balancedsolderingxlr
I'm aware that the structure of a balanced cable is an integral part of maintaining signal quality.
If I was to solder two XLR cables together in an effort to make one longer XLR lead, what would be the potential consequences? Would the it lead to a degradation of the signal because of an interrupt to the shield and twisting of the pairs? Is there any difference to just plugging two XLR leads together?
No problem. I had to look for a picture that illustrates the technique:
You make a PCB with plated through holes on the PLCC's pads, so at a 1.27 mm pitch, and mill the four sides so that you get the half holes like in the picture. These are easily solderable on the old PLCC footprint, it's an often used technique, called castellation.
A picture of a complete board:
and another one:
or this one from a question posted 1 minute ago:
You get the idea.
You'll have to find a part which fits inside this small PCB, but given the miniaturization of the last years that may not be a problem.
edit 2012-07-15
QuestionMan suggested to make the PCB a bit larger so that the PLCC's solder pads are under it. For BGAs the solder balls are also under the IC, but that's solid solder balls, not paste, and I don't know how solder paste will behave when squeezed between two PCBs. But today I bumped into this IC package:
It's the "Staggered Dual-row MicroLeadFrame® Package (MLF)" of the ATMega8HVD, and it has pins under the IC as well. This is 3.5 mm x 6.5 mm, and weighs a lot less than the small PCB. That may be important, because thanks to the low weight capillary forces of the molten solder paste can pull the IC to its exact position. I'm not sure if that will also be the case for that PCB, and then positioning may be a problem.
You don't mention exactly what kind of resistors they are, but for "normal" through hole ones the best way is to first wrap one resistor's leg around the other resistor's leg, then wrap that resistor's leg around the first resistor's leg. So you end up with this:
The resistors hold themselves together and make it really easy to solder. It's a tough connection that won't easily break.
Depending on the kind of wire you're using you can use the same technique. It's also common to "insert" the resistor lead into the middle of the strands of stranded wire for soldering.
Best Answer
For the things one usually uses XLR for (Low impedance audio balanced lines, sometimes RS485 (DMX) and sometimes small DC power, it will likely be absolutely no issue, all this stuff is fairly robust, and it is not like anyone ever claimed that an XLR was a controlled impedance connector (Or suitable for any frequency where one would care).
On a theoretical level you have an impedance discontinuity and a break in the shield, but I can usually find something actually important to worry about.
Unless you are doing something weird, it will be fine, but for neatness I would normally fit a male/female connector pair and then just plug them together, in a mad scramble however, tape and twisting will generally work in a pinch.