[Ti] line-in on my Al-book - no signal

[Dennis Fazio]

--On Monday, December 29, 2003 11:36 PM +0300 "Dr. Trevor J. Hutley" <hutley at geneva-link.ch> wrote:

[...]
> HOWEVER when I select lin-in, there is NOTHING.
> No movement on the "meter" at all.
> The gain is set at maximum.
[...]
>
> Is there anyone with a 3.5 mm jack line-in mic that is working OK with a regular microphone?
>
> Or anyone who knows of an explanation for my observations?

Probably the signal level of the microphone is inadequate to drive the line-in port.

As an experiment, I connected my Aluminum 15 inch to my hifi output and turned on the FM radio. I got a good signal level on the Sound Preference panel meter, and using Audiocorder, I saw plenty of signal. Audiocorder allows you to "play through" so when I clicked that button, the radio music came out through the PowerBook internal speakers. All well and good.

So, there's nothing wrong with your setup. Next, I needed to try a microphone. Luckily, my son got a 4-track recording outfit from his dad this Christmas and in there was a Teac dynamic microphone. Unfortunately, it had a 1/4 inch phono plug output. Well, for you, Trevor, and since my curiosity was highly aroused now, I made up a patch cable from what I found in my old audio plugs and cable box. It's been a while since I've had the soldering iron out, and I only burned one finger slightly.

Anyway, with a 1/4 in phone to 1/8 in male mini adapter in hand, I plugged in the microphone. No signal. However, I found if I blew real hard into the mike (not a good thing to do generally), I could see the input level meter flash the lower one or two bars briefly.

If someone were to do a search for the input level requirements of the line in jack, they might find it requires 80 or 100 millivolts or something like that, which I think is well above what a microphone can put out, but it's been a long time since my radio and hifi days, and I don't remember the numbers too well anymore.

I think it really is a "line in" jack and not a microphone jack. Some microphones may have a large enough output level, but most of the better ones are low output and require a preamp/mixer before feeding a recorder.

At least that's my theory. If you have another audio source, like a cassette tape, portable CD player, or stereo amp output, see if you can get adapters to go from there to your powerbook and if that will work.
-- 
Dennis Fazio
dfz at mac.com