I have been recording my vinyl to hard disk using Audacity for some time. I’ve gotten pretty good results, but I’ve lately run into a problem that has raised a question for me.
My setup has gone through 3 evolutions:
B&O 2404 turntable with MMC4 cartridge → Yamaha R900 receiver’s phono preamp → iMac (late 2006 white plastic Intel Core 2 Duo) line in .
Yamaha receiver removed and replaced with TC-750 preamp from phonopreamps.com .
MMC4 cartridge replaced with SMMC3 cartridge from Soundsmith .
Now, in the original setup (#1 above) I typically had to set the input gain in Audacity to somewhere between 0.2 and 0.4 in order to get a good S/N without clipping, and 0.4 was rare. It seemed sort of low to me but I didn’t give it much thought.
When I went to #2, I had to set my input gain even lower, typically less than 0.2 .
Now that I’ve gone to #3, I have to set the input gain lower still, and on some LP’s a setting of 0 still results in some clipping. This prompted a discussion with the ever-helpful Ed at phonopreamps.com, and he maintains that my iMac’s line-in (which also doubles as an optical digital in) is really a mic-in. He states: “iMacs do not have analog line inputs, only an analog mic level input (and a Toslink optical digital line in which shares the same jack).”
I don’t doubt him, given the evidence I am seeing with my own eyes, but why then do the specs for the iMac at http://support.apple.com/kb/SP28 say that it is a line-in (and optical digital)? What the heck is going on?
I think he’s misinformed. Traditionally, Macs have had a very well behaved Stereo, High-Level Line-In and no provision for built-in microphone save some Macs can use an iPhone headset, but that’s like the batty aunt locked in the attic. We don’t talk about her.
I have, with these fingers produced multiple commercial sound tracks on several different Macs. I know it’s there and I know it works.
Windows Laptops typically have very sensitive Mono Mic-In and many are missing the blue Stereo Line-In.
There are variations. Leave Audacity closed and go into your Mac system preferences.
Apple > System Preferences > Hardware > Sound > Input. You should see a bouncing blue light sound meter and a volume slider. See if there’s any position of that slider that results in upper third bouncing of the sound meter without clipping.
TC-750 preamp
I have one of those. Or more accurately, I got one of these for my sister in Schenectady.
Leave Audacity closed and go into your Mac system preferences.
Apple > System Preferences > Hardware > Sound > Input. You should see a bouncing blue light sound meter and a volume slider. See if there’s any position of that slider that results in upper third bouncing of the sound meter without clipping.
With the slider all the way to the left, the peaks are nearly all the way to the right.
On the iMac I use for recording LP’s, I see in Audio MIDI Setup that the range of dB values for the line-in is 0 to 22.5 . On the other hand, the range on a different, newer iMac that I have is -12 to 12 . So for whatever reason, the older iMac can’t gain down below 0dB. I will try to record my hotter LP’s with the newer iMac and see if I can get it to gain down to an acceptable level.
Weird - it’s like the line-in on the older iMac is trying to be a compromise between a line-in and a mic-in .
Yep, the newer iMac (with a -12 to 12 dB range) had no problem getting the gain level correct. So I’m chalking the older iMac’s audio up to just being weird.
