The Portaphile MICRO is a smaller version of the original 627 portable headphone amplifier. The MICRO measures just 3.49″L by 2.6″W by 0.71″H excluding the knob which adds another .62″ to the length. Each panel is milled out of a quarter inch solid block of aluminum and takes between 3 to 4 hours per panel. The milling work in each amplifier alone is about 6 to 7 hours. The panels are then shipped out to get Type 3 annodized in black. All of the lettering is milled and the rest of the case has a powder coated finish.
As for the inside, a choice of two opamps (MUSES01 or OPA627s) is presented and is followed by a total of 6 Burr Brown Buffers (2 per channel). The MUSES01 are a bit brighter than the ultra smooth OPA627s. OPA627s are standard, MUSES01 is an add-on option. Both amplifier share a very close sound signature, smooth effortless sound.