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Macbook pro line out to M-Audio Air 192|4 not working??

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Macbook pro line out to M-Audio Air 192|4 not working??

Postby Floating Above » Fri Sep 04, 2020 12:15 pm

Hi all,

I am new to computer music.

I just purchased a M Audio 192 | 4 audio interface and connected it by Usb to a 2011 Macbook pro and sounds quite good.

I wandering if I can connect the line out of a second Macbook Pro 2011 (yeah, they are exactly the same) to the line in of the audio interface...

This would be great as I could monitor the sound of both MacBooks via the huge knob in the audio interface, this would save me going under the desk to monitor volume in my amp which only has + and - buttons and not a knob!

I have actually made the connection trying several good cables but the sound through the speakers is low and lacks definition...

is it possible that the line in of the M-Audio is defective? I have also plugged in a cd player to the line in of the audio interface and its the same behaviour!

Thanks for your help!

best
Jorge
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Hugh Robjohns » Fri Sep 04, 2020 12:18 pm

I suspect the problem is with your cable.

The line out from your Macbook and CD player are unbalanced and stereo. Whereas the line input of the interface is balanced and mono.

So, if you've made up a cable with a TRS minijack at one end and a TRS quarter-inch jack at the other, you will get very little!
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Floating Above » Fri Sep 04, 2020 12:49 pm

Thanks for replying, but the M Audio interface only has 1 line in and is stereo. From the M Audio Air 192 specs:

Line Input 1 (balanced 1/4" [6.35 mm] TRS)
FREQUENCY RESPONSE 20 Hz – 20 kHz (+0.05 dB)
SIGNAL-TO-NOISE RATIO 101 dB (1 kHz, +4 dBu, A-weighted)
THD+N 0.003%
MAX INPUT LEVEL 16 dBu
GAIN RANGE 55 dB


As for the line out of the Macbook, I always used a standard audio cable with a 3.5mm metal plug for line out and it always worked with other devices, amps, etc...

What am I missing here?
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Sam Spoons » Fri Sep 04, 2020 12:54 pm

The input on the interface is mono and balanced not stereo. The confusion arises because a TRS plug (mini or ¼") is used to carry two different types of signal, stereo where the tip and ring carry the left and right 'hot' side of the signal and the cold side is carried by the sleeve/ground, or balanced, where the tip and ring carry the 'hot' and 'cold' sides of the signal and the the ground is separated from the signal*.

Depending on the amps you have used they may have an unbalanced input (guitar/bass/keyboard amps) which would usually work with a TRS mini to TRS ¼" cable but would only reproduce the left side of the stereo signal, or may have stereo unbalanced inputs (aux inputs on some guitar practice amps and on many 'smart speakers').

* The nature of balanced connections mean that when you plug a stereo signal into a balanced connection all elements of the signal that are identical in both left and right will disappear leaving a hollow sounding low level sound.
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Hugh Robjohns » Fri Sep 04, 2020 1:00 pm

Floating Above wrote:Thanks for replying, but the M Audio interface only has 1 line in and is stereo.

Er... no... it's definitely not a stereo input!

From the M Audio Air 192 specs:

Line Input 1 (balanced 1/4" [6.35 mm] TRS)

As it clearly states in the specs you've quoted, it is a single balanced input. Mono. Balanced.

What am I missing here?

Two things: First, Line Input 1 on the back of the unit is a balanced mono input.

And second, there is no stereo input on that interface.

The unbalanced stereo output from your Macbook is carried with the left channel on the tip connection, the right channel on the ring, and a shared ground reference on the sleeve.

However, the balanced mono input of the interface expects to receive the symmetrical 'hot' signal on the tip and the inverted symmetrical 'cold' signal on the ring (and it doesn't care what's on the sleeve).

The signal this kind of input 'hears' is the voltage difference between the 'hot' and 'cold' terminals. Consequently, if the left and right channels from your Macbook carry the same thing (ie, dual mono) there will be no difference on the tip and ring connections, and so no output.

If you're playing stereo music, then anything panned centrally -- like the kick drum, bass, vocals, etc -- will all disappear, leaving only the reverb and any instruments panned hard left or right.

And that's why you heard only a very low level and indistinct signal.

There are a few possible solutions to your situation.

1. You could use a minijack to dual TS cable, like this:

Image

And plug one TS plug into Line 1 and the other into the guitar input... and then try and juggle the gain controls to try and get matched levels in each channel.

2. Buy an larger interface with more line inputs.

3. Buy a monitor controller (with another big volume knob) with a stereo Aux input and use that to select between your interface output and second Macbook and feed your speakers/headphones.
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Floating Above » Fri Sep 04, 2020 3:06 pm

You guys absolutely nailed it! I now understand what the issue is... I will return this and get the Air 192 | 6 which has 2 Line ins.

many thanks!
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Sam Spoons » Fri Sep 04, 2020 3:47 pm

:thumbup:
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Hugh Robjohns » Fri Sep 04, 2020 4:12 pm

Floating Above wrote:You guys absolutely nailed it! I now understand what the issue is... I will return this and get the Air 192 | 6 which has 2 Line ins.

Option 2, then! ;) :thumbup: Good plan.

And don't forget to buy one of those 'break out' cables I mentioned earlier, too -- stereo mini-jack to dual TS plugs -- to connect the macbook to the line inputs.

In case you were wondering, the left channel from the Macbook on the tip of the minijack is wired to the tip of one of the TS plugs, and the right channel on the minijack ring is wired to the tip of the other TS plug.

When you insert a TS plug into a balanced inputs the extended sleeve of the plug connects the 'cold' terminal to the reference ground. The balanced input is still looking for the voltage difference between the tip and ring, but the tip is carrying the wanted signal and the ring is now it's ground reference... so you now have the full signal voltage again and all is well.

But of course we now need two plugs and two input channels to carry the separate left and right channels.
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Floating Above » Sat Sep 05, 2020 1:45 am

Appreciated! great help!
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby ConcertinaChap » Sat Sep 05, 2020 5:47 am

Incidentally I recently bought an Air 192/6 for my wife's computer. I'm quite taken with it. A nice, straightforward class-compliant interface with a separate button or knob for each function and a sensible set of ins and outs. You'll be happy with it.

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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Floating Above » Sat Sep 12, 2020 11:30 am

Hi guys,

so i got the Air 192 | 6 and the appropriate cable to connect my macbook 2 to the line ins of the audio interface. Sound is now fine and i control the gain of each channel through the dedicated knobs on the audio interface so they don't clip.

I cannot go above position 4/10 on both line in knobs otherwise I get clipping, which means I have to raise the volume a little more than i am doing with the macbook 1 which is of course connected to the audio interface via usb.

Another thing is the sound quality from macbook 2 is not as good as macbook 1 - lacks stereo image and depth - but I guess thats because the macbook 2 is going straight from the line 1/8 inch to the audio interface line ins, with its own internal sound card...

I want the macbook 2 to be my main music player (spotify, plex) while my macbook 1 is for studio work... so obviously I want to play spotify with great sounding results... should I get a small DAC for my macbook 2? like a Dragonfly or something? or send it through my realistic EQ?

thanks for your help!
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Hugh Robjohns » Sat Sep 12, 2020 11:39 am

Floating Above wrote:Another thing is the sound quality from macbook 2 is not as good as macbook 1 - lacks stereo image and depth ...

Have you panned to the two line inputs hard left/right in the interface control software?
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Floating Above » Sat Sep 12, 2020 1:24 pm

Hugh Robjohns wrote:
Floating Above wrote:Another thing is the sound quality from macbook 2 is not as good as macbook 1 - lacks stereo image and depth ...

Have you panned to the two line inputs hard left/right in the interface control software?

well no, i don't seem to have an interface control software... I am just going through my macbook's Audio Midi Setup, there I can see the M-Audio internal clock, can set it to 44.1, 48, 96 kHz and thats all i can do...

but mind you the sound is very good, but just lacks some crispiness and oomph only the macbook 1 is giving me...
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Floating Above » Tue Sep 15, 2020 11:06 am

I finally got it to work, thanks for your time and help!

So, from my MacBook 2, I send audio via my 1/8 jack to the 2 line ins of my M-Audio interface (attached to my main MacBook 1).

In my MacBook 1, I setup a Multi output device consisting of my M-Audio 192 | 6 and the virtual Blackhole virtual audio driver.

Finally in my Ableton Live DAW, I create a strip for all MacBook 2 incoming audio so I now have crisp sound because it is outputting through USB and not Direct from the M-Audio.

I do need to have a dedicated channel strip on my Novation Launch Control XL dedicated to MacBook 2 audio but I am still able to control both MacBooks via the big knob on my M-Audio which is the ultimate goal!

And apart from that, through my DAW I can effect the audio with Eq, Compressors etc which is an added bonus.

Amazing... again, thanks for your help!
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Re: Macbook pro line out to M-Audio Air 192|4 not working??

Postby Hugh Robjohns » Tue Sep 15, 2020 12:07 pm

:clap: :thumbup:
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