Shorting balanced inputs?

[dantwomey]

What is the best method for shorting the balanced inputs when not in use? I have read about shorting caps and I would like to do this externally (no internal jumpers) so I can switch inputs at will. Any suggestions anyone?

Regards,
Dan

[Steve Eddy]

Originally posted by dantwomey
What is the best method for shorting the balanced inputs when not in use? I have read about shorting caps and I would like to do this externally (no internal jumpers) so I can switch inputs at will. Any suggestions anyone?

Well, perhaps the simplest way would be to go to Home Depot and get some 12 gauge solid copper wire. Cut it, use some 400 grit to smooth off the ends, bend it into a U shape and insert them into pins 2 and 3. Assuming of course your inputs use female inputs.

se

[uli]

You mean 1 & 3 ??

Uli

[Steve Eddy]

Originally posted by uli
You mean 1 & 3 ??

Nope. I mean 2 and 3.

se

[moamps]

Originally posted by Steve Eddy


Well, perhaps the simplest way would be to go to Home Depot and get some 12 gauge solid copper wire. Cut it, use some 400 grit to smooth off the ends, bend it into a U shape and insert them into pins 2 and 3. Assuming of course your inputs use female inputs.

se

Or using XLR F connector with bypassed 2 and 3

Originally posted by uli
You mean 1 & 3 ??
Uli

No, 2 and 3 is good choice, 3 and 1 are bypassed when you connect unbalanced source to balanced input.
2 is hot, 3 is cold, 1 is ground

Regards

[Steve Eddy]

Originally posted by moamps
Or using XLR F connector with bypassed 2 and 3

True. Though a wee bit more expensive than a length of wire.

No, 2 and 3 is good choice, 3 and 1 are bypassed when you connect unbalanced source to balanced input.
2 is hot, 3 is cold, 1 is ground

That presupposes that there are unbalanced inputs configured in this manner. Which may not always be the case.

The reason for shorting 2 and 3 is that when unused, they act like a pair of high impedance whip antennas which can couple RF into the circuit.

Another approach would be to make a small round plate out of copper and solder a length of 12 gauge solid core to it and insert that into pin 1, which would provide shielding over the unterminated inputs.

Only problem with that is that some gear doesn't tie the signal reference grounds to pin 1, just as some cables use a telescoping shield that's only tied to pin 1 at one end (usually intended to be used at the source end).

se

[TNT]

Freinds !

You are on different kontinents. I thougth maybe Europe and USA connects XLR differently, no?

/

[dantwomey]

Isn't the standard, male XLR connectors on the back of the amp and female on the preamp?

Regards,
Dan

[Steve Eddy]

Originally posted by TNT
You are on different kontinents. I thougth maybe Europe and USA connects XLR differently, no?

The actual standards (IEC, AES, ANSI, SMPTE, etc.) are for pin 2 positive, pin 3 negative and pin 1 ground/shield. Some comapanies don't pay any attention to the actual standards that have been established and some will wire pin 3 positive (Jeff Rowland for example). However as far as I'm aware, all use pin 1 for ground/shield so if you're going to short pins 2 and 3, it doesn't matter whether pin 2 is positive or negative.

se

[Steve Eddy]

Originally posted by dantwomey
Isn't the standard, male XLR connectors on the back of the amp and female on the preamp?

As per AES14-1992, outputs are to be male and inputs are to be female.

se