Amplifier and Speaker A/B switcher

to compare speakers from one amp, or switch which speakers are playing: I used an older version of this Niles unit, individual volume control for each set of speakers

https://www.crutchfield.com/p_190SSVC4/Niles-SSVC-4.html

smaller 2 speaker set unit

https://www.crutchfield.com/p_190SSVC2/Niles-SSVC-2.html

I used to demo 3 amps: Fisher 30 wpc Tube Mono Blocks 80az; Fisher 35 wpc 500C stereo tube receiver; McIntosh 250 wpc SS MC 2250 stereo amp.

Start with some hooks behind each speaker at 'reachable height'

Cable from each speaker with female banana long enough to hang on a hook behind each speaker.

3 sets of speaker wires (1 set/amp). I wrapped each set of speaker wires with different color electrical tape at each end to know which amp.

With male banana plugs that have tightening pins (also hanging from 'reachable hooks'. They insert loose, then tighten the pin. Tightening because frequent in/out not good for regular banana plugs

https://www.parts-express.com/Stacking-Banana-Plug-with-Dual-Set-Screws-Poly-Carbonate-Sh-091-3608?quantity=1

Lastly, you need to make A,B,C pencil marks on your volume control so they are 'matched' volume when comparing.

Same thing comparing cartridges, pencil marks to match volume.