Hi, Funharp
This is a subject of constant confusion among many. Because I make
volume controls I confront it every day. Let me try to clear it up
for you. There are low impedance and high impedance mics. Duh, you
knew that. Virtually ALL low impedance mics have XLR connectors. They
are all wired the same way. The signal is on pins 2 and 3, and
NEITHER of these is connected to ground, which is connected to the
shield of the cable and pin 1 of the connector.
Unfortunately, SOME high impedance mics, like the later JT30's,
Hohner BluesBlaster and some Shaker mics, have XLR connectors to.
These are NOT wired like low impedance mics. Here, the signal is on
Pin 2 OR Pin 3 and the ground/signal return is on pin 1.
The Shure 545 confuses the issue even more. The latest models have an
XLR connector, but can be user-modified via a jumper on the back of
the XLR connector to be high or low impedance.
Now -let's talk about the other end of the picture, the device you
connect your mic to. This means a PA, a guitar amp, a wireless
transmitter, etc. These devices have "impedance" too and the CORRECT
way to connect a mic to the device is to be sure that the impedance
is matched - either low at both ends or high at both ends. PA XLR
inputs are ALWAYS low impedance. Guitar/harp amp inputs are ALWAYS
high impedance. Whenever you see an XLR connector on a device other
than a mic, you can safely assume that is a low impedance device, and
when you see a mono 1/4" input you can safely assume it is high
impedance.
Confusion arises due to what I call "the cheater cable." This is a
cable that has an XLR connector at the mic end and a 1/4" male at the
amp end. It is for connecting high impedance mics like the
BluesBlaster to a guitar amp. High impedance at both ends - all is
well, NOT cheating. However many owners of these cables use them to
connect a low impedance mic to a guitar amp. This actually DOES work
but it is technically incorrect -it is cheating - you have an
impedance mismatch and you won't get the most out of the amp or the
mic. The correct way to connect the mic to the amp is to use an
Impedance Matching Transformer ("IMT"). Now, the "device the mic is
connected to" is the IMT, which IS low impedance on the mic side. It
has a transformer inside which steps up the impedance so the amp side
is high impedance.
I make volume controls for both High and low-z systems. In the case
of one for a High-impedance mic and cheater cable, it LOOKS just like
the low impedance model (XLR at both ends) but the are NOT the same
internally. My low impedance control won't work with a high impedance
device at the other end, JUST LIKE THE FIREBALL volume control won't
work this way.
As for wireless - it gets a bit more confusing still. First, remember
that the mic only cares what it is connected to - in this case, the
wireless transmitter. It doesn't matter how the receiver is connected
to the amp. There are both high impedance (think "AKG Guitar Bug")
and low impedance transmitters (think AKG SO40.) My high impedance
controls work fine with the guitar bug. But the impedance of the
wireless transmitters vary. The AKG and Samson are higher than a
typical PA, enough so that I make a different low impedance control
for them. This is what Jason Ricci uses, for example, with his SM57
and wireless transmitter. Some wireless transmitters, Shure
beltpack wireless systems, are "universal" - they are very high
impedance and will work with both low- and high-impedance mics.
Because of that they won't work with my low impedance volume controls
- so I have yet another design to cope with them.
The solution you propose, (two different adapters XLR to 1/4 female
to plug in a "guitar bug" like the one from AKG. So to speak one High
to High impedance (XLR to 1/4 jack), and one low to high (XLR to 1/4
including a impedance matching transformer) WILL work for you with
the Guitar Bug.
As you can see, there is a lot of reason to be confused. But there
are people out there who can help "just make it work." I build all my
controls and adapters using a modular system. You choose the
connectors at each end. In between, you can have nothing (i.e., just
a straight adapter from one kind of connector to another), or you can
add a volume control, an impedance matching transformer, or both. The
reason I can be in this business and not worry about competition from
high volume manufacturers is precisely what is discussed here. There
is no one-size-fits-all solution, and often I have to exchange
several emails with customers before we can determine what the best
solution is for them.
I hope that helps!
/Greg
http://www.blowsmeaway.com
http://www.bluestateband.net
From: funharp <funharp@xxxxxx>
Date: July 30, 2008 3:00:58 PM PDT
To: harp-l@xxxxxxxxxx
Subject: [Harp-L] Wireless/Impedance/Adapters - Christelle
Hi all,
recently there was a thread about wireless systems.
I am still confused about some things:
for instance: the Hohner Blues Blaster and the Shure 545 both have
XLR connectors, but I do need another cable than I use for a vocal
mic like the Shure SM 58 or for the Fireball V. They are
differently wired, because the first two are High impedance while
the latter two are low impedance. Is that correct?
Could I use two different adapters XLR to 1/4 female to plug in a
"guitar bug" like the one from AKG. So to speak one High to High
impedance (XLR to 1/4 jack), and one low to high (XLR to 1/4
including a impedance matching transformer) ?
Or is there another way to use different mics (the above are the
only ones I have - not much for a harmonica player ;-))) with as
little as possible gear fot going wireless?
Thanks in advance
Otto
PS: before I forget: a question to Christelle: Is it only the
volume control of the Fireball V not working when connected to the
AKG wireless system or is there no signal at all?
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