Level-Shifting Control Voltage

[WhenBoredomPeaks]

http://www.musicfromouterspace.com/analogsynth_new/HOT_TIPS/PDF/DCCoupledLevelShifter_assembly.pdf

Can i use this circuit to offset/shift the level of a Control Voltage?

I wanna feed the CV out of the MeatSphere (which operates on +9V) into a bipolar supply synth filter which works with bipolar CV.

To simplify it, i kinda want it to make a 0V - +9V signal into a -4,5V - +4,5V signal.

[Seljer]

Yes, that circuit would do exactly what you want

[Gurner]

I'm not so sure that cct will do what you want. The cct you linked to will put a DC offset on the output related to the DC level on the +ve pin. For example, put +2V on the +ve input pin you'll get +2V on the opamp output ...it's directly related.

therefore if you put a CV between 0 & 9V on the +ve pin ...that's what you'll get out (you've not shifted the DC level)...whereas I reckon what you (possibly)  seek is to dynamically remap your incoming CV (so that +9V input  = +4.5V output and 0V input = -4.5V?). If so, I don't immediately have an answer!

[WhenBoredomPeaks]

Yes, that circuit would do exactly what you want

let's hope!

I'm not so sure that cct will do what you want. The cct you linked to will put a DC offset on the output related to the DC level on the +ve pin. For example, put +2V on the +ve input pin you'll get +2V on the opamp output ...it's directly related.

therefore if you put a CV between 0 & 9V on the +ve pin ...that's what you'll get out (you've not shifted the DC level)...whereas I reckon what you (possibly)  seek is to dynamically remap your incoming CV (so that +9V input  = +4.5V output and 0V input = -4.5V?). If so, I don't immediately have an answer!

I want to do this:



Like move it down a few volts on the Y-axis while preserving it's shape

[Seljer]

The second opamp is a differential amplifier, it the subtracts the DC offset set with the potentiometer from the inverted input signal, inverting it back in the process

You could also pull the same thing off with just one opamp if you needed to

[WhenBoredomPeaks]

The second opamp is a differential amplifier, it the subtracts the DC offset set with the potentiometer from the inverted input signal, inverting it back in the process

You could also pull the same thing off with just one opamp if you needed to

So the circuit you posted can do the thing i draw in the post before yours?

[ElectricDruid]

Yes, it will.

And I don't agree with Gurner (Sorry!) - the original circuit you posted will do what you want too, though you'd want to double the feedback resistor RFB to 20K to increase the gain from x0.5 to x1.

Tom.

[WhenBoredomPeaks]

Yes, it will.

And I don't agree with Gurner (Sorry!) - the original circuit you posted will do what you want too, though you'd want to double the feedback resistor RFB to 20K to increase the gain from x0.5 to x1.

Tom.

Cool!

Thanks guys!