Page 1 of 3

Ugly waveforms

Posted: Mon Jul 09, 2012 12:41 am
by NickGrouwen
Hi, first off I want to say Audacity is the sh!t, I've been using it for 6 years now and it's just the simplest program ever!

Lately I've been running into a problem. Until a couple of months ago, I've been recording guitar tracks (clean signal) and what I would get are smooth, dynamic, curvy, full waveforms (beautiful like the curves of a woman lol). These waveforms mean that the signal is perfect for processing with an ampsim. After the ampsim, the waveform would resemble the clean guitar signal, dynamic, and in turn, pleasing to the ear. My guitar sound was PERFECT.
Image
This is the only clean signal I still have left from that period. Notice how smooth and dynamic and round it looks, right?

However, a couple of months ago, all of a sudden when I'm recording guitar tracks, I noticed that I'm getting these nasty, flat, ugly, spikey, "cold and sterile"-looking waveforms like in the image below:
Image
These waveforms mean that the signal is not good for processing with an ampsim. It already sounds a tad harsh and it already looks distorted. So after this signal goes through the ampsim (same settings of course) it sounds NASTY!! And I have the gain at 2,5 out of 10!!! Now I'm crying and crying, because only a couple of months ago, I had the PERFECT guitar sound, and now I don't anymore =(

Now this might not have anything to do with Audacity itself, but the thing is, this has been happening with another guitar as well. After my first guitar started giving me these ugly waveforms, I switched to my other one and that one gave me smooth waveforms again!! I was soooo happy!

BUT, after 2 weeks, I started getting the same ugly waveforms again like with my first guitar!

What is going on here??

I know that power chords have cleaner waveforms than bigger chords, like major and minor chords, I know that. But I'm still having this problem even with power chords!

I'm using a t.bone USB-1G cable which connects the guitar to a USB port on my laptop.

I'm thinking of getting a new humbucker pickup and see what it does, but before that I'm really really really hoping you guys might know the answer to getting those nice round dynamic waveforms back. It's probably got something to do with the guitar signal itself, however, this problem just suddenly came out of the blue one day! I never messed with my guitar, didn't change the strings, didn't damage the pickup or something, nothing at all! And then one day I'm just getting these ugly waveforms. Same thing with the second guitar.

I'm hoping you guys are familiar with this because I am clueless as to what is going on =(

(Excuse me if my English has some mistakes)

Thank you,
Nick

Re: Ugly waveforms

Posted: Mon Jul 09, 2012 1:05 am
by steve
NickGrouwen wrote:Hi, first off I want to say Audacity is the sh!t
I presume that you mean the bees knees.

Check that there are no Windows sound "Enhancements" enabled (see here: http://manual.audacityteam.org/man/FAQ: ... hancements)

Re: Ugly waveforms

Posted: Mon Jul 09, 2012 7:21 am
by NickGrouwen
steve wrote:
NickGrouwen wrote:Hi, first off I want to say Audacity is the sh!t
I presume that you mean the bees knees.

Check that there are no Windows sound "Enhancements" enabled (see here: http://manual.audacityteam.org/man/FAQ: ... hancements)
Hi! Yeah, the bees knees, the shiznit, the tits, whatever you want XD

I have already looked into that ("Windows Conferencing" I think it was called) but there were no changes I could make there =(

Re: Ugly waveforms

Posted: Mon Jul 09, 2012 11:33 am
by steve
NickGrouwen wrote:"Windows Conferencing" I think it was called
You must have spoken to Kozikowski. He was the only person in the world that calls it that. Now there's two of you, perhaps the term will catch on. ;)

Could you post a short sample so that we can examine it more closely (see here: http://forum.audacityteam.org/viewtopic ... 49&t=64936 )

Re: Ugly waveforms

Posted: Mon Jul 09, 2012 2:58 pm
by NickGrouwen
Cool! Here are some short samples.

As you can hear, it doesn't actually sound that bad but before a couple of months ago I used to get WAY cleaner signals from my guitars, which in turn would result in way better distorted guitar tracks that I could turn up very high without hurting my ears, it didn't sound as harsh.

Re: Ugly waveforms

Posted: Mon Jul 09, 2012 7:37 pm
by steve
There are some strange little spikes in the spectrum view, but nothing obvious to suggest where they are coming from.
The spikes are exactly 20 ms apart, which is a frequency of 50 Hz.
Are you located in a country that has 50 Hz mains electricity? If so then you may be either picking up interference from somewhere or you may have an earthing (grounding) problem.
firsttrack000.png
firsttrack000.png (147.05 KiB) Viewed 2995 times

Re: Ugly waveforms

Posted: Mon Jul 09, 2012 7:54 pm
by NickGrouwen
steve wrote:There are some strange little spikes in the spectrum view, but nothing obvious to suggest where they are coming from.
The spikes are exactly 20 ms apart, which is a frequency of 50 Hz.
Are you located in a country that has 50 Hz mains electricity? If so then you may be either picking up interference from somewhere or you may have an earthing (grounding) problem.
firsttrack000.png
Hi THANKS VERY MUCH for the technical answer, I think I understand what you're saying and I had no idea about this! In fact yes I do live in the Netherlands, 50 Hz.

I'm going to check for any interference or grounding problem, right now, I'll Google around a bit! =D

Re: Ugly waveforms

Posted: Mon Jul 09, 2012 11:44 pm
by DVDdoug
It's hard to tell by looking at the waveforms... I think the time-scale is different and it makes it look like there is no sustain on bad/distorted waveform.
Now this might not have anything to do with Audacity itself,
It shouldn't... Once the signal is digitized by your t.bone gizmo, Audicaty is essentially just routing the digtial data to your hard drive and saving it in an audio format. The recording software rarely has any effect on sound quality (unless something is really wrong).

Oh... What version of Windows are you running? There is a "microphone boost" option (maybe only in Windows 7?) that can sometimes mess-up recording, if Windows "thinks" your interface is a USB microphone. I believe that does alter the digital data stream!

Your levels look OK (not maxed-out/clipped), but have you tried turning-down the guitar's volume control? I think the t.bone might be getting over-driven, or maybe something's gone wrong with it. I doubt the guitar is the problem, but it could be... You don't have an amp sao you can listen to the guitar "directly"? If you think the t.bone might have "gone bad" and you want to try something else, Behringer also makes a low-cost guitar-USB interface.

If there is a guitar repair shop nearby, they might be willing to check-out the guitar at no cost and give you an analysis/estimate before you jump-in and start changing pickups. If they tell you the guitar is OK, then you know it's your interface.

Re: Ugly waveforms

Posted: Tue Jul 10, 2012 9:57 am
by NickGrouwen
DVDdoug wrote:It's hard to tell by looking at the waveforms... I think the time-scale is different and it makes it look like there is no sustain on bad/distorted waveform.
Now this might not have anything to do with Audacity itself,
It shouldn't... Once the signal is digitized by your t.bone gizmo, Audicaty is essentially just routing the digtial data to your hard drive and saving it in an audio format. The recording software rarely has any effect on sound quality (unless something is really wrong).

Oh... What version of Windows are you running? There is a "microphone boost" option (maybe only in Windows 7?) that can sometimes mess-up recording, if Windows "thinks" your interface is a USB microphone. I believe that does alter the digital data stream!

Your levels look OK (not maxed-out/clipped), but have you tried turning-down the guitar's volume control? I think the t.bone might be getting over-driven, or maybe something's gone wrong with it. I doubt the guitar is the problem, but it could be... You don't have an amp sao you can listen to the guitar "directly"? If you think the t.bone might have "gone bad" and you want to try something else, Behringer also makes a low-cost guitar-USB interface.

If there is a guitar repair shop nearby, they might be willing to check-out the guitar at no cost and give you an analysis/estimate before you jump-in and start changing pickups. If they tell you the guitar is OK, then you know it's your interface.
Hi DVDdoug, thanks for helping!

I am running Windows 7 Home Premium 64-bit. If I go into the control panel and select my t.bone device, it says that the microphone boost is at "0", so I believe that is not the problem. It does have this thing called "AGC", which I think means "Automatic Gain Control". I tried unchecking this and seeing what happens, but nothing really helped. The AGC was checked by default anyways so...

Yes indeed I always record my guitar tracks with the volume knob turned about halfway for more clarity and less drive, this is just a personal preference =D I never have the volume knob set too high. The thing is it shouldn't matter whether I have the volume know on my guitar turned WAY down or WAY up (before clipping of course =P)
Because back when I didn't have this problem, my guitar signal's waveforms would look really good either way.

I guess something could be wrong with the t.bone device, which would be weird since this thing is still pretty new, haven't dropped it or otherwise damaged it, it used to work fine. I already ordered my new guitar pickup and I'm gonna switch the neck pickup this week regardless of all this since what I'm using right now are stock pickups anyways, and I'm looking for a bit of a better tone =D Maybe it'll fix the problem, I dunno. If doesn't, I'll buy a new interface, I think I know which Behringer device you're talking about =D

I'm still looking into any sources of interference and grounding problems. I'm getting my new pickup probably today, and I'm hoping to have it installed by Friday, so I'll report back here ASAP =D

Re: Ugly waveforms

Posted: Tue Jul 10, 2012 11:48 am
by steve
One of the difficulties for us is that we don't know what it sounded like before the problem.
In isolation (with nothing to compare with) the recording does not sound bad at all (I've heard very much worse :D).
For you it is different because you are comparing with how it sounded before, how you want it to sound. All that we can do is to try and pick out any technical faults in the recording, such as that slight 50 Hz buzz. Interesting it is a "buzz" rather than a "hum", which suggests that the mains interference has mostly been rejected, other than a small amount of higher frequency harmonics.

Do you use any pedals with your guitar or are you straight into the USB-1G?
What sort of computer are you using? If it's a laptop, have you tried running on batteries?
Avoid fluorescent lights, in fact, try making a recording with no electric lights on.
NickGrouwen wrote:This is the only clean signal I still have left from that period. Notice how smooth and dynamic and round it looks, right?
Waveform images are not a very reliable way of analysing sound quality. It's possible to have waveforms that look very different but sound identical, or waveforms that look virtually identical but sound very different.

This is the last note from the right channel of your "clean" sample (made mono for ease of comparison), and below it the "perfect" image that you posted:
firsttrack000.png
firsttrack000.png (8.7 KiB) Viewed 2970 times
Image

Going just on the waveform, the most obvious difference is the the "perfect" note has a noticeably stronger sustain. I'm not a guitarist - what would cause that? Strings? Plectrum? Humidity? Compression?