AB testing USB DAC dongles

[Kevbaz]

I have started to build a collection of USB dongle DACs and USB DACs which I would like to blind AB test with my son switching the headphones between them without me knowing which is which.
This is for fun but also to help me understand objective vs subjective by building my own experience.

My question is can unplugging and plugging in the headphone from Dongle DACs like the below damage them. I can’t see anything around short c.c.t protection in the specs for them. Or am I worrying about something that’s not an issue.

Dragonfly Cobalt
Hidizs S8
Hidizs S9pro
Maybe also Chord Mojo

Also any advice on what is easiest way to level match them or do you just use your ears,
Cheers
Kevin

 

[DVDdoug]

Also any advice on what is easiest way to level match them or do you just use your ears,

I think the trickiest thing will be keeping a constant level when you switch back-and-forth.

Ideally, you should use a multimeter and measure the voltage with a test tone, with the headphones connected. So, you need some kind of Y-splitter to connect the meter and headphones at the same time because the headphone load might change the voltage. (Audacity can generate test tones.)

Or if you have a soundcard with a line-input you can plug the headphone-output to line-in, and use the "VU" meter in Audacity to check the levels. (A multimeter will give you more resolution.)

My question is can unplugging and plugging in the headphone from Dongle DACs like the below damage them.

What is a blind ABX test? To make it truly random your son should flip a coin and it's probably easier if he does the coin-flips and determines the sequence in advance. You should also decide on the number of trial in advance. Note that an ABX test ONLY determines if you can reliably hear a difference. It doesn't tell you which is better or what the differences are.

If you can clearly hear a difference you no-longer need random testing but you might still want to keep the testing blind before you decide which one you prefer.

Also if you hear a difference, try to think in scientific/engineering terms (noise, frequency response, distortion) rather than "audiophile" terms/concepts like "detail' or anything like that...