Owners Manual
7
Operating the MPA-201
Using the variable IMPEDANCE control
In order to properly reproduce the correct frequency response of
any given microphone, the output of the mic and the input of the
mic pre must have the correct impedance match. e general rule of
thumb (and correct electronic design) is that the input impedance of
the pre amp should be 5 times greater than the microphone’s output
impedance. Most modern microphones have an output impedance of
200–250 ohms, so an input impedance of 1200 ohms, which is typical
on many pres, will match correctly. However, there are many wonderful
vintage microphones and some new ones with, especially ribbon mics
that have a lower impedance of around 50 ohms. e MPA-201 has a
variable impedance control to change the input impedance from 1200
to600or300ohmsallowingyoutoconnectavarietyofmicrophones
correctly.Ohbytheway,….Sometimesyoucangetanawesomeresult
byusingthe“wrong”setting.Forexample,let’ssayyouhaveanice
condenser microphone with a sweet high-end airy lift with an output
impedance of 200 ohms, but you want a slightly darker sound, set the
inputimpedanceto600oreven300ohms.Asalways,experimentation
can be the best teacher, so plug in and listen.
Using the HIGH PASS FILTER
Any good mic pre should have, at least, a basic high pass filter in
order to reduce low frequencies you do not want, or that are just
not produced from the signal source you are miking. A high pass
filter, (sometimes called a low cut filter), will allow signals above
a determined frequency to pass, while the frequency below that
determined frequency will be attenuated. Using the High Pass can
really help clean up, and many times tighten up the bottom end of your
mix, or help eliminate low frequency rumble on stage in a live sound
application. e MPA-201 has a variable high pass filter from 18 to
350Hzallowingyoutoadjustthelowfrequencycutopoint.eMPA-
201’s variable High Pass Frequency control lets you tailor the low cut
for the sound source you are recording. For example, you may want to
setthehighpassto100Hz,whenrecordingavocal,oruseasettingof
300Hzwhenmikingamandolin.