magnetic tape erase/record circuit question

[Alex Eisenhut]

https://www.effectrode.com/knowledge-base/delia-derbyshire-recording-the-future/

The 1960s were so cool.

[CaptDon]

I suspect if you are loop recording with the erase head active and switch to the dummy during recording you will get one hell of a thump on the tape which will keep getting reproduced. It may decay or may become louder. On pro machines the bias ramps up and ramps down so as not to leave any magnetization in the head. Recording is not amplitude modulated bias. The bias remains fixed (there are dolby exceptions) during recording and in many ways serves to continuously demagnetize the recording head. Non-symmetrical record audio waveforms would leave residual magnetism in the head and produce horrible results. Tape recorders that use erase magnets are pure junk and end up with horrible S/N ratios. They were merely cheap toys for kids!!! It is kind of amazing that good recording results are obtained when increasing the bias and then suddenly the high frequency response falls off a cliff!!!!

 

[person552]

"Thought I'd keep on putting my notes in here, in case someone ever wonders .... haha what are the chances that anyone else will come here looking for this info?"
Well I am. So here is a post of a video where user "simply" lifted ground on erase head:

You can jump ahead to ~7:20 to see the finer details. It seemed to work (for him) on this particular 4 track Tascam PortaStudio02 MKII
And another video in use:


I have the same exact deck and considering doing the same (for same purpose also) - although not so sure after reading this thread.

[CaptDon]

Wow, that seems like the hard way to do things, and probably warbles like crazy. There are so many relatively inexpensive 'looper' pedals and boxes on the market today for solo guitar acts (which I hate for several reasons). They have lots of features you will never get with magnetic tape, and magnetic tape delays have lots of bad artifacts you won't get with digital delays. You need to be careful to have a loop gain of .999 or less. If the gain exceeds 1.0 the loop intensifies like delayed microphone feedback and eventually mushes out to a distorted mess. I loved the delays in the Yamaha SPX90 and the GPX50 Guitar units. There are so many today to choose from!!! Cheers!!