I recently tried building an ABY box with isolating transformers on the outputs, and I just could not get it to work (well, everything worked, apart from the constant buzzing that I could not get rid of, which was incredibly frustrating).
I then pulled out most of the components, just leaving the switching and LED indicators, which worked without any buzzing; however, I did want a phase switch, which brings me to this.
It’s a simple opamp buffer running on a dual rail supply for ample headroom, and it also has an inverter to flip the phase of channel B if required, or maybe you just like the sound of out-of-phase amps.
Any dual opamp can be used, and if you only have 7660 instead of 1054 for power inversion, just remove the cut between pins 1 & 8. If you feel uncomfortable about the lack of a capacitor on the buffer’s input, there’s room to add one – I’m sure you can see where and how.
If you have two amps and no switcher, you’re really missing out – buy or build one.
A/B/Y AMP SWITCH BOX – VERO LAYOUT
