MDAC First Listen (part 00100111)
- Thread starter Rosewind
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ti33er
pfm Member
Thanks John
Of course I am still hoping/aiming for Vishay ZFOILs etc to be added to mine and built into the Chassis you have for me, by your meticulous hand...it's what I meant, which is more important to me (personally) than MiniDSP integration.
Thanks again
Paul
occamsrazor
pfm Member
Taking a break from MDAC2... an MDAC question. I'm planning to do this:
MDAC > Balanced XLR > Monoblocks > Speakers
and
MDAC > Unbalanced RCA > Subwoofer that has L+R RCA line-level inputs.
The subwoofer can accept a single RCA input instead of L+R, but am I right in thinking that if I were to use a Y-cable from both RCAs of the MDAC to a single RCA on the sub - i.e. combining both left and right channels - that this would also somehow (unwantedly) combine the balanced output channels as they are on the same output circuit? Or am I wrong?
Just wondering as I need a 10m cable so a single lead would be tidier and seemingly cheaper than a pair....
MDAC > Balanced XLR > Monoblocks > Speakers
and
MDAC > Unbalanced RCA > Subwoofer that has L+R RCA line-level inputs.
The subwoofer can accept a single RCA input instead of L+R, but am I right in thinking that if I were to use a Y-cable from both RCAs of the MDAC to a single RCA on the sub - i.e. combining both left and right channels - that this would also somehow (unwantedly) combine the balanced output channels as they are on the same output circuit? Or am I wrong?
Just wondering as I need a 10m cable so a single lead would be tidier and seemingly cheaper than a pair....
Great news re the potential tie up with miniDSP John.
Ive been dabbling with a umik, REW, a basic parametric equaliser in the VLC player and trying to integrate a subwoofer.
Tbh the more I read in the area, the more I realise I don't know, but in any case I'm enjoying more bass and just as importantly more controlled bass.
I'm certain with a hardware based solution built into the MDAC2 ,then i'll make more progress + be able to have the same benefits on analogue sources using your ADC.
Ive been dabbling with a umik, REW, a basic parametric equaliser in the VLC player and trying to integrate a subwoofer.
Tbh the more I read in the area, the more I realise I don't know, but in any case I'm enjoying more bass and just as importantly more controlled bass.
I'm certain with a hardware based solution built into the MDAC2 ,then i'll make more progress + be able to have the same benefits on analogue sources using your ADC.
You need both rca outputs connecting independently to the sub.
If you do what you're suggesting with a Y connector, you're effectively shorting the mdac's outputs together.
Very exciting news on the miniDSP front :-D Nice one John!
Back to a basic question from a new follower of the thread, with regards to the limited initial production run for the m-dac2:
Does this mean there could only be this one production run?
I really hope there will be more as it sounds like it is rather an outstandingly designed and spec'd product.
If I were moving to DIY active speakers in the future, at this moment I would guess it is not a 100% certainty that I would be able to purchase follow on slave m-dac2's at some point down the line?
Sorry to pose such a question but I'm just wondering about building a rather snazzy dac/XO combo, over time..
Cheers
Back to a basic question from a new follower of the thread, with regards to the limited initial production run for the m-dac2:
Does this mean there could only be this one production run?
I really hope there will be more as it sounds like it is rather an outstandingly designed and spec'd product.
If I were moving to DIY active speakers in the future, at this moment I would guess it is not a 100% certainty that I would be able to purchase follow on slave m-dac2's at some point down the line?
Sorry to pose such a question but I'm just wondering about building a rather snazzy dac/XO combo, over time..
Cheers
occamsrazor
pfm Member
Thnaks for confirming. Figured that wouldn't work but wanted to check.
moosemeat
pfm Member
John said yesterday "I have no idea what will happen with MDAC2 beyond the initial units, maybe someone will licence the design... who knows my only concern is our "few" PFM units after 3 years of my life developing the design, it be nice if the MDAC2 platform saw life beyond the initial batch but nothing I've made any serious consideration for ATM - I'm a designer not a production manufacturer...."
Nice! Minidsp is a very flexible platform. Groundsound or Hypex is also very nice, would be a nice partner for the mdac2...full active speaker design
http://groundsound.com/dcn24rpc.php
https://www.hypexshop.com
http://groundsound.com/dcn24rpc.php
https://www.hypexshop.com
Cheers, my brain did not want to understand it the first time I read it ;-)
moosemeat
pfm Member
Either way, everyone involved is a winner, right?
I think John's efforts on this project are deserving of far more than he would receive from the current xxx allocated units, so perhaps having a driver for licensing is a good thing.
I also expect the hifi world at large would be rather grateful to have the opportunity to partake in MDAC2 also.
Of course, I am merely speculating.
I think John's efforts on this project are deserving of far more than he would receive from the current xxx allocated units, so perhaps having a driver for licensing is a good thing.
I also expect the hifi world at large would be rather grateful to have the opportunity to partake in MDAC2 also.
Of course, I am merely speculating.
JohnW
pfm member
I've had very good initial results with the "Complete gain stage" - it worked first time which is truly amazing,
There are 2 problems I need to solve:-
1. Hum level is high at about -125dB, it should be atleaat -145dB so I need to find out whats up.
2. stability into capacitance loads is poor - but I know from my recent experience with the output stage that the simulated results are a poor, so I need to measure the "real" Gain and Phase margins - this is easy to resolve I just need to spend a little time with the network analyser.
I can see the Hum problem causing me a little grief, but I'm not worried yet...
I'm SOOO please that its "working" on first try, this is a totally new circuit design - only seen life in a computer simulator and its works on first try!!!
Lets just hope the hum is not a show stopper...
I'll get some sleep and work on it later - but I'm really pleased!
There are 2 problems I need to solve:-
1. Hum level is high at about -125dB, it should be atleaat -145dB so I need to find out whats up.
2. stability into capacitance loads is poor - but I know from my recent experience with the output stage that the simulated results are a poor, so I need to measure the "real" Gain and Phase margins - this is easy to resolve I just need to spend a little time with the network analyser.
I can see the Hum problem causing me a little grief, but I'm not worried yet...
I'm SOOO please that its "working" on first try, this is a totally new circuit design - only seen life in a computer simulator and its works on first try!!!
Lets just hope the hum is not a show stopper...
I'll get some sleep and work on it later - but I'm really pleased!
So, if I remember correctly, this would mean that you could have the output of the amps/speakers set to have max above the pain threshold, and still not be able to hear the hum?
But for some people that's still high!
Thanks for all your work on this, John. We will be happy with whatever finally comes out.
JohnW
pfm member
Just a daily update, sadly rather slow day as I've been looking into improving the stability into capacitive loads - (much higher then any typical cable - but I want to insure the design is stable in all systems).
I'm refining the simulations and measurement results - just slow / hard work.
Hopefully tomorrow will be more constructive.
I'm refining the simulations and measurement results - just slow / hard work.
Hopefully tomorrow will be more constructive.
JohnW
pfm member
This weekend I've been getting to grips with the "high" hum level (around -120dB).
I've now managed to reduce hum spurie it to around -140dB on both Balanced and unbalanced outputs.
Unbalanced Noise floor 0dB Referenced 2.2Vrms:-
https://dl.dropboxusercontent.com/u/86116171/MDAC2 SE 2V2Rms.jpg
Balanced Noise floor 0dB Referenced 4.4Vrms:-
https://dl.dropboxusercontent.com/u/86116171/MDAC2 BAL 4V4Rms Ref.jpg
What I now need to work out out is how to modify the design to incorporate the required modifications to reduce Magnetic pickup in the feedback lines.
I'd like to target the MDAC2 with the industry's lowest THD & highest dynamic range of ANY DAC on the market so this posses engineering challenges.
My target is an Awtd dynamic range of around 135dB and THD 0.00002% - I'd like MDAC2 owners to have the best engineering DAC money can buy I don't ever want to spend 3 years of my life working on a DAC design again!
Sorry for the rather cryptic post, just posting as I finish up in the lab for the evening and rather exhausted...
I've now managed to reduce hum spurie it to around -140dB on both Balanced and unbalanced outputs.
Unbalanced Noise floor 0dB Referenced 2.2Vrms:-
https://dl.dropboxusercontent.com/u/86116171/MDAC2 SE 2V2Rms.jpg
Balanced Noise floor 0dB Referenced 4.4Vrms:-
https://dl.dropboxusercontent.com/u/86116171/MDAC2 BAL 4V4Rms Ref.jpg
What I now need to work out out is how to modify the design to incorporate the required modifications to reduce Magnetic pickup in the feedback lines.
I'd like to target the MDAC2 with the industry's lowest THD & highest dynamic range of ANY DAC on the market so this posses engineering challenges.
My target is an Awtd dynamic range of around 135dB and THD 0.00002% - I'd like MDAC2 owners to have the best engineering DAC money can buy
I don't ever want to spend 3 years of my life working on a DAC design again! Sorry for the rather cryptic post, just posting as I finish up in the lab for the evening and rather exhausted...
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