This has always been a mystery to me so here are a bunch of questions I hope someone can help with. The search function on here comes up with nothing except for a for sale ad that mentions the tape path has been demagnetised - does this mean that the heads are not the only parts that needs to be done?
What kind of demagnetiser should I look for? The ones on auction sites are scarce on details. Years ago I saw a cassette shaped one that you put in the deck and it had a light inside it, all the others I've seen are handheld.
How do you use them and how often should it be done? How do you know if you've done it properly?
What benefits do you notice? Is it just in the high frequencies?
Thanks in advance.
Edit: this is for a 2 head deck if that makes a difference.