My point was that the talk about pin 2 vs pin 3 in terms of signal polarity is irrelevant when it comes to balanced cables. Since they are wired 2 to 2 and 3 to 3, they will work with either pin 2 "hot" or pin 3 "hot", and there are no special cables needed for one convention vs. the other.
Yes, that's correct, Mike. Best regards, -- Al |
To add to Ralph's (Atmasphere's) comment, although the following paper is oriented toward pro audio equipment, I've quoted an excerpt that seems relevant:
https://www.rane.com/note110.html
Since standard XLR cables come with their shields tied to pin 1 at each end (the shells are not tied, nor need be), this means equipment using 3-pin, XLR-type connectors must tie pin 1 to the chassis (usually called chassis ground) -- not the audio signal ground as is most common. Not using signal ground is the most radical departure from common pro-audio practice. Not that there is any argument about its validity. There isn't. This is the right way to do it. So why doesn't audio equipment come wired this way? Well, some does, and since 1993, more of it does. That's when Rane started manufacturing some of its products with balanced inputs and outputs tying pin 1 to chassis. So why doesn't everyone do it this way? Because life is messy, some things are hard to change, and there will always be equipment in use that was made before proper grounding practices were in effect.
Regards, -- Al |
@Celander, re the "balanced standard," aka AES File 48, the following is from a post dated 3-22-2013 that Ralph provided in this thread. Also see my follow-up question later in that thread, and Ralph's response.
A good reason to go balanced is the advantage of being able to run
really long interconnects, so you can place the amps close to the
speakers and avoid sonic degradation on account of the speaker cables.
The
balanced line system was created to get rid of interconnect cable
colorations. It works really well! However in order for that to happen the preamp must support the balanced line standards (which have been in
place for decades).
Most high end audio balanced preamps do not
support the standard! As a result with such preamps you will encounter
variable results as far as interconnects are concerned.
Here is the standard:
1) pins are: pin 1 ground, pin 2 and 3 are signal. 2)
Ground is ignored- the signal occurs only between pin 2 and 3 (this is
where most high end audio preamps have a problem- as soon as there are
signal currents in the shield of the cable, the construction of the
cable becomes critical). 3) the cable will be a twisted pair for the signal with a shield (tied to pin one only) 4)
the output of the preamp should be capable of driving a low impedance
load (2000 ohms or less) without loss of voltage, without increase in
distortion and without loss of bass (this is the other big area where
high end audio preamps have a problem, and also results in cable
sensitivity).
Note: this does not mean that the output impedance
of the preamp is this value, it means that it can *drive* this value.
If there is a question, both the 1KHz output impedance and the 20Hz
output impedance should be well below 300 ohms!
The actual
standard is 600 ohms and you will have a lot of manufacturers of
balanced products tell you that since the amps being driven have a much
higher input impedance, that this does not matter. Such is incorrect if
you want cable immunity! It is the higher impedance nature of
single-ended preamps and amps that spawned the interconnect cable
industry. Such is not needed for balanced as long as the standards are
used.
Now some people want proof of this sort of thing- after all
what I am saying here is that the interconnect should not have an
audible quality in the system. So here is the proof. The first
manufacturer of high end cables was FMI in Minneapolis, Minnesota.
Robert Fulton, the proprietor, created the first cables in which in was
claimed that they made an improvement when installed in a system. That
was the late 1970s.
However in the late 1950s, the record labels
were turning out recordings that are revered to this day (the better
your system gets, the better these recordings sound). In many cases the
microphone signal had to go over 200 feet to get to the input of the
tape recorder- how did they do that without an exotic cable? The answer
is the low impedance balanced line system.
So- if you want that
same cable immunity that the recording and broadcast industry has
enjoyed for the last 60 years, then your preamp should support the same
standard. This takes the cable out of the system equation, and also its
cost.
Regards, -- Al |