Phase Issue

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dpaterson
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Phase Issue

Post by dpaterson » Fri Jun 29, 2018 10:40 am

Hello.

Well: I've been working (practicing) hard as opposed to butting in on threads around these parts (you'll be proud of me Mark) so time to try resolve one or two issues that have cropped up in the past few weeks or so: out of phase being one of them.

As many may know: I do everything in stereo. So to this end: when recording I have two Marshall CODE amps. micd. up (then through a desk and into my PC). Works perfectly. BUT: the other day I connected them direct via USB and something came up. The two recorded (mono) tracks, when played together out of Mixcraft, without panning them (hard left and hard right), have a definite flanging type of effect (I use the word effect loosely here). On my first test I used ASIO4ALL and I could very clearly see that the tracks were out of alignment (the track for the left amp. was slightly ahead of the track for the right amp.). By nudging one of the tracks I ALMOST managed to get rid of this flanging but not quite. I then tried the same thing using the Windows WAV driver. The tracks were not quite as out of alignment as they were with ASIO4ALL but were still out of alignment nevertheless (and I've not been able to eliminate this flanging effect either). Any ideas as to why this is happening (or, for that matter, what exactly IS happening)??? What is strange (to me): identical amps., identical USB cables, both into the same hub, absolutely no difference between the two. So why would one track not be aligned with the other???

Regards,

Dale.

rrichard63
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Re: Phase Issue

Post by rrichard63 » Fri Jun 29, 2018 10:49 am

If I'm reading your post correctly, you are mic-ing the amps separately. How precisely are you positioning each mic? Does moving one mic a tiny fraction of an inch (and leaving the other where it is) change the result in any way?

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dpaterson
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Re: Phase Issue

Post by dpaterson » Fri Jun 29, 2018 10:53 am

Hello.

Actually: the micd. amps. come out perfectly every time. It's when recording from the amps. direct via USB that the problem occurs. I could actually understand if it was the other way around!!!

I bought a plugin just yesterday (Voxengo's PHA-979) (Phase Alignment Plugin) (yeh: another "special deal") but try as I might: even with nudging the tracks and using the plugin things are just too out of kilter with each other (I think).

I do think it's a phase issue because if I do pan hard left and hard right things sound great (again) (although not as good as the micd. amps. but that's another whole story on its own).

Regards,

Dale.
Last edited by dpaterson on Fri Jun 29, 2018 10:58 am, edited 1 time in total.

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Acoustica Greg
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Re: Phase Issue

Post by Acoustica Greg » Fri Jun 29, 2018 10:54 am

Hi,

Try right-clicking on one of the sounds and selecting: Properties > Phase > Invert.

See if that helps.

Greg
Mixcraft - The Musician's DAW
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dpaterson
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Re: Phase Issue

Post by dpaterson » Fri Jun 29, 2018 10:59 am

Tried that. Sounds weird. Almost like the sounds become chopped or divided in the middle (really don't know how to describe it).

Regards,

Dale.

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Acoustica Greg
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Re: Phase Issue

Post by Acoustica Greg » Fri Jun 29, 2018 11:09 am

Hi,

In that case, you probably need to tweak your microphone placement.

Understanding Audio Phase


Greg
Mixcraft - The Musician's DAW
Give it a try here: http://acoustica.com/mixcraft/
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dpaterson
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Re: Phase Issue

Post by dpaterson » Fri Jun 29, 2018 11:12 am

Err...

Again: got no issues with the amps. micd. up. Only when recording direct from the amps. via USB (sorry: maybe I should have noted that the CODE amps. have USB ports for MIDI control and recording i.e. you can record direct via USB from the amps.).

Regards,

Dale.

rrichard63
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Re: Phase Issue

Post by rrichard63 » Sat Jun 30, 2018 4:01 pm

dpaterson wrote: ... got no issues with the amps. micd. up. Only when recording direct from the amps. via USB (sorry: maybe I should have noted that the CODE amps. have USB ports for MIDI control and recording i.e. you can record direct via USB from the amps.). ...
I did indeed misread your original post, which may be partly (but only partly) due to not knowing that there are amps with built-in interfaces. So, I can see why this is frustrating. The most common explanations don't appear to be relevant.

Do I understand correctly that you are recording from both amps simultaneously? Could it be that your ASIO and/or Wav drivers can't quite cope with two USB interfaces at the same time? I know that RME's drivers can handle multiple RME interfaces (they are treated as one unit by the software). But I don't know about other brands.

You describe the effect as like flanging. If I understand that term correctly, it's caused by small variations in the speed of playback (from the days of reel-to-reel tape). The analogy makes me think there might be something in how the software is handling the multiple data streams that is causing this.

Hopefully someone who knows more than I do about A/D conversion and software drivers will be able to figure this out.

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Mark Bliss
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Re: Phase Issue

Post by Mark Bliss » Sun Jul 01, 2018 7:23 am

I can only guess, as some of this goes well beyond the scope of my knowledge, especially in the digital processing realm.
But not only do you have two source paths with many circuits that have the potential for minor non-linearities, but you are passing through two different A/D converters that are not linked by a common digital clock, so even slight sample rate calculation variances could be the cause.

I kind of find it an odd application of the devices to be honest Dale. I am not familiar with them at all, but I suspect it is unusual and not intended/supported by the manufacturer?

While testing reveals two intended identical signals arent as identical as hoped, panning two identical signals would not really do anything. They do need to be different to have any useful effect when panned. But the difference you discovered may not be the most desired result. But I dont know the intent either......

Oh, :lol: Dale, I don't recall writing anything about "butting in" on threads, and have no desire to come across that way.....
If I have pointed anything of that type out, it was merely intended as a suggestion for getting better answers as when people really need to start a sep/new thread. That's all.
Stay in tune, Mark

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dpaterson
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Re: Phase Issue

Post by dpaterson » Sun Jul 01, 2018 2:39 pm

Hello.

Mark:

Nope. The "butting in" comment was mine (sometimes I feel that way i.e. poking my nose where it, by rights, probably shouldn't be)!!! LOL!!!

Good thinking (about the different A/D converters etc.). I was just a little surprised is all i.e. that I had two identical USB devices, following the same physical path into my PC (into Mixcraft), but the tracks are out of alignment (and therefore out of phase). As I said somewhere above: I would have understood it if I had issues with the amps. being micd. up but not direct. Anyways. It was just an experiment. The USB direct sound out of these amps. I don't like very much anyway i.e. you lose that "speaker sound" (in spite of you being able to select different cabs. in the presets). Matter of fact: when I started out with this new digital stuff I only had one amp. and via USB the sound was so dry that it was just terrible. So I started using some of these stereoising plugins but was warned NOT to (and that most sound engineers would not use them) (blah,blah,blah). After about eighteen months or so at this new digital stuff: I'm wondering if that advice was any good as there sure are a lot of plugins for "widening" mono sources. If they were THAT unpopular or simply "do not use" well, then, dunno why there's so many of them. Anyway and long story short: I figured "well if you're wanting to do everything, particularly guitar, in stereo then may as well get two identical amps. (and then landed up with five) (another long story not relevant here though). So yeh: was just wondering why the anomaly really (very very happy with the sound I get with the amps. being micd. up). And of course there's my favorite argument: I make a point of wanting to record what I sound like live as opposed to the live sound being terrible but once mixed and mastered it sounds great. That's cheating in my humble opinion. Could it also be the reason why some acts sounds appalling on stage but produce great albums??? LOL!!! Ok. So it may be utopia (but it's my utopia and what I strive for anyway): ONE take and I want to sound on the recording exactly the way I sound through my amps. and PA system. If I can achieve that I'm happy (and I know that may be some revelation coming from me after all the time I'm spending mucking about with plugins!!! LOL!!!).

rrichard63:

Thanks for the post. Correct i.e. recording from both amps. at the same time via USB. Could very well be the drivers (or the A/D converters Mark mentioned). As I noted previously: with ASIO4ALL the tracks were further out of alignment than they were with WAV. But could not correct the phase in either recording test. And yeh: the flanging effect (really does sound like a proper guitar flanger effect but there isn't one in use) is very noticeable. BUT: it's almost imperceptible if I pan one (mono) track hard left and the other (mono) track hard right (which if I'm not mistaken is "classic" out of phase symptoms). As to which software may be having an issue handling the multiple data streams I do not know. I'm leaning toward to the drivers (possibly even the PC hardware i.e. when multiple USB devices are connected to a hub do they not share data and does not one take priority over the other???).

Anyways. It was interesting (and maybe there is a fix). As I said: was really just a test. I really don't want for better sound than my amps. being micd. up, then through a mixer, and THEN recorded via USB from the mixer to one stereo track in Mixcraft (for the sake of completeness: the two mic. / amp. tracks on the mixer are panned hard left and hard right while recording and the resulting stereo track, even when mixed down to mono, is perfect).

Thanks for all the input.

This stuff is absolutely fascinating really. Loving every minute of it (the learning process).

Regards,

Dale.

rrichard63
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Re: Phase Issue

Post by rrichard63 » Sun Jul 01, 2018 4:35 pm

dpaterson wrote: ... As to which software may be having an issue handling the multiple data streams I do not know. I'm leaning toward to the drivers (possibly even the PC hardware i.e. when multiple USB devices are connected to a hub do they not share data and does not one take priority over the other???). ...
Having read Mark's hypothesis -- converters not synced to the same digital clock -- I now think that's likely to be the answer. Thanks, Mark.

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dpaterson
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Re: Phase Issue

Post by dpaterson » Mon Jul 02, 2018 12:02 am

Hello.

As a matter of interest: are you (both) referring to the A/D converters in the amps. themselves???

Regards,

Dale.

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Mark Bliss
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Re: Phase Issue

Post by Mark Bliss » Mon Jul 02, 2018 9:55 am

Yes, that's my guess. Two different converters reading bits but not in synch. But like I said, a guess. This knowledge is not on my pay scale......
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rrichard63
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Re: Phase Issue

Post by rrichard63 » Mon Jul 02, 2018 10:28 am

Me too. I was referring to the A/D converters inside the amps. From what you have said elsewhere in this thread (to the effect that they use generic Windows audio drivers), I infer that there's no way to lock them to the same digital clock source.

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Mark Bliss
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Re: Phase Issue

Post by Mark Bliss » Mon Jul 02, 2018 10:33 am

Also no way to edit the ID in the serial data packet transmitted to the receiving end. (other thread on ID)
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