Tape Wave Synth Idea

[ionbattle]

Hello everyone, my name is Jason.

So I had an idea to put a pot in front of the power to a cassette drive motor and record a waveform onto a cassette and by reducing/increasing the voltage change the speed of the motor and thus the pitch of the waveform.  Where am I going to run into problems here? 

I'm a beginner and new to these forums, so let me know if I'm being an idiot or in the wrong place.

Thanks!

[greaser_au]

Jason,

This is definitely something for doing on the computer these days. As an example, have a look at 'Audacity' - it's free!!!

However- to answer your question: Cassette drive motors are usually speed controlled. If you think about it, it's a necessary thing - otherwise your music would have bizarre pitch changes. The capstan roller  (the skinny one that the rubber pinch roller rides on in play mode) also has a large flywheel behind the deck to smooth out any very short-term variations. In the old days the drive was either a mains powered synchronous motor (like in the old garrard-style turntables), or in portables, a low voltage DC permanent-magnet motor with a 'governor' - a weight on a contact mounted on the motor armature  (usually a pair of them!).  These days it is usually tachometer-driven PWM (pulse width modulation) drive circuit (still usually self-contained inside the motor casing). if you drop the voltage low enough you can lower the speed but then it's all over the place as the loading on the motor changes (which it does - wildly-  in a cassette).

If you really, Really REALLY want to play with this idea, and you have a modern tape deck  - say less than 20 years old-  have a look on the back of  the drive motor,  there is likely a little hole - inside there is a small screwdriver slot that controls the speed.  If you wreck your expensive tape deck it's your responsibility!

warning Warning WARNING.  DANGER, WILL ROBINSON:  Mains connections inside these things are seldom nicely dealt with and taking the cover off could be lethal!

And.. just for interest's sake, I'd  suggest that you investigate the operation of a device called a 'mellotron'...

best wishes, and welcome aboard!
david

[PRR]

As David says: there's a trim-pot on the motor. For a hasty-try, just diddle it with a screwdriver. (Don't expect to ever get back to perfect pitch again.) If it becomes a beloved effect, take out the motor, pry the cover (often a rubber cap), unsolder the trim pot, measure it, and run wires out to a same-value panel pot for easy diddles.

A different trick: rub your finger on the tape reel. This is the *origin* of the term "flanging". Not easy on cassette, but there's a big flywheel which is easy to rub. (Watch out for line voltages.)

And yes, doing it on PC is The Modern Way. Audacity will do it, and comes on all platforms. Processing files, it becomes easy to change pitch and speed separately. I have sped-up a dragging performance without fouling the pitch; you could wobble pitch and leave the tempo the same.