efm-vca5 preview

[tomg]

Here is a preview of the dual-vca5. The vca5 should probably be called a 
"vca construction set". There are 2 vcas, a adsr, a lfo and mix/shifter/inv
components. Comes with it's own on-board power supply (natch). 

The vcas are diff-transistor type. After looking and listening to my vca
collection it seemed the obvious choice. Most ota based types drag the
signal very close to ground before amping the hell out of it. I believe 
this causes the signal to be very thin sounding at low levels. This vca
seems much better, sounding full even when  barely audible....to me 
anyway.

The adsr and lfo are the usual stuff. I modified the lfo so if could be 
patched into one of the vcas. If the output is then patched through
the other vca it forms a vclfo with separate rate and range cv controls.

If the lfo output is sent through the mix/shifter/inverter then sent to
the vca cv-inputs. You can engage the shift function and use the lfo
to x-fade the vcas or plug a cv in the mix-inputs and x-fade with that.

Even though the adsr-output only goes positive once shifted and 
inverted it may also be used to x-fade the vcas.

>From the look of it. The pcb is probably going to be in the $12-$14 
range.

http://www.mindspring.com/~vco/vca5/vca5.html

-tg (almost ready to ms-20)