So if a balanced dual mono/stereo preamplifier has both XLR and RCA
outputs, and both outputs from XLR or RCA or moving signal from a
separate mono channel for left and right, then in essence their both
balanced cables doing the same thing. Interconnects are nothing more
than ground connectors. As I already pointed out, no one called XLR
cables balanced cables for almost forty years until the 80's when dual
mono/stereo components were on the rise having the option of XLR or RCA
outputs. If XLR cables were invented in the 80's for the sole purpose
only to use with high end dual-mono components, then technically it
would be a balalanced cable only, not a cable that was given the
nickname "balanced" due to its great ground properties which works best
with noisy components especially noisy tube amplifiers.
Al addressed this correctly. I do have the feeling though that you did not read my post carefully. XLR connections were in wide use in the 1950s- my Ampex 351-2 tape machine, built in 1957, uses XLRs exclusively.
They were used by the recording and broadcast industries beginning in the 1950s, and their introduction to high end audio was made by me in the late 1980s (we introduced the first balanced line product for high end audio in 1987).
The reason XLRs are used for balanced operation is that the relationship of both the non-inverted and inverted signals with respect to ground is identical. This is important for a proper balanced connection and is something an RCA connector simply can't do.
A very well designed solid state preamp is quiet as a tomb and its
redundant to use a 1 meter pair of XLR's since there is no noise to deal
with. To create this myth that XLR cables have an effect on the quality
and quantity of the music signal is outright fraud. The quality is in
the recording itself whether its vinyl or CD and has nothing to do with
the wire or the connector. If its a very bad recording its going to
sound like crap regardless what cable your using, XLR or RCA. Now if you
have a poorly designed preamp with a high level of cross talk and noise
than the XLR will help to flush out the noise at the output. Its just
wire with a good ground, its not a "mini preamp, a "processor", or a
buffer like many in the high end retail continue to perpetuate to make more money.
This paragraph is full of outright falsehoods so I will attempt to set the record straight.
The noise of the preamp is a different thing from the noise that can enter a cable. It does not matter if the cable is 6" or 60 meters. Balanced operation still has a noise advantage with respect to the cable, and the additional advantage of being able to eliminate cable artifact. If you had to pay big dollars for a single-ended cable because that was the one that sounded right, that's the kind of artifact I'm talking about!
Now balanced operation within something like a preamp can also have lower noise but for entirely different reasons. For example, we use differential amplifiers in our preamps; for a given stage of gain, a differential amp can have 6db less noise than its single-ended counterpart.
Differential amplifiers are in common use in many solid state power amps and many opamps. They are used because they offer lower noise and also greater power supply noise rejection. They can be executed in tubes as well (the first production opamps were made in the 1950s by George Philbrick and were all-tube).
The bottom line is balanced operation is used to reduce or eliminate the sound an interconnect cable might impose in the system, and also to reduce or eliminate noise that might be impinged on the cable by power cords, magnetic fields and the like- these are things single-ended cables cannot do. This is why all recordings since the 1950s employ balanced line connections- its not just so that the cables can be run a long ways, but if you sit and think about it, the fact that the technology prevents the cable from modifying the signal does also imply you can run the cable much longer distances without troubles. This can be quite advantageous in the home; I keep my amps right by my speakers with short speaker runs, and run the interconnect cables about 30 feet to my preamp which is located at the spot in the room with the least bass (room nadir). In this way I get considerably more definition and less coloration.
Again, you'd think that audiophiles would be all over that!
I knew Robert Fulton as he lived here in town. He was the guy that founded the high end audio cable industry. Back in the late 1970s he had a high end RCA cable, and his Fulton Brown and Fulton Gold speaker cables.
If you run RCAs, the cables to make the connections are the hidden cost of any preamp. If you run balanced, and the equipment supports the balanced standard, the cables are cheap but the sound is better than the best RCAs.
So Ralph, based on your engineering knowledge, why would ARC make those
design choices? Can you hazard a guess as to what the most likely
reasons would be? My experience tells me that there must be trade-off
considerations-at this level of audio, there always are.
You are correct. There are several ways to do balanced operation with tubes. If you want to support the balanced standard though, your options become limited because of the low input impedances the standard requires you to be able to drive, and also there is that issue with ignoring ground as I stated in my first post.
In the old days of tubes, an output transformer was employed. That is how my Ampex recorders (which are single-ended internally) drive balanced lines. When transistors came along, and in particular solid state opamps, it became possible to direct-couple the output. But even with solid state, transformers are still in common use even today.
We developed a third means, which is a direct coupled balanced vacuum tube output, for which we also developed a patent. I'm pretty sure ARC didn't have any interest in infringing the patent, using output transformers or a solid state output, so they used the only means left to them, which was to not support the balanced standard. They knew they had to do something because balanced operation offers too many advantages to ignore!
As a result, you can easily hear differences in balanced cables while using their equipment. This is entirely because the balanced standards are not being observed.
