Measuring Microphone

Here are a few pics of my measuring microphone setup.  It uses the common Panasonic WM-60 electret insert in the end of a brass tube, and a preamp design by Eric Wallin.  The mic capsule was calibrated by ME Sound, who are unfortunately no longer in business.

The microphone wand uses a brass tube 1/4" ID and about 12" long.  The mic capsule is a press fit into the end (photo above right), and the other end is soldered to the cover of an RCA plug (photo at right).  An inline socket could be used here if it is desired to use a standard connecting lead.

The Wallin preamp (preamp1) was built into an old Fender microphone casing.  The original ball grill was replaced with the battery compartment and output jack (which switches the battery on) as shown above right.  An RCA socket was fitted to the XLR end for connection to the wand as shown above left.  The original on/off switch was utilised for gain switching, and the overload LED can be seen between this switch and the battery cover.  To get all this to fit in the casing, I used two dual opamps (TL072) instead of the single quad opamp in Eric's original design.

View of the microphone ready for measuring.  The use of the old mic casing for the preamp means a standard mic holder and stand can be used.