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MDAC First Listen (part XXVIII)

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ag66 said:
I'm sorry because I know this has been answered before, but I've tried and haven't been able to find the answer.

Currently my MDAC is connected to my amp using the RCA out. I want to connect a headphone amp and I guess I have to use an XLR to RCA cable (headphone amp only has unbalanced inputs).

I remember someone posted a diagram that showed how to wire such cable. Does anyone have the link, or remembers how to make the connection?

Thanks

Andres
Click to expand...

Andres,

https://dl.dropboxusercontent.com/u/86116171/xlr-rca.JPG
 
Alavan said:
Hi guys, Has the second stage begun? When shall we pay the second installment?
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The second stage payments will be invited within the week - once I've issued the PCB files, I'm just working on the connectors and output relays then its completed.

While is just a prototype of the new analogue stage its been designed as it will appear on the final MDAC2 PCB - with output relays and Connectors etc.
 
Achim said:
Hi John,

is there a way to recombine the current XLR pos and neg outputs in order to do the sum and difference decoding? Maybe using decoupling via transformers or resistors?

I would like to try this out as it will give zero L-R-jitter, and that should be even better than other strategies of fighting jitter.

Cheers,
Achim
Click to expand...

Without thinking too deeply - its not something that can be dematrixed too easily without active stages - you might be able to get away with a funky combination of transformers (you will require Common Mode rejection) - but this really calls for Opamps...
 
jirij said:
Hey, that's a nice idea! Take a piece of audiophile-forbidden fruit, like "EQ", embed it in a nice small box and never mention "EQ" or "VST", just that it somehow improves the sound based on "decoding" and "encoding". And people will buy it! :D

For once, this is not foo - equalization brings real improvements when done right, professional sound engineers know this. It just doesn't need to be obfuscated.

I'm sure JohnW (and Dominik) will look into various ways to further improve the sound reproduction using the FPGA array, whether it means trying various new filters or anything else. :)
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We have a whole host of ideas we will like to try once the MDAC2 platform is ready - its exciting as we will be able to post the various firmware here for "independent" feedback :)

We can also initially add any ideas "double blind" (where even I don't know what's what) as we did internally during the digital filter development... for oneself its satisfying to know you had been able to reliably choose an option even if you have only unproven theories as to why it might sound better / different.
 
paulski said:
John, Is the TDAC still going to happen at some point?
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Paul,

MDAC2 will have the Digital front-end of the TDAC Dual ESS9018 + FPGA etc, at a later date I'm still hoping to design the TDAC - if only for myself (and a few others) :)
 
fusion5 said:
They use a "Line Driver" (small Class A/B circuit with a 100% feedback) to correct for any influence of cables and following input stages. The "Line Driver" is not part of the M/S encoding section.

Physics is not my area of expertise. I've heard the power amps which use the same technique. They sound great.
Click to expand...

I mention briefly in an earlier post, but on the prototype analogue stage PCB I'm working on the Balanced output connectors are a 5W XLR types to facilitate "Remote feedback Sense" where the feedback signal is taken at the end of the cable run thus reducing / removing the sonic effects of cables and connectors.

The idea behind Remote Sense feedback is that the external cable and connectors are nor included within the MDAC2 feedback loop and any "errors" such as cable resistance & capacitance will be sensed and corrected - and one would hope remove or atleast reduce "cable sound".

Taken a step further, and the RS can be extended internally to compatible power amplifier designs (MIMP / MAMP) fitted with 5W XLR audio inputs so that the remote sense loop now includes the amplifiers input connector and a section of its internal signal path...

The remote sense feature can be enabled via an onboard relays so I can (once again double blind) toggle between standard and remote sense option to see if its worth considering as a production variant.

The remote sense makes even more sense for high Quality headphone users... (with a custom cable and dual 5 pin XLR's).

If the results prove positive then MDAC2 will be offered in two variants Standard or Remote Sense (RS) we can add go-faster stripes :)

The complication of the RS version would be the requirement for custom cables - but we "suspect" that it will reap such a benefit that we will be forced into the "complexity" of providing the solution.

I requested decent quality PTFE 4 core + shielded cable sample from Chord - who I'm thinking along the lines will proved the custom cables.

As I say, if the results are positive, then the we will still offer MDAC2 with "standard" 3 Pole XLR's for those who would not need the feature (as it limits the cable choice).

The RS is only applicable to the Balanced output (and balanced driven headphones), the use of Single Ended RCA is so suboptimal anyway....
 
JohnW said:
I mention briefly in an earlier post, but on the prototype analogue stage PCB I'm working on the Balanced output connectors are a 5W XLR types to facilitate "Remote feedback Sense" where the feedback signal is taken at the end of the cable run thus reducing / removing the sonic effects of cables and connectors.

The idea behind Remote Sense feedback is that the external cable and connectors are nor included within the MDAC2 feedback loop and any "errors" such as cable resistance & capacitance will be sensed and corrected - and one would hope remove or atleast reduce "cable sound".

Taken a step further, and the RS can be extended internally to compatible power amplifier designs (MIMP / MAMP) fitted with 5W XLR audio inputs so that the remote sense loop now includes the amplifiers input connector and a section of its internal signal path...

The remote sense feature can be enabled via an onboard relays so I can (once again double blind) toggle between standard and remote sense option to see if its worth considering as a production variant.

The remote sense makes even more sense for high Quality headphone users... (with a custom cable and dual 5 pin XLR's).

If the results prove positive then MDAC2 will be offered in two variants Standard or Remote Sense (RS) we can add go-faster stripes :)

The complication of the RS version would be the requirement for custom cables - but we "suspect" that it will reap such a benefit that we will be forced into the "complexity" of providing the solution.

I requested decent quality PTFE 4 core + shielded cable sample from Chord - who I'm thinking along the lines will proved the custom cables.

As I say, if the results are positive, then the we will still offer MDAC2 with "standard" 3 Pole XLR's for those who would not need the feature (as it limits the cable choice).

The RS is only applicable to the Balanced output (and balanced driven headphones), the use of Single Ended RCA is so suboptimal anyway....
Click to expand...

Brilliant. Could this be extended to the loudspeakers; again when using balanced amps and probably some level matching..?
 
Achim said:
Thanks, John - funky transformer solution here:
http://www.jensentransformers.com/as/as065.pdf
Click to expand...

Yep - that's the idea, but decent transformers cost serious money... I'm not a fan of transformers (I've not listened to the Mega expensive units)... from experience I'm aware how the transformers in my ESLs negatively effect there SQ.

Small transformers also saturate very quickly with any DC offset, MDAC can have upto 10mV DC offset on its output, nowhere near enough to cause any problems in a normal situation, but worth considering with small core transformers, you might need to add AC coupling - again not the best option for SQ.
 
JohnW said:
I mention briefly in an earlier post, but on the prototype analogue stage PCB I'm working on the Balanced output connectors are a 5W XLR types to facilitate "Remote feedback Sense" where the feedback signal is taken at the end of the cable run thus reducing / removing the sonic effects of cables and connectors.
Click to expand...

I think the hairs on the back of my neck are already standing up in anticipation :):)
 
JohanH said:
Brilliant. Could this be extended to the loudspeakers; again when using balanced amps and probably some level matching..?
Click to expand...

The MDAC2 has already over 200dB of feedback at DC with 120dB at 20KHz, with a custom designed amplifier it could be possible to include the Amplifier gain stage itself, but the not with your Ncores with there horrid modulated phase shift out of there loop BW...

I did leave the cryptic line "the remote sense loop now includes the amplifiers input connector and a section of its internal signal path" thinking along these lines for the MIMP / MAMP :p
 
Trojka said:
Hi...it's been a while...did I miss anything? Any news? Firmware upgrades (I'm on A10, I think)? New amp designs?
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Trojka,

No nothing really, been working on the MDAC2 design which will keep me busy until Q2 next year... :)
 
JohnW said:
The MDAC2 has already over 200dB of feedback at DC with 120dB at 20KHz, with a custom designed amplifier it could be possible to include the Amplifier gain stage itself, but the not with your Ncores with there horrid modulated phase shift out of there loop BW...

I did leave the cryptic line "the remote sense loop now includes the amplifiers input connector and a section of its internal signal path" thinking along these lines for the MIMP / MAMP :p
Click to expand...

Wasn't considering the NCores for this but my soon to be Circlotrons...
 
fusion5 said:
I've received my second MDAC today. It's an unmodified unit I bought on ebay.

Just compared it to my L2 FUSION. It's good but the FUSION is way ahead.

@tunkejazz: To me the L2 FUSION doesn't lack anything.
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Due to lack of time, I'm left with a standard MDAC - hard to go back too ....
 
John, how are the upgrades going please. It doesn't look like I will be getting mine back before Christmas as I was really hoping. Thanks.
 
IanM,

Absolutely you will have your unit before Christmas - I'm working on yours and Ale69 unit as soon as I've issued the Prototype PCB files early next week - so they should ship out by next Friday at the latest- with a 7 day delivery service.
 
JohnW said:
IanM,

Absolutely you will have your unit before Christmas - I'm working on yours and Ale69 unit as soon as I've issued the Prototype PCB files early next week - so they should ship out by next Friday at the latest- with a 7 day delivery service.
Click to expand...

Thankyou!
 
JohnW said:
I requested decent quality PTFE 4 core + shielded cable sample from Chord - who I'm thinking along the lines will proved the custom cables.
Click to expand...

Would something like Van Damme Starquad Cable do the job? I'm already using that between my MDAC and EAR890.
 
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