Checking guitar output level with a common multi-meter?

[Eddododo]

Curious of a good way to very vaguely check output voltage of a guitar/bass for someone without a scope..


Mainly trying to get a sense of the extreme peak output I used a looper pedal (unity output) and recorded a few layers of open string strum as well as high-energy low notes (bass has a thunderous and focused low B), then checked the AC voltage across hot/ground. It is a proper wall of sound.
I know this isn't the most clear nor scientific approach, but is this likely good enough to figure out an ballpark maximum output? I'm only concerned that I'm not missing peaks beyond what's shown.

I played around with trying to fashion some kind of LED setup as an 'if lit, it exceeds X volts' but I didn't dig super far.

As a very quick and dirty test, does this seem useful at all, or is it likely far too unreliable for even the blurriest measurements?

edit: meter goes down to a 200mv setting..
got consistent ~.5v readings from the 2v and 20v range, both on the looper and clumsily doing the same thing direct from the bass
meter spec'd at 10Meg Zin, with a 50-500hz range (which honestly seems okay for a bass guitar)

[mozz]

Some meters do have a peak hold function but not common multimeters.  The looper probably has a limit to it's dynamic range.  Yes i would say 500mv or a bit more is gonna be your peak. I can check if you want, tell me what kind of guitar and pickups.

[PRR]

> check output voltage of a guitar/bass for someone without a scope..

Yeah, get a 'scope. Nothing touches it for this use.

If 'scopes are illegal in your town, you could use precision rectifier peak detectors.
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/peak-detector/

In concept, you could use an adjustable gain amplifier, adjust for clipping, figure clip level, do math. But "clipping" is ill-defined on the ear, especially if you are changing gain at the same time.

> 50-500hz range (which honestly seems okay for a bass

Bass can have content way past 1kHz. But yes, on both/most instruments the "power body" is mostly below 500Hz. The extra rattle on some basses (Rickenbacker?) tickles the ear, and may distort funny, but is usually lower amplitude.

[Elektrojänis]

I've used following method a few times every now and then:

Connect computers sound output to the input with a cable with bare wires so you have something to connect your metr probes to. You could also use a splitter-cable or adapter or something.

Play back a sine wave from the computer and measure it with your meters ac voltage function. For the freqency of the sine wave, see the spec of your meter. something between 100 Hz and 500 Hz is likely to be suitable. Also record a bit of your sine wave back in to the computer through the cable. Make sure you record only through the cable and not through the internal record what you hear thing. Make sure the recording does not clip/distort. If it does, set the levels again, measure again ad record again. This is now your reference level and reference recording.

Unplug the cable from the output of the computer and connect your guitar to the input. Play and record your test chords and licks.

compare the waveforms on the recording software to the reference recording. Now you can calculate the voltage amplitude of the parts of your guitar signal you want.

The recording software usually shows the amplitudes in dBFS. that means the loudest possible sine wave is 0 dB and everything else is negatve numbers. Thecdifference of 6 dB is half or double the voltage. If you want to calculate the differences accurately the formula is easily found on google. You can also find online calculators for it.

The method is less complicated than it first seems and the upside is you only need equipment you are likely to have already. One problem with this is that the input impedance of the regular computer inputs is low. That will eat up some signal from guitar pickups and affect the accuracy. You might use a buffer (like a pedal with a buffered bypass) there. If you have a separate audio interface with guitar input, this will not be a problem.

I hope this description is good enough for understanding my method. I'm currently on mobile and english is not my primary language.

[Eddododo]

> check output voltage of a guitar/bass for someone without a scope..

Yeah, get a 'scope. Nothing touches it for this use.

If 'scopes are illegal in your town, you could use precision rectifier peak detectors.
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/peak-detector/

In concept, you could use an adjustable gain amplifier, adjust for clipping, figure clip level, do math. But "clipping" is ill-defined on the ear, especially if you are changing gain at the same time.

> 50-500hz range (which honestly seems okay for a bass

Bass can have content way past 1kHz. But yes, on both/most instruments the "power body" is mostly below 500Hz. The extra rattle on some basses (Rickenbacker?) tickles the ear, and may distort funny, but is usually lower amplitude.

I've been using REW (room eq wizard) for freq response, and I realized it has a scope function. I'm still getting the hang of it, as calibrating things can be fiddly and it's prone to bugs that require a relaunch, but I think I've gotten to a place where I can reasonably trust what I'm seeing


That said, if anybody has some good suggestions for decent hobbyist scope, I'm all ears! I'm just never sure what I'm looking at vs what I need

As far as bass response- 500 is a low cutoff if I had my druthers, but as far as what's going to be clipping things, it's an okay starting point.. if the meter was a better option generally, I could live with that limitation (or yknow, get a different meter)

[mark2]

That said, if anybody has some good suggestions for decent hobbyist scope, I'm all ears!

For rough measurements and visualization, it's hard to beat those little DSO138 or DSO150 scopes. I paid about $20 for mine as a partially-assembled DIY kit.

They come in a variety of packages and states of assembly, but they're all pretty much the same.