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#1
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balanced output terminology
This is not the usual question you see on this forum, but here goes anyway.
I'm translating a review of an SACD player (from German) and I can't for the life of me figure out what the reviewer is trying to say in one particular section. He's describing the player's balanced output, and says something like: ".... balanced circuitry, which uses sophisticated filtering to ensure that the signal is not connected to ground in the normal way along with the high frequency residual part of the digital signal (since this has a detrimental affect when it travels around the rest of the hi-fi system), but is transposed in common mode at the output." Can anyone make sense of this? Stephen |
#2
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On Sun, 19 Sep 2004 23:02:13 +0100, "Stephen McLuckie"
wrote: I'm translating a review of an SACD player (from German) and I can't for the life of me figure out what the reviewer is trying to say in one particular section. He's describing the player's balanced output, and says something like: ".... balanced circuitry, which uses sophisticated filtering to ensure that the signal is not connected to ground in the normal way along with the high frequency residual part of the digital signal (since this has a detrimental affect when it travels around the rest of the hi-fi system), but is transposed in common mode at the output." Can anyone make sense of this? They are planning to march into Poland again :-) |
#3
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Stephen McLuckie wrote:
This is not the usual question you see on this forum, but here goes anyway. I'm translating a review of an SACD player (from German) and I can't for the life of me figure out what the reviewer is trying to say in one particular section. He's describing the player's balanced output, and says something like: ".... balanced circuitry, which uses sophisticated filtering to ensure that the signal is not connected to ground in the normal way along with the high frequency residual part of the digital signal (since this has a detrimental affect when it travels around the rest of the hi-fi system), but is transposed in common mode at the output." Can anyone make sense of this? It's rubbish speak. Balanced circuitry has two signal carrying paths of opposite polarity, mainly to avoid noise pickup that is picked up equally *in phase* by both signal paths ( common mode interference ). Balanced circuitry does *not* have " sophisticated filtering to ensure that the signal is not connected to ground in the normal way ". I suspect he may have been referring to a DAC output. These often have differential ( or balanced if you like ) outputs that then require connection to a low-pass filter. If the following low-pass 'anti-aliasing filter' has a balanced input, it will reject any common-mode noise ( i.e. noise that appears *in phase* on both the outputs of the DAC ) caused by the chip itself or poor pcb layout. I have implemented several of these. The reviewer certainly doesn't know how to express himself intelligently ! Graham |
#4
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"Stephen McLuckie" wrote:
This is not the usual question you see on this forum, but here goes anyway. I'm translating a review of an SACD player (from German) and I can't for the life of me figure out what the reviewer is trying to say in one particular section. He's describing the player's balanced output, and says something like: ".... balanced circuitry, Balanced output which uses sophisticated filtering to ensure that the signal is not connected to ground in the normal way along with the high frequency residual part of the digital signal (since this has a detrimental affect when it travels around the rest of the hi-fi system), isn't referenced to ground. Since the digital stages are, then you may be carrying "noise" on that ground to other components (which is not likely in quality components) but is transposed in common mode at the output." balanced output, not referenced to ground. Can anyone make sense of this? Stephen advertising babble to impress you with the output stage of this device. |
#5
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"Stephen McLuckie" wrote ...
This is not the usual question you see on this forum, but here goes anyway. I'm translating a review of an SACD player (from German) and I can't for the life of me figure out what the reviewer is trying to say in one particular section. He's describing the player's balanced output, and says something like: ".... balanced circuitry, which uses sophisticated filtering to ensure that the signal is not connected to ground in the normal way along with the high frequency residual part of the digital signal (since this has a detrimental affect when it travels around the rest of the hi-fi system), but is transposed in common mode at the output." Can anyone make sense of this? If you required to preserve the marketing babble in your English translation then your text seems opaque and meaningless enough to appeal to the dilletentes who have more dollars than sense. :-) OTOH, your question would appear to indicate that you recognize that it is rubbish. Hopefully you have the opportunity to clarify it. It may take nothing more than saying that it has a balanced output. Perhaps adding a sentence or two describing the actual advantages of balanced lines would be appropriate (or not, depending on the projected audience?) |
#6
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On Mon, 20 Sep 2004 00:02:13 +0100, Pooh Bear
wrote: Stephen McLuckie wrote: This is not the usual question you see on this forum, but here goes anyway. I'm translating a review of an SACD player (from German) and I can't for the life of me figure out what the reviewer is trying to say in one particular section. He's describing the player's balanced output, and says something like: ".... balanced circuitry, which uses sophisticated filtering to ensure that the signal is not connected to ground in the normal way along with the high frequency residual part of the digital signal (since this has a detrimental affect when it travels around the rest of the hi-fi system), but is transposed in common mode at the output." Can anyone make sense of this? It's rubbish speak. Balanced circuitry has two signal carrying paths of opposite polarity, mainly to avoid noise pickup that is picked up equally *in phase* by both signal paths ( common mode interference ). Balanced circuitry does *not* have " sophisticated filtering to ensure that the signal is not connected to ground in the normal way ". I suspect he may have been referring to a DAC output. These often have differential ( or balanced if you like ) outputs that then require connection to a low-pass filter. If the following low-pass 'anti-aliasing filter' has a balanced input, it will reject any common-mode noise ( i.e. noise that appears *in phase* on both the outputs of the DAC ) caused by the chip itself or poor pcb layout. That sounds about right, although strictly speaking it's an anti-imaging filter in a DAC, anti-aliasing filters belong in ADCs. I have implemented several of these. The reviewer certainly doesn't know how to express himself intelligently ! More likely he simply doesn't understand the technology, as is common with audio reviewers. :-( -- Stewart Pinkerton | Music is Art - Audio is Engineering |
#7
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On Sun, 19 Sep 2004 23:02:13 +0100, "Stephen McLuckie"
wrote: This is not the usual question you see on this forum, but here goes anyway. I'm translating a review of an SACD player (from German) and I can't for the life of me figure out what the reviewer is trying to say in one particular section. He's describing the player's balanced output, and says something like: ".... balanced circuitry, which uses sophisticated filtering to ensure that the signal is not connected to ground in the normal way along with the high frequency residual part of the digital signal (since this has a detrimental affect when it travels around the rest of the hi-fi system), but is transposed in common mode at the output." Can anyone make sense of this? If that's a literal translation, it may simply be that technical German has its own peculiarities! What he's trying to say is that the player uses a pair of DAC chips in differential mode, feeding a reconstruction filter which has a differential input, so that any 'rubbish' which is common to the output lines of both DACs (common mode) will appear in phase at the input of the reconstruction filter, and will be rejected (common mode rejection ratio, or CMRR is a standard specification for differential devices), while the antiphase DAC outputs will be passed through the reconstruction filter, and will appear at the output in a cleaner form than would otherwise be the case. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
#8
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Brilliant! Thanks for all the explanations. The description is indeed, as
you recognized, of the DAC output. I have now been able to rewrite this so that it makes sense. I think the problem was both my lack of expertise and the writer's inability to express himself clearly. It doesn't sound as if he understood what was going on either, but was just repeating a garbled version of what he had been told by the designer. Stephen |
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