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  #61  
Old 24-06-17, 09:38 AM
Bob L Bob L is offline
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Quote:
Originally Posted by davidismynaim View Post
would a MCRU LDA linear power supply work with the MDAC2, or is the new PSU a whole different topology/connector?
The MCRU unit, and the similar Swagman,are only "3-rail" supplies, like my home-assembled dual Calex supply, and connect via the original 9-way DIN connector on the back panel. Fancier versions ( see my comment above about 5- rail supplies) have to work with the outer sleeve removed, and some dangling wires (see Miterdog's "plydac" pictures a week or so back).

John commented earlier that the PS input to the MDAC-2 is a D- connector, "to make it easier for Home builders" (maybe not his exact words) to connect on their own supplies, but I think this means at least a "5-rail" supply. You and I are in the same position- when we get the MDAC-2, all we can do is entrust our old supplies to the mercy of e-Bay.

Last edited by Bob L; 24-06-17 at 09:40 AM. Reason: typo
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  #62  
Old 24-06-17, 10:23 AM
misterdog misterdog is offline
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I'm aiming for a neater final solution though.



Decent power supply makes for a BIG difference in SQ. with the Mdac so I assume it will also do so with Mdac 2.
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  #63  
Old 24-06-17, 02:41 PM
JohnW JohnW is offline
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Quote:
Originally Posted by sprint View Post
My understanding was that the original MDAC power supply was deemed to be OK and that only after some test/trials had been done to show that there was a significant improvement in SQ that any replacement would be recommended?

Since the MDAC2 still awaits manufacture is it currently known that an alternative external PS is/will be required and that significant SQ will be achieved as a result?
1. The AC linear supply cannot supply the required power for the MDAC2.

2. It does not provide isolate for the Digital and Analogue sections

3. Has no isolated tapping for the Streamer PCB

4. External PSU's (with the internal PSU PCB modified / bypassed) on the MDAC brings a significant step improvement. The MDAC's non optimal Grounding arrangement on its Mini-Din due to lack of contact poles significantly degrees the MDAC's performance. Adding an external PSU without resolving this limitations does not help much (such as adding the MRCU).

The PSU is the foundation of any audio product - compromising here is a sure recipe for failure.
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  #64  
Old 24-06-17, 03:26 PM
JohnW JohnW is offline
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Quote:
Originally Posted by Bob L View Post
The MCRU unit, and the similar Swagman,are only "3-rail" supplies
In fact the MCRU is only a 2 rail supply.
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  #65  
Old 24-06-17, 03:32 PM
JohnW JohnW is offline
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Originally Posted by cstanpfm View Post
HI John, must it be this model or any USB DVD drive will work with the data been bit accurate & clock locked to the system audio clock?
In theory all USB drives should work, but some drives have VERY high / nasty current peaks during seek that can trigger the USB current limit - this is especially true with cheaper drives from China that compromise on the internal PSU bulk decoupling - or have non optimised servo control loops (peak seek current is a consideration when optimising the servo circuit coefficients).
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  #66  
Old 24-06-17, 03:44 PM
timola timola is offline
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Quote:
Originally Posted by misterdog View Post
I'm aiming for a neater final solution though.
What a mess! modern art?
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  #67  
Old 24-06-17, 03:58 PM
JohnW JohnW is offline
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Quote:
Originally Posted by davidismynaim View Post
would a MCRU LDA linear power supply work with the MDAC2, or is the new PSU a whole different topology/connector?

John, if I want to include streamer/ADC options for MDAC2, is my existing 400 contribution sufficient or am I in need of additional payments? Thanks
The MCRU upsets me somewhat as its expensive to my eyes - but to be far its "typical" of HiFi industry charges, but if you compare the engineering, internal component count and the amount man hours that has gone into the MDAC2 over these past years - then I'm being stupid for not taking the same path!

If I where to ponder if, I'd get depressed as I pump everything into my work, and it takes its toll... I've just spent over GBP40K on a mini SMT line, yet can ill afford to take Renata on a holiday... on top of that we are kitting out a 3rd bench position for a yet to be found engineer to help with production. This means "duplicating" the test equipment required as I cannot pull equipment of Jareks or my lab bench.

When I see a simple PSU sold for so much - I feel stupid for always taking the hard route!

In answer to your question, the MCRU is only a dual rail PSU - we need 7 PSU rails for the MDAC2 with decent current for the Streamer board (12V 1.5V to 2A max).

Also the Digital and Analogue PSUs sections need to be galvanically isolated.
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Last edited by JohnW; 24-06-17 at 09:55 PM.
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  #68  
Old 24-06-17, 04:02 PM
JohnW JohnW is offline
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Originally Posted by timola View Post
What a mess! modern art?
Arh the good old days of Rats Nest point to point wiring!
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  #69  
Old 24-06-17, 05:40 PM
YNWOAN YNWOAN is offline
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No wonder some valve gear goes up in flames with matches wired into them....
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  #70  
Old 25-06-17, 02:23 AM
Bob L Bob L is offline
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Quote:
Originally Posted by JohnW View Post
In fact the MCRU is only a 2 rail supply.
Thanks John- I shouldn't have reported my guess as fact...

Cheers

Bob

p.s. Just to amplify your point about the costs of other LPS supplies, I think this means that the MCRU at 360 does more or less the same as a single Calex, which cost me 20 (but it does look much nicer...)

Last edited by Bob L; 25-06-17 at 03:03 AM. Reason: ps added
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  #71  
Old 25-06-17, 03:08 AM
davidismynaim davidismynaim is offline
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Quote:
Originally Posted by JohnW View Post
The MCRU upsets me somewhat as its expensive to my eyes - but to be far its "typical" of HiFi industry charges, but if you compare the engineering, internal component count and the amount man hours that has gone into the MDAC2 over these past years - then I'm being stupid for not taking the same path!

If I where to ponder if, I'd get depressed as I pump everything into my work, and it takes its toll... I've just spent over GBP40K on a mini SMT line, yet can ill afford to take Renata on a holiday... on top of that we are kitting out a 3rd bench position for a yet to be found engineer to help with production. This means "duplicating" the test equipment required as I cannot pull equipment of Jareks or my lab bench.

When I see a simple PSU sold for so much - I feel stupid for always taking the hard route!

In answer to your question, the MCRU is only a dual rail PSU - we need 7 PSU rails for the MDAC2 with decent current for the Streamer board (12V 1.5V to 2A max).

Also the Digital and Analogue PSUs sections need to be galvanically isolated.
John, so sorry this triggered such remorse with your approach. I do hope that you can look back at your last few years with pride and hopefully designs and products that can result in a decent financial return for you. Staying true to your principals is a worthy endevour, I just hope you find commercial outlets that can be rewarding too, striking a balance is never easy.

Btw, this is my friends psu, that I have on long term loan, so I was just interested in whether it had any role to play with MDAC2.

Do let me know if I need to contribute anymore based on my desired configuration of MDAC2-Streamer-ADC for analogue input so I can avoid the need for a preamp. Thanks
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  #72  
Old 25-06-17, 03:24 AM
misterdog misterdog is offline
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Quote:
Originally Posted by Bob L View Post
p.s. Just to amplify your point about the costs of other LPS supplies, I think this means that the MCRU at 360 does more or less the same as a single Calex, which cost me 20 (but it does look much nicer...)
The Calex supply is 96 now it has an ROHS sticker.

I find it amazing that people will spend 360 on a LPSU for a 600 DAC.

The benefit of the full 5 rail supply probably warrants such but the benefits of swapping out the supplied power brick brought minimal gains.
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  #73  
Old 25-06-17, 03:32 AM
misterdog misterdog is offline
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Quote:
Originally Posted by JohnW View Post
Arh the good old days of Rats Nest point to point wiring!
Imagine trying to design a pick and place machine to do that
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  #74  
Old 25-06-17, 03:35 AM
stephengrenfell stephengrenfell is offline
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Quote:
Originally Posted by JohnW View Post
If you plan to use the MDAC2/FDAC with an external USB device (such as streaming audio via a PC) then yes the Detox is beneficial - but if your just planing to use the internal streamer, then no need for the Detox.
Hi John,

For those folks who have ordered Detox (before the streamer option existed), but now plan to use only the steamer and not USB into MDAC2, what do we do ?.

Personally : I don't care about loosing the DETOX development fees (this is part of the deal), but I don't particularly want to splash out on the Detox manufacturing fees if I no longer need it and will likely not use it.

Thanks
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  #75  
Old 25-06-17, 05:10 AM
Dark Energy Dark Energy is offline
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MDAC PSU

Replacing the MDAC PSU can give you a small improvement but you can do it simply enough, I think a zener (or similar) referenced capacitance multiplier/gyrator would be as good as anything. While I no longer have an MDAC I do have the service manual, super regulators are overkill here. There are some expensive power supplies being offered with "over enthusiastic" performance claims. You could tweak a Hi-Cap to work, it's not ideal, the regs would run hot and the input/output differential on the LM317K wouldn't look nice, but you know how "complex" a Hi-Cap is, so building something more appropriate isn't too difficult.
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