Doing this quickly is the key before you forget what the other sounded like compared to the previous test.
So I decided to build a quick and dirty passive universal A To B test switch PCB......................
The PCB Layout (The Capacitors are optional)
It is universal in the fact its bi-directional and takes either phono (RCA) or Jack.This comes in handy when testing audio at line level or output level in the case of headphones.There are provisions for input/output capacitors which comes in handy when testing audio differences between using input capacitors and when none are used.
Various scenarios and test uses:
1) Switching between 2 inputs such as iPod and PC
2) 2 different sources (eg comparing 2 different headphone amplifiers) with a single pair of headphones
3) Switching compare between 2 different types of headphones quickly for audio differences
4) Input capacitor testing (one type versus another of one type verses none)
5) More stuff than I can think off at the moment :)
Eagle files inc PDFs are available in the files section
The Switch used is a DPDT (Dual Pole Dual Throw) ON-ON configuration meaning it swaps "ON" state between one side and the other switching 2 contacts at once (Left&Right channels).
As the switch is only dual pole the ground is not broken during switching a better choice would have been a rotary 3 pole (Switches Left,Right & Ground outputs) 2 conductor ( 2 different sources/inputs) make before break multiway selector switch but I did not have one in my parts bin.
I think it turned out well for what it is and its a pretty useful tool to have lying around in the lab.