MUSICAL APPLICATION :
The 902 Voltage-Controlled Amplifier is used in any circumstances where variable gain is desired for gating or modulating AC or DC voltage sources. Articulation of a tone or sound, utilizing oscillators, controllers, envelope generators and the VCA is the basic traditional patch around which most performance oriented synthesizers are based. In this normal routing situation, the audio signal is sent through the signal inputs and outputs of the VCA, the envelope generator voltage is patched to the control input of the module, and the Control mode switch set on exponential.
In addition to DC control voltage, the VCA can be controlled by varying voltages (AC) from sources like the 901 or 921 Oscillators. Slowly varying control voltages (2-9 Hz) can create tremolo or echo like effects upon an audio signal. Audio control frequencies create sidebands with often clangorous effects, usefull for a variety of audio timbres and percussive sounds.
The inverting outputs of the VCA can be useful for spatial modulation, signal inverting of control voltages, controlling two oscillators in contrary motion with a single control signal, and various amplitude sampling arrangements.
ELECTRONIC SPECIFICATION :
Signal Input frequency Response : DC to 50kHz
Control Input frequency Response : DC to 50kHz
Signal Imput Impedance : 10KΩ nominal
Equivalent input Noise(20-22kHz) : -82dBm
Control input Impedance : 100KΩ nominal
Ouptut Impedande : 680Ω nominal
Power : +12V@50mA / -12V@40mA
FUNCTION DESCRIPTION :
The 902 Voltage Controlled Amplifier is a differential input and output circuit which gives an overall voltage gain of 2 (6 dB) when manual control potentiometer is at maximum, or when a control voltage of 6 Volts is applied to the control input. Two modes of gain response are available : Linear and exponential.