What causes these artifacts?
I am running N-Track 3.3 build 1516 (had upgraded to 5 and had nothing but problems so I switched back) and have been experiencing problems during any part where an instrument rings to silence.
A fuzzy/farty kind of artifact creeps in and overtakes the part.
The source is clean as far as I can tell.
I am running a Strat through a POD XT Live diretly into a Terratec ews88MT with no effects via N-Track and as I listen to the source during the recording, it is very clean and clear.
Upon playback the tone is very good, but as the final chord fades out, I am getting the above artifact.
I have had problems with this for quite a while with a variety of parts, but I used this example because I’m fairly confident that the source is clean and it seems the potential for user error is low here.
Does anyone have any thoughts?
Thanks, Chris
Hi, Chris,
Since you notice the noise as the last chord fades away, I would suspect noise coming from the Strat’s single coils, such as lights or electronic equipment can cause. Are you heavy compression as part of your POD XT sound, or do you have a compressor plugin assigned to the guitar track? This would account for the noise not being audible during the song and only at the end. The noise could also be coming from an effect within the POD that is before the compression in the effects chain. The compressor would lower the noise relative to your guitar, and as the guitar fades away at the end the compressor opens up gradually and lets the noise come through.
When I play my vintage Strat, I almost always have to sit in just the right position to minimize any noise that it picks up from stuff in the room.
Hope this helps.
Don
Yup. What Don said…
I have a POD XT Live and a Strat as well. Almost all of the medium to high gain sounds from the POD suffer from the effect you describe. It is more noticeable with single-coils but is still present with humbuckers. It’s really a pain to get a nice clean fade-out. Especially of a big, final KERAAANGGG type power chord or something.
Work with the settings in the POD. Maybe fiddle with the compressor (if it is use) and even lower the gain settings for the amp model. I’m finding that less is more in a lot of cases.
D
PS Oh yeah… this is probably not an n-Track thing as I haven’t recorded anything using n for a long time. I see it in other software too. The trouble persists even when I use the POD for gigging. I keep the pinky on the guitars volume knob for a smoother, relatively noise free fade-out.
I think it’s somthing else. 
THIS will happen for any sounds…not pod specific…those issues with the pod doing that could be happening for similar reasons, like when the guitar fades to silence in the pod itself. Can’t do much about it if it’s coming out of the pod that way.
That said…
When a sound fades to silence there is a place where it fades into the noise background. That’s tape hiss, or it’s dead silence when recording digital. Down at the noise floor there aren’t enough bits to represent sound that low in volume so it pops in and out of sound and silence. It sounds like crap, sputtering, graininess and a whole bunch of other words that shouldn’t be used here. Digital can represent low volumes well, that the lower bit rate the worse it is.
This can be very noticeable when the source is 16 bits. 24 bits is much much better. This is one area that the difference in 16 and 24 bits is most noticeable.
Dithering can help, since dithering is little more than noise added to the source. It’s sort of like putting some tape hiss back into the recording.
It probably won’t be noticeable at all if the sound doesn’t fade, fades really quick.
This is one of those reasons 16 bits is not enough.
Dunno if I’m talking about the same thing here, but listening to chords ringing out completely through my POD 2.0 I hear some ‘pixelation’ (think lo-rez picture blown up to a size too big to look good) just as the chord dies out & silence takes over.
From memory this is more apparent with dirty sounds than clean ones, but I’m not really sure…
Anyhow, I blame the AD/DA converters in POD-land.
You are right phoo. Didn’t think of that one. I wonder if Lost is recording 24 bits?
You are not imagining it Terje. It’s there. I got my XT Live because the “powers that be” will not allow amps on stage at church where almost of my live playing happens. They make us use processors and in-ears for monitoring. If it weren’t for that, I’d still be tube-ampin’ and stomp boxin’… poo on this modeling crap. Can’t beat the real deal!
D
So, what’s the bit depth on PODs?
I’m too lazy to look it up right now, it’s late over here 
Yeah…I bet anything the pod is doing it in its own processing.
Pixelation is a perfect visualization.
Quote: (teryeah @ May 20 2008, 3:49 PM)
So, what's the bit depth on PODs?
I'm too lazy to look it up right now, it's late over here
The XT, XT Pro, XT Live and newer X3 series claim 24 bit AD/DA. Dunno about the original POD and POD 2.0.
When I get a chance, I'd like to hook mine up via USB and record skipping the DA step of the process. Just to see if the SNR is improved by a significant amount.
D
PS What are you gonna SLEEP or something? Sheeeessshhh...
Hi Gents:
RADAR Wayne and I would have these discussions of what he would describe as D/A-and A/D Converter JITTER…
I wonder if that would describe what is happening here…
As the amplitude of the analogue signal fades into nothing’ness the A/D converter is frantically searching for something to convert…
It begins to convert noise-floor into nothing…
Then… The D/A Converter has it’s HAND into the chain as the Digital file gets converted back to Analogue on the Repro…
Bill…
Thanks all for your responses.
I think Phoo and Woxnerw might be on the right track, but it will take some doing to verify.
The reason I don’t think the Pod is causing the issue is because I am listening to the POD in phones during the takes and it fades with very good clarity.
It is only on PLAYBACK that I hear the artifacts.
Additionally, I had similar issues on other tracks with fading chords where the POD wasn’t in use.
In any event, I greatly appreciate all your advice and I’ll be sure to post an update if I get to the source of the problem.
Chris
I have an EWS88MT, but not a POD and have never had any problem like this. What version of the Terratec driver are you using. The current version is 5.5.1b I believe (I’m at work, so I can’t verify). BTW the Phase88 driver works with the EWS88MT.
Paul
Paul, I’ve been using the 5.47.3.138 driver and the Phase 88.
I’ll try to dig up the 5.5.1 or whatever more recent driver might be available.
I’ll kick myself if it’s something that careless that’s been causing these problems.
Phoo, I believe I am using 24 bits (unless there’s something I don’t know about), so that might eliminate that possibility.
Woxernew, do you know of any way to avoid those noisy conversion issues?
Thanks again all,
Chris
Quote:
I believe I am using 24 bits...so that might eliminate that possibility.
It makes things a LOT better, thought it won't completely eliminate it. What it probably means is that it's the pod processing which has already been pointed out that a possibility. I hear similar artifacts while using the GuitarPort. I think Teryeah's comment about pixalation hit it right on the the head. Knowing your recording 24 bits already really swings to vote in the other direction.
Hi LostNSpace:
The converters on that audio card should be pretty good quality…
“JITTER” shouldn’t be an issue with that card…
Unless…
maybe your system has a Stressed Power Supply…
If you put your hand near the cooling fan…
Is the power supply running warm?
Have you ever ripped a CD to a folder on your hard drive and then played a song from that CD through your audio card and listened to the Tail-end of a song and heard the same effect?
Just checking…
Is the issue with your audio card while recording?
or while it’s playing back ?
or is it there while recording and repro’ing…
?
Is this issue something that has just happened…
OR…
Has it always been there…?
Bill…
Chris, I just sent you a PM. Yes the EWS88MT is a 24bit card.
Another thought, would there be a problem with samplerate setup differences in the EWS88 and the POD (eg. one might be set at 44Khz and the other at 48Khz)?
Hey what’s with this Member Rating thing? Is a 5 good or bad? If it’s good, there’s no way I can claim the same knowledge and helpfulness as Bill, Phoo, Learjeff, etc.
Quote: (woxnerw @ May 23 2008, 6:06 PM)
Is the issue with your audio card while recording?
or while it's playing back
? or is it there while recording and repro'ing..
?Is this issue something that has just happened..
OR..
Has it always been there..?
Bill, the first three questions are difficult to answer because (admitting there's something I've potentially overlooked with N-Track) I've never been able to listen to the track I'm recording while I'm recording it.
I'd always been able to do that when I'd recorded with analog equipment, but something I find VERY frustrating about this software.
The issue is not new.
I've had it on parts I'd recorded where there is a cymbal/keyboard/reverb/etc. fading.
I'd only mentioned the pod because it was the one source I'd heard going IN to my card that I was certain was ringing down to silence with clarity.
If there is some way that I could listen to the track going IN after it's passed through the Terratec/CPU/ circuits and software before playback, that'd certainly go a long way toward diagnosing the problem.
I agree…
It’s hard to identify…
It’s like the roof don’t leak when the sun shines…
OR…
I only need to fix the roof when it rains…
OR…
something like that…
Do you use-or-install effects (to the track) when you record the track ?
OR do you record your tracks “DRY”…
?
Asking the A-to-D Converter to multi-task is quite a stress promoter…
especially when asking them to convert effects at the same time…
Lots of guys record effects and get away with it…
BUT sometimes you have to trade-or-give up something to arrive at the “End Product”…
Well…
Bill…