equalizer?

[whitebroncoii]

Just connect the return signal (pin 3) to ground (pin 1)

Manfred

Although Europe has always configured an XLR-3 with pin 2 hot and pin 3 cold, US audio products were mixed. Older Altec electronics were pin 3 hot. In the big picture this is not an issue because it will not physically hurt anything. However, grounding pin 3 on a pin 3 hot circuit will invert the phase and there are audiophiles among you that may not be able to sleep knowing the phase is reversed. I simply think it is a good idea to check the data sheet for the "hot" pin and ground the "cold" pin when connecting RCAs to balanced inputs.

[techmecca]

terminology

balanced connections will have a hi, lo, and ground
hi can also be called +, or ?+ or hot ...
lo can also be called low, -, or ?- or cold ...
ground can also be called C, or common, or shield ...

unbalanced connections will have one signal wire and a ground or common
signal wire can be called hot, or tip, or ?
ground as above can be called C, or common, or shield ...

pin and terminal are used here interchangeably

with xlr's - on gear with balanced in and out the signal hi and lo wires will be on pins 2 and 3 but when pin 2 was eventually standardized to be + or hot it took a while for manufacturers to conform and there was no magical wave that went out and converted all the pin 3 hot devices to become pin 2 hot... so it's case by case with anything old... though older gear from usa was mostly pin 3 hot and older gear from europe was pin 2 hot... and in newer gear some manufacturers never changes because they had already sold a zillion SM57's or whatever wired pin 3 hot and were not going to change - screw the standard. Anyone remember the AES show where they were handing out the little cardboard spinner wheels with 3,2,3,2,3,2,3,2 around the circle and the arrow you spin to decide the wiring standard? further back anyone remember the bikini clad dbx girls and Larry Scully handing out packs of rolling papers with his phone number printed as if penned in on the inside flap - ah those wuz the days - the Waldorf - when swag was swag.

anyway...

connections

unbalanced sources to balanced inputs are easy - the unbalance signal goes to the balanced hi pin (or terminal) and the unbalanced common goes to BOTH the balanced low pin and the common pin... this works almost universally with both active balanced input and transformer balanced inputs. If you have the phase wrong it still works.

balanced outputs to unbalanced inputs can me more problematic...

transformer balanced outputs can have the balanced hi output terminal going to the unbalanced signal pin (tip or whatever) and the balanced signal low and common terminals would go to the unbalanced common... if you have the phase wrong it still works. Note that since unbalanced inputs are often high impedance you may need to have a terminating resistor across the (transformer) balanced signal pins (hi and lo) to provide some loading and reduce a HF peak or resonance in some outputs... most transformer outputs were designed to look into 600 ohms - I find that 1000 or 1200 ohms works fine with some gear and other gear really does not need to be terminated... depends on the amplifier and transformer combo so YMMV (Your Mileage May Vary)

now... here's where it can get messy. Active differential balanced outputs feeding into unbalanced inputs can be more difficult especially in some gear with poorly designed output amplifiers. Active balanced outputs will have an amplifier driving each output pin - one drives the hot pin "phase +" and the other drives the low pin "phase -" - same signal but fase phlipped. Decently designed gear will have a cross-coupled feedback that will sense when the one or the other signal pin is shorted to ground and remove some feedback from the amplifier driving the un-shorted pin so that the level remains constant... in well designed gear this circuit is completely symmetrical so either hi or low pin can be shorted and the remaining pin will retain level relative to ground. HOWEVER in other gear the feedback and level comp thing only works if low pin gets shorted to ground... and sadness will result if you have the phase wrong. In BOTH cases the amplifier driving into the shorted pin will not turn off - it will drive distorted audio to ground, as current, so if your ground is not solid and draining off this current you will get some of this distorted audio popping up elsewhere in your system as crosstalk and not very clean crosstalk at that. In stereo systems the effect is that of cluttering up your imaging, among other things - and it's just not clean. So, if you terminate an active signal pin to ground, the level may stay the same, but you do run the risk of introducing some distortion and crosstalk into your system. Furthermore YET OTHER active balanced outputs actually CAN'T have the low signal short to ground because that low side amplifier is driving the high side amplifier - which is inverting and driving the hot pin... I've seen this in some gear and it's really annoying (old old old Wheatstone consoles for one).

In any case when - even if your level compensates and the output amplifier is really groovy and symmetrical and your ground is good and drains all the distorto audio away, and all that, you WILL loose 6 dB of headroom in that output.

Now... IF you have some gain down stream and can afford to loose 6dB in level you can choose NOT to short the low side pin of your active balanced output and just connect your balanced output hot pin to your unbalanced input signal pin and your balanced output common/ground pin to your unbalanced input common/ground pin and leave the balanced low pin hanging free and not driving distorted audio current to ground and alls good - you will have 6dB less level and 6dB less headroom but as long as you can make it up later you are fine... and in most stereo playback systems you will have more gain than you need downstream.

okay - so I hope that was readable and useful

have a nice day