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  #1  
Old 10-16-2006, 06:25 PM
lee_tree lee_tree is offline
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Calibrating an audio meter

I've recently purchased an audio meter to sit next to my old Urei 1620 mixer. However it seems useless unless properly calibrated....the manual mentions something about a special CD with 0db.....

Whats the best way to calibrate the meter ?

How does the CD work as I though the meter was dependent on volume ?

Any help gratefully appreciate
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  #2  
Old 10-26-2006, 06:08 PM
pevie pevie is offline
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You ideally need a cd or hi-fi test record that gives you a constant signal of 0 db. Play the cd or record and adjust ( use a small blade screwdriver ) the two tiny white screws on the far left of your meter until the meter holds steady at 0 db, easy !
A decent hi-fi shop should have a test cd or maybe someone else on the board knows where.
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  #3  
Old 10-26-2006, 06:36 PM
pevie pevie is offline
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http://soundeffects.com/soundcheck2.html
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  #4  
Old 10-26-2006, 06:38 PM
thermionic thermionic is offline
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Neither a test record or CD will help to calibrate the meter unless you have a TRUE RMS multimeter.

The vinyl's output level will depend on the efficiency of your cartridge, and carts vary like mad, so that's a no-no.

Likewise, a CD will be calibrated to 0dBfs, which is a digital standard and its relationship to the analogue output level from your DAC's buffer will vary (if you look at the CD player's manual, it should tell you the analogue reference voltage for 0dBfs btw).

The only way to calibrate your meter will be to play either a CD or Test Record, or - better - connect an oscillator, BUT measuring the output of the device with a TRUE RMS multimeter so you know the absolute voltage.

In all honesty, if you're unsure, just use your ears:

Drive UREi until it distorts audibly. Set this as the upper threshold for the meter, above what you consider to be a safe working level.

An example: you might want it to distort 12dB above what you consider is a safe PEAK level. Adjust the meter to clip at +12dB and you'll know that you have 12dB in hand before it clips if your peaks hit 0.

I can tell you exactly how to calibrate it by the book, but unless you have a TRUE RMS multimeter, you're on a sticky wicket. Even if you have the kit to calibrate, you might use some “artistic license” in calibrating anyway, so a lack of test gear isn’t a big deal, unless you really want to calibrate it according to UREi’s ‘specs.

Justin

edit: If you like maths, you probably could calibrate it by the book without an RMS meter, but you will have to trust all the manufacturer's levels on the tone record and cart etc, so it's a tad risky.

Last edited by thermionic : 10-26-2006 at 06:41 PM.
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  #5  
Old 11-01-2006, 12:48 PM
lee_tree lee_tree is offline
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Hi guys, cheers for the help.

Think I'm going to use it as a meter that tells me when the compressor is going to kick in on the amp, rather than a true 0db meter as seems far too difficult to set up properly.

Cheers
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