When you say that you hear the "play back", do you mean that you hear it at the time it is recording? Or do you mean that it will play back the recording after
the recording is completed?
For looping, what you're after:
- is a record head laying down the audio to the tape
- and a playback head placed at some distance from the recording head
The playback head of course needs an amplifier, when the recording head is also using it's own (two amplifiers are required).
The amount of delay is dependent upon:
- tape speed
- distance of the playback head from the recording head
Based upon what I see in the pictures, it appears you have one
amplifier (unless there is more somewhere). I only see 3 transistors, so there must be more electronics hidden somewhere else (there is usually an oscillator to erase the tape ahead of the recording head).
So for you to have a functional looper, you'll need two amplifiers that operate simultaneously. One recording, while the other is amplifying the playback head.
To control the delay, you have to be able to move the playback head, or alter the speed of the tape.
The project sounds a bit ambitious to me. But let us know if you can simultaneously playback while recording or not.