How to make a Speed Calibration tape

[miroslav]

..to Tim Beck!

At the end it's not about 15ips, but insead, it's all about WhatEver-MRL-machine-ips.
As long as we ALL agree that MRL's machine is STANDARD, then we are all happy cats ..heh heh heh , as all we really asking for is to get "standardised" .

Or you can do it without MRL, all you need to do is to find the way to actually measure the "actual" speed of tape on your deck.

And that's possibly the best point/reason to use the MRL tape...because your deck will then be set up to a single standard (assuming most people just opt for the MRL tape instead of some homebrewed approach).



First off...I doubt anyone's homebrewed attempts would reach the same level of anal precision as MRL's (I mean that in a good way), though it’s possible if you have the right equipment, in top shape, all calibrated from the start...etc.
But even if you CAN make your deck's speed more accurate and closer to 15ips using your homebrewed approach than you could with MRL's tape…..
(1)Would that be a quantifiable and audible improvement?
(2)Would that be really “better” if you are living/working in a studio industry that uses the MRL tapes for standardization?
IOW...if other machines are running at speeds that are in +/- error margins, and yours is perfectly dead-center in-between those margins…what would it really mean having your machine perfectly centered?
How would you use that to your benefit?
And that’s assuming that most decent machines are pretty darn stable, especially if you’re running them with some form of sync box…so the possible 0X.X% errors you might have with your transport hardware are probably less than what you already get just from the stretching and tension on the tape itself.
So would you be chasing “perfection” to no avail, as the tape kinda works against you…?

I dunno...just some random thoughts…maybe none of those questions are that important.

Of course...doing all that kind of experimentation just for "fun" is a totally different and a very valid reason, so yeah, we should all do what is fun for us.

 

[Dr ZEE]

I just want to say this, as it seems like we are running a bit in circles here and are getting carried away from the specifics of the "idea" (as I understand it , of course - imho, that is).

This "idea" here is specifically and only about making your own "tool" for adjusting/setting the tape speed. Nothing else.
If practically succesful, then this tape-"tool" in combination with a frequency counter would provide a user with ability to check/adjust any tape speed on any deck (that can "accept" that tape). If someone faces such "task" than having such "tool" seems to be pretty "beneficial"
In short, having a tape-speedometer in your "lab" is pretty cool.
***********
A note on "standards" in general.
The plot of any standard is NOT accuracy per say. BUT! The Plot of any standard is an AGREEMENT.

When using any "standard" as refernce for "calibration" the actual accuracy of the the calibration will still depend on the accuracy of the equipment used during/for the calibration procedure.

Introduction to standards shall start with introduction to understanding standard as concept in general.

***********

A note on neophytes:

I see a neophyte not as someone to be taught, but rather as someone with the choice and potentials to learn. And there's a fundamental (philosophical) difference between the above two "views"
***********

A note on invention vs. "just messing around with stuff" :

Invention is an established and recognised form of the consequence of "just messing around with stuff"

 

[Beck]

..to Tim Beck!


Or you can do it without MRL, all you need to do is to find the way to actually measure the "actual" speed of tape on your deck.

Yes Mike, I understand how/why standard speed tapes work and all that goes into it, so we're good on that point.

So, again, Ethan's "idea" is all about figuring out the period of recorded tone(or puls) on tape. If you know the distance between periodic waves/pulses on tape (or total amount of periodic waves/pulses per known length of tape), then your frequency counter can be used as speedometer.

And this is why I asked exactly what you meant by a pulse. So, if it's a periodic tone, what is the duration of the tone? If the tone is 0.25 seconds long (for example) it will be recorded over 3.75 inches of tape... if the tape is moving at 15 ips.

And how close together are the pulses (that is, how much tape does the silence take up in between pulses?)

Depending on what speed this experimental tape is recorded, it will be different. And since we don't know where the machine is speed wise, we are back to square one, are we not?

Are we starting with a machine running at 14.5 inches/second or a machine running at 15.75 inches/second? Well we don't know. Maybe I still don't have a good picture of the nature of the pulses or bleeps, or even if that's what they are.

I've thought of other ways, like leader timing tape and a stopwatch, but then the individual’s reaction speed comes into play. If you have the reaction speed of a fighter pilot maybe you'll be fine. But then you send your tape to Bubba's studio across town so he can add some percussion and he set his machine up the same way, but had 3.5 bottles of Beck’s Beer before he did the calibration.

And if we’re using an electronic (optical or something else) sensor to reduce impact of human reaction speed we have to know the latency of that circuit.

One important thing to keep in mind here is that it doesn't take much of a speed change for your song to be playing in a different key on another deck if standard means aren't observed.

Another studio or duplication house can always rough check the accuracy of your speed compared to “Standard” with the test tones you should be putting at the beginning of your master tapes. One hopes it will be within an acceptable window so coarse adjustments won’t have to be made.

 

[Dr ZEE]

Tim, you are almost there ...heh heh heh
You know what's funny (or sad ... or - for me) was that when Ethan said it does not matter what speed and frequency the tape is being recorded first - at first I though that he's out of his mind ... hah hah
Forget about oscillator frequency and "unknown tape speed" for a start.
Just think of "Ethan's Speed Tape" as electronically marked "timing tape".
As you "record" the tone (or puls , square, sine...what ever) of what ever frequency - you leave periodic magnetic "marks" on tape. There is "physical" space between those marks. You can't "measure that space with a ruler, but you can calculate the total amount of "marks" per measured segment of tape (- famous 25 foot!!!, that is )
The actual value of "space" between the "magnetic marks" is not the target, but rather it is the "reference". Again, Ethan method is not per say about measuring the space between "marks" on tape, but instead - figuring out total amount of (assumingly periodic!) "marks per measured segment of tape) . Once you figured it out you can use that tape to find out the actual speed of tape using Frequency Counter.
When you play back that tape the frequency counter will show you actually the frequency of magnetic MARKS on tape (say, hoamount of "marks" that are passing the head per second). As you know the "physical distance" between those marks in length units (inch/sm) (in actuality - total amount of periodic marks per known length of a segment of tape) you can calculate the actual speed of tape (length unit (inch/sm) per second that is.
Practically, to adjust the speed or "set" a desired speed, you do it a bit differently - you first "calculate" the frequency of the "target" speed and adjust the "tape speed" to match that frequency.

wheeeeewwwww
***********

now, again, the practical implimintation, accuracy and usability/applicability - this are a "separate" issues really. all was pointed out already.

*******
p.s.

oh, and, btw, and I know, that this sure WILL NOT help anyone anywhere in any way, BUT!, here I go:
Time and Space are not issued by an Agency, but are God given.

 

[Dr ZEE]

a bite of humor:


Got Speed?

 

[pianodano]

a bite of humor:


Got Speed?

Yepper. This will tell how fast it's going.



http://usrecordingmedia-store.stores.yahoo.net/quanplastiml.html

http://www.online-stopwatch.com/large-stopwatch/


No fooling either.

 

[miroslav]

I just want to say this, as it seems like we are running a bit in circles here and are getting carried away from the specifics of the "idea" (as I understand it , of course - imho, that is).

...........


Invention is an established and recognised form of the consequence of "just messing around with stuff"

Yeah, it may be a bit circular, but that's normal IMO when exploring new territory.
Someone tosses out an unusual idea, and people will ask all kinds of questions and/or go off on tangents, and maybe even some of those questions might come off somewhat in opposition to the initial "idea"...but I think that is what makes for great discussions, that back-n-forth "tug of war", and that will often spawn even more ideas and possibly expand on the initial one.
The "picking away" at the original idea actually helps better define it and even make it stronger.

If I didn't keep asking Ethan about what he was suggesting...I might have just dismissed his idea and never quite gotten it clarified.

 

[Dr ZEE]

......I might have just dismissed his idea ...

I've done so, and for an embarrassingly long period of time ..heh heh

Speaking of time again, Ethan will have to rely on "no time" excuse for some time, because I personally will be waiting for practical results all that time

Speaking of "impact" of a "great discussion" , this got me in to "an idea" to maybe to try something out (in a style of "just messing with this stuff" ).
I wonder, if I throw together a notch filter, then "tune" my generator to the "black hole" of it, then record that signal on tape, then play it back, sent the output through that notch into a preamp circuit (just for level adjust) and then to a AC meter and start messing around with tape speed... I wonder if this will give me some sort of "observation" in action.
Ok, idea is an idea and then - back to "no time" point

 

[Beck]

Ok Doc, I understand more of what you're trying to do, but it still won't work if the speed of the deck the "marks" or tones are made on is still unknown. They are to be recorded, correct? By nature of the magnetic tape recording process speed dictates time and frequency.

I'm not saying the idea will ultimately not work; I’m trying to understand as many details of the idea as possible so I can help iron out any bugs that may be overlooked.

Ironically though, IMO the only way the prototype can be tested is to buy an MRL tape to test the method for accuracy.

*******
p.s.

oh, and, btw, and I know, that this sure WILL NOT help anyone anywhere in any way, BUT!, here I go:
Time and Space are not issued by an Agency, but are God given.

I appreciate your independent spirit, Mike. I too bow to no one but God. However, a train finds its purpose on the track that was prepared for it. It's freedom and ability to function depends on it staying on track. One might say the train limited by the track, but it would be much more limited if stuck in the mud.

Now I'm just waiting for Ethan to reply and say ZEE has it all wrong...

 

[Beck]

Truth be known, I'm really being difficult because I've been working on my own idea.

First you convert 88 mph into inches per second and... well I was standing on the toilet seat hanging a picture on the wall, I slipped and hit my head and I got this idea...

https://www.youtube.com/watch?v=lfnAb11wKQc

 

[Dr ZEE]

heh heh ...Take me "back" there...where I will be...

By nature of the magnetic tape recording process speed dictates time...

Nothing nor anyone dictates time. It does not even exist..heh heh . (BUT!!!!this would be a separate discussion, or would it not? ...)

By nature of the magnetic tape recording process speed dictates ... frequency.

Aha!!!!!!! ...and so, the play-back signals' frequency can be "traced back" to speed, as long as you know the distance between cycles (marks on tape).

At the "begining" we don't know the tape speed.
To find out we run the tape and periodically mark it (simply, recording periodic signal on it).
Then we cut a measurd segment of that tape and count amount of marks within that segment.

I am going to use metric system for "easier" rounder numbers and to honor french fries

Say you cut 1 meter of tape that you just pre-recorded with a periodic signal of unknown frequency.
You run that segment and count total amount of "cycles" on that 1 meter segment.
Say you get 100,000 cycles.
So you know that you have 100,000 cycles per 1 meter, which gives you 1000 cycles per cm.

This is al you know at this point: You have a tape that has 1000 cycles per each cm on it.

Now you play that tape and measure the output signal's frequency.
Let's say you get 1,000 cycles per second

So
You have:
1,000 cycles per second
(while running a tape with...)
1,000 cycles per each cm

So now you know that you run that tape at speed equal 1 cm per second.

Turn up the power, reach 19,000 cycles per second on your frequency counter and you set your machine to 19cm/sec.

Now, let's play some real ROCK, baby ...!!!!!!!! heh heh

I appreciate your independent spirit, Mike.

It's not a spirit. It's an Ideology, based on a chosen philosophical view.

...Now I'm just waiting for Ethan to reply and say ZEE has it all wrong...

me too

 

[Dr ZEE]

grrrrrrrrrrrrr
forgot visual note ...
here it is

 

[Beck]

It's not a spirit. It's an Ideology, based on a chosen philosophical view.

No kiddin'?

See in my case I have an independent spirit due to stubborn Scottish genes... I was born this way.

But anyway the term "Spirit" is just a figure of speedch.

 

[Dr ZEE]

..... I was born this way.

That's cool - , and I'll take it as : "You had no choice"
***********
Speaking of "figures" , here are "formulars", as without a sexy formular it's not a theory heh heh:

to figure the Tape speed as it's running:

V(t)=F(out) / P

or to figure out Output Frequency for a Desired Speed:

F(out)=V(t)xP

V(t) - tape speed inch or cm per second
F(out) - output frequency (cycles per second)
P - amount of cycles per inch or cm on tape

 

[Beck]

The original sine wave signal can be any frequency. I picked 1 KHz. It is of unknown accuracy but is presumed to be somewhat stable.

The term pulse is used to represent 1 cycle of that original sine wave.

Any deck can be used to record that sine wave. The decks speed is unknown but the wow and flutter are presumed to be less than 1% (ie not obviously audable)

The tape is a known length. By cutting a fixed length of tape and putting leader on it we have defined one of our references to the accuracy of our length measurement.

A counter in total mode will count each and every cycle.

Run the tape on ay deck with the counter hooked up and we get the number of cycles on that length of tape. Run it at any speed, we don't care. The counter is only counting cycles.

With a known length and known cycle count we have all that is needed to calculate the frequency of the recorded signal at our target tape speed (or any other tape speed).

IN the example given in the beginning of this thread, 25' of tape with 20,000 cycles on it yields 1 KHz when your deck is going 15 ips.
25' = 300"
300" / 15ips = 20 sec
20,000 cycles / 20 sec = 1 KHz

If you counted 19,500 cycles then

19,500 / 20 sec = 975 Hz

This is now your target calibration frequency for setting speed....

Regards, Ethan

I actually missed this post before somehow.

Hmmm... I'm thinking.

 

[Dr ZEE]

humor break

Time for a humor break.

...Ethan... .… he’s always thinking.

..Hmmm... I'm thinking..

Sh$t happens, man.

 

[Beck]

But that Dr ZEE... what was he thinking?

...................

 

[Dr ZEE]

But that Dr ZEE... what was he thinking?

Heh heh...
I was desperately trying not to, but since it occurred against my will, I was thinking about thinking as an unfortunate circumstance of life.

Then I was "thinking" about who would be the best to ask to bring to life what I was thinking about, and I've figured, these guys:

 

[evm1024]

Found a little time.....

.... So I measured out 25' of old tape and spliced some leader and trailer on it. I tried to get the tape 25' within a few 10th of an inch. I included a little tension which streched the tape by about 1/4 of an inch.

Then I printed a 1 KHz signal on it. And then I played it back and ran it through my counter in totalize mode which counted the cycles on the tape.

After counting the cycles a few times (about 20) I got an average cycle count of 20112. (the high u20161 and the low 20049)

This works out to 67 cycles per inch or 1005.6 cycles per 15 inches.

15 inches being 1 second at 15 ips so the signal on tape at 15 ips would be 1.0056 KHz.

Just a few photos:

The whole setup BR-20, scope to make sure of what er are counting, counter in total count mode.

One pass of the tape (taken after the test....and 20239)

During the test with the counter counting up and the sine wave off the tape on the scope.

Regards, Ethan

 

[Beck]

Nice work so far, Ethan.

Now the proof off concept test:

(First, if you don’t have one make your own speed tape with a 3kHz signal to get your machine back in the ballpark to where it was before the following test).

Next, turn the speed adjustment to an extreme direction to produce an unknown speed. Then make another tape at the unknown speed and use it to bring your machine back to where you believe the machine is now… roughly 15 ips.

~Tim