I understand that my new cash balance plan creates a trust. Is it an Irrevocable or Revocable trust?

Neither of the terms Irrevocable or Revocable trust apply to your retirement plan, because those terms are for personal trusts. The 401(k) and cash balance plans are set up through your entity, and these plans do have some similar qualities to both the irrevocable or revocable trust functions. However, your plans can’t actually be labeled as either.