Rumours of a CD Revival...

On ABX - I have found Butterworth to be one of the level headed people writing on audio on the net, and here is a link to a relevant article by him:

https://hometheaterreview.com/why-do-audiophiles-fear-abx-testing/

Unfortunately, he has not expressed any views on any conclusion he may have reached, but one thing that he also leaves unexplained is how any ABX box does level matching of signal voltages necessary to achieve the necessary identical sound levels.

He does say this though: The problem for audiophiles is, ABX testing has, to date, rarely revealed differences in sound among audio electronics components.

Also, even a much simpler A/B switcher than the ABX box in the link can suffice for amateur tests IF the level matching can be done well enough. It ought to be easy to build or get such a simple switcher that does not add its own issues to the test.

Kumar,

Typically, there will be an input attenuator as part of the ABX box. This will be used while testing devices  that may not have input or output attenuators. For a power amplifier that has no input attenuator, the test will require two trips through the ABX box-- before and after the device(s) under test.

If you are a fan of low output impedance power amplifiers, fat wire, and high damping factor, power amplifiers with output impedance in the range of 0.00x Ohms are common. If you are not familiar with the terms, they are not very related to the recommended load impedance for the amplifier. Relay contact resistance is commonly in the 0.1 Ohm range. In an otherwise low impedance speaker wiring setup the relay contact resistance becomes a factor. It is common for power amplifiers to include a relay that keeps the amplifier disconnected from the speakers while the amplifier powers up and powers down. This protects the speakers from difficult to control transients. Very high quality amplifiers tend to omit this relay -- claiming that it injures sound quality. If this is true, why would one want to insert a relay in the test setup?

That is why I would just use a simple switch and do a A/B test and get most of the outcome reliability that adding the X will deliver but with all the complications of the ABX box. The unsolved problem will still be getting the same sound levels for A and B, and that needs to be quite precisely achieved to get a reliable result in both cases.

ABX protocol is better than AB no doubt, but for this kind of testing to satisfy just oneself, I believe that AB is adequate.