Transposition of Hz/V

Am I correct in understanding that division/multiplication is how to transpose Hz/V? Things I have read suggest that a linear VCA is needed for transposition with a keyboard, but could simple transposition be achieved with a passive voltage divider?

I found this[PDF]
and this
as possible solutions. That being said, I haven’t looked particularly deep at the two links, since I don’t really deal with Hz/V in my rig. If I did, I’d probably get one of the multitude of Hx/V to V/Oct converters available on the market.

Ah that could be quite useful, but I don’t need to convert to or from V/Oct. My application is transposing output from a scale quantised sequencer. It will only do C major or C minor and I want to be able to get other keys easily. I think an attenuator would be enough, but I’m curious if anyone else has any experience. Halving the signal should take everything down by an octave so I’d only an need an attenuator to take the signal from 100% to 50%.
So a voltage divider with a resistor the same size as the potentiometer between the divider and ground should give me that… I think.

Well, we can only talk from our own perspective, no? :slight_smile:

Best of luck, and do let us know if you figure it out - might be useful to someone taking the same, or a similar path.

Yes, in Hz/V, transposition is equivalent to scaling (applying gain to) the signal.

> but could simple transposition be achieved with a passive voltage divider?

If you want to build a transposition pot, that you would tune with your ears by listening to the sequence… yes it’ll work.

If you want to build a circuit that achieves a very specific transposition on the 12TET scale, a passive circuit will not work because the output impedance of your source / input impedance of your destination will have to be taken into account - and they might vary from destination to destination or source to source.

>If you want to build a transposition pot, that you would tune with your ears by listening to the sequence… yes it’ll work.

Yeah, this is the plan. I just want to be able to tune the scale to another key and then leave it rather than use transposition as a performance tool. My primary instruments are stringed so I have plenty of ear tuning practice. Thanks for the confirmation. I might build a DC coupled buffered attenuator into a powered ‘toolbox’ with various utilities at some point (I don’t thinking I’ll be dipping my toes into the eurorack waters until I have a bigger place).

Given that the notes in the scale will get closer together at the lower range of the pot, I have an idea that an audio or reverse audio taper might make it slightly easier to dial the lower notes in but I’m not sure which. Although maybe it would take it too far the other way.