Utilizing a magnetic tape playback/rec head as an erase head.

[ritzysheens]

Howdy!

I'm working on an audio hardware design project utilizing cassette tape as the medium. I have the ability to use 3 tape heads in my design. If possible, I'd like to use all playback/record heads for a number of reasons.

I understand the differences in the way an erase head is manufactured vs. a play/record head. The thing is, I'm not looking for erase head performance in one play/rec head. If I could get the play/rec head to even erase 30-50% of the signal, it would be adequate.

I'm completely open to any ideas and input!

 

[ritzysheens]

Circuit examples for AC bias circuit for cassette record head

Howdy! I'd really appreciate any help finding examples of an AC bias circuit specifically made for recording onto tape. I've done some scouring on the net and have come up empty handed. I'm definitely a newb, so any help is much appreciated!

 

[BradtheRad]

I'll relate my experiments with a reel-to-reel tape deck...

I have tried putting a guard over the erase head, or disconnecting the erase head. Then I recorded as usual. I found that this partially erased the previous recording.

You may find it is 30-50 percent attenuation, which you state would be satisfactory.

I'd really appreciate any help finding examples of an AC bias circuit specifically made for recording onto

I believe the bias is a 19 kHz sine wave. Its voltage amplitude needs to be strong enough to coerce the particles to move. But its amplitude cannot be so strong that it causes all the particles to align all the way (which would be saturation).

By keeping the bias within that middle range, it deposits your audio on tape, with high fidelity.

I was going to say the bias works like amplitude modulation. As I think about it, I don't know that this is correct. It would need to be a much higher frequency than 19 kHz.

The bias should have no DC component. If it did, then it would magnetize the head. The idea is to run only an AC bias to the head. Even so, heads require demagnetizing every so often. However cassette decks are not so prone to this, I've read.

 

[FvM]

Tape recorders have a separate erase head for two reasons:
- perform erase during (before) recording
- completely erase the track despite of recording head tolerances and the gap between both stereo channels by making the erase zone slightly wider than the recording zone

 

[ritzysheens]

Tape recorders have a separate erase head for two reasons:
- perform erase during (before) recording
- completely erase the track despite of recording head tolerances and the gap between both stereo channels by making the erase zone slightly wider than the recording zone

I understand the purpose and design of the erase head, but clarification is always helpful. My whole idea is to try "abusing" a play/rec head as a pseudo erase head.