Wolfman; with the amp or preamp powered off, measure resistance between pins 1 and 3 with an Ohmmeter. If you see something less than 1 Ohm then the pins are tied together like Atmasphere says. If the meter reads open (infinity) then it must be a true balanced circuit.
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Wolf, I bet your preamp is balanced. But like a lot of modern studio gear, the outputs are probably set up so that the non-inverting occurs between pin 2 and pin 1 (ground) while the inverting output occurs between pin 3 and pin 1. How it *should* work to get cable immunity is that the signal occur between pin 2 and pin 3 while pin 1 is ignored and only used for shield. But today a large amount of studio gear ignores this grounding issue, thus you are hearing differences in cables in the studio. Trust me on this one- the reason the balanced line system came into existence was to solve that very problem. I can do into the history of it if you like; but in a nutshell what is happening is that if you hear differences in cables then the equipment does not support the standard. |
My pro mixers with balanced, low impedence ins and outs certainly "support the standard" or I wouldn't be able to use 100' snakes for clean signal...Better mic cables do sound better in my experience, as I noticed when recording music for a TV show we used to do...I was recording direct to digital with a Mackie board using a high sensitivity phantom powered condensor mic and used very good headphones...the better cables were clearly better sounding. |
Ralph (Atmasphere), thanks for what as I see it is really excellent info and background, including the proof that is provided in your first post above, which strikes me as extremely persuasive. A few days ago I provided a link to that post in a couple of the ongoing cable threads. Wolf, keep in mind that even if the equipment has very low output impedance and very good drive capability, it does not meet the standard if it connects XLR pin 1 to circuit ground, as opposed to chassis. As Ralph indicated, and as is indicated in Figure 1b and some of the text in this paper, it is very common for pro equipment (as well as consumer equipment) to connect pin 1 to circuit ground, in violation of the standard. Ralph, is there any threshold that can be defined for how low the resistance that may be designed into a component between circuit ground and chassis ground can be without defeating the purposes of the standard? Also, to eliminate interconnect cable differences is it necessary that the component output actually BE driving a low load impedance (2000 ohms or less, to use your figure), or is it just necessary that it be CAPABLE of doing that? Thanks again. Best regards, -- Al |
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