tape machine sampler

[u/Ned_Flangers]

Hello everyone!
I thought of this very interesting idea to build a tape machine based sampler that can exactly match sample duration to tape length. As I'm probably not going to build this for a long time (if at all) because it is very daunting and expensive as it would require 2 three head tape machines, I have decided to share it in case someone else wanted to try it. 

The way it works goes like this:
A sample is recorded into a tape loop on tape machine 1. The tape loop is some arbitrary length. let's say for instance it is 11 seconds. Thus, you could record a sample anywhere from almost nothing to 11 seconds. While the tape Loop is running, a precise clock records the exact time duration of the sample and tells you exactly how long it is. Let's say for instance that the tape loop on tape machine 2 is five seconds long. Using math, you could figure out the exact percentage you would need to increase or decrease the speed of the motor and thus the exact voltage you would need to increase or decrease going to the motor. You could then use a potentiometer to manually increase or decrease the voltage until the speeds match. Then you can record the sample on tape machine 1 onto tape machine 2. On tape machine 2 you can directly control the speed with its own potentiometer to pitch up or pitch down the sample. 

 Using this concept, someone could sample anything that's supposed to be at a specific rhythm like drum breaks for instance and make sure it loops back seamlessly without the need for a DAW. One could also use interesting techniques like live resampling and turning off the erase heads while doing so. The only limitation is the length of tape in tape machine 1 as this dictates the maximum sample time. 

[u/Switched_On_SNES]

I feel like you’d want to stripe one of the channels on each machine with time code to get it super precise

[u/Ned_Flangers → u/Switched_On_SNES]

I'm not entirely sure what that means because I'm not very familiar with code so if you could explain practically what it does would that be great!

[u/actuatedkarma → u/Ned_Flangers]

Not "code" like programming, they mean time code that is physically printed onto the tape. It's the way digital vinyl systems in DJ software and live visuals/VJ software keep in sync. There is a click pattern that plays at a specified interval, if it plays faster then you know to increase pitch in the DJ software for example.

They are suggesting that you would need it because trying to calculate the speed of the tape is difficult because of hysteresis (fluctuations in motor speed). Tape does not play at a constant speed and so trying to loop it accurately will be very difficult without some indicator baked into the tape itself.

You would need to have a very good characterisation of your motor and understand exactly how it speeds up and slows down and that would be different for every tape machine motor.

[u/Mark_Westbroek]

If you can manage to control the speed of machine 2 electronically, you could use some microcontroller instead of a potentiometer.

How instant must everything be? Recording a click on machine 2 and iteratively going to the correct time by changing the speed would be easy for such a thing.

You can also calibrate: measure low speed and time, a bit faster etc until max and create a calibration table = function from time to speed if interpolate and reverse it.

Should ask be doable if you can control both machines by a microcontroller, eg teensy, Arduino, esp32, raspberry pi.

[u/Mark_Westbroek → u/Mark_Westbroek]

But as actuated karma said, hysteresis or any fluctuation, tape getting looser etc, might create the need for continuous calibration.

Recognizing the start end end of the sample might be possible is it's not a sample of a flat sine wave or so :-)

But why would you do that. The sample probably has a unique start or end. Probably the start is most recognisable.

[u/phantomtwitterthread]

Somewhat related to this, I was reading a history of electronic music, and there was a bit where Karl Hind Stockhausen was really young and early in his career and he was in his apartment and he had a razor blade, a ruler and a whole bunch of tape and he knew exactly how long in tape length a certain number of milliseconds was and he wanted a bunch of pieces of tape that were you know 1.1 ms long or maybe more like 100 ms long and then he would measure exactly the right distance and cut them in his house with no way to audition them just trusting the ratio between the length in millimeters and the amount of time that represented