What needed is flat frequency response not from mic to loudspeaker (which can sound very bass, mid bass and treble heavy) but from singer's vocal chords to listener's brain [Lowe, Morgan].
A suitable adjustable setup could be as follows:
producer's brain - singer's vocal chords - mic at a suitable distance - passive variable slope low cut filter - small turn ratio step up transformer or input transformer to a one electron tube or JFET active mic booster - mic preamp - recorder - monitoring headphones or loudspeaker- producer's brain or listener's brain
(Making sure the following preamp is not transiently overloaded or s problems will occur).
The variable slope passive high pass filter can be a box with switchable inductors which are connected in series with a variable resistor or potentiometer. The L R in series combination is then connected across pins 2,3 (microphone's output).
Indicative values of inductance can be 10mH, 20mH, 40mH etc.
A variable resistor of 1KΩ should be adequate.
Once suitable favorite values of L, R are found, a neat and compact filter can be made inside a Neutrik XLR modules barrel, see Pleiades (R,L) filters inside XLR female to male adaptor made from Neutrik modules bought from Mouser.
The passive step up transformer can be a 1:2 or 1:3 turn ratio.
The active JFET mic booster amp can be a Pleiades K177, see schematic.
The active electron tube booster amp can be a Pleiades V6 which is powered by a single battery, see schematic including use of CV2269 electrometer tube requiring only 1.2V for both filament and plate.
An active bipolar transistor booster can be a Pleiades BC109, using the BC109 bipolar transistor as used on the EMI TG 12345 mixer.
An added advantage of above setup is very low noise ie high signal to noise ratio, world class or possibly state of the art.
Reference:
Sound Picture Recording and Reproducing Characteristics - D. P. Lowe, K. F. Morgan - Journal of the Society of Motion Picture Engineers
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