This listing is for a HeadRoom Portable Micro amp, an American-made headphone amp with built-in crossfeed circuit (to fix the "blob in the middle of your head" imaging headphones often provide) and three levels of gain. S/N 1012 with a build date of 2/20/08. Here is a review of the PMA.



There are two flaws on this amp. There is a little bit of abrasion on one of the rubber corners, and a spot on the finish of the metal body nearby. These flaws are pictured below:



This Portable Micro Amp is the previous generation. (The above-linked review is of the generation I'm selling.) The differences between the previous PMA and and the current generation are as follows:
(1) New one has built-in Li-ion battery; this one uses twin 9V cells (not included)
(2) The new one has only one amp module. The old one offered a "Home" upgrade module, which is what's in this amp. See below.
(3) This one has a big honking linear power-supply that weighs a more than the amp. The new one cannot run on its wall-wart, which is only used to charge the Li-ion battery. (I own both the old and new one; I'm keeping the new one because it's a lot more portable, with the smaller wall-wart.) Here's a picture of the amp and PS together, with a magazine for scale:

And another:


As mentioned above, there was a stock module and an upgraded module. This amp has the upgraded "Home" amp module (green board), as opposed to the "Portable" module (red board).



Here's what the manual says about the module:
Quote Originally Posted by HeadRoom Portable Micro Manual
he Micro Amp can be upgraded to the Desktop Module. This little green module contains all the electronics for a Desktop Headphone Amp. There are two 4-layer circuit boards (one each for the left and right channel) that are con- nected with a series of header pins used to solder the module to the main cir- cuit board. This module is designed to sound great but must provide at least 20 hours of play time on four D-cells in the Desktop Portable Amp. It uses Burr- Brown (Okay, now TI) 2134 op-amps for the internal input buffer, crossfeed, summer, and power amp voltage gain stage. The output current amplifier is our version of the highly regarded Diamond Buffer discrete transistor design by Walt Jung. Resistors are 1% metal thin film, and caps in the signal chain are polyphenylenesulfide (poly film); these are MUCH higher quality parts than you’d ever find in a typical consumer electronics product.
No longer have original packaging, but will be shipped securely.

Price: $250 shipped CONUS.

Selling because it's kind of silly to have 3 headphone amps and this one currently gets the least use of my three.