I'm currently trying to record a pulse train used as a tempo clock for music instruments (e.g. output of Korg Volca 'sync out') onto my Fostex M-8 reel-to-reel recorder, with the aims to then reproduce the recorded pulses to act as a clock source for the instruments. A working demonstration of this using a different tape recorder can be seen here in this youtube video, so I know it's possible to get working.
My problem: When I use my recorder pulse signal as input to a Volca Bass unit, I'm getting very erratic behavior where the playback is irregular and at a different tempo than when I recorded the signal.
I'm using a Roland tr-09 as my clock source, and the output of the trig jack gives a nice clean square wave:
The captured signal from the output of the reel-to-reel gives a slightly attenuated pulse, with a very long discharging tail from a negative polarity back to zero.
I'm getting this weird capacitance looking discharge. Is this just the nature of the tape that's causing this? Is there something about a DC component being filtered out? Why did the demonstration in the linked video work, which is also recording onto tape, but I'm getting this result?