Originally Posted by jh901
This advice is inaccurate as it implies that:
1) The design of the analog output stage bears no significance on the output signal
2) All DAC implementations are virtually identical and sound the same
3) All balanced designs are the same whether "fake" or true full balanced
Please don't put words in my mouth by rewording what I've written and announcing to all "what he is really implying is", as you have in the above quote. I also made it clear that those three things I
listed weren't 100% absolute conditions without possible exceptions
by my use of the word "rarely".
As for single-ended vs. balanced, how can anyone have a view on this without having heard an end to end balanced (differential) system?
By reading independent test reports of third parties, rather than blindly accepting the exaggerations of the manufacturers and dealers, which show that using a unit's balanced connections are not "automatically" superior, at all. Take for example one of the amps very commonly used with the AV7500, Marantz's own MM7055. It has measurably inferior
performance using its balanced connections in terms of distortion, crosstalk, and noise
"THD+N from the amplifier was less than 0.007 percent at 1 kilohertz when driving 2.83 volts into an 8-ohm load using the RCA input. When using the XLR input under the same conditions, THD+N was less than 0.014 percent
. Crosstalk at 1 kHz driving 2.83 volts into an 8-ohm load was –85.57 dB left to right and –84.22 dB right to left using the RCA inputs and –81.05 dB
left to right and –81.09 dB
right to left using the XLR inputs. The signal-to-noise ratio with an 8-ohm load from 10 hertz to 24 kHz with “A” weighting was –111.44 dBrA using the RCA input and –98.63 using the XLR input
Source: Home Theater magazine Marantz AV7005 Surround Processor and MM7055 Amplifier HT Labs Measurements
[Not that I'm claiming this is typical of RCA vs XLR, however. I'm just showing that "it depends".]
Using XLR connections doesn't inherently have less noise in a small wire run, consumer system. The noise of the source device (the disk player and prepro in this case) is added to the noise of the next device in the chain (the amp) with either
form of connection, which as I've demonstrated (in the linked to example) may actually have more noise in the case of the XLR method. A balanced connection, including a "truly fully balanced all the way from start to finish" system, simply has a better mechanism in place to reduce the pick up
of extraneous noise entering the wire itself, called "common mode noise" [technically, it picks up the noise too, but it cleverly picks it up twice and uses one of the two in reverse phase, combined with the other one, to cancel out the common mode noise picked up along the way]. All systems have some noise, at least if you stand close enough to your speakers to hear it, but this noise is not
generally from extraneous sources we must fend off, [being picked up through the wire transmission], rather it is mostly just inherent to the devices themselves, internally, even if they weren't connected to anything.
The classic noise this does, at times, stop from entering is 60 Hz AC hum, especially problematic with long (+2 meter) cable runs. This is not a common complaint within the 9000+ posts I've read in this thread (since I was here since the very beginning), of AV7005 owners (not to be confused with ground loop induced noise, which does
occur with both RCA and XLR equally. The balanced design doesn't help that
.) In some even rarer instances balanced connections also may reduce AC radio interference and some, but not all forms, of "buzz noise" (also more typically ground loop induced, in my experience, hence no advantage with XLR there either, but this is not always the case).
But now the most important part. That constant level "hiss" sound one hears when they place their ear inches away from their front speakers while their disk player is in pause mode? NADA. No improvement with XLR over RCA [not that most of us are in a position to easily test that because one would first have to verify that the amp, etc., had identical performance using both RCA and XLR connections, which as we've seen is not always the case,
since only then
would we know for sure that it was the wiring
we were using (and not the devices themselves) that was altering the noise level.]
That faint, constant level hiss without a pattern, beat, or specific frequency [we hear when sticking our heads next to the speakers] is just the sum of all the components' inherent noise, mostly Johnson–Nyquist (thermal) noise, all added together. Wiring has no way to reduce that, in fact the job of good
wiring is to perfectly preserve whatever comes out of one device and faithfully pass it along to the next without
alteration, hiss and all. This is very
important to me so I typically buy my wires at Radio Shack, Monoprice, Amazon basics, and sometimes hardware stores (thick lamp cord, for example), rather than the snake oil often peddled by audio dealers, which sometimes mucks around with the wire's L, C, and R to effectively equalize the frequency response subtly, a classic method they use to hoodwink unsavvy consumers by introducing a non-flat frequency response to make it audibly "better". [Not to imply that the cheapest, thinnest stuff one can find almost anywhere is always
adequate, but perfectly acceptable wires with "perfect" audible performance, in even the best of systems, can often be quite inexpensive].Edited by m. zillch - 3/1/13 at 12:38pm