evm1024
New member
I think you are confusing operating level with bias setting. I know of no analog tape that is/was spec'd for a +9 over-bias setting. I also doubt that the erase and record heads would be happy having that much current going through them. I suggest you find out what the set-up requirements are for whatever tape you intend to use before modifying your machines.
Nope, not confusing MOL with bias settings. Perhaps did not state it well.
A 185 nW/m tape will require a certain bias level. A +3 tape will require about 3 dB more bias level to be properly biased. Ditto +6 and +9 tapes. In other words bias levels track MOL. We are talking absolute bias level here not relative level (ie 4 dB overbias).
Most decks that I have run across that were speced for 456 will not output a bias signal at a level sufficient to achieve the required bias signal with a +9 tape to bias it properly.
I should have written "...allows proper bias WITH a +9 TAPE while moving the pot TO the middle of its range"
Regards, Ethan