that 2181 vca question

[JAY X]

Hi!

I'm starting using vca circuits. I draw a standard 2181 vca circuit from the douglas self small signal book.

I will attach mono jacks to all inputs and outputs.
My question is if the CV input should be AC coupled or not?

Thank you for your advise!!
Jay x

 

[gyraf]

..ask yourself: What would you want to use the CV input for..?

/Jakob E.

 

[JAY X]

Hi Jakob!

Ok! now i start to understand...

If it is for just volume control with a pot and +/-15v... DC coupling.
If it is for modulating the VCA with an LFO... AC coupling.

 

[JAY X]

Hi!

Attached is the same schematic with the AC coupled CV input.

I have added the 51R/ 2n2 cap at the output of the opamp, like in the Aplication notes of THAT 2181 demo board. The output of the opamp driving the control port MUST be low impedance... So i added these parts in the schematic. ¿¿Maybe not necessary??

As for the resistor values (100K/ 10K) at the CV inverting amplifier, maybe I can replace them for lower values ( 10K /1K) as far as the NE5532 can drive them.

jay x