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#1
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setting bias (again) when there's no peak
just curious: the usual instructions for setting bias is to turn the
bias control until it peaks, then continue until it decreased by the correct amount (usually -3dB). on this pr99 i'm trying to nurse back from years of public radio station duty (volunteer-staffed), the needles are at their maximum at one extreme of the bias pot. i went ahead and set it until the meter read the correct amount, and the high frequency sounds good on playback, so i'm going with it, but, it bugs me. it bugs me that the peak isn't within the bias pot's range. . . any thoughts? cheers, chris deckard saint louis |
#2
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setting bias (again) when there's no peak
mr c deckard wrote:
just curious: the usual instructions for setting bias is to turn the bias control until it peaks, then continue until it decreased by the correct amount (usually -3dB). on this pr99 i'm trying to nurse back from years of public radio station duty (volunteer-staffed), the needles are at their maximum at one extreme of the bias pot. i went ahead and set it until the meter read the correct amount, and the high frequency sounds good on playback, so i'm going with it, but, it bugs me. it bugs me that the peak isn't within the bias pot's range. . . What tape are you using? Are you sure you have enough bias to handle it? You did turn the level of the oscillator down so that the meters were low enough that you could find the peak? But you still turn it all the way to the right and it just keeps going higher? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#3
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setting bias (again) when there's no peak
What tape are you using?
brand new ampex, er, quantegy 456 Are you sure you have enough bias to handle it? no. i'm still kinda new to this -- although i understand it all in chunks, i've yet to assimilate it all into a working picture. . . the source of the problem could be my shaky understanding of flux and overbias (as i said, i understand them as souvereign concepts) -- my mrl tape is 355nW. i understand this is where to run 456 since it is a +6dB tape. You did turn the level of the oscillator down so that the meters were low enough that you could find the peak? yeah, i set my 10k tone so that it showed 0db on the deck's meters, then worked from there. But you still turn it all the way to the right and it just keeps going higher? yes, it doesn't decrease. --scott thanks, chris |
#4
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setting bias (again) when there's no peak
mr c deckard wrote:
What tape are you using? the source of the problem could be my shaky understanding of flux and overbias (as i said, i understand them as souvereign concepts) -- my mrl tape is 355nW. i understand this is where to run 456 since it is a +6dB tape. I'd run it at 185 personally... running that machine much higher than 250 is really a bad idea and the head electronics are apt to saturate before the tape does. But your bias problem has nothing to do with the operating level. You did turn the level of the oscillator down so that the meters were low enough that you could find the peak? yeah, i set my 10k tone so that it showed 0db on the deck's meters, then worked from there. But you still turn it all the way to the right and it just keeps going higher? yes, it doesn't decrease. Can you make it increase in the opposite direction? I'd suggest trying a lower bias tape to see what is going on. Say throw a reel of Radio Shack Concertape (red oxide tape, +185 tops) on there. You should have no problems finding the peak on that. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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