MDAC first listen (part V)

[TimR]

Hi tim,

File sent - good luck (did the SBT arrive yet?)

Hi John, SBT turned up yesterday - much obliged.
I've just loaded up Adrian's modified kernel. Couldn't believe how far he has bought this patch since John Swenson's (very much appreciated) early work, and how easy it is to install/remove. He really does deserve a huge credit for getting it to this stage. I also had a quick go with one of his later Kernel versions and I was able to also get 192/24 material from the SBT SPDIF!

Just orderered a USB hub and will have a try later with the USB isolator to see if I can hear any difference.

 

[sam_cat]

I your case I would suggest leaving the display on or you could power it via a plug/switched socket with a LED 'On' indicator or get two post-it notes and write 'On' on one and 'Off' on the other and put the appropriate post-it note on the front of the M-DAC.

All IMO.

You could use a Oneclick (http://www.oneclickpower.com/store/) and use the socket thats turned on by the dac being on to power a small led lamp or similar?

Sam

 

[JohnW]

I thought of something last night, the main reason I would upgrade the firmware is for the display dimming on/off function but I realized it may be a bit problematic because there's no other power indication which might cause some confusion as to whether the DAC is on or off. Would it make any sense to leave a small circle of pixels lit to indicate power on when the screen is turned off?

Correct - in fact its a legal requirement to indicate "power" so we planned to just leave a block of pixels "dimmed" in an used corner.

The "display off" option would have a timer - as the CDQ.

 

[JohnW]

I have the latest software build - but I would like Dominik to clean up the "Absolute" Frequency counter as it jumps about distractingly on higher DPLL settings.

It also gives me sometime to test before public release.

 

[JohnW]

Missing it, a bit, yeah. The CDQ is still a fantastic component and I'm not at all unhappy with the sound but the MDAC is better. I've got this dilemma about whether to move the CDQ to the second system and do without vinyl and cd replay in the main system for a while, or to live with the CDQ in the main system and MDAC in the second.

If CDQ+ is going to be next year I'm tempted to get the OLED/Transformer to the CDQ in the meantime - are you likely to be back up this way over the next few months?

Yes the CDQ is good - but I think you will find the more you listen to your CDQ you will notice how much better the MDAC really was - MDAC is more realistic - less digital - not to say the CDQ sounded digital, but in comparison the MDAC is more "real".

I'm REALLY struggling with workload - I really have no idea when I'll be next up in Scotland - with our dogs its not so easy to get to the UK - we cannot fly, only drive which its a pain...

As soon as the budget DAC and MPAX are designed I'll come over - I'll be able to breath a little.

This budget DAC is really depressing me, the PCB layout is so laborious, boring & hardwork...

I don't think the OLED upgrade is going to bridge the SQ your after... Although I could really tweak your unit if I had it here in Czech Rep. maybe jump on a WizzAir flight over to Bruno for a weekend (or during the week) with your wife while I make you a super CDQ

 

[JohnW]

Yeah, I'd love to see source renaming, it would also make my girlfriend happy who I keep having to explain that COAX1 actually means the Sonos!

Ben

Hi Ben,

Its not so easy to add an option to name the inputs - but maybe when Dom has a free moment we can build you a "Ben's" version of the software - just tell me the names of the inputs (each input can only be 5 characters long) - cannot promise when Dom will have time but....

John

 

[JohnW]

just to arrest the eerie silence awaiting the software release, I'll chuck in some questions about power for eager MPAX awaiters...

1. I'm sure it's been mentioned, but when's the latest ETA for the 1st and 2nd production batches?

2. Should a DIYer want to build their own external DC supply, what are the power input specs? Will the MPAX be providing a single +15VDC rail, and what would be the expected peak/avg current draw (and would it depend on what's connected to the outputs etc)?

thanks! /dom

Hi Dom,

I don't recall the exact PSU currents, but the external supply needs 3 supply rails:

+15VDC for the digital sections (~250mA)

+15VDC for the analogue (~400mA)
-15VDC for the analogue sections (~200mA)

The HQ internal upgrade PCB will split the MDAC's analogue PSU supplies... I'd be happy to sell the upgrade board as a standalone part for the DIY'ers with a mating PSU cable when the design is completed.

John

 

[JTC]

I could really tweak your unit if I had it here in Czech Rep. maybe jump on a WizzAir flight over to Bruno for a weekend (or during the week) with your wife while I make you a super CDQ

Very tempting... I just did a quick scan for flights but can't see anyone flying from Edinburgh to Brno - but seriously tempted nonetheless....

 

[JohnW]

John.

Are there any measures to absorb RF in your products. Such as ...

http://www.farnell.com/datasheets/318301.pdf

Been reading such info on retro-fitting AV products.

They're a tad expensive so I',m not sure whether this sort of thing is applied to a lot of equipment.

If they are worth applying , where is the best place to stick them?. Would need to now if it would be safe , as some of the examples are actually stuck on components and boards where as others are on the casing. In which case heat may be an issue.

Any guidance would be appreciated.


Cheers

Hi Phil,

By carefully design there is an amount of RF filtering and isolation between circuits - that's not to say the any additional attention would not be beneficial - reducing RF is always a good idea.

You have to be careful not to upset the Clock edge speeds - slower clock edges = greater Jitter, so EMC countermeasures need to be applied with understanding of the effect on the circuits performance.

A cursory look at the Specs. and these foils only seem to reduce by 4dB to 10dB at lower frequecnys, they seem geared more towards GHz region (Mobile Phones etc) then the 100MHz and less where most RF energy is radiated within the MDAC.

John

 

[gh0st]

Hi Dom,

I don't recall the exact PSU currents, but the external supply needs 3 supply rails:

+15VDC for the digital sections (~250mA)

+15VDC for the analogue (~400mA)
-15VDC for the analogue sections (~200mA)

The HQ internal upgrade PCB will split the MDAC's analogue PSU supplies... I'd be happy to sell the upgrade board as a standalone part for the DIY'ers with a mating PSU cable when the design is completed.

John

Thanks John, sounds tempting as a project, my soldering iron's getting twitchy. Then again, I just finished a mammoth project and swore never to do another one... guess some people never learn

Would it be advantageous for the two analogue rails to track one another?

/dom

 

[JohnW]

Very tempting... I just did a quick scan for flights but can't see anyone flying from Edinburgh to Brno - but seriously tempted nonetheless....

If you ever wanted a cheap break and get your super CDQ then Wife says cheap flights (some unknown airline) Edinburgh to Prague... we could collect you from Prague and arrange accommodation - depends where your Wife wants to visit I guess (Prague is best) or the mountains...

I must confess to being a bit of a snob when it comes to flying (I spend so much of my life on planes) - I dreaded the thought of flying WizzAir after being treated worst then cattle by RyanAir, but I must say WizzAir was REALLY great - a budget airline that treats people with common decency... the planes where clean, decent legroom, great crew and great check-in staff - no grief about luggage etc... the cabin crew where Eastern European - and where really nice (in all respects)....

But I degrees...

 

[JohnW]

Thanks John, sounds tempting as a project, my soldering iron's getting twitchy. Then again, I just finished a mammoth project and swore never to do another one... guess some people never learn

Would it be advantageous for the two analogue rails to track one another?

/dom

Hi Dom,

No not really, they just need to be stable before the Mute relay operates (you would not want DC offset on the outputs).

There's mufti stage regulation on the Analogue rails within the MDAC... IIRC first to 12V then to 8.5V for the CROSS stages.

I'm working on so many designs at the moment that I find it hard to recall "older" designs... old age hitting me...

John

 

[gh0st]

Hi Dom,

No not really, they just need to be stable before the Mute relay operates (you would not want DC offset on the outputs).

There's mufti stage regulation on the Analogue rails within the MDAC... IIRC first to 12V then to 8.5V for the CROSS stages.

I'm working on so many designs at the moment that I find it hard to recall "older" designs... old age hitting me...

John

...resisting the urge to start a BOM...

My idea would be to make two separate supplies from the linear reg'd designs on http://amb.org - one ±15V supply for analogue and a different one for +15V on the digital side.

 

[JohnW]

...resisting the urge to start a BOM...

My idea would be to make two separate supplies from the linear reg'd designs on http://amb.org - one ±15V supply for analogue and a different one for +15V on the digital side.

http://gilmore2.chem.northwestern.edu/ubb/showpage.php?fnum=3&tid=6525

Looks like a good place to start (although not a Shunt design).

IMO shunt regulators sound best - but they need careful design not to mention substantial heatsinking - MPAX going to be one big Shunt Reg

I've not seen any designs on the internet that I'd think - hey that's a clever design... but then I've not really search - more like "encountered"...

John

 

[gh0st]

http://gilmore2.chem.northwestern.edu/ubb/showpage.php?fnum=3&tid=6525

Looks like a good place to start (although not a Shunt design).

IMO shunt regulators sound best - but they need careful design not to mention substantial heatsinking - MPAX going to be one big Shunt Reg

I've not seen any designs on the internet that I'd think - hey that's a clever design... but then I've not really search - more like "encountered"...

John

yep that's the design I was talking about, from Ti Kan (amb); one sigma22 dual rail for analogue and one sigma11 single rail for digital.

My SBT is powered by a 9v sigma11 that I built, and I've got two sigma22s for a balanced headphone amp, I'm very pleased with them.

 

[desp_erado]

Hi Ben,

Its not so easy to add an option to name the inputs - but maybe when Dom has a free moment we can build you a "Ben's" version of the software - just tell me the names of the inputs (each input can only be 5 characters long) - cannot promise when Dom will have time but....

John

Hi John,

Wow, that would be great if you could! Very kind of you to offer. In the future, maybe their could be an accompanying .txt file that it read pre-programming? Although, thinking about it, I guess not if the firmware binaries are embedded in the flash .exe and are pre-built.

If you/Dom did get chance to (no rush, maybe on the Lakewest version when it's released) they would be:

COAX1 -> SONOS
COAX2 -> CD
OPT1 -> PS3
OPT2 -> CABLE
USB -> USB

Thanks!

Ben

 

[mark.king]

Hi John a quick question for you or anyone else.

I have the MDAC and am wondering how high end I can go with headphones. Since my partner and her kids moved in I find it harder to sit down and blast music out at the levels I like (Martin logan Clarity speakers) and am considering getting some really good cans. I may even consider Grado GS1000i or Sennheiser HD800 if the MDAC can get the best out of these.

All thoughts are welcome.

Cheers

 

[PhilCTTE]

Hi Phil,

By carefully design there is an amount of RF filtering and isolation between circuits - that's not to say the any additional attention would not be beneficial - reducing RF is always a good idea.

You have to be careful not to upset the Clock edge speeds - slower clock edges = greater Jitter, so EMC countermeasures need to be applied with understanding of the effect on the circuits performance.

A cursory look at the Specs. and these foils only seem to reduce by 4dB to 10dB at lower frequecnys, they seem geared more towards GHz region (Mobile Phones etc) then the 100MHz and less where most RF energy is radiated within the MDAC.

John

Thanks very much for the reply. Can't see much scope for your average user in implementing the right shield absorber/reflector without indepth insight to the design spec. Problems with obstructing air flow is another problem.

Further discussion here ..

http://www.avforums.com/forums/hi-f...-tiles-shielding-ers-fabric.html#post16677681

hope you don't mind me quoting your response.

 

[gh0st]

Hi John a quick question for you or anyone else.

I have the MDAC and am wondering how high end I can go with headphones. Since my partner and her kids moved in I find it harder to sit down and blast music out at the levels I like (Martin logan Clarity speakers) and am considering getting some really good cans. I may even consider Grado GS1000i or Sennheiser HD800 if the MDAC can get the best out of these.

All thoughts are welcome.

Cheers

I'd suggest adding Beyerdynamic's flagship T1 to your list, I can vouch for great performance of the MDACs headphone amp with those, and FWIW, IMHO etc, these are better than the HD800 in most circumstances (flame war ahoy!)

Also in that price bracket is the Audeze LCD2, which I've not yet tried from my MDAC, but I'd be very surprised if it didn't drive them extremely well.

 

[JohnW]

My SBT is powered by a 9v sigma11 that I built

Are you sure 9V? The PSU supplied with my SBT is 5V - 9V is going to push the dissipation within the SBT - if not exceed the Capacitor voltage ratings - I could be wrong...

John