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Need help setting up iMac to receive audio via line-in

S

stringtheorist

macrumors regular
Original poster
Apr 1, 2008
244
0
I want to send a signal from my guitar processor to my iMac for recording in applications such as Garageband. Using the digital line-out from the processor I tried to connect to iMac using a 3.5mm stereo cable. However, when trying to set up a track in Garageband I could not get an input signal. In the MIDI/Audio app I have set input and output devices to built-in devices, and in sound preferences I have set the track to receive from the line-in jack. I messed around in Garageband with all the input options for the audio track but I still couldn't register a signal, yet my processor LED meter shows it's outputting fine.

I really need help here. Do I need a special cable or something? I can't understand why this topic isn't fully addressed in the supporting literature for Garageband or Logic or in the iMac OM. Would appreciate any support I can get.
 
You mention using a digital output from your audio equipment to RCA. That doesn't "compute".

Digital would be either optical "TOSLINK", or coaxial (looks like RCA, but "orange" - and "isn't"), neither of which will connect the way you describe.

If optical, you will need a TOSLINK to 3.5mm adapter. When the Mac detects the optical signal, you will have the option of selecting that as an input.
 
gr8tfly said:
You mention using a digital output from your audio equipment to RCA. That doesn't "compute".

Digital would be either optical "TOSLINK", or coaxial (looks like RCA, but "orange" - and "isn't"), neither of which will connect the way you describe.

If optical, you will need a TOSLINK to 3.5mm adapter. When the Mac detects the optical signal, you will have the option of selecting that as an input.
Click to expand...

Ah, many thanks. Could you just take a look at this and tell me if this is the kind of connecting cable I need? (I just ask because the connector which goes to the processor's RCA-style plug doesn't look like it should mate with it. It appears to be shaped like a USB connector. :confused:)
http://cgi.ebay.co.uk/Optical-Jack-...3|66:2|65:12|39:1|240:1318|301:1|293:1|294:50
 
I'm a bit confused about this TOSLINK connector. I've checked my processor's user manual and it definitely states that digital output is provided on an RCA connector.
 
stringtheorist said:
Ah, many thanks. Could you just take a look at this and tell me if this is the kind of connecting cable I need? (I just ask because the connector which goes to the processor's RCA-style plug doesn't look like it should mate with it. It appears to be shaped like a USB connector. :confused:)
http://cgi.ebay.co.uk/Optical-Jack-...3|66:2|65:12|39:1|240:1318|301:1|293:1|294:50
Click to expand...

That looks like it. The "D" shaped, squarish, connecter is the TOSLINK optical. The Mac has a combination analog and digital connecter for both out/in. The 3.5mm plug has an optical opening at the tip. It might be cheaper to get a TOSLINK to TOSLINK, then a TOSLINK to 3.5mm adapter (and more versatile). The adapter is very cheap (like a few dollars ($)). Anyway, it's fiberoptics :).
 
gr8tfly said:
That looks like it. The "D" shaped, squarish, connecter is the TOSLINK optical. The Mac has a combination analog and digital connecter for both out/in. The 3.5mm plug has an optical opening at the tip. It might be cheaper to get a TOSLINK to TOSLINK, then a TOSLINK to 3.5mm adapter (and more versatile). The adapter is very cheap (like a few dollars ($)). Anyway, it's fiberoptics :).
Click to expand...

OK but taking a closer look at the TOSLINK connector I'm pretty sure this isn't going to connect to my processor. It's an RCA jack.
 
stringtheorist said:
I'm a bit confused about this TOSLINK connector. I've checked my processor's user manual and it definitely states that digital output is provided on an RCA connector.
Click to expand...

Is the plastic ring inside the RCA orange? That's a coaxial digital output and needs the corresponding input at the other end. It's the same signal as the optical (TOSLINK), but sent over copper wire. There's no easy way to go from that to optical (requires a converter box).

You probably need something like this, plus a TOSLINK > 3.5mm (like I mentioned earlier): http://www.amazon.com/Cables-Go-Coaxial-Optical-Converter/dp/B0002J2MV4/ref=sr_1_1?ie=UTF8&s=electronics&qid=1243754681&sr=8-1

(This might help - I had TOSLINK on the brain: SPDIF is the protocol, TOSLINK is the optical cable. SPDIF can be sent over either medium (coaxial or optical))
 
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gr8tfly said:
Is the plastic ring inside the RCA orange? That's a coaxial digital output and needs the corresponding input at the other end. It's the same signal as the optical (TOSLINK), but sent over copper wire. There's no easy way to go from that to optical (requires a converter box).

You probably need something like this, plus a TOSLINK > 3.5mm (like I mentioned earlier): http://www.amazon.com/Cables-Go-Coaxial-Optical-Converter/dp/B0002J2MV4/ref=sr_1_1?ie=UTF8&s=electronics&qid=1243754681&sr=8-1
Click to expand...

It's not orange, it's black (the corresponding digital input is white). Does that make a difference?
 
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stringtheorist said:
It's not orange, it's black (the corresponding digital input is white). Does that make a difference?
Click to expand...

Probably not - it's just the convention I've seen when mixed with the analog L/R RCA's.

Check out the link I posted - I think that's what you'll need, plus the fiber optic cable and adapter to 3.5mm. It goes from coaxial digital to optical digital, which is what the Mac needs.
 
gr8tfly said:
Probably not - it's just the convention I've seen when mixed with the analog L/R RCA's.

Check out the link I posted - I think that's what you'll need, plus the fiber optic cable and adapter to 3.5mm. It goes from coaxial digital to optical digital, which is what the Mac needs.
Click to expand...

Brilliant. Thanks for responding so quickly and for being so helpful! :)
 
gr8tfly said:
Hope that's it - does the processor's manual say "coaxial" anywhere? I think I've got it, but just to make sure so you don't order the wrong stuff (that, and I hate to be wrong ;) )
Click to expand...

This is all it says in the manual:

Digital audio output is provided on both RCA and XLR connectors. Digital in is provided on an RCA connector. You can connect an AES digital source (XLR connector) to the RCA digital input jack using commonly available AES to SPDIF adaptor cables.

These are the items I'm looking at. Have I got the right ones?

http://cgi.ebay.co.uk/TOSLink-SPDIF...s=66:2|65:15|39:1|240:1318|301:1|293:1|294:50

http://cgi.ebay.co.uk/Coax-Coaxial-...3|66:2|65:12|39:1|240:1318|301:1|293:1|294:50
 
stringtheorist said:
This is all it says in the manual:

Digital audio output is provided on both RCA and XLR connectors. Digital in is provided on an RCA connector. You can connect an AES digital source (XLR connector) to the RCA digital input jack using commonly available AES to SPDIF adaptor cables.

These are the items I'm looking at. Have I got the right ones?

http://cgi.ebay.co.uk/TOSLink-SPDIF...s=66:2|65:15|39:1|240:1318|301:1|293:1|294:50

http://cgi.ebay.co.uk/Coax-Coaxial-...3|66:2|65:12|39:1|240:1318|301:1|293:1|294:50
Click to expand...

The key is "SPDIF", so you should be good to go with the coaxial <> optical. Looks like the eBay items are what you need.
 
 
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