I found a way to play without activating Space Age (it works with the fork version).

1) Close Factorio.

2) Copy the following folder: Program Files (x86)\Steam\steamapps\common\Factorio\data\space-age\sound\entity\electromagnetic-plant

3) Paste it into: Program Files (x86)\Steam\steamapps\common\Factorio\data\base\sound\entity

4) Go to the mod folder: augmentor-fork_1.0.4\prototypes\entity\augmentor-sounds

5) Open the files and press Ctrl + H (Find & Replace):

Find: space-age, replace with: base, Click Replace All

The mod should now work without Space Age enabled.
You may need to repeat 2 and 3 steps every time Factorio updates

Fixed in forked version (when space age is not loaded, augmentor will use assembling machine 3 sounds).

Hello,

As of version 1.0.4, Space Age DLC is NOT mandatory (hopefully). I added your updates to this project Crethor.

Best Regards!

I'll mark my fork as deprecated, thanks for getting the original updated!