That was the standard and had the very significant advantage of simplicity of the signal path. More recent marketing efforts promote balanced connectivity. Balanced topology imposes twice the circuitry into the signal path. Abandoning single-ended is not an advancement.@perazzi28 This statement is false. The best way to implement fully balanced circuitry without transformers is to go fully differential. This does not require 'twice the circuitry'. Add about 50% and you will be closer. And there are advantages: for example for a given stage of gain, you can have up to nearly 6dB less noise, and distortion will be reduced as well. In addition the circuit is far less sensitive to power supply noise and of course can reject noise at its input caused by hum fields and like impinged on the interconnect cable.
The cost of the parts does not seem to be a consideration; there are a good number of balanced line preamps available that are less expensive than single-ended preamp with which they easily compete.
Finally the balanced line system was created with two purposes; the first to eliminate ground loops, the second to eliminate the artifact of interconnect cables (if you've ever heard a difference between interconnect cables you know what I'm talking about). To make this happen there is a standard (which does not exist for single-ended connections so its a bit of the wild west 70 years on since hifi was created). It is known as AES48. FWIW, most 'high end' balanced audio products don't support the standard, which means that not all the benefits of going balanced will be realized with such equipment. If you've based your comments on hearing such gear, its no surprise you've come to your conclusion. But once you've heard balanced line executed correctly there's no going back. The improvement isn't subtle.
