Just a quick note to shown some of the audio adapter cables I made, in case others are interested. I cut up short premade BNC jumpers and line spliced them to a 5 foot length of star-quad stage cable, chosen for it’s flexibility and freedom from interference pickup. I wanted to avoid the potential magnetic sensitivity of widely separated + and - cables.
I in-line spliced the center conductor, slid the braid back over and solder tacked it together, then I slid a 2.5" piece of 1/4" soft copper pipe over it all, flattened slightly at one end to accommodate the two coaxes. It provides additional shielding and mechanical protection. Then covered it all with shrink wrap. I built two of these with 1/4" TRS connectors and two with Neutrik NC3FM-C-B bisexual XLR connectors. They can be either male or female. Quite handy for test cables. I also bought a few BNC to RCA cables for the unbalanced hifi stuff. This should allow me to plug into almost anything.
Then I built a couple of adapters into 2x2" cast boxes from Parts Express. One is the loudspeaker impedance adapter, with a 0.1Ohm sense resistor on the low side of the line, the other is a 20 dB stereo/balanced pad for looking at the outputs of pro power amplifiers with 3 digit voltage and 4 digit power levels. Quite a few of these are self-bridged, driving both sides of the line, neither side grounded, hence the need for two-in-one. I bought the sense resistor and the 0.1% precision resistors for the pad at Newark. The 9K Ohm resistor is a 10K and a 100K in parallel. I measured the pad at 20.06 dB, so I’m very happy.
I realized I hadn’t calculated the power absorbed by the attenuator resisters. I’m changing the 20 dB Pad to 40 dB, 100K to 1KOhms. And yes, I thought about it before I actually smoked it.
JohnG, Most other connectors are bidirectional, meaning a 1/4" or an RCA can be either an input or an output. With the XLR, male is always output and female is always input, except for some very old commercial mixers. So XLR cables are always male on one end and female on the other. The Bisexual XLR makes no sense except for adapter cables with a 1/4"TRS or some other connector on the other end. For that purpose, however, I love them. I’ve used them on patch cables with a 1/4"TRS for at least 12 years and now with the BNCs and they have been perfectly reliable. I can even plug two of those patch cables together M-to-F to get a 1/4" to 1/4" cable. It’s certainly worth the extra cost to reduce the number of patch cables I need to carry flying to a job.
The purpose of the EMC connectors is to create an efficient and short VHF and UHF connection from pin-1 to the shell and/or chassis of a device. They can be quite useful if the device has an RF sensitivity. Other than cost, there is no real downside to using them, but they are a band-aid for devices with RF sensitivity, including on pin-1. If pin-1 is taken directly to the shielding enclosure, as AES-48 requires, there is not need for them. In the case of QA-403 adapters, the BNC shield/shell is connected to the metal so no pin-1 sensitivity.
