This review has been entirely rewritten. Initially it was very uncomplimentary because of the horrendous ground loop hum and sensitivity of the footswitches that led to all sorts of crackling.
It turns out that it was faulty, because the replacement worked just fine. No hum, no buzz, no crackle, no adverse effects whatsoever. Just clean and noiseless switching. Great! Or at least, that is what I thought.
To save time in case the second one turned out to be just as noisy, I also ordered FIVE other ABY foot-switchers, hoping that at least ONE of them would work! This enabled me to run some side-by-side tests of each one of them to determine their respective pros & cons.
The HUGE advantage the Fender ABY box holds over all the more esoteric and more expensive models is its passive operation. No need for an annoying little 9v PSU & cable, just a 9v battery to power the status LED's. I anticipate that, running just those two LED's, the battery will be good for many years !!
BUT, BUT, BUT ... the tests revealed that the Fender is a tone sucker. And not just a little bit. It sucks all the presence and punch out. Great for a jazz lounge ... maybe.
FYI, I did take the opportunity to try the other units but his particular review must deal only with the Fender ABY box. The other units listed below are reviewed on their respective pages:
1. Lead Foot ABY
2. Old Blood Noise Endeavors AB/Y Switcher
3. Radial Engineering Tonebone Twin City ABY
4. Morley ABY PRO Selector
If you want my conclusion, the ONLY one worth considering out of this selection, if you want clean, transparent, colourless operation with no ground loop issues or snap, crackle and pop, is the Morley. But you will have to dig deep, it ain't cheap.
Finally, thank you Thomann for your excellent returns policy that has permitted me to conduct a meaningful comparison after the first unit proved faulty.