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31.153.103.175
In Reply to: RE: BNC-)RCA adapter posted by Thorsten on February 20, 2014 at 10:00:34
that you have just invented a whole new language to describe essentially an edge triggered phenomenon by filling the text with multiple buzzy words that have no clear meaning.
This may 'fool' some inmates.
Follow Ups:
Fred,
I am attempting to explain layman's terms, to the best of my abilities, in my third language (so forgive me smalls slips) why and under what circumstances a small change may create a great impact.
I was not talking to you.
Yes, we are dealing with edge triggered systems with on average 5-10nS risetime (much faster and the EMC cop's come and get you). And this signal is transmitted through a transmission line (technical definition).
If the impedance of source and sink (Transport or DCC = source, DAC = sink) is the same as as the transmission no reflections occur. In the real world such system do not exist but can only be approximated.
But it is also critical to understand what really happens in this system.
If the impedance is incorrect anywhere for a distance that is a substantial fraction of the rise time of the signal or if source/sink termination differs from characteristic impedance of the cable, reflections will happen. If the discontinuity is shorter,no appreciable reflections.
If (and ONLY IF) these reflections from mismatches arrive at the sink within the trigger window of the SPDIF receiver and are large enough to shift the trigger point will they have any impact at all.
Now for some more facts.
A RCA Socket and Plug cause a discontinuity of around 600pS (to convert to distance, the signal-speed is usually around 70% of light-speed). The Plug itself has around 52 Ohm impedance, the socket has a higher impedance, more around 65 Ohm.
Using a RCA-BNC adapter with an RCA socket shortens the discontinuity to around 300ps, or slightly greater than a BNC socket and with a slightly worse impedance match. The differences are almost at levels where one might blame experimental error, but they are repeatable.
Relative to the signals rise-time and accounting for the reflection ratio, the difference between RCA Socket with BNC Adapter and pure BNC is small and the RCA Socket and RCA plug is greater, but still low enough not to be an issue at the usual rise times.
Now if someone decides to have a rise time much faster than a few nanoseconds (which for many reasons is not a good idea) they need to worry more. But only if the receivers switching transition time is actually much faster than that of common SPDIF receivers (meaning the common SPDIF receiver Chips are not used.
Something you may not completely grasp is the concept of appropriate technology.
The iLink costs 249 USD (ex. tax) worldwide and it is aimed at "common technology" DAC's. This means they use generic, off the shelf SPDIF receiver solutions, nothing fancy (which accounts for 95+% of what is out there).
Non of the receiver chips from Asahi Kasei, Cirrus Logic, Philips, Texas Instruments, Toshiba and Wolfson Micro benefit from excessively fast rise times. They switch too slowly.
They do benefit dramatically from correct signal levels though and from not having a lot of reflections bouncing around the interface. That needs the correct termination impedance at the SOURCE, across a wide frequency range, then mismatches at the sink will matter modestly if at all.
So, the bottom line is simple.
The iLink is designed not according to platonic ideals (such as the ideal chicken coop with platonic ideal chicken sh!t) but according to what deliver the best possible results in the real world for the largest number of our customers(the 95% with "ordinary" DAC's). Had we had any concern that BNC connectors (rather than RCA with BNC adapters) would deliver this, in the real world, we would have put a pair of PCB mounted BNC's there.
Now, I know you will never buy one, because it does not have a BNC connector and you will rail in futility at the insult of not having a BNC connector (but instead a system designed to work correctly even sans BNC or more precisely with a BNC adapter).
And you know how much that does really concerns me or anyone at iFi? As long as we get to match or even beat the guys who charge twice as much or more and fit BNC's in the real world:
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)
about this response except that the argument originated from an inmate's desire to change his connector. I offered my 2p but then you said in 'layman's' term (which I thought confuses) that this was completely unnecessary simply because you had made the compromises in the iLink that iFi makes. Some of these were to me unreasonable restrictions on use, such as a short dedicated cable which you provide for your device only, or to use a bnc-phono adapter. The short cable restricts the placement of satellites devices which is simply a nuisance and 75R adapters are not commonly available. For some who use satellite devices, they already have an expensive arrays of bnc cables and therefore would not want to mess about with phono digital connections.
I respect design compromises, but if you are categoric about your choices being the only correct ones, then you need to explain in clear terms the rationale and not indulge in the kind of marketing words that iFi uses on it's website (or use buzz words that some inmates may think are justifications that have no real technical meaning).
Fred,
> such as a short dedicated cable which you provide for your device only,
It is neither a dedicated cable nor for our device only. It is an industry standard 75 Ohm coax cable fitted with BNC connectors on both ends. It is perfectly usable with any BNC socket/adapter equipped device. It is short as it is normally preferable to place the DCC as close to the DAC as possible.
> 75R adapters are not commonly available.
That is why we include two of them. So you can use the included Cable and the iLink with either RCA or BNC equipped DAC's, with minimal compromise and no need to buy any additional items.
> For some who use satellite devices, they already have an
> expensive arrays of bnc cables and therefore would not want
> to mess about with phono digital connections.
So, they can simply use one of the included RCA-BNC adapters and use whatever BNC cable they like. And as remarked, the compromise of RCA plus adapter is rather small, in absolute terms, compared to a BNC socket.
I already pointed all of this out in prior posts, but you seem to avoid carefully reading anything that might correct your misconceptions and keep spouting nonsense.
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)
Then it makes absolutely no sense to fit phonos on the iLink. Why have adapters at all?
Please note that what makes sense to you may make no sense to others. Technology push is the one thing to avoid if you want to make and sell tens of thousands and not thousands.
On the question of words, I read nothing into strings that have no particular meaning in the context of a discussion.
Hi,
> Please note that what makes sense to you may make no sense to others.
Rather the reverse.
To most people who buy a low cost DCC having BNC's makes no sense whatsoever.
Only for a tiny minority (including you) is BNC on DAC's even a topic.
And they would in most cases never use something so cheap with their expensive dCS Stacks or similar DAC's, believing that anything low in cost could not be good enough anyway.
We serve the majority, no a vocal minority of dissenters who must find fault in everything and can never be satisfied anyway. So as said, please do not buy this product, it is not for you, it is for everyone else.
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 your arguments.
I was you who raged against BNCs for reasons which you invent from post to post.
If you make equipment for the masses, you should refrain from making hyped claims on your website, as are in the cases of the iLink and USB filter.
Hi,
> I was you who raged against BNCs for reasons which you invent
> from post to post.
To quote Carrie Fisher "I don't know where you get your delusions, laser brain.".
I have not "raged against BNCs".
I have merely pointed out that the case for "75R BNC for SPDIF über alles, über alles in der welt" was by far less strong than it has been presented by some.
I pointed out that many pieces of gear even though fitted with 75R BNC's, present anything but a 75R impedance over the necessary frequency range so the 75R BNC's are totally wasted.
And I noticed that in fact that in the REAL WORLD the difference between RCA and BNC in a correctly designed system with normal rates of rise time amounts to Feck All.
So, all the time the message was never "BNC's Suck for SPDIF" but rather "The FUD spread by some that RCA's are massively worse than BNC's for SPDIF is a load of old bollox".
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)
Itis now clear that you are posting on your third language
Here's the problem some of us have, Fred.
We understand the technology. We understand the physics and electrical engineering of signal propagation on transmission lines. We understand how receiver circuits work. We understand how clock recovery circuits work, We understand the mathematics and logic of channel coding. We understand the principles of communications engineering and how to relate channel noise to bit error rate. We understand why the physical layer was designed the way it was, and how the budget (e.g. amplitude and time as embodied in eye patterns) represents various engineering tradeoffs. We have worked on systems other have designed that failed through inappropriate use of edge triggered logic and have learned how to properly design systems that use multiple clock domains. We understand the system aspects of what happens to digital waveforms after they have been buffered and clocked into a separate clock domain. We understand the potential impact of this on the analog output from a DAC. Some of us have designed systems that operate at these data rates and at data rates that are two or more decimal orders of magnitude slower and faster than what are used in digital audio.
Then someone like you comes along, who fails to demonstrate more than a rudimentary understanding (such as I might have understood at age 13) who then puts us down, accusing us of being ignorant or deceptive. When we challenge you to explain the logic behind your arguments, you don't follow through. Some of us are more than a little fed up.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Tony,
I do not want to get too involved in this love fest, but maybe what is missing is the practice side of good engineering? It is one thing to theorize, but another to apply it. Maybe part of the reason for the disconnect???
regards
Bob
I will leave it up to you to decide out who has designed stuff and who hasn't, who knows how to listen and who doesn't, and who knows how to think logically and who doesn't. The posts are out there. One of the great virtues of the Internet is the burden it places on readers to separate sheep from goats.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
"I will leave it up to you to decide out who has designed stuff and who hasn't, who knows how to listen and who doesn't, and who knows how to think logically and who doesn't. The posts are out there. One of the great virtues of the Internet is the burden it places on readers to separate sheep from goats."
Well, you have designed real things, and I have worked in a mental institution serving soup to nuts... So someone else must be spending time with the farm animals. ;)
You have consistently posted airy fairy mishmash postulations on digital audio.
You neither have the quality of audio system or computer system to assess SQ, and yet you keep on trolling on the same clocking stuff.
Just what is your qualification in electronics other than working in computing?
For your information, I practised professionally in measurement and control for many years and taught the subject at university level. Have you ever done so?
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