Bulk Erasing and BIAS noise

[oldvinyldude]

There is a recent thread asking about the wisdom of bulk erasing tapes before recording over them.

I have read elsewhere in the Tape forum, about the benefits of bulk erasing, vs letting the erase head do the job. For this thread, let's omit discussion of poor alignment allowing adjacent tracks to bleed through. I am trying to zone in on the "Bias noise" question.

In these discussions, I have read that bulk erasing will reduce "bias noise" and lower the "noise floor" by 3db.

In practice, what does this really mean?

If say, a deck has a 60db S/N ratio, does this bulk erase increase it to 63db?

Is bias noise something that is added to the "hiss" level that is heard with no recording and playback level (volume), turned way up?

In practice, is there a real world benefit in noise levels upon playback, when bulk erasing prior to recording vs letting the deck's erase system (presuming it's working properly itself) ?

 

[oldvinyldude]

Yes. No.

Bulk erasure returns the tape to virgin noise. Virgin noise is a few dB lower than bias noise, but this is pointless: once you make a recording on that tape bias noise will pop up.
You can not avoid that.

There were decks that could disable their erase head for recording on new tapes, but this was mostly a marketing gimmick. In the end such practices do not lead to less noise or distortion. Bias noise is caused at the recording head anyway ...

Seems WernerO has provided my answer-thanks!

I will bulk erase to remove any chance of old material appearing on new recordings, whether by my user error or poor alignment of machine making the prior recordings.

 

[Numone]

Yep, proper bulk erasing will bring back the background silence of virgin tape. Has to be a decent eraser though as, in my experience, many of the cheaper ones aren’t up to the job, especially through the 10.5” aluminium reels. I have a Leevers Rich professional flatbed eraser, which has four coils and will erase a 10.5 reel in a quarter of a turn however, it always gets a full 360.