Calibration tapes,tools etc.....

  • Thread starter Thread starter j.harv
  • Start date Start date
Ok just figured out how to get the 1k tones etc....
Just one question...do these downloadable tone generators rely on a good internet signal? Because all of a sudden my 1k signal is doing a morse code kind of thing.Its sounds like it's glitching.


update. I think the headphone jack on my laptop is a little dodgy.
 
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Ok. Got that figured out. But I think the multimeter I bought might need calibrating.
It just doesn't seem to want to settle on 0.
I've let it sit for 5-10 min,but it won't zero out. And I really still don't know how to use/read the thing.
 
Don't worry about it "settling on 0". Are you talking about when it's just sitting without the probes touching anything? If that's the case it is likely sensitive enough to pick up stray RF noise in the environment. Until it's got a job to do it won't settle.

Did you get a manual with the meter?

And did you find the first part of the setup and calibration procedures in the 388 manual?
 
If you didn't get a manual with the multimeter here it is:

http://assets.fluke.com/manuals/8060a_3vimeng0200.pdf

Look on page 2-12. It shows you how to have the probes connected for voltage measuring, and figure 2-6 on that page takes you step-by-step through setting the meter up to measure AC volts. You want to set the range switches to 2V, and the AC/DC switch to AC. Audio voltage is AC.
 
Thanks a lot for that SB.
I have the meter set up the way you described.The numbers are floating around 156.Goes up and down from from there. Thats kinda where it's sticking at.
Setting up the meter is what kind of confuses me. I just didn't know what voltage to set it at and why.
Im like Charles Ingalls from a Little House on The Prairie trying to fly a spaceship when it comes to this kind of stuff.
Im looking at the 388 manual. Im just not sure what the first check should be. There are quite a few. Im guessing in the recorder /reproducer section adjustment? The recording level adjustment?
The other thing that confuses me about the tone generator is what volume do I set it at.???
There is a volume adjustment on the generator.Do I crank it? Just not sure what level this tone should be fed into the 388?
 
I've been slowly filling my bench out. One thing I've been told is to get an AC voltage meter with an movement meter not a digital readout, as it is easier on the eyes. I also have aFluke meter for everything else. Look on craigslist, which is where I got the Fluke and the 'scope
 
Hah!

Charles Ingalls split logs and made a tight fitting smooth hardwood floor for his house with nothing but an axe! He'd have figured out a space ship no sweat and you can too. :D

Adjust the level of the tone generator so your meter reads about 316. That's millivolts, so 0.316 volts which is the equivalent of -10dBV which is what the manual calls for.

Go to page 1-12 in the maintenance section of the 388 manual and look at figure 1-4-1. That's where the meter adjust trimmers are behind the left trim panel. Now go to page 1-16 and follow the instructions to calibrate the PGM meters.

Once you are comfortable with that procedure, if you want, you can do the similar procedures for the main meters in stereo mode and aux/eff mode on page 1-13 and 1-14 respectively.
 
Alright. Thanks.
Just still confused how to set the tone generator with the meter. Do I put a probe in the headphone jack of my laptop to get a reading.??? This is usually what messes with me.
Also is there a simple test I could do with this meter to see if its working properly? Hook it up to a battery....etc.
I still think it might be messed up because as Im looking at it right now the meter is reading 468 and it's constantly fluctuating up and down in this high range with nothing being probed.????

Also,for when when I actually start to do the actual tests,is there any way to keep the probes in place?
Seem like it might be tricky making adjustments while trying to hold the probes and read the meter.
 
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Ok i think I might have figured out how to measure the volume of the generator.But im not getting accurate results.
I plugged a 1/8 stereo plug into my laptop,there are 2 rca plugs on the other end.I put the positive probe on the center of the rca plug and the negative on the outer ring. This was picking up the volume output,I think?
I downloaded the tone generator you suggested and I noticed there is an amplitude adjustment which im guessing is volume because I entered -10dbfs but his registered around 358 on the meter. Not .316.
I just want to get this accurate as possible.
 
Try adjusting the amplitude in the test tone generator application until you get around 316mV. It doesn't have to be perfect, but closer to 316mV from 358mV would be better.

Can you take a pic of the meter with it measuring something? Just want to make sure we are talking same-same here.

Yes it can be tricky to have the probes measuring while tweaking the trimmer on the machine, but remember you are only going to set the output from the PC once. Then you plug the cable from the PC into the appropriate jack on the 388 and measure from the corresponding buss out jack so you can stick one probe in the RCA jack and let it sit there and then hold the other to the sleeve of the RCA jack and your other hand is on your trimmer tweaker.

You'll get it.

You're getting closer.
 
Thanks again!!! I just couldn't get the meter close to. 316 without it being quite away from. 316 db.
The generator volume control goes up and down in notches if you know what I mean. And it doesn't really want to get close. I'll try again when I get home from work.
 
You also have a volume control for the output from that line out jack on the PC. What operating system does your computer have? If it is a windows based computer, generally speaking, there is a little speaker icon on the lower right of your task bar and if you click on that you'll get a volume slider.
 
Ok.Been messing with the volume controls on the computer and tone generator for about 20 min.
The best i can get is between 0.311-0.314. Cant get it on 316.
Im guessing this is close enough. Will start probing the 388 tommorow.
But just to be sure.The meter has to be set to volts and it has to be set to 2. ???
Thats what its at right now.
 
Well,I couldn't resist. I thought i'd try to calibrate the first meter before i hit the hay. Did what the manual said, got a reading of about 0.311 out of the pgm out jack with a 1k tone.And about the same(.311) going in to the PGM in jack. The vu meter hardly moved and it's not really that loud with headphones.
The thing Im not sure about is the vu meter. It says it should register at 0 vu. This is where im a little dumb. Is this the 0vu in the red section or is this the lowest part of the meter below the -20. Because the -20 area is where im at with the tone going in. i curiously tried to adjust the trim pot,but there isn't much range on it and it obviously didn't move the needle that far.
More tommorow.....
 
...

.316V = 0VU, so .311V would read a hair or 2 below 0VU. As long as the reading on the PGM OUT jack says .316V the VU meter should read 0VU.

Even tho your input may be .311V, or even some other voltage, you may manipulate several controls (Trim, Ch. Fader, PGM Master Fader) to get .316V on the program out jack, and therefore get 0VU reading on the VU meter.

(Haven't looked at the 388 manual), the VU meter trim on the front of the meter is not the adjustment to be turning. There should be a Meter PCA with adjustments for the VU meters. This will give you a fairly large range of adjustment. The adjustment on the very front of the meter is a fine adjustment, and probably shouldn't be messed with.

:spank::eek:;)
 
the ones on the front of the meters are to set their mechanical zero, (far left side of meter, done with power off). That is not to be confused with the 0db you are trying to adjust for which is the area of the meter where the black section meets the red section.
 
Thanks Reel / mdainsd. I adjusted the proper trim thats located behind the left wood panel.(R101)
Im just not sure if I have to get the needle thats in the red area on the vu meter or is 0vu at the lowest point of the vu?
Because when I feed the tone into the 388 the needle hardly moves(around-20). And I am getting around a 0.311 reading on the tape out.When I adjusted the trim pot the all the way the needle barely moved to the right.Just a few db.So there's no way I can get it up to the red meets black section.I have the pgm masters in the shaded areas too.
 
Guys, there's no trim adjustment on the 388 meters themselves. He's doing the proper tweaking in the proper place. And ARP the control surface trim controls don't affect this test...the point of measurement is at a pass-through from the point of input. Let's not confuse young Mr. Ingalls the cosmonaut.

J.harv that's why I wanted you to put up a pic of your meter measuring something so I can see how you have it set and see what the display on the meter shows. Can you do that? I want to confirm you have it set right because what I'm suspecting is something isn't right. At about 316mV the VU needle should be at the "0VU" that is at the black-meets-red point. If the meter is showing around -20VU then that is actually about 31.6mV. I want to see your mutimeter. I think your tone generator output is low by a factor of 10.

Also, 311, 314...that is well close enough. Notice the 388 manual is even less picky and says to set the voltage to 0.3V which is 300mV. So, don't sweat that part. The *important* thing is that you are reasonably close to the standard, and that all meter/channels are set to the *same level*. This is, in essence, what "calibration" is after all, and why it is also referred to as "lining the machine up"; making all the tracks/channels the same.

ALSO! You said you were measuring from the TAPE OUT jack? That should be the PGM OUT jack.
 
This is a another reason I picked up a Leader LVM volt meter. My Fluke usually jumps around between .307-.320 something range. It drove me crazy with the numbers changing so I bought the used Leader. It's a specific purpose meter, but does the job.

Do you have an extra small mixer you can use?

I initially did the same thing with my laptop, but found it was too difficult to fine adjust the volume, so I just hooked the output of the laptop to a small mixer and was able to easily get -10 out of the mixer. Plus the Leader has an analog meter which is much easier to read in this situation (for me anyway).

In addition, the mixer I had also provided the proper "load" as was recommended in at least my Tascam 38 and 42 manuals.

SB is correct, .311, or even .300 is close enough. Not sure if the 388 calls for the cal tests to have a load though.
 
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