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Phil Allison[_4_] Phil Allison[_4_] is offline
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Default Anything to say on Speakons

John Williamson wrote:

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** Most of John's post is pure myth - the benefits of balanced mic lines are way overrated. ( more later)


For professionals, the advantage of balanced signal connections is that
we can connect any pair of balanced items together, and it all "just
works", even over long connections (I use 25 metre microphone leads,
often with a couple of joints in them, for instance, running parallel to
a line level return in the same loom.


** Agreed - unbalanced *multicore" cables can be a disaster. I have seen examples of internal cross coupling causing massive supersonic oscillation in a PA system.


Some on here have mentioned using
microphone leads a quarter of a mile long with no major problems.).


** An unbalanced line using good RF co-ax would go much longer - long as it is driven by a low Z mic. The capacitance of such co-ax is way less and the mag field rejection is actually *better* - see note.


The
only noticeable distortion is from the diaphragms inside the microphones
and monitors. Using that length of connection on an unbalanced wire only
needs someone to turn a fluorescent light on in a nearby room, and you
have interference on the signal, and as for cellphones...


** The issue here is only poor shielding, good RF co-ax ( RG58 or RG59 comes to mind) is normally well shielded.

Note: The internal symmetry of a co-ax cable is the secret to its excellent mag field rejection. Equal and opposite currents inject into the core and shield from a nearby AC mag field - so complete self cancellation.

OTOH with a twisted pair cable, the rate of twist per foot is critical to mag field rejection, but even the best will pick up hum from a supply frequency transformers when it gets too close - including the tiny ones in wall warts.

The "balanced is best" fallacy is historical nonsense based on a false comparison between a 200 ohm or 600 ohm mic and a long obsolete 50kohm one.

The ONLY real advantage of a 2 wire "balanced" mic line is when used for carrying phantom power to a mic or device that needs it ( eg a DI unit).

** Go ahead - make my day:

Make a lead using 20m or so of RG59 with an XLR at each end, wired with each pin 3 linked to pin 1. Use it with a 200 ohm mic of whatever brand.

Wind one turn around a wall wart transformer and note there is no hum.

Now, do the same with any of your twisted pair leads.

Who wins?


..... Phil