Re: RE: [Harp-L] Wireless/Impedance/Adapters - Christelle



Nice clear description, Greg!  Not to muddy the waters, but I thought of one possible complication:  tip-ring-shield (TRS) jacks on some PAs like the Mackie 12.  These are 1/4" female stereo jacks.  I think they can accept both "stereo"-type 1/4" male plugs, and mono plugs (sometimes plugged only halfway in), and, if its a stereo male plug, some these TRS jacks handle two mixer channels, or the two sides of a stereo signal input.  Can't some of these be low-impedance?  Your description is still rock-solid, Greg, since you stipulated "mono" 1/4" jacks on amps and PAs, but since the mono and stereo jacks look just the same, I thought I'd bring this up.
-John T

======= At 2008-07-31, 22:35:11 you wrote: =======

>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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= = = = = = = = = = = = = = = = = = = =
			

Best regards.				 
john
jjthaden@xxxxxxxxx
2008-08-01





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