This is the Eden Microphone Preamplifier from Expat Audio.
It comes are a completed module that only needs to be hooked up.
In fact, all it needs is power, input, output and a gain setting resistor.
It's assembled and tested here in Texas, USA.
It has flat THD+N at 30dB of gain as low as 0.003%, all the way to 30kHz (higher I believe - but the audio test kit isn't quite up to it).
At 60dB of gain (max setting) the THD+N is still very impressive at 0.04%. (again, flat all the way!)
Users Guide: Available for download here: Expat Audio Eden Mic Pre PG2.0 Users Guide
Floorplan: (used for drilling the holes in the right places in your case) available for download here: Eden System Footprints
4ch 1U Builders Presentation: Download PDF
Kit list for Mouser & Amazon: Download Excel File
Front Panel Express File with template for 3 button controller: Download FPD File
Acoustic Guitars really do well with an Eden!
Rather nice vocal too I think.
"My initial impression so far is that these really are most excellent preamps for when you need some more inputs. (and who among us couldn't use a few more inputs!?!) -For the price they're incredible, and they fit comfortably into tiny spaces. -A single-gang pot (readily available) or -alternatively- a multi-position switch and resistors (for stepped-gain applications) is all you need other than an input connector, an output connector and power.
Simple, VERY affordable, but incredibly impressive figures. Listening impressions are "super-clear"."
"So far I am VERY impressed. It has oodles of clean gain - in fact +60dB in total.. I did a couple of quick tests with some ribbon mics and their is no audible hum or hiss even at full gain. The sound is rather neutral and uncoloured in character - I'll try to post a frequency sweep next week but I expect it to be flat. It is a good option for ribbons where clean quiet gain is essential. It will certainly get used in our studio." - User Zebra50 on Groupdiy: http://www.groupdiy.com/index.php?topic=51531