Low Microphone Input Level: Shure Microphone/Griffin iMic Incompatability?

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Level 1

4 points

Low Microphone Input Level: Shure Microphone/Griffin iMic Incompatability?

I am trying to do home recording of voice and acoustic guitar through a microphone. The volume levels coming into the computer are extremely low, so I suspect I have the wrong hardware, but I not sure what I can do to correct it.

I am trying to record on Garage Band 1.1.0. I have a Shure "100WD Pro Microphone System" with a "8900W Dynamic Cadioid Microphone". The microphone has a dynamic range of 50-15000 Hz and an impedance of 600 ohms. I have this plugged into a Griffin "iMic External USB Sound card". The Griffin adaptor is plugged into one of my Mac's USB ports.

I have made sure that the Griffin adaptor switch is set to "Mic" rather than "Line" input. In the system sound control panel I have the "iMic USB audio system" selected as the input device and the input volume turned all the way up. In Garage Band I have to crank the track input volume up to the point of distortion to record any sound at all. At this point, Garage Band is unusable for me.

I've read Hang Time's Garage Band FAQ and suspect that the problem lies with some incorrect configuration of microphone and USB adaptor, but I'm not sure where to go from here.

I'm also getting the "Disk Too Slow" error. I gather that the fix for this problem is to buy an external FireWire harddrive, and assume the error is unrelated to my low input line level.

Questions
...Any idea what's wrong?
...Is my specific Shure/iMic setup known to be problematic?
...What microphone/adaptor hardware should I buy to do home recording? I don't need anything fancy. A bare minimum that works would be great.

Thanks.

PowerBook G4 12" Mac OS X (10.3.9) Shure Microphe (600 ohm), Griffin USB iMic

Posted on Jan 29, 2006 5:26 PM

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Answer 1

HangTime

Level 9

53,853 points

Jan 29, 2006 10:54 PM in response to billmcn

I tried several searches on "100WD Pro Microphone System" and either got nothing on the links, or a "The product is no longer available", so I have no idea what exactly it is, and what it does. But before we waste a whole lot of time, let's check one thing:

I have made sure that the Griffin adaptor switch is set to "Mic" rather than "Line" input.

Are you sure? It's counter intuitive, you set the switch away from the mic icon to be in Mic-Level mode. --Hang

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Answer 2

billmcn Author

Level 1

4 points

Jan 30, 2006 11:54 AM in response to HangTime

This is the Shure microphone I'm using:

http://www.shure.com/microphones/models/100wd.asp

I agree that the switch on the Griffin iMic is a little confusing. I tried both switch positions. One position gave me the low input signal decribed above and the other position gave me no input signal at all, so I assume the former is the Mic input.

Also, I may be using a slightly different version of the iMic than what you're thinking about. My iMic doesn't have any microphone icons printed on it: the switch is just labeled with text that says "Mic" and "Line in". (Or something to that effect; I'm at work now, so I can't check.) I'm not sure exactly what model number I have, but it's a small white disk, which looks slightly different than the small gray disk that a Google Image search turns up. Regardless, it's a Griffin iMic that I bought at the same Apple store as the Shure mic because the guy there told me that they would work together.

PowerBook G4 12" Mac OS X (10.3.9)

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Answer 3

HangTime

Level 9

53,853 points

Jan 30, 2006 12:48 PM in response to billmcn

Re: the Model

Interesting. I didn't know they'd changed the iMic at all ... and yes, the grey one is what I was using last year.

Looking at the link you posted, I see it comes with an XLR to 1/8" cable, but it says nothing about a HiZ->LoZ transformer. I believe that this could be the problem. Here's a pic of one:

The silver thing is the matching transformer. I'm sure I've seen these for around $10-$12 ... I'll take a look and post back.

--HangTime [Will Compute for Food] B-|>

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Answer 4

HangTime

Level 9

53,853 points

Jan 30, 2006 12:55 PM in response to billmcn

I found this one in my bookmarks for $11

http://www.8thstreet.com/product.asp?ProductCode=9767&Category=Microphones

and I also found them for $10 at musiciansfriend, and $15 at Amazon.

I can;t say with absolute certainty that this is the problem, I'm puzzled by the fact that they include the cable, it's not something you purchased separately.

$11 isn't much, but perhaps you could give tech support at Shure a try and see what they think of my answer.

In short: the iMic has a High Impedance input, and if that model of Shure mic is Low Impedance, then you need a matching transformer between the two.

That's what I believe, see what Shure says --Hang

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Answer 5

billmcn Author

Level 1

4 points

Jan 30, 2006 1:48 PM in response to HangTime

The Shure microphone did not come with any impedance matching component.

I'll try your suggestions. Thanks.

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Answer 6

billmcn Author

Level 1

4 points

Jan 30, 2006 1:59 PM in response to HangTime

Possibly relevant FAQ entry from the Griffin site:

http://www.griffintechnology.com/support/imic/IMIC-022.php

PowerBook G4 12" Mac OS X (10.3.9)

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Answer 7

HangTime

Level 9

53,853 points

Jan 30, 2006 2:45 PM in response to billmcn

http://www.griffintechnology.com/support/imic/IMIC-022.php

Yup, that's dead on. Note they mention the Matching Transformer.

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Answer 8

billmcn Author

Level 1

4 points

Feb 1, 2006 7:55 PM in response to billmcn

I tried using an impedance transformer, but I still have the same problem.

I bought a "Matching Transformer Audio Adapter" from Radio Shack. The package says that it matches a low-impedance balanced microphone to a high-impedance unbalanced input. I plus this adpater into the XLR jack on the back of my microphone and then use a 1/4" to 1/8" converter cable to plug it into the iMic.

After doing all that I have the same problem: extremely low input levels.

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Answer 9

HangTime

Level 9

53,853 points

Feb 1, 2006 8:37 PM in response to billmcn

<sigh> I remember very clearly testing this out for a girl almost two years ago, the only difference was that I used a rackmount Transformer (wireworks, I think). I'm starting to think the iMic itself might be defective.

Tell you what, I'm going to go rummage around the studio see if I can find the old iMic, an SM57, a straight XLR->1/4 cable, 1/4->1/8" adaptor, and a matching transformer.

If I can find everything, I'll try several combinations and let you know what I find...

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Answer 10

HangTime

Level 9

53,853 points

Feb 1, 2006 10:23 PM in response to billmcn

I was unable to find a straight XLR->1/4" cable in my gack box, but I did find the other things.

SM57 -> LoZ-HiZ transformer -> 1/4"<->1/8" adaptor -> iMic -> Computer

What I found was that with the switch set to either Line or Mic I got a level. In fact set to Mic level it was WAY too sensitive, with it set to Line-Level it sounded great.

Unfortunately I think you're going to need to talk to Griffin Support, it really does seem like a problem with the iMic B-(>

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Answer 11

HangTime

Level 9

53,853 points

Feb 1, 2006 11:03 PM in response to HangTime

Now I'm even more confused. As I mentioned previously, I was getting a signal that was actually way too hot. That seemed odd to me, so I quit and relaunched after a few more tests, now I am getting a fairly low level as well. As long as I sing directly into the mic, and kick up the level a bit using the Overdrive effect I'm getting a pretty good signal, but it is definitely recording low

For anyone that's reading this wondering if I screwed up and was using the internal mic, I tested for that by gently tapping on the SM57. Even little taps pinned the meters, so I know it was the SM57 recording.

Still, when I switched to Line-Level, I could get a singal. a VERY low one, but it definitely registered.

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Answer 12

Feb 2, 2006 4:13 AM in response to HangTime

I had a problem with my iMic cutting out and failing, and Griffin were very good and sent a replacement FOC all the way across the atlantic - worth a try?
The replacement works fine on GB 1.1, with a Stagg MD-3000SC QUALITY DYNAMIC MICROPHONE, Specs as follows:

polar pattern: cardioid - output impedance: 600 ohm ± 30% @ 1 khz - sensitivity : -74 db ± 3 db (0 db = 1v/µbar @ 1 khz) - freq. response: 80 hz to 15 khz - directivity > -18.8 db @180°(average) - body material: metal - net weight: 290g / 10.2oz - supplied in protection box including 6 m xlr/phone plug cable - colour: shiny chrome.

Maybe not as high quality as a Shure but it works.

eMac 1.25GHz Mac OS X (10.3.4) 768 ram

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