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Author Topic: Audio RMS volt/level meter?  (Read 3865 times)

Hal Bissinger/COMSYSTEC

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Audio RMS volt/level meter?
« on: December 23, 2010, 01:11:14 am »

I'm just browsing the latest issue of Sound and Commununications and an article "What's in Your Test Kit". Under essential basic test gear the author lists an audio RMS volt/level meter with a minimum 20Khz bandwidth, calibrated in volts, dBU and dBV also having various time weightings- slow/fast/peak. I find that interesting. Does such a thing exist? Closest that I'm familiar with is the NTI XL2 but that only displays voltage I believe.

-Hal

Ivan Beaver

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Re: Audio RMS volt/level meter?
« Reply #1 on: December 23, 2010, 08:58:53 am »

It is really handy to have an old fashioned ANALOG meter to measure music type signals.

Much easier to "average".

The old Hewlett Packard 400 meters are really good for that.  Large scale-accurate to well past the audio range-can measure very small to large (300V) volts.  THey don't have any weighting scales on them-just flat.

You can get them pretty cheap (at least as compared to what they cost new)on Ebay.
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Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

Rob Timmerman

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Re: Audio RMS volt/level meter?
« Reply #2 on: December 23, 2010, 10:57:32 am »

Many of the higher-end Fluke DMMs will do this (except for the varying time ranges, I believe)
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John Roberts {JR}

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Re: Audio RMS volt/level meter?
« Reply #3 on: December 23, 2010, 11:07:20 am »

Hal Bissinger/COMSYSTEC wrote on Thu, 23 December 2010 00:11

I'm just browsing the latest issue of Sound and Commununications and an article "What's in Your Test Kit". Under essential basic test gear the author lists an audio RMS volt/level meter with a minimum 20Khz bandwidth, calibrated in volts, dBU and dBV also having various time weightings- slow/fast/peak. I find that interesting. Does such a thing exist? Closest that I'm familiar with is the NTI XL2 but that only displays voltage I believe.

-Hal

and they want ice water in hell...  Laughing

I am not convinced that RMS is really necessary. Many a system was successfully debugged using a Simpson 260, but you you need to understand the limitations of your equipment.  There have been several models of premium (Fluke) hand held VOM with RMS and decent audio bandwidth available for a long time.

I haven't seen any with all of the features you listed but there may be one somewhere. Sounds like a dedicated audio test unit. Could be built into one of those hand held scopes.

JR

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Tom Young

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Re: Audio RMS volt/level meter?
« Reply #4 on: December 23, 2010, 06:40:49 pm »

Hal-

Although I have not yet used this function on my XL2, on page 92 of the current manual it clearly states that the XL2 "measures the absolute level of the input signal. The units dBu, dBV, V and dBSPL are selectable."  It simultaneously displays the THD, frequency and weighting curve applied.

I'll try this over the holidays and report back.

BTW - the XL2 manual is not only printed at an inconvenient size (aprox half 8-1/2" x 11"), it is also not thorough nor as well-written as I would have liked.

But overall I am very happy with this tester. They continually post new firmware versions (but not too often) with small improvements as the need arises.

HTH-

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Tom Young
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Email: dbspl@earthlink.net
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Ivan Beaver

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Re: Audio RMS volt/level meter? Accuracy important?
« Reply #5 on: December 23, 2010, 07:44:28 pm »

Of course it all depends on exactly what you are trying to do.  If you are trying to do a precision alignment, then accuracy is important.

Bt if you are just trying to do some troubleshooting, then it is not so important (just like having all the different scales).

If there is no sound coming out of a loudspeaker, and you should be measuring 20VAC on a loudspeaker cable, but if you meter is wrong and either reads 15 or 25V, is it really important?  NO.

You are getting voltage at that point, so the problem is somewhere else.  

Same goes for impedance/resistance.

Let's say you should be reading 5.3 ohms resistance on a 8 ohm loudspeaker.  But your "cheap" meter is showing 4.5 ohms.  Is the loudspeaker likely to be bad (especially if the complaint is no sound)? NO.  The problem is still somewhere else.

Lots of troubleshooting can be done by just being in the ballpark.

Now if you are doing specs for a spec sheet or setting precision voltages, then that is a different story-and you need more accurate gear.

So it begs the question-What are you here to do?  And what do you need to do the job?

Many times when doing troubleshooting, I grab the meter/tool that will give me the quickest results to help me narrow it down, not always the one that will give me the most accurate answer.  Unless that is what I need to do. and then I will grab the tool that will give me the most accurate answer.

I remember in my first TEF class, the theme was "What are you here to do".  And don't waste time taking measurements that really don't matter to the customer and you don't need and do nothing to guide you to the actual problem.  They may be interesting, but not needed-and who is paying you-and for what?

If the complaint is there is a hum in the system, then measuring the reverb time is really not doing you any good. Rolling Eyes

With a tool that gives you all kinds of options, you can waste a lot of time doing/measuring things that will not guide you to the answer any better than a lesser tool.

And for the example above, the problem was the speaker wire was chewed through by a rat.  So if the voltage was "off" coming from the amp really doesn't matter.  All you needed to know was that there was signal coming out of the amp and that the loudspeaker was not open (resistance measurement).

I'm not sure what the point of this post is-so sorry if it is just rambling a bit. Rolling Eyes

I guess I missed my whole thing of "getting to the point" Laughing
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

Hal Bissinger/COMSYSTEC

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Re: Audio RMS volt/level meter? Accuracy important?
« Reply #6 on: December 23, 2010, 09:32:58 pm »

I agree that for general troubleshooting your best tool is your brain. I guess the purpose of my post is more of "if this is so important why is there nothing out there?" I can see it being useful for setting levels. The XL2 has been on my wish list for awhile so I have no hands on experience with it. I have had a MR PRO for a number of years and have been happy with NTI.

-Hal
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