Friday, I captured a recording of a friend playing guitar. I had both the direct feed off his guitar and a condenser mic on his guitar. I was interested to note that the above zero half of the direct line off his guitar seems to always be light above zero.
 
Could this indicate a bad battery??
 

 
Once in the past, I had an underpowered pre-amp and it cut all the above zero parts of a wave form firmly, but it was consistent at a particular point, as if limiting the signal only above zero. In this case, it appears to be compressing the signal only above zero.
 
This is another image of the same guitar recorded with the RME in January. This image doesn't show the imbalance... This image is from January 2015 (MLK day).

 
Another difference between the two recordings is that the two recordings is that the unbalanced image I was recording using the High Z setting on my Audient ASP880 which I just picked up.
 
http://audient.com/products/asp880?gclid=CjwKEAjw25SoBRCMn7Gc97Knj0ISJAC7vaMrBQkoXadG7aMqUF3NhRsso7SkWhHX0RUAxGJu1p-63hoCgmnw_wcB
 
I'm concerned that maybe this device should not have been set to hi-z when recording the acoustic electric. But I kinda thought that recording this type of guitar was what the ultra high-z setting was for.
 
So now I'm worried. I have a big session today and I'm not sure what setting to use on the acoustic electric guitar (other than to not use the audient for it. :-)
 
Edit:
I just tested my Seagull Acoustic Electric on all the Z settings on the Audient and the wave-form was even on all three settings.

Magnetic pickups need a high input impedance (ideally in the region of 1 MOhm) otherwise they lose volume and treble. A low impedance input connected to the pickups has the effect of reducing the signal strength, which is most noticable as treble loss.

Anything with a pre-amp in it usually has a low impedance output and is much less fussy about what it's connected to. Though using a DI box generally gets better results than using a jack to XLR cable.

Personally I'm not inclined to record piezo pickups unless there's a particular reason for doing it. They mostly have a brittle, spiky sound which requires quite a bit of processing to make acceptable. Though they have the advantage that two otherwise different guitars with the same pickup/preamp built in will often sound very similar (or can be made to sound similar).

As for "unbalanced" looking waveform graphics, if it sounds right it is right. I recorded a Doepfer Dark Energy II a couple of days ago which I'd set up to do an analogue kick-drum kind of sound using lots of resonance on the filter. Four beats to the bar, the first beat's graphic was almost entirely below the line, the second's almost entirely above it and so on. Despite that they sound the same, or the same within the limits of analogue anyway.

I have had issues with active pickups through DI boxes in the past with a Peavey bass. New batteries didn't seem to help.
 
Rocky

I think Beepster noticed a similar problem when using a 70's amp/preamp as the input?

I'm wondering if what we're seeing is a side-effect of how Sonar draws the graphics rather than something "real". In other words, if it wasn't for having a picture to worry about we wouldn't be giving it a second thought.

The interesting thing is that the sound seems to be fine. I can rationalise my "kick drum" by thinking it's not impossible that, entirely by coincidence, the synth was patched to output opposite phases of exactly the right duration at exactly (or as near as matters) the same time.

That doesn't seem to make sense for guitars though....

Not A sonar side effect. It is audible when you listen discriminately. Wasn't there on the live gig a few months ago. It isn't there today using my guitar and the same input. I think it is with trying replacing the battery. More to come.

bapu
I think Beepster noticed a similar problem when using a 70's amp/preamp as the input?

Indeed I did and it the wave looked very similar to what Geoff posted (except it looked more compressed in the top half of the clip).
 
I have since done quite a bit more recording using the same output and the result has been the same. I have also been paying close attention to the wave being drawn in the parent track as it is recorded and it looks perfectly balanced. It only goes wonky after I stop recording and the wave redraws in a lane. There is absolutely no noticeable degradation of sound quality so tlw may be right in his guess that perhaps Sonar is doing something strange when redrawing.
 
However I have also done a little more research about "balanced" signals and it seems this could be from some kind of issue where one pin is getting slightly more juice (or a different type of juice) than the other for some reason. This would kind of jibe with a battery dying on an active pickup I think (I ain't no electrical talkin' dude).
 
Either way, as was said to me multiple times when I reported the issue if it sounds alright there is no problem and off kilter waves like this are common and normal... just not usually for signals like a guitar.
 
The only potential problem I've found mentioned anywhere about this type of out od whack wave is that when running it through something like a compressor the effect may be hit harder than normal by the negative phase of the wave (or positive I guess if the wave was off kilter in the other direction). This makes it so the compressor will be working harder on one side harder than the other and thus reducing the desired effect (because it is not hitting the other side evenly.
 
I think in that case if it a major problem a possible fix/workaround could be to use a two stage compression set up where the first compressor takes care of the uneveness of phase cycles then the second would be what you would normally get your compressor to do.
 
Not ideal but it might work IF there is a problem.
 
Sorry if that is dumb or doesn't make sense. I'm still kind of trying to understand it all myself.
 
 
Cheers.

I know when the battery gets low on my a/e guitar, the signal gets distorted. Maybe the waveform in Sonar is affected by that?

+1 to TLW's first post.
 
A battery replacement is definitely something to try, but another thing to consider is the placement of that piezoelectric pickup... it is right at the string node (under the bridge), so is where it will pick up every harmonic it can respond to. This often utterly defeats the "acoustic" sound you want to hear.
 
In the past I have used a very old Dean Markley "in the hole" passive pickup which is pretty decent and great in a pinch or loud environment (where a mic may not make the cut). The definite benefit of this is it is centered at the same region the acoustics are (the displacement of the string base tone is much more powerful than any harmonics). It is essentially a warm, removable humbucker that will fit any guitar with a standard sound hole.
 
For your situation, if you already have a good mic setup for recording to your liking, I would stick with that. Recording the piezo is fine, but that output is not even close to "ideal," even if it were perfectly recorded (and the battery "fixed" it). Don't feel the "need" to use that output if you have a better recording.

Thanks to everyone for the input. It looks like a battery issue.