Toy keyboard project – Wah circuit

I am working on this new/old/hearandnow project.

I am trying to take a crappy second hand synth keyboard that I got from a new Value Village a few weeks ago.
second hand synth from Value Village #2

I want to repackage it using only one (maybe two) of the octaves on the keyboard. I will just use a simple pitch bend (1M pot) connected to the timing of the motherboard to get whatever ocatave leval I am looking for. The basics for any bend really.

second hand synth drum patterns - Some are doubled up

My main goal is to add a few simple effects to the keyboard output and the amplify it. Sounds simple.

Attempt 1 – Simple Low Pass Filter

The reality, for me anyway, has been a bit of a nightmare. I can’t seem to do anything except volume control. The last few attempts have been low pass filters. I started with a simple RC (Resistor – Capacitor circuit) circuit where the resistor was a 10k volume pot in series with the signal out and a .1uF capacitor branched off to ground. I played with the values of the potentiometer and capacitor until I found something that looked like it would work.

here is a basic schematic:
Simple Low Pass Filter for Toy Synth Circuit Bend

It didn’t really work. I posted some “help me I’m an amateur and an idiot” posts on an electronics forum. They told me I needed to amplify the output. I read that last bit after I had started onto another more complicated project.

you can veiw the “help me I’m an amateur and an idiot” post here:
Low pass filter – help me!!!

Attempt 2 – Simple Active Low Pass Filter

The next thing I tried was an active low pass filter. This involves an op-amp… apparently.

This is what it looked like on paper.
Active Low Pass Filter Schematic

I also posted some more “help me I’m an amateur and an idiot” posts here:
Active low pass filter – Help me!!!

Now I am onto bigger and better things… If I could only get them to work.

Attempt 3 – Simple Wah Filter Circuit

Here is the schematic to a simple wah pedal circuit using the TL082 dual operational amplifier.
Simple Wah Circuit Schematic using the TL082

I bread boarded this all up and all it did for me was, again, volume control… more control than the other two examples… but still just plain old volume.

At first I was just stoked that something was happening. Then I compared it to my guitar wah pedal. It wasn’t even close to cool.

So what did I do? You guessed it. I posted some more “help me I’m an amateur and an idiot” posts.
View them here:
wah circuit help

So that’s where I’m at with my new amazing project involving some do it yourself analog filters and a crappy second hand synth.

No real progress at all.

But I’m not giving up!

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