So now that I am back from uni for Easter, I have a fair bit more time on my hands. I have begun the process of building the entire circuit on a breadboard. This process has been rather slow because at each point I have experimented with different designs to (hopefully) ensure that I am choosing the best component and structure for my purpose.

mixer_circuit_breadboard
This is the current state of the breadboard layout. I have attempted to make it as neat as possible. (However, I refuse to trim resistor leads).

While I am using dual op-amp chips, in order to make my life easier I am spreading the circuit out by only using one op-amp from each chip for now. The overall circuit will be clearer if I draw it out:

Mixing_circuit_cad
I have attempted to break the circuit up into sections so it is easier to see how each part functions.

The circuit so far takes an input from the tape head, amplifies it and mixes it with the guitar signal. It also drives the cassette player motor.

I did have a problem with noise from the motor being transmitted along the power lines. This was sorted out by adding 10uF decoupling capacitors across the 10k resistors.

In other news I have modified the tape so that I can fit two tape heads in – one to write and one to read.

Modified_tape
I just cut out a little plastic.
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