Important Tape Calibration Question

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thereelman77

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Hi their.

I am running two decks: An 8 track 1/2" Teac unit and an Otari MX-5050 B-2HD.

I'm sure this has been answered in other places, but for my sake, I want to know for sure:

Is tape calibration NECESSARY on both decks in order to use them correctly? I haven't calibrated them since I bought them and have recorded many tracks using them.
Basically, I want to know, that when the time comes to calibrate (I haven't gotten all the tools yet), will everything I have recorded up to that point be able to playback correctly, AFTER I calibrate the unit.

The teac deck, believe it or not, seems to be more correct-on calibration than the Otari deck, just simply by watching the meters. I say 'believe it or not' because you would not believe the conditions I rescued the Teac deck from. The Otari deck has had more issues, but was kept in better conditions.

I just want to know if I should stop recording IMMEDIATELY and calibrate the decks NOW. I've been thinking more and more lately that the current album I'm working on, may not playback right, after I get them freshly calibrated.

Any ideas, links, feedback, or opinions will be greatly appreciated.
 
Just watching the meters won't tell you the most accurate story....and yes, if the decks are out of calibration in any significant way, the stuff you already recorded may not play back as best as possible.

For some things, calibration is about making your machine equal in response to a set standard so that those tapes will play back the same on other machines. In some aspects if calibration, if you only record and play back on your machines, it's not as critical...but there are other aspects of calibration that affect the actual ability of the deck to record and play back as optimally as possible, so not doing will hurt your own recordings even on your own decks.
 
Thanks for the response miroslav.

I do know not to trust the VU meters, I guess I was just saying that for the sake of the question.

I understand what you are saying.
At some point when I get the deck calibrated to MRL standards, I want to make sure the tapes will be playable. When you said "In some aspects if calibration, if you only record and play back on your machines, it's not as critical" that's something I feel is critical. The problem is, (as far as my young tape knowledge goes) their is no way to test the decks calibration level, unless I actually go thru the process of re-calibrating it, correct me if I'm wrong.
 
Do you print calibration tones before you record? If so you should be able to cal to those for reproduction. If not, well...
 
No I have not. But I'm not too concerned, since one tape we're only using one song off of the entire tape and the 2nd reel, we're going to re-record over completely. I'm going to buy a sine wave generator, which I'm assuming is where I print my tones to tape from. If I print the tones NOW though, when I go to calibrate it to MRL standards of my tape (SM911/ +6), will the tapes playback correctly? I just don't want their to be overly distorted or noisy/quiet signals playing back from the tape since it's been calibrated differently. I am in a position to get some MRL test tape, apparently Audio Village in California has new MRL tapes ($119 for 1/4", $199 for 1/2"!!!). I really am not looking to blow all the cash on those right now. But if I can print the tones to tape and calibrate later would that work? Or should I just get the deck set up completely before I record more.
 
The way to do it is to calibrate your repro with the MRL, then set bias and calibrate your record electronics with the oscillator tones, then when it's all calibrated you print your cal tones to the first minute or two of tape. For my machines I do 1khz, 10khz, 100hz. BTW I just bought a 1/4" shortform 4-tone MRL tape from Sprague for $100 when I had my 2-track deck's heads relapped. Yeah it's annoying how pricey MRLs are (mine came on freakin' 7" plastic flanges for crying out loud, not even an NAB reel for my pro machines) but what can you do, MRLs are essential for proper calibration.
 
thereelman77 said:
I just want to know if I should stop recording IMMEDIATELY and calibrate the decks NOW. I've been thinking more and more lately that the current album I'm working on, may not playback right, after I get them freshly calibrated.
Click to expand...

Basically yes. The first thing to do when you buy a new (old) deck is to have it calibrated. Otherwise, as you have rightly guessed, whatever you record will be off to some degree. Head alignment is the biggest gotcha if its terribly off from spec. Levels can be compensated for. Usually a deck drifts out of spec slowly over time, unless there is significant impact from rough shipping or something. If you can play tapes on your Tascam that were recorded on your Otari and vice versa with no big problems you're probably ok as far as things being within reason. The first thing to invest in is a calibration tape if you're going to do this all yourself.
 
Beck & briank, thanks for the responses.

Both of your advice has helped me greatly.

For starters, I'm not sure whether to invest in the 1/4" or 1/2" MRL tape. Because I don't have enough money for both AT THE SAME TIME, I have to decide which deck I NEED to calibrate more than the other for now..I plan on getting them both done soon, but one before the other. Something I'll need to figure out myself, but I'll try and keep the thread posted on what is going on.

Luckily since we won't have any sessions anytime soon, I will have the next few weeks to get the deck calibrated. I'm gonna' order some MRL in the next day or 2.

I've been looking at the Rolls MO2020 Testoscillator, it is ROLLS and is cheap$$, but it looks like it would do the job.

What kind of Oscillators do you guys use, just curious?
 
thereelman77 said:
What kind of Oscillators do you guys use, just curious?
Click to expand...

I either use the one built into my console which is nice, I can do frequency sweeps, pink and white noise with it, or (I hate to admit it :D ) I also have a multi-channel calibration tone session on ProTools that I can easily patch into the tape inputs.
 
thereelman77 said:
I really am not looking to blow all the cash on those right now. But if I can print the tones to tape and calibrate later would that work? Or should I just get the deck set up completely before I record more.
Click to expand...

Printing the tones next to the sessions you've already recorded (without changing any machine adjustments) will give you a frequency calibration reference which you cannot achieve any other way. Potentially, you can correct your existing recordings for frequency response errors even after recalibrating with an MRL tape.

Your tape machine may or may not be playing back its own recordings correctly now. The only way to find that out, on a channel by channel basis, is to print tones and observe them on playback. You can observe that now as well as after a playback calibration.

Understand that an MRL tape only calibrates the playback section of the machine. When that job is done, you put the MRL safely away.
Now the harder job begins of aligning the record section of the machine to the playback standard to which it has just been aligned. Usually that involves three adjustments per channel: level, bias and hi eq.

But right now, you could also try and align the record section of the machine to the current playback setting of your machine. Of course this will not affect your previously recorded material in any way, only new material you might record.


Playback alignment, which uses the MRL tape, is done much less often than record alignment. This is partly because record alignment usually goes out of whack more quickly than playback calibration. Also, record calibration is dependent on the tape type, whereas playback calibration is independent of tape type, though you can calibrate playback to anticipate different flux levels.

A simple listening test to see if the playback calibration is within ballpark between the channels is play back a completely blank tape. Listen and compare the tape noise between channels. It should sound identical in level and character across all channels.

Tim
 
OK,

I will give a try perhaps running some tones thru my Logic Pro. Otherwise I will just have to buy the oscillator.

Tim,

Your explanation clears everything up a bit for me: MRL for playback, Oscillator tones for recording.
It's funny that you're saying to play a blank tape and check the noise level. That is something I did by accident about a month ago and I checked the hiss levels on each channel. I was going to mention that in an earlier post, but it didn't seem like it was significant. I am currently building a wooden rack-stand for the teac deck, so I will give it a try when we finish it (hopefully tomorrow). Otherwise I'll haul it in and run it thru my mixer.

I may just print some tones to the tape and do what you say; "print tones and observe them on playback". That will at least tell me if my calibration is BADLY off. Luckily only one tape will have been wasted if that's the case, as the other one will be recycled and recorded over again.

I will keep the forum posted.
 
thereelman77 said:
OK,

I will give a try perhaps running some tones thru my Logic Pro. Otherwise I will just have to buy the oscillator.

Tim,

Your explanation clears everything up a bit for me: MRL for playback, Oscillator tones for recording.
It's funny that you're saying to play a blank tape and check the noise level. That is something I did by accident about a month ago and I checked the hiss levels on each channel. I was going to mention that in an earlier post, but it didn't seem like it was significant. I am currently building a wooden rack-stand for the teac deck, so I will give it a try when we finish it (hopefully tomorrow). Otherwise I'll haul it in and run it thru my mixer.

I may just print some tones to the tape and do what you say; "print tones and observe them on playback". That will at least tell me if my calibration is BADLY off. Luckily only one tape will have been wasted if that's the case, as the other one will be recycled and recorded over again.

I will keep the forum posted.
Click to expand...

Oh no! Please for your sake... for Christ sake do not listen to anything in Gillett's post #10. Some of it is somewhat applicable to cassette and some of it is just plain bizzare, but as for calibrating reel-to-reel... OMG NO!

This is the rub with web forums and I always recommend people use them as a starting point rather than to find the definitive answer. Many people get their misinformation on the web in the first place and simply pass it around; often more mangled depending on an individual’s ability to comprehend and then retain something that is foreign to them.

Even trying to discern the correct answer by majority doesn’t work. In fact, it’s more likely when dealing with a specialized field like recording that only one or two responses in a thread will be correct.

So take everything with a grain or salt… even what I say. I can tell you I've been doing this stuff for 33 years and you can take my advice to the bank with confidence, which is true, but everyone is just another voice on an anonymous web fourm, at least until you get to know the members here a lot better. We have a few making mischief and playing "expert enginneer" on HR, and one in particular in the Analog Only forum. Above all, research, research, research, before you even pick up a screwdriver.

The difference between aligning a newly acquired deck of unknown history and routine maintenance of a deck in an environment where its been regularly maintained is the difference between night and day. Your decks fall in the newly acquired category with more question marks than anything else as far as alignment. So a full alignment is in order.

Once the input/output line levels are set, proper calibration ALWAYS starts with a standard MRL calibration tape or equivalent. The frequencies on the calibration tape not only give you the flux reference level (AKA record level), but is also necessary for head alignment and EQ response curve calibration. You absolutely cannot do a proper calibration without a prerecorded tape from MRL, TEAC, Fostex, STL or BASF. MRL is the only one still making them, but you may find others NOS from the above companies.

I'm running out to the store for a bit and will be bcak to explian calibration in more detail with some links. Keep your shirt on!

Running tones with Logic Pro or anything else will tell you nothing about the accuracy of your alignment at this point, nor will listening to tape hiss.

:facepalm:
 
thereelman77 said:
OK,

I will give a try perhaps running some tones thru my Logic Pro. Otherwise I will just have to buy the oscillator.

Tim,

Your explanation clears everything up a bit for me: MRL for playback, Oscillator tones for recording.
It's funny that you're saying to play a blank tape and check the noise level. That is something I did by accident about a month ago and I checked the hiss levels on each channel. I was going to mention that in an earlier post, but it didn't seem like it was significant. I am currently building a wooden rack-stand for the teac deck, so I will give it a try when we finish it (hopefully tomorrow). Otherwise I'll haul it in and run it thru my mixer.

I may just print some tones to the tape and do what you say; "print tones and observe them on playback". That will at least tell me if my calibration is BADLY off. Luckily only one tape will have been wasted if that's the case, as the other one will be recycled and recorded over again.

I will keep the forum posted.
Click to expand...


Of course the complete and best way to go is to calibrate the playback first, using a reference tape. A full service and alignment can be quite time consuming , and requires the correct tools.

Depends on one's capabilities and patience too. Some people find it a breeze to do. Others find it impossibly difficult.

But if as you said, buying a cal tape is not practical for you at this time, you can still do a rough test of the playback function by the listening method we discussed. If that seems reasonably OK you can attempt to adjust the record parameters - if they need adjusting.

There are other mechanical issues which can affect the sound of course too. Tape heads get dirty, wear, get magnetised, get out of alignment, etc etc. It goes on.

Cheers Tim
 
Beck,

Do not fret good sir!! I have not done anything yet. We are still working on building our stand, I'm not trying anything until we're done.
I understand where you are coming from.

For the record: ANYONE OUT THEIR WHO READS HIS POST WRONG do not start a "who knows more" debate (I do not mean sound rude or anything :D).
I respect the fact that Mr. Beck is being open, honest, and stating his own opinion based upon his experience.

But I do understand where you are coming from. I realize that tape calibration is not something to just half-ass or screw around with. From what I've researched, some have run tones thru digital software with little success, but they have done it. Even like briank mentioned earlier "I hate to admit it, I also have a multi-channel calibration tone session on ProTools that I can easily patch into the tape inputs". Myself, it doesn't make sense to run tones thru the computer. I figured it wouldn't hurt to try it out though, at least just see if anything was seriously out of whack. I would never base my calibration completely off of that.
But even to me, running DIGITAL tones on from an un-set level to the ANALOG deck, never made sense to me.

And yes I have done my fair share of research, I had been researching for almost 2 years before I got a lucky deal on the Teac. I was shooting for an Otari, but wasn't in my price range. I knew the steps involved in maintaining it and I took the risk(s). So far, it has been successfully paid off.

Tim,

Well buying 2 MRL tapes is not practical for me right now. I'm in a position where I could only order the 1/4" or the 1/2" but I'm not sure which one to get first, since it could be a few weeks before I get the next MRL tape.
Obviously their could be mechanical issues, but when first got it, I spent a decent few days cleaning the unit thoroughly and I only have had one problem with the pinch roller, which went away. The heads are in feasible con-dish- 80-85%. I haven't de-magged yet, which is something I will do.
NOW, while I am tempted to adjust the parameters and I am very tempted (I'm ambitious in those sort of things), I most likely will just wait for the MRL tape. I will ABSOLUTELY try out the method we discussed, checking the noise levels and such, but I probably won't mess with any of the parameters. When I got my first tape machine (4 track Teac 3340s) one channel was slightly off calibration and I tried messing with it blindly. LEARNED FROM THAT MISTAKE PRETTY QUICKLY!!
 
The MRL is an essential tool....but alone, it will not give you a complete deck alignment and calibration.
Ideally you do the mechanical alignment/calibrations first, and then move to the electronics, because mechanical issues will affect the electronics.
That said...the mechanicals are not needed often, but good to do at least the first time so you know you are starting with the best possible platform for setting the electronics.

If you have the manual with alignment/calibration insturctions...you will see the proper sequence.
How much the mechanical stuff is off will depend on the age, condition and usage that the deck saw. I it's in fairly tip-top shape you could skip past some of the real involved mechanical stuff as on most decent decks, things are designed to last and stay in place for a long time...but again, doing an as complete setup at least one time will get you that much closer to optimal operation, otherwise, you may have to over do the electronics to make up for mechanical issues if you just go for the electronic calibration.

Yeah...it takes time! :D
Even a 2-track can be involved when doing complete setup.
I spent a couple of days overhauling my 24-track 2" when I got it. I didn't have the tools to do the tension and W&F stuff, which is at the beginning of a complete setup...but I could see from basic checks that it was probably in the ballpark, so I did everything else mechanical and then the electronic. I've since acquired the tools I was missing, so I plan to go back and just recheck everything from the first step to the last.
 
+1 to that.

thereelman77 said:
Myself, it doesn't make sense to run tones thru the computer. I would never base my calibration completely off of that. But even to me, running DIGITAL tones on from an un-set level to the ANALOG deck, never made sense to me.
Click to expand...

My previous post disappeared, but I'm in full agreement with this. One would have to have a way of verifying proper operating levels of soundcard output before proceeding with this method. I think this is a basic point that's often overlooked.
 
When using tones from my DAW for calibration...I would always check the output levels with a DVM rather than just rely on the DAW meters.
 
thereelman77 said:
Even like briank mentioned earlier "I hate to admit it, I also have a multi-channel calibration tone session on ProTools that I can easily patch into the tape inputs". Myself, it doesn't make sense to run tones thru the computer.
Click to expand...


Woops, you misunderstand me. I DO NOT use ProTools in place of an MRL tape, that doesn't work. I use ProTools ONLY as a multichannel tone generator, nothing else! Literally I just have some channels set up with a tone generator plugin on each track that I can mute and unmute depending on what tone I need for my record cals. It acts exactly like that Rolls tone generator you were looking at, or my console's oscillator. The only reason I sometimes use ProTools for my tones is because some of the pots on my 32 year old console are getting tired and the buss levels are sometimes a little off, so when I'm calibrating my 1" 8-track machine it's quicker and easier to use a ProTools session that's pre-set for 8 channels of 1khz, 10khz, and 100hz tones output at +4db for doing my record calibrations, that's it, and as Miroslav says, yes you do need to measure the DAW outputs with a voltmeter and make sure you're getting proper +4db levels out of it (you should be getting 1.23vAC on the jack), you can't trust the DAW meters.

A DAW WILL NOT take the place of an MRL, you absolutely need an MRL to calibrate your repro electronics, nothing else will be accurate or worth your time. Then when the repro levels are set with the MRL, you use your tone generator to calibrate the record levels to the repro levels, that's the only thing I brought up the DAW for, if you have a DAW that has a tone generator plugin then you don't have to buy a stand-alone oscillator, that's the only reason I brought up the ProTools tones. I hope this clears things up!
 
briank,

Ok, yes I did mis-understand you, sorry. This whole process is new to me. Bottom line, the one thing everyone is saying, the MRL tape is NECESSARY. I'm gonna' get the 1/2" reel ordered asap, hold off on the 2 track for abit. It has a OSC tone built in and I have the manual, I'm going to see what the deal is with that.

I understand what you are getting at, just trying to save yourself having to buy the oscillator tool, which is smart, considering your old console.

But in the meantime, I'm going to get the MRL tape and most-likely get the Oscillator, just to have a tone generator. I don't like dealing with all that crazy digital stuff and besides I really don't have an interface, so I'd have to run it from the headphone jack out. I do have a 2 channel A to D converter box, but I really don't like using it. I mean, I would almost like to save the $60 and run the tones thru the DAW, but I feel like having to have a computer around all the time, especially if I move the tape machine to another studio and such, would become a hassle. As far as that goes, I'm up in the air, but I feel that just getting the oscillator would be easier for me.
I do have a voltmeter from Radioshack as well.

We're finishing the stand tonight and I will FINALLY be able to set the unit up in a decent manner to get this calibration rolling.
 
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