getting to know the mx5050 BII 2-track 1/4" machine. its been sad and lonely for a while but i fired it up today to hopefully get it setup right. very interested in using it for mixdown. machine is in NAB, mid flux, and fast (15 ips) mode.
for you tape geeks, tell me if this calibration method sounds alright. its a bit self-designed, but levels and transients are seemingly accurate and in tact. sounds ****ing cool and good. heres my method:
-1K tone at -16 dbfs out of logic via apogee DA16x calibrated to 0
- in source monitor mode on the deck, input on the otari set to make the meters hit 0 vu with a little give and take of vu meter calibration and input knob adjustment (11 o'clock)
running a pink noise generator out of logic at about -8 dbfs, with an analyzer plug right after it showing an averaged EQ slope like this (level is set to slope visually with the pink line guide). this pink noise reads at about -1.5 vu on the machine input.
-recording noise to tape and monitoring off the repro-head via AD16x (at 0) back into 2 channels in logic (L/R), each with the same analyzer plugin (as was monitoring immediately after the pinknoise generator before). machine output is in SRL (standard reference level) mode.
-adjust bias, highEQ, and lowEQ recessed pots to make the monitored green average line as identical to the pink reference line as possible (as it was from the generator before conversion/tape
Tracked a mix which peaks at -4.5 dbfs, reading between -3 and +1 vu. In A/B comparison the tape mix sounds great and seemingly very very similar in all the right ways. similar looking waves, identical levels, very similar transient information. only differences are sonic: a beefier bottom, more flattering midrange, and more sparkly top.
a few questions to really understand this and perhaps take it to the next level: does this calibration method equal a "neutral" tape transfer (somewhat dependent on the RMS/peak info of the mix i suppose)? do you think im hitting tape at a "safe" level right now? how many more db would be considered "hard," or how many less would be considered "soft." is it strtictly a feel thing or are there some sort of guidelines that people have been following for years? how does the MX5050 compare to a fancier 1/2" deck?
one thing i will point out is that theres a tiiiny bit of an inconsistent clarity to the tape. its a relatively new RMG reel, and the heads were just cleaned with 91% isopropyl alocohol. there are tiny dropouts, or perhaps instantaneous dissapearance of the high end. is this normal for a machine of this kind? got it off ebay last summer. seems to be in decent condition. i think the guides and lifters are pretty worn though.
Your method is generally fine for setting record cal, but:
-Repro must be calibrated first; head azimuth, repro EQ, fluxivity. You need an MRL tape.
-Not sure why your reference line slopes; I would think a RTA of pink noise would show flat, but I am not familiar with your analyzer.
-For record bias, I would start by trying the tape manufacturer's recommendations, usually a sine tone like 10kHz and overbiasing (bringing the bias up until the audio output peaks and then decreases). Then I would check the THD and listen to some low tones for modulation noise. Then I would tweak record EQs for flattest response, and maybe a little adjustment of bias. Then check everything again.
-Small amounts of HF variation are part of tape life, and there are dozens of causes, some of which you can control, and some which are harder - a little wear of the tape; guides too wide or too narrow and tape too wide or too narrow (bad slitting), wear groove on the heads with tape width variation; bad tension control, bias too low, etc. Assumes the tape path is absolutely clean. An Otari like that, I would put it on it's back and check the tape movement and path very carefully.
-your method may give slightly different results than someone who uses a range of discrete sine tones to do the calibration.
-as to how hard to hit the signal, well you can argue endlessly. Generally, high levels will have more distortion, self-erasure and saturation. Depends on what fluxivity you chose for zero, the tape charactistics, the program material, and so on. Assumes all the electronics have the headroom.
-Repro must be calibrated first; head azimuth, repro EQ, fluxivity. You need an MRL tape
My opinion is that this guy is right...
Without having the repro aligned to a measured nW/m, then you really have no idea what nW/m is being recorded on the tape. That's the purpose of the MRL...a known, lab verified nW/m level for playback. Once you get the playback side right, then you can make adjustments on the record side & use the playback side as an nW/m meter..
With that said, you wouldn't need an MRL every time. A flux loop driven by your D/A would be awful handy to keep it lined up, and would allow you to align it (everything but azimuth) with your computer instead of an MRL. Get a tech to line it up to your RMGI tape with an MRL, then take the machine home. Before you put tape on the machine again, put the flux loop on the playback head & drive the 5050 meters to 0 with logic, then repeat with the rec head. Write the logic levels down, or create a session you just recall to align the repro side of the machine again.
Quote:
there are tiny dropouts, or perhaps instantaneous dissapearance of the high end.
Without having the playback aligned, it's kinda tough to guess what this could be. Record bias, bad cap in hi freq eq, hi freq eq off enough to distort occasionally, head gunkin up & then letting go of goo...who knows.
-Not sure why your reference line slopes; I would think a RTA of pink noise would show flat, but I am not familiar with your analyzer.
Double check the settings on your RTA/FFT plug & the db/octave slope of your noise sample. There are different slopes (ie:-3db/octave, -6 etc etc) and your screen shot looks like -3db/octave noise being measured with a 0db/octave scale.
I bought 2 Otari MX 5050 MKIII-8's last month and spent a lot of time figuring out how to calibrate itthem correctly. The procedures in the manual are a good starting point, but they don't seem to be in the correct order.
After a lot of experimenting and research, I have come up with the following procedure. It seems to work really well. I would interested in getting people's feedback.
The procedure is written specifically for my setup, so some parts won't directly apply to anyone else but me.
One of my machines is NAB and the other is IEC. I bought an NAB MRL, so I have to shift some of the values when calibrating the IEC machine. MRL has the shift tables on their website.
What about demagnetizing the heads? How often should that be done?
Before putting the MRL tape on for sure.
In normal operation, maybe once a week? I don't actually use my machines that much so I demagnatize and clean the tape path before putting any tape on.
Watch out for discrepancies on the outputs of your interface feeding the tones to the 5050. We tried sending tones through our old 192 to the MX-5050 for calibration, and after some head scratching, realized that the outputs of the 192 weren't matched.
from a different thread, jaddie has kindly informed!
Quote:
Originally Posted by jaddie
Nope, not in my manual either.
You'll need the test tape to cal the play head az, then adjust the record head to the play head. You can get started without the test tape if you don't mind the fact that tapes you record may not be easily played on machines aligned with a test tape, as you may have non-standard azimuth.
Use a plug-in or analyzer that will display an X/Y display, left on X, right on Y. In-phase is a flat trace at 45 degrees, low on the left, high on the right. Proper azimuth is when all frequencies play in phase with minimal variance. Some is normal, guidance is not exact.
Looking at the top of the head assembly, you should see three adjustment screws for each head, one toward the front of the head, one to the back and one to one side. The azimuth adjustment should be the one to the side. You can check this by turning the adjustment screw while looking at the head face carefully. It should more or less rotate about a horizontal axis extending from the head face to the back. Don't change the adjustment screw until you have an alignment tape to put it right.
Don't forget to az the play head first, then calibrate play EQ, then check play azimuth again and fine-tune if required. Check at several frequencies, not just one. Two is good, three is better, rapid sweep is even better.
When aligning the record side, remember that changing bias and EQ affects phase, so before you set record azimuth, do a basic bias set up making sure both channels are biased identically. Peaking at 1KHz is ok at this point. Then adjust record azimuth. If you adjust azimuth first, and bias settings are not identical for both channels, then you correct the bias, azimuth will be wrong. Once you get record azimuth right, do a final bias adjustment (peaking at 10KHz, then over-bias by xdB) and of course EQ, both of which end up being sort of iterative. Keep an eye on channel phase, as bias and eq will affect it at the top end.
I bought 2 Otari MX 5050 MKIII-8's last month and spent a lot of time figuring out how to calibrate itthem correctly. The procedures in the manual are a good starting point, but they don't seem to be in the correct order.
After a lot of experimenting and research, I have come up with the following procedure. It seems to work really well. I would interested in getting people's feedback.
The procedure is written specifically for my setup, so some parts won't directly apply to anyone else but me.
One of my machines is NAB and the other is IEC. I bought an NAB MRL, so I have to shift some of the values when calibrating the IEC machine. MRL has the shift tables on their website.
Nice job. In your "Level and VU calibration" section it looks like your plugging the signal generator into the individual inputs on the back of the machine. The manual states to just use the External Osc input on the front of the machine which sends the signal to all of the channels. With your method you have to re-patch to every input on the back of the machine for each channel.
Interestingly enough, the previous owner hand wrote your method above as a suggested alternative to the manual's direction. I wonder...
I don't see this doc on here, so I figured I'd post it. It's a COMPLETE alignment and calibration manual for the MX 5050, straight from Otari. Includes all repro, rec, wow & flutter, azimuth, zenith etc etc. Definitely a must have if you own this machine. To complete all the alignments, you'll need an oscilloscope, signal generator (that can accurately put out +4dBm), MRL calibration tape at your desired level of flux, and a wow/flutter test tape, frequency counter, etc.
I bought 2 Otari MX 5050 MKIII-8's last month and spent a lot of time figuring out how to calibrate itthem correctly. The procedures in the manual are a good starting point, but they don't seem to be in the correct order.
After a lot of experimenting and research, I have come up with the following procedure. It seems to work really well. I would interested in getting people's feedback.
The procedure is written specifically for my setup, so some parts won't directly apply to anyone else but me.
One of my machines is NAB and the other is IEC. I bought an NAB MRL, so I have to shift some of the values when calibrating the IEC machine. MRL has the shift tables on their website.
After a quick read there are lots of errors in this procedure. I'm sure that if you follow the Otari documentation you will get better results. And the Bill Vermillion article is pretty good.
Last edited by Radardoug; 22nd November 2011 at 06:37 PM..
Reason: More info.
getting to know the mx5050 BII 2-track 1/4" machine. its been sad and lonely for a while but i fired it up today to hopefully get it setup right. very interested in using it for mixdown. machine is in NAB, mid flux, and fast (15 ips) mode.
for you tape geeks, tell me if this calibration method sounds alright. its a bit self-designed, but levels and transients are seemingly accurate and in tact. sounds ****ing cool and good. heres my method:
-1K tone at -16 dbfs out of logic via apogee DA16x calibrated to 0
Hi,
Two things
Calibrate from and to the daw at -18 dbfs as gives you a little more headroom to push the tape and be able to recapture in digital.
go with iec instead of nab eq curve in 15 ips as your noise floor will go down a touch. Ive always got better results like this.
When working on tape machine equipment, I always check the mechanical aspects of the machine first such as physical head alignment, the tape path for cleanliness, belts and tape tension, using a tentelometer, including pinch roller pressure, using an accurate spring tension scale and of course degaussing the entire tape path. This might take 15 to 30 minutes, depending on the machine. After finding that all these are within specs, I continue with the machines set-up or service whatever it needs. Several times I found my self chasing an electrical problem only to find out latter that it was a mechanical problem. Yours seems as if it is an electrical problem, but I found out by inspecting what's right in front of your eyes, sometimes saves a lot of time trouble shooting.
I don't see this doc on here, so I figured I'd post it. It's a COMPLETE alignment and calibration manual for the MX 5050, straight from Otari. Includes all repro, rec, wow & flutter, azimuth, zenith etc etc. Definitely a must have if you own this machine. To complete all the alignments, you'll need an oscilloscope, signal generator (that can accurately put out +4dBm), MRL calibration tape at your desired level of flux, and a wow/flutter test tape, frequency counter, etc.
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