Please help me with audio as if I'm a n00b.
May 27, 2011 9:19 PM   Subscribe

Please help me with audio as if I'm a n00b. I have a couple components from the mid-90s and a 2007 iMac and I want to do a few specific things.

I have an Onkyo tape deck and an Onkyo Receiver/Amp. The back of the tape deck looks like this and the back of the amp looks like this.

I want to (a) digitize a few cassette tapes and (b) stream the iMac's output through the amp and speakers. I'm confused by the Rec/Play inputs and outputs. Should the tape player output go to REC or PLAY? What's the difference between Tape 1 and Tape 2 and Tape-2 Monitor on the display? Do I need to switch things up for each case? I have the RCA/1/8" adapter that plugs into the back of the iMac and plays audio, but can I plug it into the amp in such a way that I don't need to move it to digitize cassettes? Please tell me exactly where to put the red wire and the white wire for each of these purposes. Or, do I need to buy a new component?

Thanks for your help and your one-syllable-word replies.
posted by bendy to Technology (8 answers total) 1 user marked this as a favorite
It's context sensitive. On the tape deck "rec" is input. "This is what I'm getting that I want to record." Play is output. "This is what I'm playing that I want you to send to another component". Line-In and Line-Out are other names for these.

On the Amplifier, "rec" for Tape 1 and Tape 2 is an output. "This is what I want to send to you to record". Hook "Rec" to "Rec" in the typical Tape Deck/Amp process and you'll be able to record onto tapes. Tape 1 and Tape 2 are there to help you use two tape decks at the same time (which would allow duplicating tapes, or using two types of tape decks (reel-to-reel, anyone?).

Play is an input on the amplifier. "This is what I'd like to receive from another component." Play to Play is the normal hookup to play back tapes from the tape deck. You can take that directly to the Mac or you can bring that into the amp and use Tape 2's rec output to connect to the Mac. The main difference would be that the amp may let you equalize or otherwise adjust the sound. I'd rather go straight to the computer, but it's your call (and an easy experiment, so try both).

Phono and CD are just additional Play inputs that work with non-recording devices.

Now, there's a difference here that will be a big deal. A standard 1/8" output on your Mac, the kind with the headphone icon, outputs at a different level than a stereo expects for a component. The output level is called "mic level" (and other things, but that's good enough for now) or "line-level". The tape deck, when it says "line in" and "line out" is describing both the expected signal level and the direction the signal flows.

The difference between the output level for a line signal and a mic signal is the reason your iPhone cassette tape adapter works so poorly in the car.

Given all this complexity, my personal recommendation is to get a USB based audio adapter for your mac. I've had pretty good success with a Griffin iMic, which gives you switchable line/mic in and line out. You can hook it up to the system and cable it up and it will be available as an input and/or output source. It also comes with vinyl/tape recording software and cost me about $40. You'd also need 2 suitable RCA to stereo cables.
posted by Mad_Carew at 9:54 PM on May 27, 2011

"Line In" and "Line Out" are the unambiguous labels on that IMHO: they always refer to signals going in/out of the object they're printed on. (So you'd connect one thing's "line out" to another thing's "line in". Presumably the amp's "tape play" is a line-in input, so that you can connect your tape deck's "play" to your amp's "play".)

Red is the right-hand channel, white is the left-hand channel, (and on a TV, yellow is the picture signal). Connect white to white, red to red, etc.

You can connect the mac's output to any of the line inputs, whichever makes the most sense to you (don't connect it to the phono in, because phono inputs are special— but the others are all just generic line-in inputs, labeled to correspond with the amp's controls).
posted by hattifattener at 9:55 PM on May 27, 2011

Your mac's audio output is a perfectly normal line out; just connect it to the line in of your amplifier.

To digitize cassettes, just plug your tape player's line out to the audio in of your mac. You may have to reduce the level of your mac's input (in software), but it can absolutely take a "line out" signal. (source, source).

Unless something is defective, you should be able to get good results without buying any gadget.
posted by Monday, stony Monday at 10:59 PM on May 27, 2011 [1 favorite]

"Your mac's audio output is a perfectly normal line out; just connect it to the line in of your amplifier."

Well it's not, exactly - by the specs linked, it's a headphone output (<24Ω, 1.6V). Line level is different (100~300Ω, 0.5V).

That said, the impedance isn't going to make too much difference unless you're an audiophile - maybe a bit of extra hiss - and drive level should be OK if you connect it up to the receiver's CD input (which are normally 1~1.5V anyway).

The "line in" on those (& most) Macs is a bit of an odd beast - it's a mix of both line-in and mic-in. Its 20KΩ impedance nominally flags it as a high-impedance mic-in, but mics will require the Mac's input gain control to be wound up to 10~30dB. With it wound down to -3~0db, it makes a decent line-in (albeit with a 100Ω->20kΩ impedance mismatch, which again will have minimal affect). Certainly I wouldn't worry about it when transferring tapes, which are noisy enough to start with that you'll likely want to do some software noise reduction anyway.

Short version: neither are perfect for connecting to your setup; an audiophile will cringe if you tell them; but both will work just fine.
posted by Pinback at 12:18 AM on May 28, 2011

You need two 1/8 to RCA adapters, one for audio out from your mac and one for audio in.

Think of your Mac as a second tape player you're plugging into your system. Plug your line out on your Mac to "Play" on Tape 1 and your line in to "Record" on Tape 1.

Now, with the receiver set to Tape 1, you should hear the audio coming out of your Mac. You should also be able to hear on your Mac anything that is played through your receiver (tape 2/radio/etc.)
posted by davey_darling at 4:35 AM on May 28, 2011

20 kΩ is a ferpectly ordinary line input impedance.
posted by Monday, stony Monday at 9:33 AM on May 28, 2011

You may want to take a look at the iMic. It goes into USB and comes with software to digitize audio.
posted by Gungho at 9:51 AM on May 28, 2011

Thank you all so much. I've wondered about some of these things for years and have never figured them out. I think I have an iMic sitting around somewhere, so I'll try that too. Thanks again.
posted by bendy at 4:42 PM on May 28, 2011

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