[sdiy] single transistor VCA (was OTA VCA)

Mattias Rickardsson mr at analogue.org
Thu Mar 23 15:52:42 CET 2017


Hi,

isn't the transistor placed in the wrong direction?
http://electro-music.com/forum/phpbb-files/ms20vca_156_961.jpg

And... what do you mean you went without the OP-amp buffer? :-)

/mr


On 23 March 2017 at 15:43, Elain Klopke <functionofform at gmail.com> wrote:
> Hey all....
>
> So I breadboarded this up:
> http://gaje.jp/blog/wp-content/uploads/2011/12/ms_type_vca.png
>
> I used a 2N3904 and didn't have an op amp buffer so went without it. the CV
> input was provided by the two diode, two resistor and a cap AD generator.
>
> And no sound.
>
> Now with the labeling of 2.5V I'm guessing that the circuit is being run off
> of a 0-5V power supply and the 2.5V is acting as a virtual ground. Since I
> don't have the op amp in my circuit, I just went with connecting those 2.5V
> bits to ground.
>
> I'm going to be putting together a bipolar power supply this weekend, so
> I'll give it another go then.
>
> Also, my 2N3904 could be fried. The bag of them has taken a spill a couple
> times and I've had to scoop them up by hand and put them back....
>
> Tips, tricks, and scathing criticisms welcome as always
>
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