I run an all balanced system. I connect the balanced output of the Rossini to the balanced input of my Accuphase preamp. There appears to be a phase mismatch however. dCS factory set Pin 2 of the XLR connectors as ‘hot’ (+ve) with Pin 3 (-ve), whilst Accuphase factory set the opposite ie Pin 3 of the connectors is designated as ‘hot’ (+ve) and Pin 2 (-ve). In both cases Pin 1 is ground.
The Accuphase pre does allow for the balanced polarity to be changed so in practice I can match the dCS and Accuphase polarities. I just wonder if it is just Accuphase that is out of line with the ‘balanced’ norm and if it really matters if units are connected together with differing balanced phase polarities ??
I never figured out the history on this one, but as Ermos mentioned the standard in Japan is pin 3 hot and always has been. The rest of the world is the opposite. In my experience though most recent Japanese equipment recognizes this discrepency and provides the ability to switch this.
There are several explanations of why pin 2 or pin 3 is/ was hot:
Three-pin in audio use
EIA Standard RS-297-A describes the use of the three-pin XLR - known as XLR3 - for balanced audio signal level applications:
Pin Function
1 Chassis ground (cable shield)
2 Positive polarity terminal for balanced audio circuits (aka “hot”)
3 Negative polarity terminal for balanced circuits (aka “cold”)
Prior to the introduction of this standard, the wiring of pins 2 and 3 varied. The pin 2 “hot” and pin 3 “cold” convention was typically used by European and Japanese equipment manufacturers, but American companies used pin 3 “hot” and pin 2 “cold”. This caused problems when interconnecting equipment with unbalanced connections. The pin 3 “hot” convention is now obsolete but is still found on vintage equipment. Pin 1 has always been ground and/or shield if the cable is shielded, and many connectors connect it internally to the connector shell or case.
I have a Vivaldi and a c3900 and i have it inverted. It does sound different, probably a little cleaner although to be honest I haven’t done any extensive comparisons. The good news is their new preamps will remember the setting for each input.
The Rossini can also be set to output XLR reversed, i.e. the Accuphase way. If you have the dCS Remote, the “Phase” button accomplishes this. Haven’t found this setting in the Mosaic app; doesn’t mean it isn’t there though, I just haven’t found it
It’s also possible it can be found in the menus on the device itself, I just haven’t looked since I DO have the remote.
Please do not confuse Phase with Polarity, these are different!
With phase, we are shifting the position of a waveform relative to another in time (degrees of cycles). With polarity, we are positioning the waveform as either right side up, or upside down relative to its original state. I.e. we are flipping the +/- orientation without changing the waveform’s position in time.
Correct we are discussing Polarity. I just want to be sure I have consistent polarity all along the signal path, box to box.
So my mc cartridge output goes to the balanced inputs of my Phono preamp with Pin 2 +ve. Balanced outputs of the Phono amp and my Rossini go to my Preamp balanced inputs. Pin 2 +ve. Balanced Preamp output to the balanced input of the Power amp. Pin 2 +ve.
Polarity on the Accuphase phono, pre and power amps can be set to match the Rossini Pin 2 +ve standard.
I have not found a dealer ever mention the importance, or otherwise, of consistent polarity along the signal path - perhaps in practice it doesn’t matter but to satisfy my audio OCD I need to make sure it is.
I set polarity of all my gear to the standard: 2 + (hot) / 3 - (cold).
My pre is fully balanced, so the polarity at the input and output is the same.
Analog outputs with native polarity 2 + (hot) / 3 – (cold) (e.g. dCS) remain unchanged.
All Accuphase analog outputs (Tuner, Phono Pre, Voicing Equalizer, DAC) are set to 2 + (hot) / 3 – (cold). Consequently the Accuphase power amp inputs are also set to 2 + (hot) / 3 – (cold).
Yeah, normally I’d agree with you here - phase shift is usually something different, and a function of a shift in time.
However, in this case, as a user-interface option, it accomplishes exactly what I intended it to do: invert the analogue output. See page 35 in the Rossini DAC manual.
Besides: the button on the Accuphase preamp that accomplishes this on a per-input basis is also called “Phase” so there’s consistency there.
Any complex waveform is made up of several superimposed harmonics of the form A sin(ωt + φ), where A is the amplitude, ω is the frequency, t is time, and φ is phase. Since A sin(ωt + 180°) = -A sin(ωt), the identity between a 180° phase shift and a negative polarity should be clear. But how much delay is 180°? Phase is just another name for delay as a proportion of wavelength (the reciprocal of frequency). That is, d = φ / 360° × λ, where d is delay and λ is period of the wave. For example, to delay a sine wave at 200Hz by 180°, we delay it by 180° / 360° × 1 / 200Hz = 2.5ms. But now imagine that instead of a pure sine wave we have a complex waveform at 200Hz with a couple harmonics, at 400Hz and 600Hz. With a little simple algebra on the equation for delay, we can see that φ = 360° × d / λ. So when we delay the whole waveform by 180°, i.e. 2.5ms, we are changing the phase of its individual components differently. The 200Hz part is delayed by 180°, as we would expect; but the 400Hz component is delayed by 360°, not 180°; and the 600Hz component is delayed by 540°, which is 180° + 360°. In contrast, when we reverse the polarity of a complex waveform, the phase of every single frequency component is changed by 180°.
Sure, sure - perhaps “Phase” is not the correct term to use for the flipping of + and - but I’m not here to argue theoretics. I’m just pointing to a user interface element that in practice, achieves a polarity flip (independent of time and/or frequency) which is what we were after.
Both dCS AND Accuphase are wrong then to use the term “Phase” - but it’s a helluvalot shorter to label a button with than “Inverse Polarity”.
My Accuphase phono and power amps provide a switch on the rear to assign the polarity of pins 2 and 3.
The Accuphase 3900 pre assigns the pin polarities on the front via a ‘phase’ switch. In both cases it is the polarity that is flipped. ‘Phase’ is not strictly, in my view, the correct term.
The C-3900 is fully balanced. Its output polarity is the same as the one at the input.
The Phase switch changes the polarity for the entire balanced preamp. Sorry that’s wrong. Correct: The phase switch can change the polarity of every single input.
In a system with mixed polarity (some 2 + (hot) / 3 - (cold) and some 2 - (cold) / 3 + (hot) IMHO it does not make any sense to change the polarity of this preamp.
The C-3900 manual supplies a table showing the circumstances when the polarity of the preamp is either left or flipped. It depends on the polarity of the input source and output amp connections.
