New M-dac power supply

[realysm42]

Got something a little special ordered for the M-dac

ETA about 2 weeks; will keep you posted.

[technobear]

Intriguing

You know of course that JW is developing his own, the MPAX which adds a few more bells and whistles as well as being a better PSU.

Not aware that he has a prototype yet - or does he?

[sq225917]

You do know that the PSRR on the Mdac is already better than -120db for most sections and around -150db for the digital line to the dac chip itself? Those numbers don't really leave much scope for improvement without major internal surgery. Certainly any external supply is unlikely to offer any benefit- maybe you could scrape a tiny bit by running a transformer for every separate voltage rail, but gains would be minuscule.

[MCRU]

Intriguing

You know of course that JW is developing his own, the MPAX which adds a few more bells and whistles as well as being a better PSU.

Not aware that he has a prototype yet - or does he?

yes he does, it was on show at munich and as to simon's post why would john make an external psu himself if nothing can be done to improve the mdac (or slightly as you say)?

worth a punt at least simon surely?

[Marco]

You do know that the PSRR on the Mdac is already better than -120db for most sections and around -150db for the digital line to the dac chip itself? Those numbers don't really leave much scope for improvement without major internal surgery. Certainly any external supply is unlikely to offer any benefit- maybe you could scrape a tiny bit by running a transformer for every separate voltage rail, but gains would be minuscule.

You're not suggesting that this (undoubtedly 'adequate'), but puny little plastic thing with its cheapo 'kettle lead', is the best that can be done, are you?







Numbers? Shmumbers... Let's see what some big 'fuck off' toroidal transformers can do instead, in a more elaborate power supply design, from someone like lurcher, Paul Hynes or Anthony TD, and then have a listen, and bugger the numbers!

Marco.

[realysm42]

You've really taken issue with that thing haven't you Marco

I'm aware of JW's stuff yeah; it's not where mine's coming from, that's all Ill sat for now.

And Simon, I have no idea what you're saying even means; to a simpleton to me (and from what I've read time and again on here) is that vanilla psu's tend to be a major limiting factor in whatever equation they're placed into, so I'm happy to have a try with something else

[Marco]

You've really taken issue with that thing haven't you Marco

Lol - it's fine, but merely 'adequate for purpose'. Looking at what is inside it, it really can't be anything else.

I'm afraid that in audio I'm from the school of 'over-specced to fuck is best', so I expect the (DC) PSUs I use on my components to be as linear as a very linear thing, weigh around 20kg, and be packed full of 'bad boy' toroids

Quite simply, there's NOTHING which has more impact on the performance of audio equiment than the power supply: it is the 'engine' which drives everything else, so in that respect, I'd rather have a Rolls Royce one at the helm, than a 'toytown' one from a Mini Metro!

Marco.

[sq225917]

Marco, you miss the point entirely. You are assuming the size of the fuel filler cap on the car has anything to do with the way it drives- in this case it doesn't.

The Mdac has multiple stages of internal regulation with banks of low ESR organic electrolytic caps specially made for the purpose. It literally does not matter what you do on the outside, if the internal stages have noise already down between -120db and -150db, fannying about with an external transformer will make exactly the square root of SFA difference. Ask Paul and I'm sure he'll explain why.

The transformer is more than 'adequate' for the task at hand, in fact its current delivery capability is several times greater than the current draw. it effectively provides nothing to the regulation of the power supply it just delivers a few rails at the correct voltage. So adding a bigger one would do nothing, adding one for every voltage rail 'might' reduce modulation and noise by a tiny amount. Adding big ass wires to it will make no difference, they are already 10x bigger than they need to be to deliver the paltry half amp it uses split across 6 rails.

The PSU upgrade that john in making adds a whole load of signal bypass and control circuit functionality as well as upgrading the PSU, the actual PSu upgrade part of the package comes from replacing the separate internal PSU board that proceeds all the rest of the dac circuity and reworking the main pcb itself to add further different stages of regulation right on top of the active circuit devices themselves.

So if Realy is having someone remove the internal PSU board and replace it with something much better, then yeh he's likely to hear an improvement if it's done well and the replacement parts do better than -120db (which is pretty damn good). But buggering about outside the box isn't going to do anything.

Of course we are assuming he means a PSU upgrade rather than a lovely new mini server or similar.

[Marco]

Hi Simon,

The Mdac has multiple stages of internal regulation with banks of low ESR organic electrolytic caps specially made for the purpose. It literally does not matter what you do on the outside, if the internal stages have noise already down between -120db and -150db, fannying about with an external transformer will make exactly the square root of SFA difference. Ask Paul and I'm sure he'll explain why.

Ok, I will, and I'll ask Paul to contribute his thoughts here, which should be interesting. I'll also ask Nick (lurcher) and Anthony TD to contribute, both of whom are also experts in PSU design, for high-end audio purposes.

I should add that, you know me, and if what you claim is true (and it may indeed be), but the ONLY way I'd believe it is by listening, and using my ears as the judge, not simply by going by what the 'numbers' say.

Therefore, if Nick (lurcher) or Paul Hynes designs an off-board PSU for the M-DAC, then I'll ensure that I listen to them and make the necessary comparison, with the unit used as 'stock', and then with the various off-board PSUs, in the equation.

I've not heard an M-DAC, so it'll be interesting exercise anyway comparing it against my 'old school' modded Sony, and see how the latter shapes up against it

Marco.

[realysm42]

How comes you've stuck with that for so long Marco, nothing you've heard yet bettered it?

Have you looked for anything else?