I’m not sure what frequency the bias is set to on the Fostex R8, maybe 145 kHz to 150 kHz.. Regardless of what it is set to, adjusting the bias changes the power of the bias frequency, and not the tone of the frequency itself. When you turn the bias higher you will just have a stronger 145 kHz tone. Likewise, when you turn the bias lower you will still have a 145 kHz tone, but it will be weaker.
If you bias a tape too high you will loose high frequency response and make the tape sound mushy. If you have an insufficient bias level you will experience distortion and brittle highs,
There’s a lot more to biasing, but that’s it in a nutshell.
