Stacking Properties

Much like typical D&D rules, you normally can’t use multiple copies of the same item as Resonance or Tuning materials (except for consumables), with the exception of consumable items (as tuning consumables just adds another charge of that consumable to your echo).
That said, just like typical D&D rules, if you have the same benefit coming from different sources, they can stack. The only exception to this are Core Augments and any materials' own overlapping augments, as noted in Creating an Echo.