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Author Topic: Unexpected distortion at student event?  (Read 5289 times)

Keith Purtell

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Re: Unexpected distortion at student event?
« Reply #10 on: December 24, 2018, 09:29:33 AM »

Blue is normally a line level input on a sound card. ...

... maybe not so much with the distortion but some strange sounding play back ...

Mike, two questions.
1-Do we need to be using the line level input, and not the mic input?
2-And is there a particular type of 1/4 inch to 1/8 inch adapter cord we should acquire?
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Kevin Maxwell

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Re: Unexpected distortion at student event?
« Reply #11 on: December 24, 2018, 10:48:55 AM »

Mike, two questions.
1-Do we need to be using the line level input, and not the mic input?
2-And is there a particular type of 1/4 inch to 1/8 inch adapter cord we should acquire?

First you have to determine what the inputs are that are on the computer. If there is a 1/8" stereo line level input I assume that it is expecting a -10dB signal. How close is the Mackie mixer to the computer inputs you want to use? If it is close enough to use a cable 10feet long or under then you could use a cable with 2 RCA connectors (take the Tape out) to a TRS 1/8" connector on the sound card in the computer, if the above assumptions are correct.
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Keith Purtell

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Re: Unexpected distortion at student event?
« Reply #12 on: December 24, 2018, 11:13:51 AM »

How close is the Mackie mixer to the computer inputs you want to use?

About 3 feet. Maybe 4 feet of cable. It may be several days before I get to the church, poke around, then get back to you.

Have a great holiday!!
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tulsaunity.com
Midas M32r soundboard
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Roland V-1HD video switcher
Canon Vixia HF G20 camcorder
vMix live video software
~ good volunteers on sound/light/video team...

Keith Purtell

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Re: Unexpected distortion at student event?
« Reply #13 on: December 26, 2018, 07:56:55 PM »

OK, details:
The short cable goes from 1/4 inch stereo plug at Sub Out to a 1/8 inch mono plug into the blue "line in" on our PC. If this is the wrong part/connection just let me know!
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Midas M32r soundboard
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Mike Caldwell

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Re: Unexpected distortion at student event?
« Reply #14 on: December 26, 2018, 08:58:48 PM »

OK, details:
The short cable goes from 1/4 inch stereo plug at Sub Out to a 1/8 inch mono plug into the blue "line in" on our PC. If this is the wrong part/connection just let me know!


Try going from the utility out using a dual 1/4 inch ts plug cable that has an 1/8 inch trs plug on the other end. That way you can adjust the level to the computer using the utility output level adjustment control.

You could also try what Kevin suggested only you do not have a separte level control on the mixer.

If you get hum or buzz when connecting the computer to the mixer that's another problem in itself to deal with.

Chris Grimshaw

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Re: Unexpected distortion at student event?
« Reply #15 on: December 27, 2018, 07:30:06 AM »

Seems to me that, instead of messing around with the 1/8" line input on a PC, it'd be much better to pick up a USB soundcard with 2x XLR inputs, gain controls, and some form of metering that'll tell you if the input is clipping.

That way, any grounding problems (hum, buzz, whatever) can likely be fixed with DI boxes.
Plus, you get the flexibility of being able to connect external mics etc.

Chris
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Keith Purtell

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Re: Unexpected distortion at student event?
« Reply #16 on: December 27, 2018, 11:26:44 PM »

Try going from the utility out using a dual 1/4 inch ts plug cable that has an 1/8 inch TRS plug on the other end. That way you can adjust the level to the computer using the utility output level adjustment control.

Mike, is "dual 1/4 inch ts plug" like the following link except 1/8 inch on other end? link to Sweetwater cable

And I gather "utility out" is what Mackie calls "Sub Out" ?

I'm intrigued with the possible results. (Fitting this into the holidays, it could be a week before I post again.)
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Focusrite Scarlett 3rd gen.
Roland V-1HD video switcher
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vMix live video software
~ good volunteers on sound/light/video team...

Kevin Maxwell

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Re: Unexpected distortion at student event?
« Reply #17 on: December 27, 2018, 11:54:42 PM »

Mike, is "dual 1/4 inch ts plug" like the following link except 1/8 inch on other end? link to Sweetwater cable

And I gather "utility out" is what Mackie calls "Sub Out" ?

I'm intrigued with the possible results. (Fitting this into the holidays, it could be a week before I post again.)

If it is a stereo line level in to the computer and you want to come out of the L/R utility outputs then use a cable like this. 
https://www.sweetwater.com/store/detail/RCC53528--roland-rcc-5-3528-3.5mm-trs-dual-1-4-inch-interconnect-cable-5-foot
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Dave Jones

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Re: Unexpected distortion at student event?
« Reply #18 on: December 28, 2018, 01:06:12 AM »

Our music director hosts a small public performance for families of her students. This year we used vMix to record video. Everything sounded fine over the speakers, and the visual indicators of sound volume on our Mackie board (and in vMix) were within range. It's the same setup we use for Sunday service. But the audio portion of the video is bad. I've Googled this and the only thing that came up was a new term for me: "gain staging." Anyway here are two links, one the wave form, and another to an audio sample. Tips?

Waveform seen in Audacity

MP3 sample student singer

Your Mackie mixer outputs professional line level nominally +4dBU which is 1.228 volts.
Your sound card inputs consumer line level nominally -10 dBV which 0.3162 volts.

As you can see, consumer and professional line levels are quite different. IE, your consumer sound card input is overloaded by the professional mixing board output. 4 times the expected voltage.

As others have suggested, get a USB audio interface with professional line level in. This will solve the level mismatch as well other interfacing issues you might have as a result of the Mackie's TRS balanced outputs on on jacks going to the 1/8th unbalanced card input.

Dave



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Kevin Maxwell

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Re: Unexpected distortion at student event?
« Reply #19 on: December 28, 2018, 09:55:04 AM »

Your Mackie mixer outputs professional line level nominally +4dBU which is 1.228 volts.
Your sound card inputs consumer line level nominally -10 dBV which 0.3162 volts.

As you can see, consumer and professional line levels are quite different. IE, your consumer sound card input is overloaded by the professional mixing board output. 4 times the expected voltage.

As others have suggested, get a USB audio interface with professional line level in. This will solve the level mismatch as well other interfacing issues you might have as a result of the Mackie's TRS balanced outputs on on jacks going to the 1/8th unbalanced card input.

Dave

That is why I suggested earlier in this thread to use the Tape outputs of the Mackie, they should be -10dBu.

And assuming the 1/8" input on the computer is stereo use a cable like this.
https://www.sweetwater.com/store/detail/CMR206--hosa-cmr-206-6-foot-3.5mm-trs-to-dual-rca-cable
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Re: Unexpected distortion at student event?
« Reply #19 on: December 28, 2018, 09:55:04 AM »


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