RE: [Harp-L] question about mic connection

["Degregorio, Jeffery" <jeffery.degregorio@xxxxxxxxxxxxxxxxxx>]

Hey Greg:

I'm kinda new to this (regarding hardware setups), but I'm looking to
get an RP355/RP255 (guitar processor) and future patches for harmonica
sometime in the next few weeks.  With what you're saying, is it the best
solution to using 1/4" input (I believe the only input option for RP355)
for the RP355 using a dual XLR mike/connection using the IMT?  Any
tips/concerns to consider regarding this?

Thanks,

Jeff DeGregorio

-----Original Message-----
From: harp-l-bounces@xxxxxxxxxx [mailto:harp-l-bounces@xxxxxxxxxx] On
Behalf Of Greg Heumann
Sent: Tuesday, April 26, 2011 9:56 AM
To: harp-l@xxxxxxxxxx
Subject: Re: [Harp-L] question about mic connection

This is an area of confusion for everyone - they don't teach you this in
school. 

The SM58 is a low impedance mic. Your amp has a high impedance input.

When you see a cable that has an XLR connector at one end and 1/4" at
the other, you're looking at a cable designed to use with high impedance
mics. Not only does it not match the impedance, the internal wiring of
such a cable is DIFFERENT from a low impedance cable. In fact it doesn't
connect at all to one of the pins upon which your SM58 is outputting its
signal. You will get some sound, but it will be about half of the mic's
output. 

The PROPER way to connect them is to use a standard low impedance cable
(XLR female to XLR male) and an "Impedance Matching Transformer" ("IMT")
at the amp end of the cable. The IMT has an XLR connector at one end and
a 1/4" connector at the other. This solution not only matches impedance
but also routes the mic's signal properly and you will get its full
output. 


For much more on the subject, you might want to read this doc:

http://blowsmeaway.com/all%20about%20harmonica%20microphones.pdf

Which is "All about harmonica microphones and then some." It covers this
subject and many more. 

/Greg

http://www.blowsmeaway.com
http://www.bluestateband.net
http://itunes.apple.com/us/album/duracool/id343874731




> From: dcarter@xxxxxxxxx
> Date: April 26, 2011 6:26:23 AM PDT
> To: "Harp-L" <harp-l@xxxxxxxxxx>
> Cc: harp-l@xxxxxxxxxx
> Subject: [Harp-L] question about mic connection?
> 
> 
>     Hey all, I have been looking into getting a Shure SM58 to use on a
> mike stand. So I can play some acousticly off of that. But they have a
> different type of connector than the amp I have, do I just get a cable
> that has the proper connector on the amp end? Or is there an adaptor
that
> I would purchase for the amp end of the cable that comes with the mic?
I
> just don't know much about this amplified stuff yet.