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Yeah, I know, a photo would help.
I bought six 10 1/2" reels of Ampex tape cheap on eBay. All are full of extremely well recorded disco music, or were until i bulk-erased them. There is nothing on the box to indicate WHICH Ampex tape type they are. All it says on the front is:
Precision Magnetic tape.
Not even whether it's 1 mil or 1 1/2 mil. (It's the former). Grey box with blue lettering on front.
Thank heaven it's not back-coated.
The reel material is unmarked grey plastic. The backside doesn't have any identifying info either. Or the spine, which simply says AMPEX.
It was definitely worth the $47 I paid for the 6 reels, but I'm just a little puzzled. TIA for any thoughts.
so is the tape shiny brown on one side / dull brown on the other side?
It's shiny brown on the backside and somewhat less shiny on the "business" side but not what I would call dull.
Just a guess would be 631. Commonly used non back coated tape by many.
to take the guess factor out, why not bias it up on your decks and see where the bias settings come in. Once you know that, you could go to the published bias tables for 3M and Ampex tape and see which one it is.
Good thinking, thanks. I'm currently leading toward thinking it may be type 642 (type 631 is 1 1/2 mil tape -- mine are 1 mil -- and identifiable by its "red oxide" color).
Yeah I've been doing some research I should have done before starting the thread :-)
631 and 641 were considered "voice grade", although I have made nice music recordings on both (as you rightly state, 631 is 1.5 mil, 641 is 1 mil). 632/642 were considered music grade. And they do make better sounding music recordings, IMO. Both are fairly low bias tape and generally speaking will not make great recordings on a tape deck biased for a high bias tape, unless there are bias / eq settings that can be used during recording. However using the low ("STD") bias setting on my Pioneer RT-707, the 600 series Ampex makes very nice sounding tapes.
"Let there be songs, to fill the air"
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