Setting Bias 1/4" vs 1/2" Tape

[astrotoy]

I have learned to set the bias and trim the recording levels on my new Ampex ATR-102, thanks to instructions from Paul Stubblebine. Fortunately I have 3 sets of audio cards for the 102 where the bias and level settings are made.  All my recordings are being done at 15ips 2 track.  I am currently using three different types of tape to record: ATR Mastering, SM468, and SM911.  The ATR tape is all half inch, the SM911 is all quarter inch. So I have used one set of cards for the ATR and another set of cards for SM911 and just switch cards, rather than having to rebias every time I switch tapes.  However, I have both half inch and quarter inch SM468 tapes.  I have set the bias and levels for the half inch with my third set of cards.  I was wondering if those settings would work for the 1/4" SM468 tape also.  It would save me from having to rebias and change level settings when I switch between those two.  The problem with the Ampex cards is that I don't see any easy way to restore an old set of settings on the cards.

Thanks, Larry

[High and Outside]

You should recheck your bias when you switch to a different width, not because the tape might be different, but because the heads most assuredly are different. You might get lucky and the two would be close enough. But probably not.

[astrotoy]

Thanks, Paul.  Will do.  Thanks to your instructions, setting the bias is not the frightening experience I thought it might be!!

Larry

[c1ferrari]

Thanks for starting this thread, Larry.  Just curious...no SM900?
Paul, excellent point regarding the heads!

[astrotoy]

Hi Sam, I am not using SM900.  I am not doing any live recordings, only dubs of tapes and some experiments with hirez digital files to tape. So I think the SM468 and SM911's have enough headroom, particularly when I am dubbing to 1/2".  I have also used the ATR tape with fine results (1/2" only), but decided that SM468 for 1/2" and SM911 for 1/4" was fine.  I do have a bunch of SM468 1/4" reels with splices that I bought from TP, when they were selling those.  I probably will use them also, when I finish going through my several cases of SM911.   The collection of safety masters appear to just about all been recorded on SM911 with a Studer A80.

Larry

[c1ferrari]

Hi Larry,

SM911 is excellent and a popular tape for studios/rock.  Indeed, it is more expensive than SM900 -- lucky for me! :-)
At one time, SM911 was less expensive than SM900.

When you're dubbing to 1/2", I expect you'll achieve very clean dubs.  When you dub from 1/4" to 1/2" -- are you recording
at 30 in/s or 15?

Happy Holidays!

Sam

[astrotoy]

Hi Sam, I am either dubbing 1/2" to 1/2" or 1/4" to 1/2" and sometimes 1/2" to 1/4".  Everything is at 15ips, the speed at which the tapes were recorded originally. 

Thanks,  Larry

[c1ferrari]

Thanks, Larry.

Sam