Exponential converters on +/-5V

Werebear · Joined: Nov 23, 2009 Posts: 63 Location: UK

Hi

it's been a while and I haven't been doing anything in ages. So I thought I would get on the horse again in stupid style and try and build a VCO that runs off +/-5V because that's the only power supply I've got components to build and money as always is tight.

I've been looking at the VCO 1 exponential converter as Scott has some sums that seem easy for calculating the centre of the expo range and the max so I assumed that putting my 5V into those equations would give me an expo that would run at +/-5V. Wrong! But at least it made a noise which is a move on from the last time I attempted expo stuff, though oddly distorted and certainly NOT 1V/octave.

So the question is is there a set of resources out there that will enable me to build my 5V synth? I know it can be done as Mutable Instruments used to run a lot of their stuff on +/-5V but I can't seem to find the sums to do it.

Any ideas? I've kept the control voltage adder at 100k and 2k feedback and altered the resistors around the expo pair only thinking this would scale for the voltage I am using. I have access to discrete components only - NPN, PNP etc., no magic monoliths I'm afraid.

Thanks

Da Bear

LFLab · Posted: Thu Mar 17, 2016 4:51 am Post subject:

To build your own psu, you need about 5GBP in parts, so if that's holding you back, you will not build any other modules, let alone VCO's.

Find AC wall adapter, build Ray Wilsons Wall wart power supply.

If you then would like to build a cheap VCO, there's an electronics for music Arp AXXE VCO clone which works, and has VERY little parts, the FET is a bit critical though, might need selection.