About rockin vcf

[honio3]

Hello everyone. This is called Rockin vcf. It is an effector designed in Japan in the 70's. You can see the effect of mutron III from the circuit diagram. The circuit diagram is attached. The link is below. https://experimentalistsanonymous.com/d ... in-VCF.gif I want to make this, so I am experimenting with circuit simulation. I am facing questions and problems there. We tested the Rockin vcf breadboard. For the time being, both power supplies are connected with two 9v batteries. It was It worked, but the result is subtle. When the envelope follower part is up, I think that the LED originally emits light from the off state according to the strength of the envelope, but since it emits light even in the silent state, the strength cannot be expressed very much. When down, the LED is on, and it goes off according to the performance of the guitar and turns on when you stop playing. Both behaviors are subtle, so it's difficult to pursue to what extent and it feels like you have to find some compromise. It's a problem like the threshold of the v / i converter circuit, but if you know anything about the problem at the time of up Please tell me.rockin-VCF.gif

[bowanderror]

Interesting circuit, wouldn't mind building it myself.

One thing to keep in mind is that the MCL723C is not of the common LED/LDR type of optocoupler used in guitar pedal, but a Lamp/LDR optocoupler. In this case it's a tungsten lamp, as you can see in the datasheet here:


Due to the different driving circuitry required, you'll likely blow up any LED you try in place of the lamp. You may still be able to find this type of optocoupler, but as that datasheet is from the 1970s, you may want to source them first.

[honio3]

Hello. thank you for your reply.
We know that MCL723C is difficult to obtain. At first, I was thinking of making a photocoupler using a light bulb by myself, but there aren't many light bulbs themselves. Therefore, we are verifying the production with LED. The problem with me is that even if I replace this circuit with an LED as it is, it may not work. The v / i converter at the bottom of the schematic drives the lamp, but in the case of an LED, where should it be connected and what should the constant be?