www.audiosciencereview.com
While I would agree there's no guarantee, and that it's possible to have an XLR connector with no differential amplifier—this is clearly deceptive. There should also be some indication of wiring on the device to avoid the pin 1 problem and some spec on CMRR.This thread provides a broad overview of various differential and single-ended configurations. What it does not do is fully address the ground loop problem and how common-mode rejection from ground or shield induced noise is impacted by the various configurations except by inference. In general an XLR connector does not guarantee true differential operation and immunity from ground loops, even with pro gear. I, and many, have fought ground loops and other common-mode noise problems in professional audio systems running only XLR connections everywhere.
Differential, Single-Ended, Balanced, Unbalanced, and all that jazz...
I posted this picture over on WBF in the middle of a long semi-fruitful discussion on the benefits and drawbacks of differential operation. Ken Newton suggested sticking with the accepted technical definitions and distinction among differential vs. single-ended and balanced vs. unbalanced that I...
Haven't encountered that issue myself. It's actually been much easier to pick devices since the field is narrower when requiring XLR. The only time I've blown a budget is when I've insisted on getting the "best" of something.
Low cost isolation transformers tend to not have good low frequency specs and the sub is used on a lfe channel, but it is a good first option.
It is if correctly implemented by all devices. Unfortunately there are still devices with 'Pin 1 problems' despite AES48 having been around for years, and well documented ways to test equipment for this problem before releasing it to market. Ground lift switches are there because of this sad reality.
Read this (in case you do not stick with simple but wrong advices):
Used to believe the same - unfortunately this statement seems to be wrong, details were discussed in this thread:
www.audiosciencereview.com
Did you get one of the isolation transformers that were mentioned in this thread? If so, did it work? If not, I suggest you try that route. I'm pretty sure an isolation transformer will get rid of your ground loop.
I have seen many quasi-differential inputs and drivers in the consumer and professional product categories (mainly mixers and some active monitors). Some weren't really even "quasi" e.g. just grounded or floated the out of phase path, and most did not state the topology, though you are right that CMRR specs (if provided) are a clue. Not sure I would say it's deceptive, though for the grounded/floating connections I'd agree, but could be misleading if you do not know about it and run into problems. It is not just a differential amplifier issue, or coupling transformer issue, but also an issue with signal return/shield connection and common-mode isolation that was sometimes the problem. I think debating cause and effect is outside the scope of this thread.
True; I usually recommend a cheap (~$50 USD) one from Amazon for subs that has decent LF response, but the OP is in Au so I didn't link it. The Extech Hum-X wall isolator is also an option here in the USA but I am not sure would work in Au.
I'm not sure what your point is supposed to be here. That paper is about proper differential signaling and shielding. Using an XLR connection neither guarantees nor is required for such.
