SPEED & CV/GATE IN MODS ON CASSETTE PLAYER

In my case, adding a potentiometer between motor and power, this quick method to control motor speed didn't work at all so I used PWM using 555 timer to control motor speed. Some benefits of using 555 timer are I can add CV and gate inputs. Probably the quick method would work with other cassette player.

SCHEMATIC

UPDATE on 20220913:

With 1uF, the motor rotates non-linearly. So you can stick with 200nF for linear rotation.

UPDATE on 20220810:

For better speed control, I replaced 200nF with 1uF and 'Linear' 100k potentiometer with 'Log' 100k one. The schematic above has been updated.

Instead of using pin4 of 555, I switched to pin2 for gate input. Both works fine but conversely. It's up to you. But keep that in mind when using pin4, switch pin of 3.5mm jacks should connect to Vcc and disconnect Vcc from pin4.

STRIPBOARD LAYOUT

UPDATE on 20220913:

With 1uF, the motor rotates non-linearly. So you can stick with 200nF for linear rotation.

UPDATE on 20220810:

For better speed control, I replaced 200nF with 1uF and 'Linear' 100k potentiometer with 'Log' 100k one. The stripboard layout above has been updated.

This cassette player has a line output which jack is stereo one but actually left and right signal summed to mono in the circuit. One thing bothering me is its output gets mute when I plug mono cable into it because 'ring' pin of stereo jack was in contact with ground pin of mono plug. If you use stereo split cable, nothing wrong with it, however if you just want a mono signal like me, unsolder the stereo jack and cut the two legs corresponding ring side.

And I encountered some issue while using CV with my eurorack modules. Those seemed like ground issue. After some investigating, I found out its line out jack's ground was floating. So you need to connect the ground pin of line out jack to other ground point.