Inside the Neutrik XLR modular adapters we have a Magnetec 073 Nanoperm core. This core is wound as inductor and connected in parallel to signal ie to pins 2 and 3. This is to low cut (or high pass) as needed to compensate for the unnatural increase in bass at various mic distances. (A directional mic at 1in as we can see on most microphone frequency response charts starts to rise in sensitivity below even 1KHz!)
Specifications of Pleiades inline filter color code.
Black : deep deep bass. ?
Red : only the deep bass is cut. 700mH
Orange : bass cut. 300mH
Yellow : bass and mid bass cut. 140mH
Yellow-Green : natural. 70mH
Green : natural and bright. 47mH
Blue. : bright. 25mH
Violet : very bright. 14mH
White. : extremely bright. eg 7mH
Inductance values are indicative. A white filter can make a ribbon mic sound amazing at 1in while electromagnetic damping from the Pleiades filter protects to ribbon from blasts of air pops etc. for a Grampian ribbon microphone 3 mH gives very interesting and natural results. (The high frequency mic content shines too.). For best results this is implemented as a Pleiades 1:4 step up transformer to make up gain, the 073 core fitted inside the XLR adaptor.
Similar codes can be used for Capacitor in parallel filters to cut high frequencies and give presence.
Reference : (Fletcher Munson curves and voice effort curves as explained in the Hollywood paper in earlier euroelectron posts):
Sound Picture Recording and Reproducing Characteristics - D. P. Loye and K. F. Morgan
Journal of Society of Motion Pictures Engineers
(Presented at the 1930 Spring Meeting at Hollywood, California)
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