Anandamaya means not a derivative from Bliss BUT Abundance of Bliss

I.1.13

विकारश्ब्दान्नेति चेत् न प्राचुर्यात् | 

vikArashbdAnneti chet na prAchuryAt

Anandamaya does not mean a modication or transformation or product of bliss but rather refers to Abundance of bliss as denoted by the suffix maya

Vikarashbdat(विकारश्ब्दात्): From the word "Anandamaya" with the suffix "Mayat" denoting modification; Na(न): is not; iti(इति): this, thus; Chet(चेत्): if; Na(न): Not so; Prachuryat(प्राचुर्यात्): because of abundance;

Commentary:

The word maya cannot mean modification because we cannot predicate such a modification to Brahman(God) who is changeless. Here Maya means abundance. Hence the word Anandamaya denotes the Brahman/Highest Self. 

Anandamaya does not mean the absence of pain or sorrow. It is a positive attribute of Brahman and not a mere negation of pain. Anandamaya means he whose essential nature is bliss. For e.g. Sun, whose essential nature is light is called Jyotirmaya. 

Background

Introduction - part1, part2, part3, part4

Sutra - I.1.1, I.1.2, I.1.3, I.1.4, I.1.5, I.1.6, I.1.7, I.1.8, I.1.9, I.1.10, I.1.11, I.1.12