We don't demag them on a session-by-session basis, but they're stored away from anything that would cause a permanent magnetic charge. It's a good idea to do that periodically.

Any dual trace oscilloscope would do. Oscilloscopes can generally handle way wider ranges of input voltage and frequency than you need for audio, but might be a good idea to make sure it can handle the levels and frequencies you're sending it.

Ha, you found the easter egg.

Do you have a copy of the manual? The azimuth procedure for that machine is certainly detailed there. You can probably find it online if you don't have a hard copy.

dolby hx pro isn't a noise reduction system, it's a servo acting on the bias levels based on the HF content of the audio signal. essentially, if there's a lot of HF in the signal, it can have the same effect as a slight over-bias, & the signal can self-erase itself a bit, attenuating the high end. with dolby hx pro, the signal is analysed (by the same sort of technique that dolby noise reduction uses, which is why bang & olufsen had to 'credit' dolby- they used some of the same patented circuit techniques) & the bias is adjusted on the fly to avoid this self-erasure. when you are calibrating the machine using tones, you don't want to be fighting this bias servo, so you disable it temporarily. it's a record-side process; doesn't have any bearing on how you play the tapes back. some high-end 1/4" machines have dolby hx-pro, but no noise reduction. you can get a lot more high end onto the tape than on a regular machine. I have a lyrec frida & a studer 807 both with hx-pro.

were you thinking of dolby-SR?

duncan rmi is correct. HX Pro isn't noise reduction, but a circuit that modulates the bias strength to improve high frequency headroom in the recording process. I encourage you to check it out. It's an interesting process that solves an interesting challenge. As a side note, that maybe I should have included in the video, It's important that you bypass any noise reduction system when aligning a tape machine.

@@duncan-rmi yes, I was actually... thinks for clarification!

@@gregnorman870 just out of curiosity, why wouldn't you want to use that system if it does in fact what you say, in improving high frequency headroom ? more headroom is a good thing, no?

Unfortunately not.

Do it regularly, but you don't need to do it before every session/ use.

Just as a matter of habit because edge tracks are most susceptible to damage and degradation, and eventually curling slightly.

@@ElectricalAudioOfficial Aha! I should have guessed that. It's been 25 years since I've calibrated a tape machine... 😳

​@@helmanfrow well, then you wouldn't ask such simple questions...

@@n123v?

Of course, NOT better, but WORSE. But, I personally like to use magnetic sound to give sound distortions to individual instruments (e.g. guitars, etc.) 😉