U87 Build guide (2019 version)
The U87 microphone is well known all over the world. It is considered a high-quality studio
microphone, that can be used in almost all recording situations.
The U87 we present here is an
exact
copy of the original design.
The only thing that is changed, is the DC/DC converter. The reason for this is, that the
original DC/DC converter uses a ferroxcube core transformer, that is hard to obtain or
produce. The alternative DC/DC converter does
exactly
the same (that is: ge60 and
-60 volts for the polarisation of the capsule), but uses different components.
But since the DC converter isn’t in the audio path, there is nothing to worry about.
The microphone uses three small printed circuit boards (PCBs), one for the DC/DC
converter, one for the audio circuit and a small one for the switches.
Before you start:
It is
very
important that you use the correct components. All resistors are color coded, so you
can find the right value by looking them up in the chart below:
But, double check the values with an ohm meter! Sometimes orange looks like red, and
68000 ohms is a different value than 6800 ohms!
But as long as you follow the instructions, there isn’t very much that can go wrong.
We will build the separate PCBs step by step. We will start with the DC/DC converter PCB.
First, we place and solder the two inductors, 68µH and 150µH.
The inductors look like a resistor but are a little bit bigger.
The 68µH inductor has the color code blue/grey/black, the 150µH inductor is marked
brown/green/brown. It is important that the two inductors are close together on the PCB, they
should touch each other.
