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How to split guitar signal?

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Re: How to split guitar signal?

Postby Wonks » Mon Sep 23, 2019 9:06 pm

Manually nudge it. A lot quicker and you know it'll be right. 2ms is for a mic 2 feet away from the speaker. Close mic the bass and it will be way less than a 1ms delay.
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Re: How to split guitar signal?

Postby gingertimmins » Mon Sep 23, 2019 9:08 pm

Wonks wrote:Manually nudge it. A lot quicker and you know it'll be right.
That’s what I thought. Thanks for confirming that it likely needs doing!
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Re: How to split guitar signal?

Postby Hugh Robjohns » Mon Sep 23, 2019 9:51 pm

gingertimmins wrote:I’ve read that due to the tiny time difference between mic’d signal and Di signal that I need to phase align the two.

You don't have to phase-align them...

If you choose to mix the DI signal and mic'd signal together (at similar levels) then the small timing difference between them may result in some comb-filtering colouration. But you may well like the effect, so I'd suggest having a listen first before dialling in the delay.

In one article it said to use a delay plug-in on the mic’d signal, set to around 2ms.

Er... No! :?

The DI signal is the direct electrical sound, arriving at (almost) the speed of light. The mic'd signal will be slightly late because of the much slower speed of sound through air -- the rule of thumb is 1ms per foot. So if you're using a delay to resynchronise the two signals, it's the DI that needs to be delayed, NOT the mic signal. And the necessary delay would be 1ms for each foot of distance between the guitar amp's speaker and the mic (or part thereof).

A better option, though, is to advance the mic signal in the DAW so that the timing of the original performance (captured instantly by the DI) is preserved. So drag the mic track earlier (to the left) to align it with the DI track. Since most people place the mic within about 6-inches of the guitar cab's speaker, expect to move the mic track only about 0.5ms or about 22 samples at a 44.1kHz sample rate -- but the correct alignment is usually quite obvious from the shape of the waveforms.

I understand that this is likely to be more important in the bass than it is the guitar...

No, again!

At low frequencies the phase shift between the DI and mic signals due to the miking distance is negligible. Consequently the DI and mic'd signals tend to reinforce each other constructively, rather than interfere destructively (which is more likely with the higher fundamentals of an electric geetar). So coluration is usually inaudible and time alignment unnecessary for a bass track.

H
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Re: How to split guitar signal?

Postby gingertimmins » Mon Sep 23, 2019 10:20 pm

Hugh Robjohns wrote:
gingertimmins wrote:I’ve read that due to the tiny time difference between mic’d signal and Di signal that I need to phase align the two.

You don't have to phase-align them...

If you choose to mix the DI signal and mic'd signal together (at similar levels) then the small timing difference between them may result in some comb-filtering colouration. But you may well like the effect, so I'd suggest having a listen first before dialling in the delay.

In one article it said to use a delay plug-in on the mic’d signal, set to around 2ms.

Er... No! :?

The DI signal is the direct electrical sound, arriving at (almost) the speed of light. The mic'd signal will be slightly late because of the much slower speed of sound through air -- the rule of thumb is 1ms per foot. So if you're using a delay to resynchronise the two signals, it's the DI that needs to be delayed, NOT the mic signal. And the necessary delay would be 1ms for each foot of distance between the guitar amp's speaker and the mic (or part thereof).

A better option, though, is to advance the mic signal in the DAW so that the timing of the original performance (captured instantly by the DI) is preserved. So drag the mic track earlier (to the left) to align it with the DI track. Since most people place the mic within about 6-inches of the guitar cab's speaker, expect to move the mic track only about 0.5ms or about 22 samples at a 44.1kHz sample rate -- but the correct alignment is usually quite obvious from the shape of the waveforms.

I understand that this is likely to be more important in the bass than it is the guitar...

No, again!

At low frequencies the phase shift between the DI and mic signals due to the miking distance is negligible. Consequently the DI and mic'd signals tend to reinforce each other constructively, rather than interfere destructively (which is more likely with the higher fundamentals of an electric geetar). So coluration is usually inaudible and time alignment unnecessary for a bass track.

H

You’re such a fountain of knowledge Hugh, thanks for the explanation!
Regarding delaying the mic/ Di signal , that was a typo on my part, I meant that I should delay the Di signal.
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Re: How to split guitar signal?

Postby James Perrett » Mon Sep 23, 2019 10:50 pm

One other suggestion - try flipping the polarity on one of the channels. Depending upon your signal chain, you may find that you prefer the sound with the polarity flipped.
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Re: How to split guitar signal?

Postby ef37a » Tue Sep 24, 2019 5:35 am

You don't of course HAVE to mix the signals 50-50. You might find one sounds much better than the other or you need just a sniff of one to sweeten the deal?

Has anyone mentioned the Aug 07 guitar recording "bible" yet?

https://www.soundonsound.com/techniques/guitar-amp-recording

Dave.
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Re: How to split guitar signal?

Postby gingertimmins » Tue Sep 24, 2019 6:46 am

James Perrett wrote:One other suggestion - try flipping the polarity on one of the channels. Depending upon your signal chain, you may find that you prefer the sound with the polarity flipped.
Thanks James, I’ve just discovered this with the drums that I’ve recorded. I checked for phase when setting up but later found that flipping one overhead (Glyn Johns) tightened the whole sound up.
This recording journey is so exciting for me. I’m learning so much and I’m lucky to have this place to come and ask my silly questions!
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Re: How to split guitar signal?

Postby gingertimmins » Tue Sep 24, 2019 6:46 am

ef37a wrote:You don't of course HAVE to mix the signals 50-50. You might find one sounds much better than the other or you need just a sniff of one to sweeten the deal?

Has anyone mentioned the Aug 07 guitar recording "bible" yet?

https://www.soundonsound.com/techniques/guitar-amp-recording

Dave.
Nope but that sounds like something I need in my life!
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Re: How to split guitar signal?

Postby gingertimmins » Tue Sep 24, 2019 6:50 am

gingertimmins wrote:
ef37a wrote:You don't of course HAVE to mix the signals 50-50. You might find one sounds much better than the other or you need just a sniff of one to sweeten the deal?

Has anyone mentioned the Aug 07 guitar recording "bible" yet?

Dave.
Nope but that sounds like something I need in my life!

Edited to add that I’m guessing you mean tho?
https://www.google.co.uk/amp/s/www.soun ... ding%3famp

Nice, that’s today’s reading sorted.
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Re: How to split guitar signal?

Postby ef37a » Tue Sep 24, 2019 7:14 am

gingertimmins wrote:
gingertimmins wrote:
ef37a wrote:You don't of course HAVE to mix the signals 50-50. You might find one sounds much better than the other or you need just a sniff of one to sweeten the deal?

Has anyone mentioned the Aug 07 guitar recording "bible" yet?

Dave.
Nope but that sounds like something I need in my life!

Edited to add that I’m guessing you mean tho?
https://www.google.co.uk/amp/s/www.soun ... ding%3famp

Nice, that’s today’s reading sorted.

The very chap.
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Re: How to split guitar signal?

Postby The Elf » Tue Sep 24, 2019 8:17 am

gingertimmins wrote:I’ve just discovered this with the drums that I’ve recorded. I checked for phase when setting up but later found that flipping one overhead (Glyn Johns) tightened the whole sound up.
That's often the case. Think in terms of how the skins are moving in relation to each mic.
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Re: How to split guitar signal?

Postby gingertimmins » Tue Sep 24, 2019 9:29 am

The Elf wrote:
gingertimmins wrote:I’ve just discovered this with the drums that I’ve recorded. I checked for phase when setting up but later found that flipping one overhead (Glyn Johns) tightened the whole sound up.
That's often the case. Think in terms of how the skins are moving in relation to each mic.

Thanks elf, so my having to flip polarity isn’t necessarily because I messed up with the placement but rather that it’s just the nature of the beast? Or a combination of both?
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Re: How to split guitar signal?

Postby Hugh Robjohns » Tue Sep 24, 2019 9:52 am

gingertimmins wrote:...so my having to flip polarity isn’t necessarily because I messed up with the placement but rather that it’s just the nature of the beast? Or a combination of both?

Nature of the beast...

Of course, it could be down to a mic cable wired up incorrectly, or a vintage mic that is wired internally such that a positive air pressure generates a positive voltage on XLR pin 3 instead of the modern standard of pin 2.

But more likely is that it's a combination of the distances between drums and mics, and the pitches of the drums.

It's all about wavelengths... The GJ technique sets the 'overheads' at the same distance from the snare, so the sound waves radiating from the snare should reach both mics in phase. Flipping the polarity of one 'overhead' should therefore result in a significant reduction in the lower frequencies of the snare sound. If it doesn't, you have a cable problem or a funny mic (or a polarity button active in the mic preamp)!

The distances between each tom and the two mics will, however, vary greatly, and so it's quite possible that the radiating sound wave from one (or more) of the toms will arrive at one mic as a compression wave and the other as a rarefaction at different frequencies, and thus some phase cancellation could occur, changing the overall tonal character of the drum kit. Flipping the polarity of one of the mics will change that character in a way that you might prefer... (particularly if you are supplementing the snare and kick drum content with separate close mics).

The alternative would be to move the mics around a bit to alter the relative distances between drums and mics and change the combined sound that way instead of hitting the polarity button (which offers pretty crude options in comparison).

H
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Re: How to split guitar signal?

Postby The Elf » Tue Sep 24, 2019 10:12 am

I will often time-align overheads (and other mic's) to the snare. Doing this I will typically see the initial transient of the snare dipping into negative. Compare this with, say, bleed into the kick mic and the same transient may be going positive.

Multi-miked drum kits are always a compromise, but by starting with over-mic's flipped and under-mic's un-flipped it gives me a starting point.
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Re: How to split guitar signal?

Postby gingertimmins » Tue Sep 24, 2019 8:26 pm

Thanks again for the detailed help! I never intended this thread turn into a drum phase thread but I appreciate your time answering my questions.
Next set of questions will no doubt be bass and guitar related!
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