• Just click on the image below for a PDF of the project details •
Alternatively, you may prefer to build a mic using a PCB rather than stripboard...
Hobby microphone builder Mic Scharf has developed a PCB for this version of the project,
which you can obtain from:
HERE
The schematic above shows the audio circuitry required to interface a conventional (non-electret) large diameter condenser microphone capsule - 'LDC' - to a microphone pre-amp fitted wih 48v phantom power.
The circuitry includes an impedance converter - utilising an OPA1641 op-amp - and appropriate output coupling capacitors and resistors.
This very simple interface uses the single op-amp as a unity gain non inverting buffer amplifier, powered by 48v phantom power from the mic pre-amp.
The circuit has a low quiescent current requirement - around 1.8mA - has very low distortion, and is only marginally noisier than equivalent impedance converters which use discrete FET inputs.
The stripboard layouts are designed to fit into that common 'donor body' - the BM800/NW700 - but also work well in Neumann 'style' clone bodies - from WGTCenter, for example... (Click on the image in the header at the top of the page to see more details).
In this 'LDC' configuration, a separate stripboard is also required to generate the external capsule DC polarisation voltage. The schematic for that circuit is shown below.
• Just click on the image below for a PDF of the project details •
As suggested, just click on either image to download a PDF which contains the schematics, circuit descriptions, and stripboard layouts for all the circuitry required.
Alternatively, you may prefer to build a VM using a PCB rather than stripboard...
Hobby microphone builder Mic Scharf has developed a PCB for this version of the project,
which you can obtain from:
HERE
• A further option you might like to consider •
It is possible to use an LDC capsule in a simpler configuration, without fitting a separate voltage multiplier for capsule polarisation.
The sensitivity will be slightly reduced - about 2dB less than the same capsule biased with 60v.
It is also only really suitable for use with capacitively coupled mic preamps that do not use an input transformer.... The asymmetric DC loading of each leg of the phantom power makes this version an unsuitable option for transformer coupled preamplifiers.
The circuit shown below uses one side of the 48v phantom power to supply c.24v to the op-amp circuitry, and the other - unloaded - leg to supply 48v as the polarisation voltage.
A simpler construction that can work pretty well - especially with higher sensitivity capsules.
• Just click on the image below for a PDF of the project details •
