WBF Founding Member
- Apr 30, 2010
Amir, how did you get pictures of my last EKG?!!!
I got a few hints from watching the founder of Wikileaks on 60 minutes last week!Amir, how did you get pictures of my last EKG?!!!
Well, no... The problem with this subject is that, in trying to be "right", we are continually heading deeper into the swamp!
Insert big grey box here...
HTH! - Don
I did a search and ran into this fun set of pictures of S/PDIF outputs of a few CD players. Any notion that the signal is "ones and zeros" and that the problem is "easy to solve" at the receiver, should be dispelled :
Correct. It is measuring sum total. BTW, I have a head a lot of horror stories of bad output. Building a good transmitter also takes good design skills which some of these companies lack.Amir, could those pictures also be showing reflectance due to incorrect termination of the output because the probe cable and oscilloscope load impedance is not equal to the source impedance? Depending on the CD players that they are measuring, the source impedance might not even by correctly 75ohms.
Please ask Gary. That is how these threads become useful. Best way to get Don and I to explain things is to ask questions. Hard to get motivated to write something long without it .I'm sorry that I'm asking a lot of questions because this will impact the analog/digital comparison that we are going to do next week. I have the Burmester Ph100 which has digital on a RCA output, and the Weiss Minerva which has digital input on an RCA input. I think that the swamp is going to be very deep, smelly, and crocodiles will abound..... and may be even a few anacondas.
What frequency would you then measure cable impedance at? The clock frequency? No cable is a perfect conductor, and the impedance is a combination of resistance (probably insignificant), inductance and capacitance (which might probably be more important at the higher frequencies). If so, then we end up having to design almost completely different cables at different lengths and for different clock frequencies!! What a swamp!
Well, many companies claim that too although WBT does build good product. Problem is, we need an *in-circuit* impedance of 75 ohms end to end. Meaning the combination of wire termination+male connector+female PCB connector and PCB traces to all add to a perfect 75 ohms. BNC connectors have been designed for this application for decades so you can achieve that target much better than just a male connector offered this way with an unknown coupling by the user (BNC connectors are locking, RCA are not).amirm, WBT claims 75 ohms characteristic impedance for at least some of its nextgen RCA plugs and sockets. If correct, problem solved if manufacturers use these or similar products?
Don and others, I haven't been keeping up just lately with what's out there in terms of cleaning up the S/PDIF signal. There was the Digital Lens, which uses a different technique, but what is out there now that works in real time, that is plug and play, to take a dirty S/PDIF in, and spit out a spiffy, laundered version, through minimal cable length into the DAC?
Whilst on my rant, whatever person designed the RCA pin and jack such that hot is made before ground should be rotting in... well, you know! It would not be too hard to adjust the mechanical assembly so the pin is recessed and ground is made first, though it would require a longer plug and jack. Maybe I'll "invent" and patent it...
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