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2.231.18.235
In Reply to: RE: Why? posted by Thorsten on February 16, 2014 at 04:14:11
In my case
4 "IF" are YES
2 "IF" (n.2 and n.4,,,the circuitry and connecting traces/wires)are IF or NOT.
It's not "jitterly" speaking better then to have 6 NOT?
>higher jitter is not always audibly "worse", it depends on the precise >jitter spectrum
Jitter spectrum?
Jitter can only cause loss of detail compressed dynamic or restricted soundstage.
Thom
Follow Ups:
too much attention to detractors who post 900 ifs when he doesn't fit the correct jacks on his own designs and then assumes that other designers do not practice impedance control on theirs. the example he gave was a $100 Chinese dac that has a digitally generate clock whichyisn't really much good anyway (yes, I have played with it)
PCB soldered jacks are difficult to change. the best way for me is to cut the pints off, then unsolder the jack anchors. Some pcb traces are very fragile and careful desoldering of what is left is necessary.
You can fit any high quality bnc 75R of your choice using short leads and keeping the correct cable separation in line with pin separation.
In most cases and with high quality dacs, there is an improvement to the sound and observed improvement in the eye pattern of the digital signal. (with a high bandwidth scope)
Fred,
> using short leads and keeping the correct cable separation in line
> with pin separation.
This is unlikely to result in anything remotely close to 75 Ohm. Eye-balling I'd say > 200R.
If there is to be any improvement I suggest Thom better get a bulkhead socket with attached Coax Tail.
Otherwise while fitting the "correct" socket Thom will create greater impedance mismatches and worse reflections than he has by keeping the RCA socket.
That said, looking at this picture:
I would recommend a brief study of the datasheet of the output transformer for starters...
http://media.digikey.com/pdf/Data%20Sheets/Pulse%20PDFs/PE-65x12_Rev2006.pdf
I think fixing some of the other problems will help a lot more than a "magic connector", though the latter no doubt makes one sleep better.
Ciao T
Sometimes I'd like to be the water
sometimes shallow, sometimes wild.
Born high in the mountains,
even the seas would be mine.
(Translated from the song "Aus der ferne" by City)
with separation of bnc connector
Fred,
> in line with separation of bnc connector
You may have observed that the connections on a BNC for soldering wires have a thin pin in the middle and wide flat tab on the ground.
If you do not use coax with this and solder the screen to that tab and leave the smallest possible gap where the shield does not cover the connector, you are at a much higher impedance than 75R.
So the BNC socket is wasted and the result is worse than keeping the RCA.
Ciao T
Sometimes I'd like to be the water
sometimes shallow, sometimes wild.
Born high in the mountains,
even the seas would be mine.
(Translated from the song "Aus der ferne" by City)
like you do and there are even more issues with jointing technique.
As I said to Thom elsewhere, a proper signal integrity check is necessary. This can be done on a 75R terminated wide band (not 150 MHz) scope.
You appear to be one of the few designers who do not want to do his best with impedance matching. This is fineif you want to voice your SQ by whatever other means.
Thank you for you advice on how to eventually desolder the PCB soldered jack.
I'm very undecided if change the jack or buy another usb to s/pdif transport with a BNC connector.
Thom
I'd a look at this, the U3 https://www.google.com/search?q=stello+u3&rls=com.microsoft:en-GB:IE-Address&tbm=isch&tbo=u&source=univ&sa=X&ei=LYMDU_HAOcO9ygOdyIH4CQ&ved=0CCUQsAQ&biw=1185&bih=595#facrc=_&imgdii=_&imgrc=Ga4gnE9RvkzJLM%253A%3Bt3BbXqES5zerCM%3Bhttp%253A%252F%252Fd1p66qganyivs8.cloudfront.net%252Fmedia%252Fcatalog%252Fproduct%252Fcache%252F1%252Fimage%252F800x600%252F17f82f742ffe127f42dca9de82fb58b1%252Fs%252Ft%252Fstello_u3_inside.jpg%3Bhttp%253A%252F%252Fwww.moon-audio.com%252Fapril-music-stello-u3-ddc.html%3B800%3B600
and it should be easy.
There is nothing to lose but make sure you can a good quality bnc 75.
Hi,
> In my case
> 4 "IF" are YES
> 2 "IF" (n.2 and n.4,,,the circuitry and connecting traces/wires)
> are IF or NOT.
>
> It's not "jitterly" speaking better then to have 6 NOT?
Well, not all of these items carry equal weight. If your source has correct 75 Ohm termination up to a reasonably high frequency and is galvanically isolated, if your cable is a real tight spec 75 Ohm cable and if your DAC has correct 75 Ohm termination up to a reasonably high frequency, then the impact of using RCA or BNC is rather small, given the frequencies at which SPDIF operates.
If on the other hand your SPDIF transmission system is fubared by a bad source, bad cable or bad receiving termination, swapping RCA connectors for BNC will not fix it.
Of course, if all else is perfect you might as well insist on BNC's for added peace of mind and to make sure "perfection" is not disturbed.
> > higher jitter is not always audibly "worse", it depends on the precise > > jitter spectrum
>
> Jitter spectrum?
Yup. Jitter can be anything, from audio range pink noise (which may give a very high measured peak-peak jitter but is sonically quite harmless) to data/signal related jitter which can measure quite low but be quite obnoxious. Plus, masking applies. So adding some random jitter can reduce the audibility of data related jitter.
> Jitter can only cause loss of detail compressed dynamic or
> restricted soundstage.
Really? That is a fact? Interesting.
My own experiences are then clearly in error. Please provide me a reference to this new information, so that I can check the underlying experiment to see if I have to change my views formed through my own experiments.
Ciao T
Sometimes I'd like to be the water
sometimes shallow, sometimes wild.
Born high in the mountains,
even the seas would be mine.
(Translated from the song "Aus der ferne" by City)
"Jitter can be anything, from audio range pink noise (which may give a very high measured peak-peak jitter but is sonically quite harmless)"
Not a major point of disagreement here, but I would say, with apologies to Douglas Adams, that random jitter is "mostly harmless".
Jitter, of whatever form, applies modulation to the audio signal. Even if it is of the random (e.g. "pink") form this will create noise sidebands around the signal. You may not be able to see this in a single spectrum plot if the jitter spectrum is broad and the modulation index is low in that it will appear as part of the noise floor. The tip off will be that if one silences the signal the jitter noise will go away. So, for example, the presence of different levels of background noise in the presence vs. absence of a 10 kHz sine wave at high level would be a clue that these effects are taking place. Since the impact of jitter depends on the rate of change of the signal being jittered, jitter would scarcely affect a sine wave at 100 Hz of similar level. While I agree that random jitter is less harmful that signal dependent jitter, I don't agree that it is "quite harmless" unless all the modulation products are well below the system noise floor (e.g. thermal noise floor).
Jitter is just one cause of signal dependent noise, of course, and there are also issues with measurement apparatus. However, it is generally possible to "read between the lines" when looking at DAC spec sheets and review measurements to see if these effects exist. (Another big source is your bugaboo regarding sigma-delta modulators, especially the one bit variety which can not be correctly dithered so as to have noise power that is independent of signal.)
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Tony,My point, perhaps made too obliquely is that:
If a DAC or CDP has (say) 100pS P-P of 1/lf noise-like jitter (that is the highest high levels at very low frequencies, perhaps below 20Hz, falling off quickly) the impact of this will be measurable and potentially be mildly audible, however it will not be obnoxious, so perhaps your "mostly harmless" is better than "quite harmless", though in queens english the two are pretty much interchangeable.
If the same DAC has (say) 100pS P-P of purely data related and correlated jitter, well, that one would be neither mostly nor quite harmless.
Yet either DAC will have 100pS measured jitter.
Ciao T
Sometimes I'd like to be the water
sometimes shallow, sometimes wild.
Born high in the mountains,
even the seas would be mine.
(Translated from the song "Aus der ferne" by City)
Edits: 02/17/14 02/17/14
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