Calibration tapes,tools etc.....

  • Thread starter Thread starter j.harv
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j.harv

j.harv

@#$%
Well...what I want to do,over the following months is acquire calibration tools for my 388.
Im in no rush to get this stuff because I know it can be expensive. I just want to learn and i know it will take time. I do have 2 Tascam 388's so I could always carefully practice on one of them. I just want to know what i would need and where to get it. For example....do test tapes have to be Teac branded? I would even be brave enough to get an oscilloscope and study up on using one.
Any thoughts on where to get some of this stuff and what exactly would be needed. I don't want to go balls out,but I would like to learn the art of a thorough calibration.
Thanks...
 
Hmmm I may be accused of spaming here but since the question has been asked. I have created a online course that deals with the basic theory of analog machines AND detailed alignment procedure for pro 3 head machines. The class can be applied to many different machines. ( 2 head machines are a little tougher)
instructions.. You would need a test tape... and for head adjustments you can sometimes get away with a accurate meter but some form of scope is best.
Here is a link to the course
https://www.udemy.com/analog-audio-tape-recorder-basic-theory-and-alignment
and here are some youtube clips that explain head adjustment and some insight to bias adjustment.
Brad Leigh's Audio Engineering Lab - YouTube
of course if you google around and search youtube you can find the info , but the goal of the class is to give the theory and ALL the steps in one place.
Brad
 
Yep, 2nd that...get an MRL tape and the one you want is the one ARP notes above.

What do you have for a demagnetizer?

Do you have a computer and some kind if audio interface? If so, I recommend just getting a free or cheap software-based oscilloscope. Not as good as an actual scope but all you're likely to use it for is azimuth and a soft scope will work fine for that and then your money is better spent on a good true rms multimeter that has good audio bandwidth specs...this you'll more likely use.
 
Thanks guys.

I have a Han-D-Mag which I've heard is one of the better ones.
I dont have an interface yet, but that seems like a good idea.Any recommedations????
And the RMS multimeter??? I will look into that too.
Now to search for the tape.
 
Hey Dave...
I went on the JRF website and the tape you suggested is listed for a 1/4" 2 track machine.
There is also a tape....21T02 that is listed for 1/4" 8 TRACK 7.5 IPS.
Im guessing they're both compatible?
 
If I were you I'd just get the tape from MRL and tell them what machine you have as let THEM tell you which one to get.

I like Fluke meters, but there are many brands. The trick is that you want one that measures accurately over the audio spectrum. How good is your meter for measuring the amplitude of 1kHz test tones if it's only spec'ed as accurate up to 400Hz?

So Google "true rms multimeter" and start browsing, and then look at the specs of the meters and if they are suitable for audio they'll usually have accuracy ratings for the AC volts setting up to 20kHz.
 
Simple question? Complicate answer!

The difference between 21T204 vs. 21T202 is not "2 track vs. 8 track". In this sense they are compatible, in that they *and all MRL tapes* are recorded full-track. The real difference is NAB vs. IEC(1) equalization curve, respectively. Without getting into theory or complicated explanations, the most concise information I could find that's definitive is:

"At 7.5 in/s two equalizations are used, but the usage is fairly uniform:
NAB = IEC2 is mostly used in US; and
IEC = IEC1 (= CCIR = DIN Studio) is mostly used in Europe."
(ref: http://home.comcast.net/~mrltapes/choo&u.pdf )

The 388 manual specifies (NAB/DIN/IEC) equalization, which probably means it's flexible enough to run either but specifies neither. The 388 is 7.5 ips. I was steered toward the 21T204 specifically for being NAB by a very knowledgable seasoned pro. I'm in the U.S.A. If I were in Europe I'd probably get the 202 for the 388.

When you talk about MRL tapes, then contemplate all sorts of recorders, track counts, tape widths, speeds, you will find (and use) different standards for different reasons/speeds/widths. There are usually solid recommendations to go by, starting with manufacturer setup and specifications. (The 388 manual is not specific). Then, there are a lot of technicalities to it & I've not absorbed it all. People who really understand this stuff well may choose different equalization curves to calibrate/record by, for a number of different reasons related to audio and the magnetic properties of tape they're trying to exploit.

In large part, the "equalization curve" business is a technical effort to get the most out of modern tape formulations, capturing the best HF content and reducing noise, as well as giving the "flattest response", but the EQ curves themselves are anything but flat. There have been several standards, and they all have optimum uses and fans as well as drawbacks and detractors.

You follow the accustomed standards for the setup, even though most if not all of these tapes (our home recording multitracks) will never see light of day, except in our bedrooms and home studios. It's more of being aligned and calibrated as concisely as possible to get best R/P response, more than having wide compatibility of machines. At least on the 388 I'd say that. A 2-track master would be different, where wide compatibility with other machines would be more important. However, getting a recorder dialed in with alignment and calibration assures maximum compatibility with other machines. These two ideas go hand in hand.

I think the 21T204 is the "most correct" one to choose for the US user & the 388. 21T202 for European setup.

http://home.comcast.net/~mrltapes/pub101.pdf
http://home.comcast.net/~mrltapes/equaliz.html
 
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Okay!

I see where the confusing info is, on the JRF website: MRL Alignment Tapes from JRF

... where the 21T204 is listed under the header [1/4" 2-tracks], and a 21T202 is listed under [1/4" 8-tracks] (both tapes being 7.5 ips). However, due to things stated above, I think this is a bit of a minomer in the header description. (Maybe just an effort to oversimplify). In reality, you can use either but you have to commit to one standard and run with it.

There is no single right answer, & is why there is such a staggering array of MRL tapes available.
:spank::eek:;)
 
Which is why I say contact MRL directly and ask. Try will for certain tell you te right tape for the 388, not to say ARP isn't right.
 
Thanks again guys.
One more quick question before I make time to go through the DIY calibration thread.
If at first I want to just check the record/playback levels to make sure what Im recording is playing back at the right volume,
is it correct that I dont need the MRL tape,just a tone generator and probably an interface to connect from computer to 388.
This is the first check I would like to do.
 
Right. The ONLY thing the MRL tape is used for is to adjust the playback levels.

Follow the procedure in the 388 manual. Tascam did a relatively good job of laying out the procedures in their manuals in a step-wise fashion. Usually meter calibration comes first, then input levels, then bias, then record levels and record response, then play level and response.

For those first couple steps you'll need a level meter and some sort of tone generator. There really isn't a reason you can't use the speaker out jack on a PC to source your tone generator software for tones to the 388.
 
Thanks again Cory.
Funny thing.....I just checked my local online classified and this exact meter was just listed.Not sure if he has the probes for it also. Would any replacement probes work,or would I need a certain type?



update...gonna go pick this meter up.Comes with non original probes.

This one is an 8060a model hope this works.

Update#2 ....guess Im not gonna get this model.Rated to 100khz.
 
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100kHz??

You wouldn't ever need anything over 20kHz!

Did you mean it's not rated over 100Hz? Which I doubt.

If it's true rms measuring and rated to 100kHz, comes with probes and works and the price is right (like similar to the others you were looking at), GET IT.
 
Ok.
I'm really not familiar with these tools. On the spec it's says volts to 100
Khz. On the model from the ebay listing you sent me goes to 30khz.
Like I said, I'm really not familiar with all this yet. Still learning.
So I should spring for it.?


update....Got it.Now I gotta figure it out.

Is there a test I could do with just a tone generator and this voltmeter.?
I did a crude test yesterday and im not sure this proved anything.I hooked a casio keyboard into the line 1 input,then
selected all 8 channels to record.I played a tone for about 30 seconds.I noticed that most of the meters were reading different levels in dB.The stereo meters were not really registering much at all. I recorded the tone and upon playback,all the meters were at different levels.Some were up a lot higher and some lower.So im guessing there are some things outta whack here. Is there a test I could do? Im gonna download a proper tone generator. I just want to know,where about in the manual is this calibration.Or do I need a few more tools????
Thanks to all.
 
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Do you have the full 388 operation-maintenance manual?

Don't overwhelm yourself with everything. It starts with getting the meters lined up. Download a freeware tone generator and use that and your new multimeter to do just that first part. That's all you need is the PC, tone generator, a cable from the line out on the PC to the 388, and your meter to set the level on the tone.
 
Yep.Got the full manual. And just downloaded the visual analyser. Got the tone generator up.Just dont know how to get certain tones.
I was looking at the recording level adjustments in the manual and it says to provide a 400hz -10db reference input.
The thing is there is a "scale" on this tone generator and it goes from 10 100 1k 10k.
Im just not sure how to get the presribed tones up.There is no 400hz on this generator.I know im doing something wrong,and its probably all there in front of me,but im not too studied in the whole hz,db,v, etc....
 
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