I was wondering if I can "upgrade" a DC biased tape recorder to AC bias with a simple circuit.
I found some schematics for AC bias circuits, but they were all very different, and I'm not sure which one is suitable for tape recorders. I was thinking maybe there's an IC for that available, but again, I'm not sure on that one.
I'd like the most simple solution, which could be easily put on a daughter board and hidden in the tape recorder. I was thinking using a 70kHz oscillator, and adding it to the signal somehow (before the DC bias, as in, removing the DC bias parts).
This is just a little project to play around, nothing serious. I'm not planning to make "professional" recordings on the tape recorder that will emerge at the end of the project. I just want a proof of concept type of thing.
OK, this is how far I've got:
Consider this circuit of the LA4160: This is a screenshot of the datasheet, page 4.
Now as you can see in the lower left corner, there is a device "Bias OSC". Given the rest of the Datasheet, I might be able to locate the point where this oscillator has to go.
But how exactly do I build this thing? Or is it an IC that eludes me?
Would be nice if someone could take a look at the datasheet I've linked, and maybe point out a thing or two, if I missed something.
Now, the oscillator needs to be a sine wave, but that's pretty much all I know. I don't know which peak-to-peak level, and I'm not entirely sure what frequency. I think somewhere around 100kHz makes the most sense.