to help. MDac + USB input section has to be able to cope with dsd.
Click to expand...

Well perhaps not a wall wart, but its very close in similarity. Only difference is its sitting further down the chain, likely because its just too heavy for the wall.
Im not sure having the transformer in the case makes it better, i think it may be more because theres more room to allow for a toroidal design.
At the very beginning john had stated the mdacs power supply weakness and planned to release a improved psu version for mdac owners to upgrade to.
 
Efski,

Sorry to hear about your troubles :( maybe one day we will be in a position to send you over a pair of our prototype MB's

I'll be online later tommorow evening with replys to all the many questions, and a project update.
 
JohnW said:
Efski,

Sorry to hear about your troubles :( maybe one day we will be in a position to send you over a pair of our prototype MB's

I'll be online later tommorow evening with replys to all the many questions, and a project update.
Click to expand...

Sounds good :)
If you get a chance to answer my question few pages back id be really happy, i'm really curious to what the answer would be.
 
DANOFDANGER said:
Well perhaps not a wall wart, but its very close in similarity. Only difference is its sitting further down the chain, likely because its just too heavy for the wall.
Im not sure having the transformer in the case makes it better, i think it may be more because theres more room to allow for a toroidal design.
At the very beginning john had stated the mdacs power supply weakness and planned to release a improved psu version for mdac owners to upgrade to.
Click to expand...
I spose Dan, but most wallwarts are switch mode AC/DC converters and IIRC the Mdac has a 15V AC/AC converter which may be a straightforward step down transformer (anyone?). It would be surprising if replacing one of these made a tremendous difference compared with replacing a complete AC/DC device because you are only replacing a part of the chain. Perhaps they have replaced other bits too (beyond individual part swapping) but is there really a circuit redesign?

Incidentally according to the HFN review the jitter on the Mdac plus is slightly higher "due to the fully-enclosed PSU". Still they refer to the Mdac's psu as a wallwart too.
 
adamdea said:
I spose Dan, but most wallwarts are switch mode AC/DC converters and IIRC the Mdac has a 15V AC/AC converter which may be a straightforward step down transformer (anyone?). It would be surprising if replacing one of these made a tremendous difference compared with replacing a complete AC/DC device because you are only replacing a part of the chain. Perhaps they have replaced other bits too (beyond individual part swapping) but is there really a circuit redesign?

Incidentally according to the HFN review the jitter on the Mdac plus is slightly higher "due to the fully-enclosed PSU". Still they refer to the Mdac's psu as a wallwart too.
Click to expand...

Yes whether just changing the transformer alone would make a big enough difference is hard to say, but if it didnt then EI transformers might be used exclusively. Which i assume the mdac uses. Johns orignal power supply upgrade which he called M-pwr i think, also included a redesigned rectifier stage. I think the torodials main attraction over EI is its ability to contain its magnetic field, which may be desirable for creating a clean power source.

From glancing at the circuitry as i pointed out, the output stage was very similar. But there are various component differences in the rectification stage and gain stage that make me ponder.
 
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