[sdiy] TB303 / Polysix VCO current mirror thingy.

Ingo Debus igg.debus at gmail.com
Sat Apr 7 15:21:50 CEST 2018


> Am 05.04.2018 um 20:14 schrieb Neil Johnson <neil.johnson71 at gmail.com>:
> 
> The two transistor SCR was also used by Jim Williams in the AN299 VCO.

Here’s another little project that uses this technique:
https://www.heise.de/select/make/2016/6/1482146036717887
(this article is in German. If you scroll down a bit you can see the schematics)

I once had a trainee build it. With the trimpot it can be tuned so that it is in tune with itself (i.e. a semitone is really a semitone) but it can’t be tuned so that it is in tune with other instruments.

Instead of the 100 ohms speaker we used an 8 ohms speaker in series with a resistor.

Ingo



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