I've run this through my head several times, and it seems pretty dang accurate to me. SOMEBODY correct me if I'm wrong. ALSO, I have a digital multimeter. WHAT ac voltage level is the equivalent of +3dB???
OTARI CALIBRATION 101:
When calibrating, the first thing to do is to clean & demag the heads and clean the guides and pinch roller. Make sure all SRL buttons on the front of the machine are depressed. Set the output and input level switches to HIGH. Play your calibration tape (I believe the Otari manual calls for a 500Hz tone........) and hook the output of your track-in-question to an AC voltmeter. (I didn't have one, so I ran it into my mixer's SUB stereo input, so I could use the master meters on my mixer to see the ACTUAL OUTPUT LEVEL.) If you measure the output of each track using an external meter, make sure that each one is of equal level on your external meter. If there's a discrepancy between tracks, you have a problem, and you need to adjust the SRL. If you’re using a 250 nWb/m calibration tape, then be sure to set the SRL level to read +3dB on your external meter. (exactly HOW TO DO THIS is a mystery to me, because I do not know the actual VOLTAGE level that +3 dB is. All I have is a digital multimeter.) In order to adjust this level, you adjust the SRL repro pots on the back of the machine.
The METER calibration pots are totally seperate. Once you have consistent output levels, then calibrate each meter to read +3dB. (this is all while playing back your 500Hz cal tape tone.) At this point, your meters should be dialed in, and you can calibrate your repro hi-F EQ using the cal tape's 10K tone. ( My guess is that this level should ALSO be +3dB.) Do the exact same above procedure, while monitoring from your SEL-REPRO head, and adjusting the SEL-REPRO calibration pots.
Now, to calibrate the machine's oscillator levels correctly, is a heck of a trick to me........After the meters are dialed in, you still need a reference to dial in the input level. You cannot use the internal oscillator to accurately dial in the input levels, because the oscillator is normalled to the input and it has its own level setting, which means it can be altered before it goes to the input level circuit. Your best option is to find an external oscillator, use your AC voltmeter to make sure it’s outputting 0dB, and plug that bad boy into your inputs to calibrate it. OPION 2 -....…..WHY didn’t I think of this before?
HERE'S THE INTERESTING PART!!!
Given that your output SRL (standard reference level) above is set to +3dB correctly, play your 500Hz calibration tape tone, and monitor say……..track 3 from the repro head. Then run a cable from the output of that track’s tape out, to the input on your track in question, like, track 1 tape input. Set this track in question to monitor input, and adjust the input calibration pot until the meter on that track’s tape machine meter reads +3dB.
Do this same adjustment for every track, to correctly set the input levels. (of course, pick a different track to monitor the calibration tape from when you set track 3, er whatever.)
NOW, ideally, all input levels should be dialed in. Monitor input on ALL tracks, and turn on the internal oscillator. Adjust every oscillator level pot until it reads 0dB.
You can then set your bias. IF using 456 tape to record with, throw on a blank reel, and record a 10kHz tone onto all tracks, monitoring all from the repro head. Adjust the bias screw until the meter peaks. You may have to fish around for this peak reading. It does not matter WHERE this peak reading is. Then, turn the bias pot clockwise until the meter is 3 dB lower than that peak reading. Do this for all tracks.
NOW, throw on a blank tape, keep the oscillator on, and record on all tracks, while monitoring from the repro head. Now, you can set each track’s record level until each one reads 0dB (on the tape machine’s meters, monitoring from the repro head of course). Then turn the oscillator to 10K, and do the same procedure to adjust the record EQ pot.
I think that about covers it. Tell me if that bit about the lack of an external oscillator is true or not????
-callie-
OTARI CALIBRATION 101:
When calibrating, the first thing to do is to clean & demag the heads and clean the guides and pinch roller. Make sure all SRL buttons on the front of the machine are depressed. Set the output and input level switches to HIGH. Play your calibration tape (I believe the Otari manual calls for a 500Hz tone........) and hook the output of your track-in-question to an AC voltmeter. (I didn't have one, so I ran it into my mixer's SUB stereo input, so I could use the master meters on my mixer to see the ACTUAL OUTPUT LEVEL.) If you measure the output of each track using an external meter, make sure that each one is of equal level on your external meter. If there's a discrepancy between tracks, you have a problem, and you need to adjust the SRL. If you’re using a 250 nWb/m calibration tape, then be sure to set the SRL level to read +3dB on your external meter. (exactly HOW TO DO THIS is a mystery to me, because I do not know the actual VOLTAGE level that +3 dB is. All I have is a digital multimeter.) In order to adjust this level, you adjust the SRL repro pots on the back of the machine.
The METER calibration pots are totally seperate. Once you have consistent output levels, then calibrate each meter to read +3dB. (this is all while playing back your 500Hz cal tape tone.) At this point, your meters should be dialed in, and you can calibrate your repro hi-F EQ using the cal tape's 10K tone. ( My guess is that this level should ALSO be +3dB.) Do the exact same above procedure, while monitoring from your SEL-REPRO head, and adjusting the SEL-REPRO calibration pots.
Now, to calibrate the machine's oscillator levels correctly, is a heck of a trick to me........After the meters are dialed in, you still need a reference to dial in the input level. You cannot use the internal oscillator to accurately dial in the input levels, because the oscillator is normalled to the input and it has its own level setting, which means it can be altered before it goes to the input level circuit. Your best option is to find an external oscillator, use your AC voltmeter to make sure it’s outputting 0dB, and plug that bad boy into your inputs to calibrate it. OPION 2 -....…..WHY didn’t I think of this before?
HERE'S THE INTERESTING PART!!!
Given that your output SRL (standard reference level) above is set to +3dB correctly, play your 500Hz calibration tape tone, and monitor say……..track 3 from the repro head. Then run a cable from the output of that track’s tape out, to the input on your track in question, like, track 1 tape input. Set this track in question to monitor input, and adjust the input calibration pot until the meter on that track’s tape machine meter reads +3dB.
Do this same adjustment for every track, to correctly set the input levels. (of course, pick a different track to monitor the calibration tape from when you set track 3, er whatever.)
NOW, ideally, all input levels should be dialed in. Monitor input on ALL tracks, and turn on the internal oscillator. Adjust every oscillator level pot until it reads 0dB.
You can then set your bias. IF using 456 tape to record with, throw on a blank reel, and record a 10kHz tone onto all tracks, monitoring all from the repro head. Adjust the bias screw until the meter peaks. You may have to fish around for this peak reading. It does not matter WHERE this peak reading is. Then, turn the bias pot clockwise until the meter is 3 dB lower than that peak reading. Do this for all tracks.
NOW, throw on a blank tape, keep the oscillator on, and record on all tracks, while monitoring from the repro head. Now, you can set each track’s record level until each one reads 0dB (on the tape machine’s meters, monitoring from the repro head of course). Then turn the oscillator to 10K, and do the same procedure to adjust the record EQ pot.
I think that about covers it. Tell me if that bit about the lack of an external oscillator is true or not????
-callie-