I have spent 15 hours and most of my weekend simulating amps so I hope that it will at least be somewhat informative.
Disclaimer,
I'm technician (not an engineer) with background in digital electronics (aka computers), this is my first attempt at designing anything analog, and I'm pretty sure it's full of mistakes.
Nothing written in this article should be taken as fact.
On amp classes:
Class A amps output slightly more symmetrical signal than class A/B, output of A/B amps can have slight imbalance between positive and negative parts of the waveform. Can that cause a distortion in class A/B output? probably. Will it be noticeable? I don't think so. But just to be safe I'll be using class A amps.
On balanced amps;
One surprising benefit of balanced amps (well maybe not surprising to people who work with analog) is that they completely cancel out any power supply noise, I was able to get very good results with spartan, simple and noisy power regulation, improving power regulation increases accuracy of the amp but not by much. Balanced amps can perform very well with inexpensive and simple power supplies.
The biggest problem with balanced amps is the same as with A/B amps, getting them to balance properly, due to tolerance in components and even thermals, there is also a possibility that components will degrade at different rates over time trowing the amp out of balance.
Another negative of balanced amps is that they will half the impedance load, if 30 ohm load is connected to the balanced amp, amp will "see"it as 15 ohm load. This makes balanced amps a poor choice for low impedance loads.
Summary
Balanced amps eliminate all the problems with power supplies, (ground pollution and noise), that makes them very cost effective, because power supply is one of the most expensive component of an amp.
Balanced amps are a good choice for driving high impedance loads.
On active balanced ground amps;
They require complicated but not that costly driving setup for generating the signals for 3 amps.
Other than higher crosstalk (75db in my design, but I'm sure it can be improved) they perform exactly like balanced (because they are balanced) but because they have one less mono amp and power supply they are even better value, especially when one considers that they don't need balanced headphone cables. They are an brilliant idea, I take my hat off to
@Jan Meier .
On single ended stereo (common ground) amps
Single ended amps live and die by their power supply. unlike balanced, single ended amps will amplify the noise from power supply, and then there is a problem of signal ground pollution, so voltage regulation most be very good both to minimize noise and drain current from ground. In short, single ended amps require expensive power supplies, which will increase the price by significant amount when compared to similarly performing balanced amps.
However it is possible to make single ended amp that will measure better than any other balanced amp if cost is not the object.
Summary:
Single ended amp will have happier time driving low impedance load than balanced amp would.
Single ended amps have potential to be the best amp possible, if you don't mind spending
of $ on it.
Single ended mono mono (separate grounds)
The same as single ended stereo but even more expensive, to go from around 107bd of channel separation to 113, Yay what a waste of money.
And that's it, feel free to repost this and tag it properly, or to reword some stuff if you want.
