SPL GoldMike Mk2 Dual Channel Microphone and Instrument Preamplifier

The SPL GoldMike Mk2 is a hybrid preamplifier consisting of a discrete transistor stage and tube stage. The hybrid design of the preamplifier combines the advantages of semiconductors (high dynamics with low distortion, low noise) with the musical qualities of tube sound (pleasant high/overtone spectrum, beautiful three-dimensionality).

The microphone class A transistor preamplifier of the SPL GoldMike Mk2 is discretely constructed from 16 individual transistors. The preamplifier features 48 V phantom power, polarity inversion, padding and a Butterworth Hi Pass filter.

The instrument input of the SPL GoldMike Mk2 is a discrete impedance converter that also operates in class A mode. The core is a low-noise field-effect transistor, which is ideally suited as an impedance converter due to its very high input resistance.

A compressor, de-esser, limiter or even a reverb unit can be switched between preamp and output. The VU shows the audio “energy” level, the clip LED warns of clipping. If optional AD converters are installed, the AD OVL LED also warns of converter overloads.

The limiter is based on diodes whose characteristic curve produces a nice, analog saturation effect and thus unobtrusively limits the signal peaks.

Its speed makes it suitable as a peak limiter, which can intercept transients in the microsecond range and can thus function very well as protection for the AD converter.

This circuit uses the pleasant sound characteristics of the coils in combination with the tube to emphasize the presence range. It is ideally suited to intensify the overtone range of voices and acoustic instruments, thus improving the ability to cut through in the mix.

The proportion of tube gain to total gain can be switched in three stages. The higher the value, the more pronounced are the saturation effects and overtones of the tube.

Transformers are used as an alternative to electronic balancing stages in the inputs and outputs. Transformers can be found in many classics of audio engineering. They make the bass and fundamental tines rounder and give it a little more punch. The high and overtone range sounds a bit silkier and more present.

We find transformers to be advantageous, especially for voices. For highest precision and speed in signal transmission (transient processing), however, electronic stages are better suited. The bottom line is that it is a question of taste and application.

In the case of SPL GoldMike Mk2, the 2161 input transformer, which is specially designed for microphone inputs, provides an additional gain of up to 14 dB (depending on the microphone), which must then be added to the scaling.

This relieves the microphone preamplifier. Since the transformer ratio passively increases the level, no noise is added. Therefore, the input transformer is more important than the output transformer in preamplifiers. However, it is only when both transformers are fitted that all positive sonic aspects are achieved – as well as increased operational reliability.