SOLVED Stereo Recording on Mac Mini


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I have a Mac Mini (late 2014) that I've been using to record my record collection onto iTunes using GarageBand. Lately I've discovered that the audio input port is dropping one of the stereo channels from my amp. I've eliminated the phonograph stylus, amp and cables as possible problems, and there is a straight cable run from the amp's tape-out plugs to the MAC - no couplers or adapters. So, it appears that the loss of channel is in the Mac itself. Is there some kind of USB-to-male-3.5mm-miniplug adapter that I can use to replace the malfunctioning line-in port on the Mac? The idea is to plug the 3.5mm mini plug into the USB adapter, and plug the USB adapter into an available USB port on the Mac, and have OS X recognize that connection as an audio line-in connection.
 
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Cory Cooper

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Hello,

A few things to try:
-Another cable
-Switch the left/right on the tape outs and see if the lost channel switches

C
 
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No, actually I need the reverse. The thing you posted the link for takes a USB input and changes it to mini-plug, whereas I need mini-plug to USB. There are plenty of such devices out there, but they all seem to be for headphones, and I'm not sure whether they would work as an audio input device.
 
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Hello,

A few things to try:
-Another cable
-Switch the left/right on the tape outs and see if the lost channel switches

C
It does. That is how I eliminated the cable as an issue. I even replaced the cables I was using with a brand new cable, but the problem remains.
 

Cory Cooper

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OK, thanks.

I would recommend a USB audio interface. Depending on your budget, devices like the Behringer UCA202 ($29 USD)/UCA222 ($38 USD) work well for this. They also have one specifically for turntable to USB - UFO202 ($29 USD).

Behringer - Computer Audio Interfaces

There are others as well, but these have pretty good reviews on Amazon.

C
 
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OK: I acquired a UCA202 and hooked it up to a USB port, connected my cables from my amp tape-out ports to the UCA202, started a recording using Garageband - and I got exactly the same results: only one channel records. I double-checked by connecting the headphones output from my tape deck in place of my amp, and got the same results there too.

So:

- problem is not with cables
- problem is not with amp tape-out; verified by substituting tape deck for amp
- problem is apparently not with line-in jack on mac (which I thought at first), since the USB connection does the same thing

The only commonality is that I'm using Garageband to do my recording, and when I have the GB monitor turned on, I only hear the one channel. It only records the one channel, too. Remember, I've already demonstrated that both my amp and tape-deck are putting out both channels.

I have a Y-adapter which I can use to put both stereo signals onto the one channel, and that works as far as hearing all the content, but I should be able to record in stereo, shouldn't I?

At this point, all I can think is that there must be an internal problem somehow with the MAC.

I have an older MAC mini I want to try to see if it exhibits the same problem, but right now, I'm completely baffled.
 
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No. That just reiterates what I've been doing all along. I was recording my collection of 45's, the vast majority of which are not stereo, and it wasn't until I started recording albums with complete audio separation between stereo channels that I realized I had a problem. For all I know, this condition has existed for some time. I was recording the Beatles "Sgt. Pepper" album, and the first song on the first side features a vocal lead-in that exists on one channel only: "It was 20 years ago today ... Sgt. Pepper taught the band to play ...". That's when I discovered I had a problem, because I didn't hear the vocal at all on the monitor. But, if I reversed the cables at the amp, then I did hear the vocal.
 
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This will be my final post on this topic, as it seems to have no resolution and the symptoms don't make sense. In addition to the above efforts, I downloaded Audacity to my Windows10 PC (a Dell Optiplex 3050) and tried to record using the UCA202 - same symptoms: missing one channel. So, I have the identical problem on two different PCs running different operating systems and using two different pieces of software. Worse, on the MAC, I have the problem using the line-in port as well as the UCA202.

As a final test, the UCA202 has an earphone jack, so I plugged in a set of earphones and switched on the monitor to see if I could hear both channels in the headset - and I can.

So, unless there is some kind of problem with the USB lead that plugs into the PC, or something else I need to know about recording stereo on a MAC or PC, I'm done with this. I've troubleshot this from every conceivable angle that I can think of, and the symptoms make no sense whatsoever. I should not be having this problem.
 

Cory Cooper

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Hello,

Sorry this is still an issue. I am still researching it.

I assume you are getting the left channel and not the right, correct?

C
 
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Cory Cooper

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Also, are you choosing Inputs 1 + 2 when setting up the track?

Screen Shot 2019-12-14 at 09.33.45.png

C
 
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No, I only had input 1 selected. When I tried Input 1 and 2 as you suggested, this then worked using the USB/UCA202 interface. So then I reverted my connection to the Mini's line-in jack, and it worked there as well. So I do not have a hardware problem after all.

The UCA202 that I bought, but no longer need, for the Mini is still useful, because my Dell W10 box doesn't seem to have a line-in jack. It has a headphones jack on the front and an audio output jack for speakers on the back, but that's all. So, I can still use the USB/UCA202 setup when I want to record to the Dell box.

I think my problem was related to not understanding the nature of the inputs. I thought that Input 1 would be the stereo input from my amp, and input 2 would be input from something else. But as you pointed out, the input apparently refers to channels. A mike would only have 1 input, but output from a stereo amp would have 2 inputs.

I've been in IT for my entire career spanning 45 years, and no matter how many platforms you have experience on, or how many certifications you have, there's always something else you need to know. This is yet another example of that axiom.

Thanks very much for seeing this issue through to the end!
 
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Cory Cooper

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Excellent!

I was hoping it was something simple and not a hardware issue.

Using Input 1 only records the left channel as a mono track, which is why you would get audio in both channels on playback. Stereo recordings would do the same, but you wouldn't get the content of the right channel in the mono file, so you would be "missing" that info.

The Behringer UCA202 is actually a better input device than the standard audio input on your Mac. It also has more flexibility.

Digital computer audio can be a bit tricky, as it is more complex than an analog audio system. It involves conversion from analog-to-digital and digital-to-analog, sampling and bits, channel assignments in software/hardware, latency during monitoring, and so much more. Non-audio people aren't aware of most of this, so it can get really confusing and frustrating. Not the same as the old days where you just connected everything with white and red cables and everything went to the correct place. ;)

I am glad it's sorted and you can enjoy your recordings. Let us know if you have any additional questions.

C
 

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