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Impedance matching Shure Beta 58A, connecting to iPod Touch
andy o
post Sep 8 2011, 10:10
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Hey guys, I've been reading up about connecting a Beta 58A which is 150 Ohm (pdf spec sheet) and my iPod Touch 4, which apparently has the same circuitry as iPhone 4, which supposedly doesn't detect any mic below 800 Ohm.

So I got the Hosa MIT-156 impedance transformer:
QUOTE
This adaptor is designed to match 600R output impedance to 2.5K input impedance. It may be used to connect a microphone to a portable recording device, camcorder, or PC.


I don't know the math of impedance matching so sorry if this is obvious. From that information, can you tell what will be the output impedance of the Beta 58 + MIT-156?

So far the Touch can't detect the rig (works for a computer mic I have though, so my cable adapters that come after the MIT-156 are working fine). And when I connect the mic to the PC via the mic inputs of either an Asus U1 or the built-in IDT sound device (on Windows 7). I get low signal and very loud hiss. What am I missing?
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mixminus1
post Jul 27 2012, 18:00
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Correct, the 58A is a dynamic, albeit a high(er)-output one, with roughly 6 dB more output than a standard SM58 due to the use of a neodymium magnet.

In the time between when I first posted to this thread and now, we actually got a few of those Shure A96F adapters at work, and I just tried it to get an SM58 into my iPhone 4.

Worked great (although I had to go in on the left channel of the TRRS breakout...not sure how it worked last time): level's a bit low with the 58 (again, a 58A would be about 6 dB hotter), but clean, with a little noise, but not bad.

It sounds like there's some kind of EQ on the iPhone's mic input (haven't RMAA'd it yet wink.gif ), at least a low-cut filter, but it would definitely be useable for "scratchpad" applications.

This post has been edited by mixminus1: Jul 27 2012, 18:00


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andy o
post Jul 27 2012, 23:43
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QUOTE (mixminus1 @ Jul 27 2012, 10:00) *
It sounds like there's some kind of EQ on the iPhone's mic input (haven't RMAA'd it yet wink.gif ), at least a low-cut filter, but it would definitely be useable for "scratchpad" applications.

Yes, I read that there's a filter which cuts lower freq's cause the mic is usually used for voice. Either Fire 2 or FourTrack (don't remember which), have an option to compensate for that digitally. That was with iOS4.3, I don't know how iOS5 changed it, but I think Garageband doesn't do it (could be wrong though).
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Posts in this topic
- andy o   Impedance matching Shure Beta 58A   Sep 8 2011, 10:10
- - mixminus1   Hmm, that Hosa adapter should at least be getting ...   Sep 8 2011, 16:29
- - Speedskater   Remember, a transformer cannot do both impedance m...   Sep 8 2011, 18:20
- - andy o   Thanks for the info. The other adapters are a 1/8...   Sep 8 2011, 18:48
- - DVDdoug   I'm thinking the problem is with the adapters....   Sep 8 2011, 20:08
|- - andy o   QUOTE (DVDdoug @ Sep 8 2011, 12:08) I...   Sep 8 2011, 21:38
- - mixminus1   Wait, andy o: you're taking the 1/8" TRS...   Sep 8 2011, 20:29
- - andy o   Gimme some time to process all the info I've b...   Sep 8 2011, 20:45
- - mixminus1   Hmm, without knowing exactly how the eBay adapter ...   Sep 8 2011, 22:08
- - andy o   No, you're right, I think it's wired exact...   Sep 8 2011, 22:24
- - andy o   Didn't work. I think something's funny wit...   Sep 8 2011, 23:23
|- - andy o   OK, I'm reviving this, cause, dumbass me, I ju...   Jul 27 2012, 06:38
|- - Arnold B. Krueger   QUOTE (andy o @ Jul 27 2012, 01:38) I...   Jul 27 2012, 15:38
- - andy o   I'm getting a lot of hiss noise because the mi...   Jul 27 2012, 16:35
|- - Arnold B. Krueger   QUOTE (andy o @ Jul 27 2012, 11:35) I...   Jul 27 2012, 19:44
- - mixminus1   Correct, the 58A is a dynamic, albeit a high(er)-o...   Jul 27 2012, 18:00
|- - andy o   QUOTE (mixminus1 @ Jul 27 2012, 10:00) It...   Jul 27 2012, 23:43
- - andy o   thanks for the recommendation, Arnold. I found it ...   Jul 27 2012, 23:59
|- - Arnold B. Krueger   QUOTE (andy o @ Jul 27 2012, 18:59) thank...   Jul 28 2012, 00:03
- - andy o   I think that would be even better, I mean I was ju...   Jul 28 2012, 00:11
|- - Arnold B. Krueger   QUOTE (andy o @ Jul 27 2012, 19:11) I thi...   Jul 28 2012, 10:49
- - andy o   What about this one AT2020? It's even cheaper,...   Jul 28 2012, 00:21
|- - Arnold B. Krueger   QUOTE (andy o @ Jul 27 2012, 19:21) What ...   Jul 28 2012, 03:39
- - andy o   Great, thanks for the input.   Jul 28 2012, 03:59
- - andy o   I have some questions about mic specs, I'll op...   Jul 29 2012, 21:10
|- - Arnold B. Krueger   QUOTE (andy o @ Jul 29 2012, 16:10) I hav...   Jul 30 2012, 11:40
- - andy o   I ended up getting the AT2035, found it for ...   Jul 31 2012, 00:58
|- - Arnold B. Krueger   QUOTE (andy o @ Jul 30 2012, 19:58) I end...   Aug 2 2012, 18:53
- - andy o   Thanks for the tip(s). I would never have consider...   Aug 3 2012, 02:26


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