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Testing Outputs With Multimeter - Need Help Please
Old 1 week ago
  #1
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Testing Outputs With Multimeter - Need Help Please

I am calibrating my monitoring chain and wanted to confirm that the outputs of my interface are +4dBu when a -20 dBFS sine wave tone is played in my DAW.

I know that a +4dBu signal is equivalent to 1.23 Volts - what I am having trouble with is my multimeter (Voltcraft VC 130). I have attached two pics showing my settings and connections. I did read the manual but I only manage to get a reading showing '125' (no decimal point) when using the 'Diode' setting, not '1.23' Volts.

As you can see from the attached pisc, when I have the sine wave playing and am connected to the TRS cable from the Interface's output I get a reading of 125 - if I increase the level of the sine wave to 0 dBFS the multimeter's display reads 280 so there is a direct increase occurring at the output of my interface.

I am just not sure if I am using the multimeter correctly? When I plugged the red cable into the 'V' input and set it to any of the Volt settings I didn't get any number/figures that made any sense or at all correlated to 1.23 Volts.

I'd be grateful for any and all tips! Thank you!!

ps - if you are wondering where the attached pics are - so am I - they did not load with the post nor can I seem to attach them after the fact.
Old 1 week ago
  #2
Lives for gear
 
🎧 10 years
You may need to make some more posts before you can add attachments.
So tell us more about your setup.

Last edited by Speedskater; 1 week ago at 08:07 PM..
Old 1 week ago | Show parent
  #3
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Quote:
Originally Posted by Speedskater ➡️
You my need to make some more posts before you can add attachments.
So tell us more about your setup.
Thanks for letting me know!

What I am aiming to achieve should be pretty simple - I've got an Orion 32+ Gen 3 interface and I want to confirm the outputs put out +4dBu when a -20dBFS sine wave plays in Cubase.

I feel like I've done most of everything correctly except I just do not understand the behavior of my Multimeter - I followed the manual's instructions for measuring volts and unfortunately the settings did not help.
Old 1 week ago
  #4
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Silent Sound's Avatar
 
5 Reviews written
🎧 10 years
What frequency are you using for the sine wave? Typically, most cheaper voltmeters will only be accurate on the AC setting at the mains frequency either 50 Hz or 60 Hz. They might work fine for an octave of that as well, say 100 Hz or 120 Hz as well, but that's not guaranteed.
Old 1 week ago | Show parent
  #5
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Quote:
Originally Posted by Silent Sound ➡️
What frequency are you using for the sine wave? Typically, most cheaper voltmeters will only be accurate on the AC setting at the mains frequency either 50 Hz or 60 Hz. They might work fine for an octave of that as well, say 100 Hz or 120 Hz as well, but that's not guaranteed.
Thank you for your reply - yeah, I started to figure this might be the issue - I paid 50 Euros for mine so it is not great but also not super cheap either.

But just so I understand correctly, if I want to test a 1kHz -20dBFS sine wave to establish if my outputs are +4dBu, won't using a 50 or 60 Hz tone not get me anywhere?

Or am I missing something?

Thanks for your help!
Old 1 week ago
  #6
Gear Nut
 
🎧 5 years
You will need to meter over a load too, like I believe 600 ohms is standard
Old 1 week ago | Show parent
  #7
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Quote:
Originally Posted by CFB4 ➡️
You will need to meter over a load too, like I believe 600 ohms is standard
Thanks for your reply - I am a total beginner - can you please explain what you mean?
Old 1 week ago
  #8
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5 Reviews written
🎧 10 years
Quote:
Originally Posted by Pilot Zero ➡️
Quote:
Originally Posted by Silent Sound ➡️
What frequency are you using for the sine wave? Typically, most cheaper voltmeters will only be accurate on the AC setting at the mains frequency either 50 Hz or 60 Hz. They might work fine for an octave of that as well, say 100 Hz or 120 Hz as well, but that's not guaranteed.
Thank you for your reply - yeah, I started to figure this might be the issue - I paid 50 Euros for mine so it is not great but also not super cheap either.

But just so I understand correctly, if I want to test a 1kHz -20dBFS sine wave to establish if my outputs are +4dBu, won't using a 50 or 60 Hz tone not get me anywhere?

Or am I missing something?

Thanks for your help!
It won't tell you what you're getting at 1kHz, no. But it will tell you what you're getting at 50 or 60Hz, which if it's fairly linear in output, like it should be, might have to be good enough. Otherwise, you're going to have to buy an oscilloscope or a fancy Fluke or some other DMM with the ability to measure multiple frequencies.

The accuracy of any calibration is going to depend on the accuracy of the tools you use. With what you have, the best you're going to be able to do is ballpark guesses. But that should be good enough for most work. Unless you have a specific outside of just general digital recording.

The 600 Ohm load is needed on the output to get a proper measurement. Usually, most circuits will output a higher level with a lower load, and a lower level with a higher load. So the load is designed to mimic the input impedance of whatever device you hook up to it. Just connect a 560 Ohm resistor across the tip and ring. Otherwise, the only load it will see is the internal load of your DMM, which is probably around 10M Ohms. 560 isn't exactly 600, and it's a measurement of resistance, not impedance, so again, you're not going to get a precise measurement, but it should be good enough. If you have a device that has a 600 Ohm input impedance, like maybe a compressor or EQ, you could try hooking it up, opening up the box, and taking a measurement at the input on the jack (or even the output on the interface).

Though honestly, I'd just stick to the ear test and trust that everything is running as it's supposed to. Unless you're doing something scientific with this, as long as it sounds good, that's all that matters.
Old 1 week ago | Show parent
  #9
Gear Nut
 
🎧 5 years
Quote:
Originally Posted by Pilot Zero ➡️
Thanks for your reply - I am a total beginner - can you please explain what you mean?
It's been a while since I did this! Basically any voltage source can give an artificially high reading if it is not loaded. So that there is consistency, the 600 ohm load is a standard. Silent Sound's suggestion of a 560 ohms i perfect. Even though I have a Fluke, i never actually used it for this kind of measurement—I used to use a 'scope and this was on a 70s Soundcraft that we had at FOH. Of course, with a scope you get peak and not RMS so you have to multiply by .707 to get RMS. Shouldn't have to do that with a good DVM like a Fluke, it delivers RMS readings on AC AFAIK
Old 1 week ago
  #10
Gear Nut
 
Glue2020's Avatar
 
Are you sure you have the multi-meter switched to AC volts ?
Specifically in the range of 0 - 10 volts ac .
Old 1 week ago | Show parent
  #11
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Quote:
Originally Posted by Glue2020 ➡️
Are you sure you have the multi-meter switched to AC volts ?
Specifically in the range of 0 - 10 volts ac .
Unfortunately since I am new here I cannot post pics otherwise I would share pics of my multimeter! It is this model: https://www.amazon.de/Voltcraft®-VC1.../dp/B00JTXENFW

But it only measures between 40Hz - 400 Hz so I do not really know how to equate that to trying to figure out if my interface puts out +4dBu with a 1kHz sine wave at -20dBFS playing in my DAW?
Old 1 week ago
  #12
Gear Nut
 
Glue2020's Avatar
 
Switch that multi-meter to the V~ setting at 200 .
Stick the multi-meter probes on the Tip and Ring of that TRS cable coming from the interface.
Old 1 week ago | Show parent
  #13
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Quote:
Originally Posted by Glue2020 ➡️
Switch that multi-meter to the V~ setting at 200 .
Stick the multi-meter probes on the Tip and Ring of that TRS cable coming from the interface.
Hi, I did just that and unfortunately nothing shows up on the display.
Old 1 week ago
  #14
Gear Nut
 
Glue2020's Avatar
 
You got a sine wave coming out of that interface , turned up ?
You got that TRS cable coming out of the correct channel with the output ?
You got that meter switched to AC volts with the probes on the Tip and Ring of the plug of the other end of that TRS cable ?
( doesn't matter which one is black probe or red probe as this is AC volts ).
You should get a reading.
Old 3 days ago | Show parent
  #15
Here for the gear
 
Quote:
Originally Posted by Glue2020 ➡️
You got a sine wave coming out of that interface , turned up ?
You got that TRS cable coming out of the correct channel with the output ?
You got that meter switched to AC volts with the probes on the Tip and Ring of the plug of the other end of that TRS cable ?
( doesn't matter which one is black probe or red probe as this is AC volts ).
You should get a reading.
Thanks for your help! I managed to get it sorted and establish a -20dBFS 1kHz Sine Wave in my DAW produces +4dBu at my interface's Outputs.
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