Measuring output voltage of a DAC/Amp with a multimeter

[Dunring]

I'm learning more about multimeters and found a lot of uses for checking cables, ohm ratings of headphones, and adapters. I just got a Soundblaster X1, but there's no measurements for it (I sent a PM to Amirm offering to send it in). I've got 3.5mm to RCA cable and want to see how much voltage it's putting out. The thing can power the DT880 600ohm well enough for fun volume listening, so it's USB 3.0 connector has to be getting more than the old Play!3 I had which was pretty low power when using it as a DAC to an amp. I did test voltage on a battery and it shows ok, but do both prongs go on one side or is it one for each L/R connector to measure what it's putting out? Don't want to short anything. This thing sounds really good but there's no information pertaining to using it as a DAC like other products they have where you can just select line out mode in software.

 

[pseudoid]

Hey @Dunring,
[I mean no disrespect...]
Best thing I could say is that you don't want to be testing headphones w/a multimeter (OhmMeter?).
The other best thing I can say is that if measuring audio equipment was simple as hooking up a DMM (any "DMM"!) to an audio piece of gear... I think @amirm would be out of a "job"!

 

[sergeauckland]

If you simply want to measure the output voltage, put your multimeter set to AC volts, across the output, play a 50Hz 0dBFS tone, which you can generate from Audacity, REW or pretty much any similar software.

Use 50Hz as multimeters are designed for mains measurements and aren't accurate above a few hundred Hz.
S

 

[Doodski]

I'm learning more about multimeters and found a lot of uses for checking cables, ohm ratings of headphones, and adapters. I just got a Soundblaster X1, but there's no measurements for it (I sent a PM to Amirm offering to send it in). I've got 3.5mm to RCA cable and want to see how much voltage it's putting out. The thing can power the DT880 600ohm well enough for fun volume listening, so it's USB 3.0 connector has to be getting more than the old Play!3 I had which was pretty low power when using it as a DAC to an amp. I did test voltage on a battery and it shows ok, but do both prongs go on one side or is it one for each L/R connector to measure what it's putting out? Don't want to short anything. This thing sounds really good but there's no information pertaining to using it as a DAC like other products they have where you can just select line out mode in software.

What make and model of multimeter do you have?

 

[pseudoid]

What make and model of multimeter do you have?

I thought "you've seen one; you've seen them all" rule applies here and that was the reason I tried to keep it as simple as the question was.
Would it have mattered if it was a HarborTool special or a Fluke?
You cannot even ask if RTFM'd, because the HarborTool version has no manual.

 

[HarmonicTHD]

I thought "you've seen one; you've seen them all" rule applies here and that was the reason I tried to keep it as simple as the question was.
Would it have mattered if it was a HarborTool special or a Fluke?
You cannot even ask if RTFM'd, because the HarborTool version has no manual.

Mine Multimeter measures up to 5khz AC, but I very much doubt the OP has a device capable of measuring anything but 50Hz AC.

So sergeauckland gave the best advice in my opinion.

 

[restorer-john]

Depends on the meter. My Fluke 87 DMM is rated up to 20kHz.

I test all my meters for their frequency response accuracy on AC. It's surprising. Some really inexpensive meters have fast A/Ds and decent true RMS converters inside and can do well over 5kHz with good accuracy. Others are hopeless above 300Hz. The Fluke 87s are good enough to use for manually plotting frequency response they're that good.

 

[Blumlein 88]

Most multimeters work fine to 400 hz, because some generators and such work at that frequency. In fact I've tested some of the really cheap electrician style meters from Amazon or big box stores. All have been pretty good to 2 khz. I of course cannot guarantee all brands are that good, but most are fine to a few hundred hertz. They wouldn't be accurate even at 60 hz without some extra bandwidth. So yeah safest advice would be low frequency, but some audio devices roll off the low end. So I'd use 220 hz or something if I didn't know for sure. Check 50 or 60 hz too. It only takes a couple more seconds and you can see if it is consistent.

As for where to measure here is a picture. You put one lead on ground and one on either the band for left or right. If you are using RCA, ground goes on the outer ring, and positive lead goes on the center tip.

 

[restorer-john]

Whoever drew/annotated the drawing doesn't know one end of a TRS plug from the other. Not sure how someone can balls-up something so simple.

The tip is always the centre pin. That's because a solid pin runs straight up the centre to the tip...

 

[Blumlein 88]

Whoever drew/annotated the drawing doesn't know one end of a TRS plug from the other. Not sure how someone can balls-up something so simple.

The tip is always the centre pin. That's because a solid pin runs straight up the centre to the tip...

View attachment 228345

Don't know if I've ever soldered up these. Lots of diagrams are just like the above. It is true quality brands like Rean(Neutrik), Amphenol, and Switchcraft have the tip in the center. However, I don't know if all brands do. In any case the exposed part is all the OP needs to know about.

Here is one of many such diagrams. I cannot find actual pictures of one made this way, but lots of off brand plugs show this kind of diagram. It doesn't make sense anyone would make it this way.

 

[staticV3]

do both prongs go on one side or is it one for each L/R connector to measure what it's putting out?

One goes to L+, the other to GND. Or one to R+, the other to GND.

Don't want to short anything.

You can't. Multimeter input impedance is in the MΩ range, so no worries there. (Unless you're somehow bridging two contacts with one probe)

Here's me checking the output voltage of a dongle with a multimeter.
I use the E1DA Cosmos Load board for probing the outputs. It's really handy.

Also important to keep in mind that you're only capturing the x-axis component of this graph basically:

You could be measuring a certain output voltage, which in reality is far past the clipping point of the Amp.
For a complete understanding you'd have to contextualize the values you're seeing on your multimeter by hooking the DAC up to an ADC/Audio analyzer as well. That's the y-axis component.

 

[Speedskater]

Well, low budget DMM don't have a low voltage AC range, so that rules them out.
But if a DMM has a 10V or 2Volt AC range it can be useful. It doesn't have to be True RMS or even vary accurate, it will still be repeatable with sine wave test tones.
You can check it's frequency response using a digital test tone file. Most CD players frequency response outputs are very good.

 

[staticV3]

Well, low budget DMM don't have a low voltage AC range, so that rules them out.

my $30 AN870 is TRMS and has a 2Vrms AC range. Is that not low budget? Is it a midrange DMM?

Edit: Even this $11 TRMS DMM has AC ranges of 60mV, 600mV, 6V, 60V

 

[Sokel]

Whoever drew/annotated the drawing doesn't know one end of a TRS plug from the other. Not sure how someone can balls-up something so simple.

The tip is always the centre pin. That's because a solid pin runs straight up the centre to the tip...

View attachment 228345

Tested an Amphenol one with the continuity function of the DMM,short left one is tip.

 

[restorer-john]

Tested an Amphenol one with the continuity function of the DMM,short left one is tip.

It's not the left or the right in a drawing that is the issue. The tip (the piece on the end) is connected to a continuous rod that goes down the centre of the plug to a rivet which holds the entire 1/4" plug together. Whether the tag is bent left of right is irrelevant, but it does highlight the simplistic line drawings mean absolutely nothing.

Traditionally, the tip is always closer and somewhat shorter due to the layers of phenolic/insulation and the sleeve of course comes next.

Here's some typical plugs:

Depending on which way it was drawn or photographed, the tip would be either left or right.

 

[Sokel]

It's not the left or the right in a drawing that is the issue. The tip (the piece on the end) is connected to a continuous rod that goes down the centre of the plug to a rivet which holds the entire 1/4" plug together. Whether the tag is bent left of right is irrelevant, but it does highlight the simplistic line drawings mean absolutely nothing.

Traditionally, the tip is always closer and somewhat shorter due to the layers of phenolic/insulation and the sleeve of course comes next.

Here's some typical plugs:
View attachment 231159
Depending on which way it was drawn or photographed, the tip would be either left or right.

Just yesterday I got eyes on a no name,cheap one that the tip was on the right,so you are right and that's a reason to always check.

 

[Frontino]

I measured a cheap Yamaha RX-V381 with a 100 Hz sine wave at 0 dBFS in all 5 channels simultaneously and linearity tops at 21.9 Vrms with master volume -4.5 dB.
That would amount to 120 W/ch into 4 ohms, but the AVR is rated 260 W at the power plug port.

Now, by looking at these measurements:

	0.1% THD	1.0% THD
2 Channels Continuously Driven, 8 ohm loads	70.9 watts	86.0 watts
2 Channels Continuously Driven, 4 ohm loads	85.9 watts	112.3 watts
5 Channels Continuously Driven, 8 ohm loads	41.2 watts	41.8 watts

It looks like the power limit is ~200 W total.

Then, with a 4 ohms load into just 1 channel, could those 21.9 V still be retained and thus get 120 W at 0.1 % THD?

Thanks.

 

[Frontino]

Small update: when lowering HDMI input at -6 dB and 4 of the 5 channels at -10 dB and the 5th at +6 dB (to compensate for the HDMI attenuation), the maximum linear voltage output is 29.00 Vrms at MV -2 dB.