[sdiy] VCO that goes SHARP in highest octaves??

Phil Macphail phil.macphail at liivatera.com
Mon Jun 20 13:21:24 CEST 2022

The LM13700 Iabc max is 2mA so 4.7k should work fine. Bigger if you don’t use such a high current in your design.


> On 19. Jun 2022, at 01:13, Neil Harper via Synth-diy <synth-diy at synth-diy.org> wrote:
> On 6/18/22 08:14, Phil Macphail wrote:
>> I think this is the most likely cause suggested so far. If the expo transistor is driving an LM13700 then there is around 10 volts across one transistor, and 0.7 across the other. SMT transistor pairs are usually not monolithic so differential heating is very likely. Placing a resistor in series from the transistor to OTA will significantly reduce the thermal mis-match,
>> Phil
> Interesting, thanks Phil. I can try the resistor, is there any rough
> values I should start with? I will also try Ian's suggestion and report
> back.
> --
> /// Neil Harper
> /// Every Wave is New Until it Breaks
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