This measurement microphone is very
much inspired / copied from Linkwitz Lab's DIY construction (se
The microphone used is the Panasonic
MCE-2000 which can be obtained from
||2kΩ, RL: 2.2kΩ
|Admiss. ambient temp.
||1.5-10V DC current /0.5mA
An electret microphone needs a bias
voltage to work. This is actually normally provided by the PC sound card, and
you can therefore normally just connect the microphone directly to the PC. But
in order to use long cords, e.g. if your measurement PC is not located near
where you perform the measurement (I use a stationary PC located in a room
The circuit is very simple. The
microphone is connected to JP2 where R1 provides a +4,5 V bias. The bias is kept
away from the amp by C2, which together with R3 provides a high pass filter. U1A
is the amp, here with a gain of 2, which is easily changed by changing R4 to a
higher value (gain = 1+R4/R5). As I'm using a single 9 V battery U1B provides a
virtual ground. As it is a single supply construction C3 is needed to remove the
bias on the output. JP1 is the battery connection, and JP1 is the amp output.
I'have tried using TL072, which works just fine, but I will try out other
op-amps as well to se whether there is any improvements in performance (which I
really doubt for these kind of measurements.)
Update September 17: In order to
use this microphone with different programs (like ETFand ARTA) that requires the
mic to be connected to the line input through a pre-amp, I have changed the gain
to 23x or 27 db by using R4=330k and R5=15k. Now it goes directly into the line
input. 27 db is a bit to the low side, but seems good enough for this purpose.
There is no audiable noise problems at all.
The PCB is double sided to provide a
ground plane, but this is really not necessary, in such a small construction. I
have had the PCBs produced by
provides a really great and fast service, and the cheapest solution for making
professional prototype PCBs. Highly recommendable.
I have a few PCBs in spare, that you
can have for 4 US$ a pcs. + shipping (normal cheap postal service). Contact me
on e-mail if you are interested.
Here is a picture
of a populated PCB
Just to try it all out, I have mounted
the mic on a pen using Gaffa tape and mounted it on an old lamp stand. I'm
working on a more permanent solution :-)
The finished casing
... and the aluminium pipe where the
microphone is mounted at the tip
The smal capsual mounted at the tip of the