While I wait for my QA403 to arrive, I’m sorting out what cables to build and would like some advice to test balanced and unbalanced components. All less than 2m length.
For unbalanced, are adapters fine (RCA to BNC and TS to BNC), or is it materially better to build cables without using adapters?
For the unbalanced cable, is it better to convert at the DUT and run a standard BNC test cable to the analyzer? Or run an audio cable from the DUT and convert to BNC at the analyzer?
For balanced, seems like you would want to use a balanced audio cable from the DUT and then split to 2 BNCs near the analyzer rather than split near the DUT like I’ve seen on a premade XLR to BNC cable.
Hi. I use BNC-BNC cables like the ones in the picture that can be found in various lengths and are cheap (Aliexpress) and, as appropriate, various adapters. I have never had any kind of problem with the use of these cables; certainly one must observe certain rules in wiring to make the various measurements correctly.
I started out using nice RCA to RCA cables ($6 for a 4’ length from Amazon) and BNC to RCA adapters to connect them to the QA40x. I came across some nice BNC-BNC RG59U cables, about 6’ long at a surplus store, and cut them in half and soldered a nice gold plated RCA connector to the cut end. These work well, though there is not going to be any measurable difference between them and the RCA cables with an adapter on them- just don’t have to worry about misplacing adapters. I came across these on Amazon, and will get a pair at some point- they seem to be decent, though not gold plated, and not the right angle ones which are pictured:
95% of what I test is unbalanced gear, but decided to make my own set of balanced input and output cables:
Thanks a lot. On those custom cables, I thought it would be preferred to use a single balanced cable for most of the length and split into separate cables maybe an inch before the BNCs. That way, both positive and negative sides stay together and within the same shield and have the same noise which can be removed by the differential input.
You are probably correct, but that would require a different cable (conductor-wise) than what I was given, I suppose. For my purposes- measuring namely older home audio gear- it does seem to work. The XLR adapter seen in the recent post could also be a good way to go as well, depending on what you are planning to test the most (XLR or RCA inputs/outputs). I was able to measure this system noise on a Krell Preamp using these cables and a QA403:
