STEREO CONTACT MICROPHONE PREAMP

from GRM / TOTES FORMAT

More info, demo-video and available over here: metsn.tumblr.com

The METSÄÄN STEREO CONTACT MICROPHONE PREAMP is a based on a ‘CHARGE AMPLIFIER’ circuit, which is commonly used in industrial grade measurement devices, such as ionizing radiation meters or X-ray detectors, it is also used in digital camera sensors. Compared to regular high impedance preamps, this one has the advantage of much less hum being added to the signal, even when used with longer cables. Plus it seems to have a much wider frequency response (at least to the ones i have previously used, i have to add). More scientific explanations can be found here. Throughout my time with experimental music, i have not found a contact mic preamp that worked this good and i have build quite a few, based on different circuit designs. Using a preamp for piezo contact mics has the benefit of better frequency response, because it is very uneven with piezos, as the higher frequencies are much more prominent, than the low end and the ‘natural’ sound of them is very tinny (something which seems to not bother many).

The METSÄÄN MACHINE is housed in black a barebones PCB material sandwich, with it’s circuitry and battery in between and the solderpoints at the bottom protected by a handcut transparent acrylic layer. The design on the upper side shows a pylon occupied by protestors, who attempt to protect parts of the south american rainforest from electrification and colonialism. The bottom side shows and unfinished high rise building in Lima. On front of the device we find the two 3.5mm inputs for the left and right contact mics and on the back end, a 3.5mm stereo output and a 2.1mm DC (9-12V) Power connector [WARNING! FIRE HAZARD! Only use the DC power connector when the battery is disconnected.] A mini ON/OFF slide switch for each channel is accessible from the open sides, to be able to only power one of the preamps, when the other is not in use, preventing uneccessary battery drainage. Power per channel is indicated by UV LEDS on top of the device and the GAIN control can be adjusted on the flush top surface with the help of a fingernail or small screwdriver (so it does not accidentally change the levels during recording). Fitting contact microphones with 1m-1.5m long leads and golden colored 3.5mm stereo jacks (modified to be mono, ring is ground) are available in the 'PREAMP+2 CONTACT MICS’ option. There are also two battery options available: Alkaline and rechargable LI-PO accu, which can be charger with a micro-USB connector and a phone charger or USB output, without taking apart the device. While charging a red LED shines and fully charged is indicated by the LED turning to green. Handmade by GRM for METSÄÄN.

Size: 10 X 5 X 2.8 cm
Input: 2 x 3.5mm mono sockets
Output: 1 x 3.5mm stereo socket
Battery: 9V DC battery (Alkaline or rechargable LI-PO included)
External PSU: 2.1mm DC (center pin positive) 9-12V

More info, demo-video and available over here: metsn.tumblr.com