Important Tape Calibration Question

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Tim Gillett said:
Funny you should talk about a "myth busting crusader"...

Hello Tim Beck. How's the crusade going up on the Mixing Forum at the moment? A bit of "outreach"? Hoping for a new recruit or two? A new candidate to groom for "your" forum down here?
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Dear Tim,

The Recording Techniques, Mixing Techniques, and Mastering Techniques forums are not digital only forums. They are recording forums. I do not see analog and digital as mutually exclusive like two different religions, or two armies facing each other on the field of battle. I'm a recording engineer, period. I have a hybrid analog/digital studio and I'm very pragmatic... I use what works and reject what doesn't, with extensive experience with all things recording in commercial and home/project studio environments. When I share my opinion that analog will work better in a given situation or discuss the cons of a digital format, I'm not trying to insult anyone's mother. I'm conversing with other adults who hopefully wish to continue learning as much about recording as they can to improve their technique and expand their bag of audio options.

“Use only that which works, and take it from any place you can find it.”
~ Bruce Lee, The Tao of Jeet Kune Do

Although the bulk of my contributions to HR have been in the Analog Only forum I've weighed in on many other topics in other forums nothing to do with analog. The most recent topic I've joined in on the mixing forum started as a question about "Analog Summing." The OP's question was whether analog summing would benefit him or not and the thread evolved from there. Knowledge is power. To understand the pros and cons of various tools is knowledge that leads to that power and greater competence in the recording arts.

I would not however hang out in the Digital Recording & Computers forum just to tell them how deluded they are at every opportunity. That would be trolling.

I think a lot of people here would be surprised they are weighing in just to agree with me because they're not. miroslav is one of my peers... fully equal and competent. We don't always agree and he can tell me things I didn't know. And that goes for many other members on this forum.
 
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My, my. So respectful. So courteous. So self controlled. Even starts with "Dear Tim"...

Whatever I said must have scared the sh.. out of him...
 
Tim Gillett said:
My, my. So respectful. So courteous. So self controlled. Even starts with "Dear Tim"...

Whatever I said must have scared the sh.. out of him...
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Dood, quit man.

Seriously, you have some good points, and some questionable points IMO.

That is not for me to decide. BUT, you seem to have a hard on for arguing here. I personally, am done hearing it.

Please do the right thing, and stop trolling the Analog forum.

It does not seem like your points are coming across very well in this forum. Just let it go please.

Jimmy.

Feel free to PM me if you would like to discuss the issues. I am here to listen. :)
 
Alright,

So bullshit aside:

Would you ALL agree that if I purchased MRL 341-673-482-103 I will be fine. If I could save the $75 vs. the MRL 31J229, I would much rather do that, which means that I can look into the 1/4" MRL tape now as well.

And back to the oscillator, the Rolls one I ordered came in, but I haven't opened it. I guess they sent it out by the time I cancelled the order, but should I just return it and save $62 and stick with my CD, or keep the Rolls.

I would rather save the cash to be honest, but if you guys recommend that I hold onto it, I would consider it.
 
thereelman77 said:
Would you ALL agree that if I purchased MRL 341-673-482-103 I will be fine. If I could save the $75 vs. the MRL 31J229, I would much rather do that, which means that I can look into the 1/4" MRL tape now as well.
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Both will get you there.
I think the main difference is in how many RW/Plays you will need with the short tape VS the long tape to get the calibration done.
 
And, for the sake of me looking around, what type do you guys recommend for an Otari MX5050 2 track 2-HD? Calibration tape that is.
 
thereelman77 said:
And, for the sake of me looking around, what type do you guys recommend for an Otari MX5050 2 track 2-HD? Calibration tape that is.
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Your Otari is a little more complicated because it not only has two speeds but is also switchable between NAB equalization and IEC1 equalization. Opinions will vary on this, but what I would do if I had your Otari is to also use a short minimalist 2-speed NAB MRL calibration tape. I use this tape myself for my Tascam half-tracks. It’s more bang for your buck than the tape offered by Audio Village.

The product number is MRL 299-008-482-112

It is 2-speed, 15 ips and 7.5 ips, and NAB EQ @ 250 nWb/m. NAB EQ is standard for North America, while IEC1 is standard in Europe. Your machine has a switch so you can use both equalizations. It makes the machine more versatile, but in my private studio I wouldn’t worry about using anything but NAB.

The tape lists for $130.00. Mine cost me $90.00 new. Prices have gone up a lot in the last few years. For me the short tapes are great because I’ve setup so many machines in the last 30 years I find myself tapping my fingers waiting for the tones to hurry up and end on the longer tapes because it doesn’t take me that long. And in a home/project studio environment once you get your machines setup you’ll find they will stay that way for a long time, even years. So whatever tapes you buy you’ll use for setup and put it on a shelf. I do recommend however that a person check calibration twice a year at least. But you’ll find it stays lined up. The check just gives you peace of mind.

In a commercial ‘round the clock studio things are a lot different. In my 20’s I worked in a studio where we checked calibration every morning.

Another option would be the long 2-speed NAB tape. The tones are the same as the short tape, but they are over twice as long in duration. The long tape is MRL 299-008-512-134 and costs about $200.00.
 
The short form MRLs are a good value and work just fine. Rewind of you need more of a tone, or let it play if you don't. You really don't need more than 1khz and 10khz tones to do the job. The other nice thing about a short mrl is that it makes you more willing to be patient and do a library wind when you're done with your cals. Not a long wait ;-)

Some MRLs have 16khz for head azimuth fine tuning but it's not super necessary. My 1/4" mrl has 1k, 10k, 16k, 100hz and since it's used on a 2track deck even the short form tones are more than long enough. My 1" mrl has 1k, 10k, 100hz. It's short form and i usually can set the 1k in one pass and 10k in two on my particular machine. I don't use the 100hz tones for anything other than a general visual reference. I cal the lo freq during the record calibration.
 
Alright, I'll look into the 1/4" MRL.
At this point I'm trying to cut the cost down as much as possible. Saving the $$ on the 1/2" tape was freaking huge.
The MRL tape for the 1/2" 8 track is supposed to be in no later than Friday of this week. I plan on starting the calibration the day of or the day after.
I'm going to copy your (briank & Beck) postings namely on the first page and print them out for quick reference.
I found this online

Analog tape recorder calibration overview tutorial

is this a pretty accurate walk through? If it is, let me know. I went back and re-read your first postings and you basically explain it in 3 steps, I just thought this walk through might be a bit more detailed, to use in conjunction with your previous postings.

Let me know dudes, thanks.
 
That's the general idea. What operating level MRL did you get? 250nwbm, 355? Presumably you're calibrating for +6 right?
 
I'm calibrating for +6, at 250nwbm, IEC equalization.

The MRL actually came today, most nicely packaged tape I've ever gotten....

I won't be starting anything until tomorrow though.
 
thereelman77 said:
I'm calibrating for +6, at 250nwbm, IEC equalization.

The MRL actually came today, most nicely packaged tape I've ever gotten....

I won't be starting anything until tomorrow though.
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Cool, so make sure you clean your tape path very well and demag the heads carefully WITH THE MACHINE POWERED OFF and make sure you keep tapes well away from the demagnetizier while you do it!


So this is the general procedure for setting +6 with a 250nwbm MRL; I don't know your specific machine so bear with me, I'm used to pro 3-head machines so keep that in mind....also, you want to do all this with the monitoring set to repro since what you're doing is calibrating the repro electronics, then calibrating your record levels to the repro standard.

Spool up and rewind your MRL to the top. Run the 1k tone and set your repro/sync cal levels to -3db on the VU on the repro card. Then run the 10k tone and again set the repro HF EQ to -3db on the VU. You can then run the 100hz and "rough in" the LF EQ but you will properly set this later.

With the repro electronics calibrated at -3db on the VU, you can remove the MRL--make sure you library wind it to tails out--and clean your tape path. Put on a fresh reel of the tape formula and length you plan to be using and wind it to the top. If you need to set tape tension for the new reel, do that too.

Set up your oscillator for 1k, 10k and 100hz tones coming out at +4db. You can check this at the jack with a multimeter, put the + probe on the tip and the - on the ring and you should be getting 1.23VAC.

Run the 10khz tone and get it recording onto the blank tape and set your overbias. You'll crank the trimmer counterclockwise until the VU hits a peak reading and then starts to fall again. Rock it around until you get the peak reading in range on the VU (you can back off on the oscillator level temporarily, or back off on the rec level trimmer if your machine has one, if you need to get it in range on the VU). Once you note the peak reading, you can trim clockwise and set the VU meter so that you're as much below the peak reading as the amount of overbias you want, so for example if you're shooting for 2db overbias and your machine peaked at +1 on the VU, you'd overbias to -1db on the VU to get your 2db overbias. The peak reading will typically vary slightly from channel to channel!

OK, with your bias set, you can send a +4 level at 1k to your recorder, print that while adjusting your record cal to 0VU. Now send 10k at +4 in record and set your HF record card EQ to show 0VU. You might want to go back to 1k after this and make sure the 1k is still at 0VU, then go back to 10k again and make sure 10k is also at 0VU, this is a good idea if your machine hasn't been calibrated in a while and it will help you know how touchy your particular machine's adjustments are. Now run 100hz and get the LF repro EQ set.

With this done, you should be able to print the three tones all showing at 0VU in record. Print then for future repro calibration to each reel of tape you're calibrating for. On my 8 track machine I like to do 30sec each of 1k, 10k and 100hz as I don't mind rewinding if needed. On the 2-track machine 15sec is fine enough for me. I like to have less tones and more recording time on my tapes =)

That's the general idea off the top of my head, hope this helps, have fun and ask questions if you need. Let us know how it goes...and treat the MRLs with kid gloves!

BTW you can also use the MRL for head adjustments (head wrap and azimuth) but that's for another discussion!
 
Ok,

So I have followed your directions and also stayed close to the teac 80 manual. The only difference that I came across was that during the MRL calibration the manual says set to -10db, but we calibrated to your -3db...

Alright, now we got to the BIAS part, but I have run into a few snags. I understand the concept and I've tried adjusting channel 1 & 2 BIAS trim pot. Now the thing I'm not understanding is how the peak-drop works. The manual says to go 3db below the peak line. The problem is, when turning counterclockwise, channel 1 didn't drop at all (nor did it drop going clockwise that much). Slightly the same for channel 2.
Now the only thing I've been able to notice, when running the 10khz tone thru all 8 channels, they all seem to peak out (when in BIAS adjusting mode) to about +1.5 to +2db. So is it safe to assume that BIAS is already set?
 
And as a side note, I have been playing my CD test tones thru my mixer with all levels set to 0db and input gain at 30.
 
Back track a bit. Are you sure you wanted to set the magnetic flux level to +6? The manual calls for +3 or the same as your 250 nWb/m cal tape. So using that tape you would set VU meters @ 0 VU The line level for each channel is separate and should be set to –10 dB.

Keep in mind that you have two distinct but interacting level systems in a magnetic tape recorder. The first is the line level. For so-called Semi-Pro units like the TEAC 80-8 the level is the input/output levels for each channel. Those should be set at –10 dB no matter what flux level you will go with. Once you get a –10 dB output to agree with a –10 dB input then you have the base line level site. Then you move to the tape flux level, which will be referenced to your cal tape.

After that you do bias calibration, which is different than the first two procedures. When you’re looking at the 3 dB down from peak it’s not related to the –3dB offset if you plan to set flux to a different flux than what the cal tape is zeroed for. In this case you shouldn’t have to worry about that, but just zero the VU meters while running a 1k tone from the call tape.

Let me know if that make4s sense before we move forward.
 
Ah yes my bad, I forgot that machine i/o's at -10 not +4db, so make sure you're sending your cal tones out at that level.
 
Beck,

I'm confused on what you are saying? We are calibrating the deck for RMG 911 +6 tape.

I think we understand, but to clarify: you mean that if I had 185 nWb/m, that's when I would calibrate so the VUs show -3db?
 
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So I'm still at the same dead end. When I turn counter-clockwise, neither channels drop down to zero. In fact channel 2 cranks to +6db on the meter and never falls below the red.
 
thereelman77 said:
Beck,

I'm confused on what you are saying? We are calibrating the deck for RMG 911 +6 tape.
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I see this as a common misconception all over the net. For this example, calibrating the deck to 250nW/m=0VU (appx. +3 over 185) puts your MOL of +6 to be @ +3VU. This enables you to go a bit into the red (to +3VU) before hitting MOL (+6db/185). If you set your 0VU @ +6, i.e., 250nW/m=-3VU, then 0VU will be your MOL (+6) and you'll hit saturation and eventually distortion at and above 0VU. @ +3VU in that case you'd be hitting +9/185, well above MOL.


thereelman77 said:
I think we understand, but to clarify: you mean that if I had 185 nWb/m, that's when I would calibrate so the VUs show -3db?
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In this particular case, that's correct. That's why the manual states set 0VU for a cal tape @ 250nW/m.
:spank::eek:;)
 
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