background image

The Oakley Classic VCA

This is a voltage controlled amplifier module inspired in part by a classic vintage design. The 
Oakley Classic VCA is based on the ARP4019 sub-module which was used on the wooden 
case ARP2600P semi-modular synthesiser. The design has a fully discrete core but uses op-
amps for input summing and the output drivers.

Two signal inputs are provided, one DC coupled and the other AC coupled. The former 
allows audio and low frequency signals to be processed. While the latter has a high pass filter 
so that it can be only used to process alternating frequencies. Both inputs can be used 
simultaneously and each one features an input level control.

Two control voltage (CV) inputs are provided. CV1 is linear and is provided with a standard 
attenuator pot that can control the sensitivity of the input. CV2 can be operated in either 
exponential or linear mode.

CV2 features a reversible attenuator. When the pot is turned right of its central position, the 
pot acts as a normal attenuator; increasing the sensitivity of the CV input. Left of centre, the 
pot will act in inverting mode and the CV will be tipped upside down so that increasing 
positive voltages will decrease the gain of the VCA.

When no input jack is inserted into the CV1 input, the CV1 pot becomes a gain control. This 
allows the pot to be used as a simple volume control but when set high it also allows CV2 to 
turn the VCA off.

The 5U version of the Classic VCA has two outputs. OUT A is the standard output of the 
VCA. OUT B, gives you the difference signal between the sum of the two inputs and the final 
output of the VCA. This is a sort of anti-output; when the VCA output signal goes up in level 
this output goes lower. You can use it as a ring modulator (with gain pot set to max) or in 
conjunction with OUT A as a voltage controlled pan. 

4

Содержание Classic VCA

Страница 1: ...Oakley Sound Systems 5U Oakley Modular Series Classic VCA Discrete VCA PCB Issue 1 User Manual V1 1 Tony Allgood Oakley Sound Systems CARLISLE United Kingdom...

Страница 2: ...The suggested front panel design for the 5U high MOTM format 2...

Страница 3: ...he main project webpage at http www oakleysound com 5uvca htm For general information regarding where to get parts and suggested part numbers please see our useful Parts Guide at the project webpage o...

Страница 4: ...input CV2 can be operated in either exponential or linear mode CV2 features a reversible attenuator When the pot is turned right of its central position the pot acts as a normal attenuator increasing...

Страница 5: ...y Classic VCA features two input signals IN1 DC and IN2 AC and each has its own level control In this way the Classic VCA can be used to mix or sum two signals together before they are processed by th...

Страница 6: ...increase the gain proportionately However it should be noted that the output signal level of the VCA cannot exceed 12 5V or so This upper output limit is restricted by the power supply rails of the m...

Страница 7: ...lthough screening is maintained It s worth filling the empty holes of the PWR pads with solder Power connections Synthesizers com The PWR power socket is to be fitted if you are using the module with...

Страница 8: ...the output of OUT B on your monitoring system You should hear a slight bleedthrough of the triangle wave input Now adjust LIN until the signal level decreases to its minimum You may have to turn up t...

Страница 9: ...e a comment about this user manual or have a found a mistake in it then please do let me know Last but not least can I say a big thank you to all of you who helped and inspired me Thanks especially to...

Отзывы: