janneman said:
It's not quite the same thing, but couldn't you test the same thing by using two identical DACs to drive with your different transports and switching between the line level outputs of the DACs ?
This would remove all issues real or imaginary which are due to switching the S/PDIF signal.
I'll be interested to see the results, however you do it.
David.
Jocko Homo said:
Well, one eye-opener (ear-opener?) for me was that test with Ivor Tiefenbrunn of Linn fame, who was unable to detect the insertion of a vintage SONY PCM-1 (with serial A/D - D/A converters) in a tape loop of his equipment. Made me REALLY sceptical about what is the limit of audibility.
Jan Didden
Dear Jan,
Do I understand well, the test You want to do is to take a given transport - prepare different technology SPDIF output drivers on it - switch the different SPDIF outputs to that same Dac? If so, then I would say the best thing is just to disconnect that same SPDIF cable at the transmitter end, and reconnect it to the competitive output. Maybe in a hidden way from the audience, under some cover.
Because in this way one does not alter the real life conditions in the transmission channel formed by the SPDIF connection, and so does not deteriorate signal integrity. Given that the possible differences are just hidden there, in the signal integrity, I think any kind of intrusion like relays / switches would heavily falsificate the result.
The same is valid for complete transports.
I do this regularly and at least for me there are obvious differences.
But then, finding the correlations between sound and technology..
For example, if you find something pleasing, one particular transport with that cable [&with those connectors..] connected to that special dac input.. None of which is respecting the standards, that is, for example the cable is not exactly 75 ohm, the Dac is spitting back on the line because of the input hysteresis, then that RCA coax output which You had mentioned on your player..
But anyway, such a test can be quite a good eye-opener.
And while trying to guess at the possible correlations, Jocko's hints are something to be contemplated over..
Ciao, George
Do I understand well, the test You want to do is to take a given transport - prepare different technology SPDIF output drivers on it - switch the different SPDIF outputs to that same Dac? If so, then I would say the best thing is just to disconnect that same SPDIF cable at the transmitter end, and reconnect it to the competitive output. Maybe in a hidden way from the audience, under some cover.
Because in this way one does not alter the real life conditions in the transmission channel formed by the SPDIF connection, and so does not deteriorate signal integrity. Given that the possible differences are just hidden there, in the signal integrity, I think any kind of intrusion like relays / switches would heavily falsificate the result.
The same is valid for complete transports.
I do this regularly and at least for me there are obvious differences.
But then, finding the correlations between sound and technology..
For example, if you find something pleasing, one particular transport with that cable [&with those connectors..] connected to that special dac input.. None of which is respecting the standards, that is, for example the cable is not exactly 75 ohm, the Dac is spitting back on the line because of the input hysteresis, then that RCA coax output which You had mentioned on your player..
But anyway, such a test can be quite a good eye-opener.
And while trying to guess at the possible correlations, Jocko's hints are something to be contemplated over..
Ciao, George
Joseph K said:
Hello George,
Yes, I had something like that in mind, but actually not modifying the transports, use as-is, just switch their signals in an A-B comparison, playing identical CDs on each transport.
I realise that unplugging-re-plugging the cable(s) is even more transparant than the best switch, but I would like to avoid the hassle and loss of time and concemtration of the several seconds it must take to change cables.
But maybe all things considered it might be best.
Jan Didden
Re: Re: Re: Re: Re: Digital stream switching
Hi Jan,
Simple with S/PDIF (Sony/Philips Digital InterFace
) doesn't really work, you must be very careful, because you may disgrace every transport you connect through the switch.
I have made a simple switch years ago, nothing special but BNC connectors, 75 ohm cable inside, double SPDT (I switched the grounds too)...
The result was a disaster:
http://www.diyhifi.org/forums/viewtopic.php?p=7622#7622
It is not easy to switch S/PDIF without mucking it up (more than it already is), and probably this is true for whatever you try to do, passive or active.
janneman said:
Hi Jan,
Simple with S/PDIF (Sony/Philips Digital InterFace
) doesn't really work, you must be very careful, because you may disgrace every transport you connect through the switch.I have made a simple switch years ago, nothing special but BNC connectors, 75 ohm cable inside, double SPDT (I switched the grounds too)...
The result was a disaster:
http://www.diyhifi.org/forums/viewtopic.php?p=7622#7622
It is not easy to switch S/PDIF without mucking it up (more than it already is), and probably this is true for whatever you try to do, passive or active.
janneman said:
Well, after several years on this forum I am slowly getting converted to the value of a comparative listening test (as long as it is blind, of course. This particular test should tell me whether all CD drives sound the same or not. I mean we know that bits is bits, but there is the issue of jitter (time distortion?). So by transparantly switching between CD drive digital outputs either there will be an audible difference or not. If there is, it's good to know because we can improve the sound by improving the CD drives/ digital output. If there isn't, there is another question: is it because all CD drives sound the same or is it because the rest of the system masks the differences?
Either way, it should prove interesting.
Jan Didden
This is part of the info i have been looking for.
For a difference in sound, the rest of the system would have to be extremely good.
also the
quailty
connectivity(i2s,spdif, proprietory, etc)
reliability
of a cd drive between different brands, old and new.
Helps when i find the right words to search with, and which to exclude.
allan
Call me crazy but
why not use relays ?
When I look at the Takamisawa NA..WK it should be good enough
http://www3.schukat.com/schukat%5Cpdf.nsf/index/D7A9070BAE9CBEB3C1256E21005439F8/$file/na.pdf
With a price of 1,5 € it seems to be worth a try.
There are more HF capable small signal relays out there.
Regards Simon
why not use relays ?
When I look at the Takamisawa NA..WK it should be good enough
http://www3.schukat.com/schukat%5Cpdf.nsf/index/D7A9070BAE9CBEB3C1256E21005439F8/$file/na.pdf
With a price of 1,5 € it seems to be worth a try.
There are more HF capable small signal relays out there.
Regards Simon
seoman said:
Simon,
There are good cases to be made that using simple relays switching high-speed signals can upset he signal integrity, timings etc.
Most high-speed switches are made using some kind of transmission line construction to avoid reflections and skewing of the waveform. That is standard hf technology. I ordered coaxial BNC relays to do this testing; haven't yet got them though.
Jan Didden
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