MDAC First Listen (part 00101111)
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JohnW
pfm member
Technically you will not damage the MDAC - but you will unbalance the XLR output with the RCA cable connected as the RCA signal is taken from the XLR's Positive phase and Ground.
As the XLR's Negative phase does not see the extra loading of the RCA cable on the XLR's positive phase you will have a mismatch of output loading impedance which technically is not a good idea.
In the practical world "technically not a good idea" does not suggest what impact it will have on the sound quality - I had presumed "not much" but then during recent listening even having the RCA connected (with no subwoofer connected at the other end of the RCA cable) noticeable effected the leading edge transients of cymbals , snare drums & top-hats, fine detail was really smeared / lost etc.
You can try yourself by just connecting a cable to the MDAC's RCA output while listening to the main speakers (via the XLRs) and see if you notice any difference (No sub connected) - if not then you should be OK to use both XLR & RCA outputs at the same time - but it did not work for me...
Thanks for taking the time John.
So I'm guessing if we're looking to drive an Amp + SUBs from either the RCA or XLR sockets, the XLR would be the natural choice?
So a pair of splitter cables, XLR > 2 x RCA Sockets
davidjt
pfm Member
JohnW,
Maybe a slightly cheeky suggestion, but as I'm tired of putting the MDAC back in it's case when I want to take it anywhere (and my woodworking and metalworking skills are about on a par - both lousy) have you tried a listening test with the MDAC naked?
I suspect it still makes a difference, as the Detox can only clean up the incoming signal, but I'd be interested in your impressions.
Maybe a slightly cheeky suggestion, but as I'm tired of putting the MDAC back in it's case when I want to take it anywhere (and my woodworking and metalworking skills are about on a par - both lousy) have you tried a listening test with the MDAC naked?
I suspect it still makes a difference, as the Detox can only clean up the incoming signal, but I'd be interested in your impressions.
JohnW
pfm member
t30,
Sorry for the delay, I'm buried in work / listening tests ATM.
For the MDAC I prefer V0.90 software for a more open sound but compared to say A08 slightly "lighter" (not so full Bass).
Compared to the Dacapo I find the MDAC slightly "dark" sounding, but that is only going from Memory - it could be my ears are ageing!
But the current version was very easy to compile when I tried it few years ago, that cannot be said for the most of other software.
davidjt
pfm Member
In my room the solution to directionality with just one sub was to place it in a corner away from both main speakers. IIRC the REL manual suggests this: counter-intuitive perhaps, but the theory about not upsetting the sound stage does work, in this set-up anyway. YMMV.
ti33er
pfm Member
I just came across someone that had his Sub directly butted up behind his couch (and another smaller Sub in a front corner of his room. Having the sub directly behind gave some real power/depth-dimension sonically!
This was an exotic setup tallying circa £80K I would think (Theta etc) with room treatment, so not just a throw it all together and let's see what happens setup ;-)
This was an exotic setup tallying circa £80K I would think (Theta etc) with room treatment, so not just a throw it all together and let's see what happens setup ;-)
Jim Audiomisc
pfm Member
But the current version was very easy to compile when I tried it few years ago, that cannot be said for the most of other software.
That's because I'm a lousy programmer and shovel all the code into one file. Still not got my head around 'make', etc.
But the real problem with my IQ test software is that you need to post process the results to make sense of them. I needed to sort out the effects of channel imbalance, etc.
Jim
On the question of outputting from both XLR and phono sockets on the MDAC and your findings, John, regarding degradation to the main outputs, I am wondering why.
I am assuming the MDAC output impedances are ultra low so one would not expect any degradation. If just connecting a single length of unterminated cable causes a degradation then maybe an imbalance to the internal NFB circuits between the + and legs is the cause?
Whatever, whether or not that were to be the case, it might be worth connecting a dummy length of the same phono cable (ideally terminated with something similar to the input impedance of the Sub) to the leg not feeding the Sub. This means gaining access to the output leg which does not terminate on the MDAC phono socket. If you have made up your own XLR cables and can solder that would be relatively easily to achieve.
If, on the other hand, it is not a question of output load being unbalanced, and the MDAC is sensitive to a small amount of additional capacitive load on one leg, then the MDAC output impedance is not low enough?
I do not have a Sub so it is not something I can try but your thoughts would be appreciated.
As always best wishes to you all. I'm very excited by the ways the projects are progressing.
Roger.
I am assuming the MDAC output impedances are ultra low so one would not expect any degradation. If just connecting a single length of unterminated cable causes a degradation then maybe an imbalance to the internal NFB circuits between the + and legs is the cause?
Whatever, whether or not that were to be the case, it might be worth connecting a dummy length of the same phono cable (ideally terminated with something similar to the input impedance of the Sub) to the leg not feeding the Sub. This means gaining access to the output leg which does not terminate on the MDAC phono socket. If you have made up your own XLR cables and can solder that would be relatively easily to achieve.
If, on the other hand, it is not a question of output load being unbalanced, and the MDAC is sensitive to a small amount of additional capacitive load on one leg, then the MDAC output impedance is not low enough?
I do not have a Sub so it is not something I can try but your thoughts would be appreciated.
As always best wishes to you all. I'm very excited by the ways the projects are progressing.
Roger.
adamdea
You are not a sound quality evaluation device
Jim I reember reading these articles of yours (as well as other stuff I can't now recall) and had come away with the impression tha the adaptive filters had never been implemented in HDCD. John W seems to be of a different opinion. I wondered whether John could perhaps identify some HDCDs which had implemented the dynamic coding.
Can you give me an idea Jim how you would see an alterntive adapative filtering (ie one not encoded on HDCD but based on analysis of the ordinary cd) might work. This raises the question of when pre-ringing might occur and might matter. I've never really been able to get my mind round the question of how steep a transient has to be for pre-ringing to be significant.
I've only ever seen it demonstrated on Hydrogen Audio using a gunshot or spark or something. It occurred to me that one way of looking at it might be that pre-ringing can only occur where there is energy in the transition band, so that the filter could adapt based on a spectral analysis of the data. At what point would one trigger the filter to change? And would one target the energy in the pre-ringing or the length? [If only there were some solid audibility data, it would be easier to specify.]
Jim Audiomisc
pfm Member
In the past I wasn't able to tell as I didn't have an 'official' HDCD decoder in any of my kit. (I do now as I bought a CA CX-U a few weeks ago and this claims to have one.) But when I used the decoder software based on code I and someone else found on the web it failed to report any such codes in any of the HDCDs I have. So I've suspected they don't normally actually get used.
If you look at the patents for HDCD they are the usual vague run-around and give no details at all. Claim all, say nowt.
I'd probably approach switching via the kind of method you outlined. i.e. look for transients which have a slew rate that approaches the maximum for the bandwidth, and then use a different reconstruction filter for those parts of the signal.
For testing adding some filter switching, I'd tend to write something like an x4 upsampler to create output files I could then play and measure to experiment.
i.e. Rip an HDCD as is. Then generate an 176.4k upsampled file from it. (You can see some simple x2 upsamplers on my software page, with a choice of filters.)
But TBH I've always felt all this was really a matter of synthesising something 'nice' rather than 'accurate'. The simplest choice would be to go to linear interpolation (a la the old 'legato link' argument that Pioneer trotted out). But take yer pick if you want to do anything like this as it all seemed to go too far to me. This seems to me to fall into the category where the user should be able to choose what suits *them*.
I *suspect* that some modern DACs do this, even with plain CD, but again it tends to be buried under suit-speak and fancy names so you can't easily get to the details.
Now I *do* have a CX-U I plan to do some wideband re-recordings off HDCDs and see if I can detect changes in waveform shape that signify any dynamic alterations in reconstruction filter. But its a challenge, and HDCD is not top of my list. (And I work slowly these days anyway.) So avoid holding your breath. If anyone else wants to try I'd suggest making a 192k recording with a good recorder from the analogue output of an HDCD player, then search for 'out of range' slew rates as a sign. Can't say more until some measurements were done as we're looking for what may be a boojum.
In addition, I found HDCDs that weren't, unlabelled HDCDs, and discs that seemed to use 'HDCD' to peak squash badly. i.e. use as a good old loudness war 'effect'. (Or a disc screwed up when mastered, mangling the codes.) So trying to work out anything from them is a nightmare.
My bottom line was to avoid HDCD as a PITA. The snag being when the music you want is on an HDCD. :-/ So I just used the peak uncompression to get versions I could play *when* they sounded better that the disc.
TBH My main frustration here is that some Joni Mitchell discs are riddled with this problem. Some sound a lot better when decoded. Others sound level crushed or lousy either way. I just wish the people mastering them had made decent, plain, CDs.
Minefield.
Jim Audiomisc
pfm Member
Coda to the above:
Perhaps worth my complaining about what may be the worst example of an HDCD foul-up I've encountered. This is the Joni Mitchell double CD "Travelogue".
I saw the review in Stereophile of this, and bought a copy from a UK dealer. The review said it was an HDCD.
What I got has no HDCD codes, and no mention of HDCD on the packaging that I can find. It is peak compressed in the way I'd expect for an HDCD. But blind level expansion to the HDCD spec causes some clicks, etc.
So when played as a plain CD it sounds quite noticably peak compressed. The voice, to me, has a "loud, too close to the mic and pulled down by a compressor" sound.
When played blind peak-expanded it is a bit better, but still sounds compressed, and with some added clicks. (Can't do a code-controlled expand as there aren't any codes!)
I *guess* that a dim bulb somewhere decided to "release it as a CD" and simply rescaled the data a bit. Thus losing all the HDCD level codes, and giving a result that *still* has almost-HDCD level compression. Which being not quite right, isn't fixed by applying the HDCD expansion.
I can't be sure of the above. Only that it sounds poor to me despite Stereophile thinking it was great. But my guess is that it is an example of how people can 'master' audio to the point of runination because they had no idea what HDCD is supposed to do. Peril of "secret sauce" techniques. I prefer open sauce. Tastes better.
So annoying as I felt it was a super performance ruined by the compression. Was the USA version a 'real' HDCD? I dunno.
Jim
Perhaps worth my complaining about what may be the worst example of an HDCD foul-up I've encountered. This is the Joni Mitchell double CD "Travelogue".
I saw the review in Stereophile of this, and bought a copy from a UK dealer. The review said it was an HDCD.
What I got has no HDCD codes, and no mention of HDCD on the packaging that I can find. It is peak compressed in the way I'd expect for an HDCD. But blind level expansion to the HDCD spec causes some clicks, etc.
So when played as a plain CD it sounds quite noticably peak compressed. The voice, to me, has a "loud, too close to the mic and pulled down by a compressor" sound.
When played blind peak-expanded it is a bit better, but still sounds compressed, and with some added clicks. (Can't do a code-controlled expand as there aren't any codes!)
I *guess* that a dim bulb somewhere decided to "release it as a CD" and simply rescaled the data a bit. Thus losing all the HDCD level codes, and giving a result that *still* has almost-HDCD level compression. Which being not quite right, isn't fixed by applying the HDCD expansion.
I can't be sure of the above. Only that it sounds poor to me despite Stereophile thinking it was great. But my guess is that it is an example of how people can 'master' audio to the point of runination because they had no idea what HDCD is supposed to do. Peril of "secret sauce" techniques. I prefer open sauce. Tastes better.
So annoying as I felt it was a super performance ruined by the compression. Was the USA version a 'real' HDCD? I dunno.
Jim
Does this new Integrated Amp's approach make modern day DAC's irrelevant?
"By connecting the output of the 2200i's preamp section DSP directly to the input of the amplifier DSP, Classe eliminates DAC and ADC conversion losses and their associated analog circuitry's noise and distortion."
http://hometheaterreview.com/classe-audio-announces-sigma-2200i-integrated-amp/
"By connecting the output of the 2200i's preamp section DSP directly to the input of the amplifier DSP, Classe eliminates DAC and ADC conversion losses and their associated analog circuitry's noise and distortion."
http://hometheaterreview.com/classe-audio-announces-sigma-2200i-integrated-amp/
Jim,
Cudos to you for bringing some science and aural experiences to our thread.
Great work, read most of your writings on your site, interesting even though not all comprehended.
/Take Care
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