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MDAC First Listen (part 00110001)

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DANOFDANGER said:
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.
Click to expand...
John seems to think that the output stage is identical. But maybe the rectification is improved.

I agree with you about the EI. So taking an external EI and replacing it with an internal transformer may require a toroidal to avoid problems
This seemed like an interesting article
http://www.soundstage.com/maxdb/maxdb071998.htm
 
Yea i did say the output stage is similar, but still differences in capacitor and transistor count at the gain stage ?

Yea iv seen that article before, toroidal seems to be most popular among high end gear. I never really see other types used unless its in cheaper or space restricted equipment.
Although some do, nad m51 comes to mind. So who knows.
Its all very fun :)
 
Linn only use SMPS in all their components now....as far as I know...They seem to sound just great too.

I know John doesn't like SMPS due to the noise produced...somehow Linn and others have a solution....and as far as I recall John had a hand in inventing SMPS in the first place!;)

SMPS are supposed to be better able to deliver more 'juice' instantly when required (to improve dynamics?)...But I guess it's a major cost saving in production and another part that can protected by IP is the real reason Linn and others use these.
 
timola said:
Linn only use SMPS in all their components now....as far as I know...They seem to sound just great too.

I know John doesn't like SMPS due to the noise produced...somehow Linn and others have a solution....and as far as I recall John had a hand in inventing SMPS in the first place!;)

SMPS are supposed to be better able to deliver more 'juice' instantly when required (to improve dynamics?)...But I guess it's a major cost saving in production and another part that can protected by IP is the real reason Linn and others use these.
Click to expand...
Uptones upcoming Mystery PSU is powered by a SMPS
http://www.computeraudiophile.com/f27-uptone-audio-sponsored/mystery-revealed-uptone-audio-ultracap%99-linear-power-supply-1-a-28609/
This also as an example of that a development project is difficult to estimate a precise time of completion. Think it was supposed to be finished in start of the year, then spring and now we have summer.
 
timola said:
Linn only use SMPS in all their components now....as far as I know...They seem to sound just great too.

I know John doesn't like SMPS due to the noise produced...somehow Linn and others have a solution....and as far as I recall John had a hand in inventing SMPS in the first place!;)

SMPS are supposed to be better able to deliver more 'juice' instantly when required (to improve dynamics?)...But I guess it's a major cost saving in production and another part that can protected by IP is the real reason Linn and others use these.
Click to expand...

Yes. Benchmark take the same position. They believe that it's a myth that linear supplies are electrically quieter than switching supplies.

- Richard.
 
Interestingly THETA don't agree with Bruno Putzeys that his nCore nc1200 sound better with his SMPS; they have deployed Linear PSUs with his nc1200 in their new Dreadnaught

Rumour has it they agree to disagree, something about a large mode at 50-60hz in Linear PSUs

Possibly John could try a Hypex SMPS on the 8200MB replacement board to see if it's any better? (No pressure intended, only if curious)! ;-)
 
Interesting reading this thread, is the JW improved MDAC project finished yet? I seem to remember reading about it 2 years ago?
 
ti33er said:
Interestingly THETA don't agree with Bruno Putzeys that his nCore nc1200 sound better with his SMPS; they have deployed Linear PSUs with his nc1200 in their new Dreadnaught

Rumour has it they agree to disagree, something about a large mode at 50-60hz in Linear PSUs

Possibly John could try a Hypex SMPS on the 8200MB replacement board to see if it's any better? (No pressure intended, only if curious)! ;-)
Click to expand...

I suspect Theta are just doing something different to distinguish their amp from the Mola Mola amps irrespective of whether it actually sounds better. Yes I'm a cynic. Bruno did something clever with the Ncore smps. You've only got to listen to the amps for proof of that.
 
DANOFDANGER said:
Just curious john, if price was no object, what are the kinds of things for the fdac you would do differently or components you would use.
I'd assume the overall topology would not differ much but use of different components.
Would you even go as far as a fully discrete dac ?
Click to expand...

Dan,

Apart from the use of tubes, the FDAC is really a "no cost spared design" - once you include the Vishay Bulk foils and full screened chassis options.
 
ti33er said:
Interestingly THETA don't agree with Bruno Putzeys that his nCore nc1200 sound better with his SMPS; they have deployed Linear PSUs with his nc1200 in their new Dreadnaught

Rumour has it they agree to disagree, something about a large mode at 50-60hz in Linear PSUs
Click to expand...

It's not a rumour. In certain Stereophile measurements you can actually see those large modes appear time and time again. I think even the measurements for the Theta's has those components. Massive toroids naturally emit stray fields, and can be difficult to contain.
 
the-mains-man said:
Interesting reading this thread, is the JW improved MDAC project finished yet? I seem to remember reading about it 2 years ago?
Click to expand...

What you refer to is now called the FDAC check out:

http://mdac2.lakewestaudio.com/

There is also a DeTox which cleans up the USB input data transfer.

Later this year you may want to ask John whether he would like to showcase these at your new demo facilities....I'm sure it would make a great event?

And a big thank you to David Brook at MCRU for fixing my 2 year old MCRU LPS for the MDAC at no cost whatsoever .....When the new ground-breaking units are delivered (FDAC and DeTox) I would be willing to loan David mine should you consider organising an event at your brand new Huddersfield listening/demo room?...;)
 
adamdea said:
Incidentally according to the HFN review the jitter on the Mdac plus is slightly higher "due to the fully-enclosed PSU".
Click to expand...

I suspect the jitter is higher as the design is not a "True" Async USB design - by that I mean the DAC's Master clock is not used to synchronise the USB interface. You can see the x3 crystals on the XMOS board used to clock the USB port, while the DAC's Master clock is hidden below - this is not beneficial to performance.

On our little XMOS DAC PCB there are two DAC Master Clocks (the silver Cans near the test terminal marked "MCK", one for 44.1KHz based sampling rates and the second for 32KHz & 48KHz based sampling rates - these are then used as the reference clock for the ASync USB Data Buffer / flow control, this is TRUE ASync USB DAC operation.

https://dl.dropboxusercontent.com/u/86116171/XMOS DAC.png
 
dtd said:
It's not a rumour. In certain Stereophile measurements you can actually see those large modes appear time and time again. I think even the measurements for the Theta's has those components. Massive toroids naturally emit stray fields, and can be difficult to contain.
Click to expand...

Mains hum breakthrough is a limitation of PSRR and Magnetic leakage, but these are design failings, not inherent problems.

You can be assured that if you measured higher up in frequency you would see leakage from the SMSP switching frequency.
 
ti33er said:
Possibly John could try a Hypex SMPS on the 8200MB replacement board to see if it's any better? (No pressure intended, only if curious)! ;-)
Click to expand...

The "Lakewest" 8200MB+ has Extreme PSRR (Power Supply Rejection Ratio), so by design its indifferent to the PSU (one hopes), however I would NEVER uses a SMPS in preference to a linear supply unless there was a good design reason :-

https://dl.dropboxusercontent.com/u/86116171/8200MB Lakewest Rebuild PSRR.jpg

In fact its extreme in all performance parameters... I just wonder how they will sound...
 
Surely Theta just use what they know. Easier to shoehorn existing linear psu knowledge into their amp than spend time developing a silent smps. Its also a usp vs competing smps ncore designs.
 
Does the Superior MDac have an upgrade to USb 2.0 ?

I still prefer the small form so where does the Superior MDac fit in with the Lite/FDac and will there be an option to opt for the Superior MDac instead of FDac (L2 I think it was) ?
 
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