The ES02 combines two functions in to a single module:-
- Preamplifier - for scaling external audio signals to EuroSynth audio levels
- Envelope Detector - also known as an Envelope Follower and which extract amplitude information from complex audio waveforms. The resulting dc voltage often drives non-linear stages, such as voltage-controlled amplifiers or filters.
The Serge Preamp and (new) Envelope Detector provide an exceptionally
responsive link between external audio signals and the EuroSerge
synthesizer modules. The key to this responsivity comes from the fact
that the detector was designed to respond to the POWER rather than to
the AMPLITUDE of a sound. Human perception of loudness is proportional
to the POWER content of a wave, rather than to its AMPLITUDE.
Detecting the AMPLITUDE of a signal produces an inaccurate envelope,
sometimes too soft, and most of the time too loud. The ES02
detector is exceptionally accurate and outputs
a control voltage envelope that is directly proportional to the
perceived loudness of an input signal. It operates over a very wide
dynamic range, in excess of 70db, (or the difference between a
whisper and a subway train at 15 feet!). The output is accurately
log-linear at 12db/V, a taper which mates perfectly with the control characteristics of the ES78 VCA. Thus it is possible, for
example, to control the loudness of a synthesizer sound by the sound
envelope of a locomotive, a dog barking, or a voice going from a
whisper to a shout. The effect is especially remarkable because of
the accuracy of response: the whisper is really a whisper, and the shout a shout.
The Preamplifier accepts a wide variety of inputs:-
Lo-Z In - accepts outputs from high-output microphones in the range 200 to 1000 Ohms (such as most electret microphones), with a sensitivity suited for close-miking applications such as instrument or voice pick-up.
Hi-Z In - accepts outputs from transducers such as guitar pickups and contact microphones. It is also suited for amplifying low-level signals from tape machines, tuners etc.
On the 3.5mm variant the [OUT] output of the preamplifier is normalised to the [IN] input of the Detector allowing access to both output signals without patching.
Sensitivity for various microphones and audio sources can be adjusted over a very wide range using the Preamp's [GAIN] control (but note, it will not cut the gain to zero).