Can the output of an instrument be measured?

[mrbeezroom]

I am trying to set the output levels of my active basses (using the preamp trim pots) so they are all relatively the same. My queston is, can a bass's output be measured using a multimeter or similar device?

[dfung60]

Yup.  You can read approximate output levels by setting a multimeter on the 2V Volts AC range, then just hitting and holding a note.  It won't catch the initial attack transient, but when the note settles into the main sustain, you'll get a relatively steady reading which you can match between instruments.  Because the attack is an important part of how you perceive the instrument's sound, it may not sound exactly right to your ears when you match sustained levels, but it's a good starting point.  If you compared your Alembic to a Hofner, you'd find that the sustain level of the Hofner to be very low relative to the attack.
 
Hooking up the multimeter is pretty easy - one probe to the tip and sleeve of a 1/4 output.  There's no polarity with AC signals.  
 
David Fung

[mrbeezroom]

Thanks, that is exactly the info I needed. I posted this same thread on Talk Bass and received the brilliant advice that I should listen to my setup. Huh, never thought of that. Thanks again, John.

[jbybj]

received the brilliant advice that I should listen to my setup   Don't underestimate your ears and your brain. These are actually very precise measuring tools, and perfectly suited to this kind of adjustment. Especially since, as David mentioned, there are properties outside the realm of measureable voltage, that affect the perceived volume. Peace, JBY  ..................             Disclaimer: This is not an endorsement of Talk Bass
 
(Message edited by jbybj on May 22, 2007)

[bsee]

I think the point is that if you want to set up for 1V output, you can't do that with your ears.  I suspect you would need something a bit higher tech than a DMM to see the whole signal.  Something hooked up to a computer to graph the levels in real time or a good old oscilloscope, I think.

[mrbeezroom]

The point, for me, is to be able to get as consistent a signal possible when switching instruments on stage. If this happens the sound man and myself have only minor tweaking left to do when I change basses. Also, I don't want to drastically change the whole mix by having a significantly different output.  
   And of course I use my ears when making changes like described above. But I don't think I am always (or even often) the best person to judge how the changes I make affect the mix. The few times I've had the opportunity to listen to my sound offstage, I am usually very surprised how different my sound is in different parts of a venue. And let's be honest, most of us only get the perspective of being right in front of our amps. So my premise is to start with a relatively consistent output between my basses and go from there.
   Just a brief story about why I'm approaching this topic. Recently at an outdoor gig, I showed the stage sound and FOH guys our setlist and mentioned where I was planning on switching basses. I also explained thst there might be a significant output change when I did. They were impressed that I even thought about it at all and really appreciated the consideration. Since these are the people that ultimately determine what we sound like to the audience, making their job a little easier and getting them on your side can only be a plus.  
  I appreciate all the input. Any suggestions or recommendations for computer software will also be appreciated.  
  And that folks is the longest thread I've ever posted.

[bsee]

I hadn't thought about it because my DMM is 20 years old or so, but the more recent ones can show you peaks rather than just current observations.  If you have one of those, it should help you with measuring the attack peaks of your signal.