BlowsMeAway In line XLR Low Impedance Volume Control


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The perfect solution to in-performance volume management for low-impedance microphones.

After introducing my Vintage control, I began to get requests for a suitable control for low impedance microphones. It took me a year to design and develop this control, but I am now using it in my performances and can’t understand how I lived without it.  Do you sing and play acoustically through the same microphone – a Shure SM-58 perhaps?  When I sing, I like the mic very close to my lips for that “proximity effect.” However at this level it isn’t “hot” enough to play acoustic harp with my hands cupped in front of the mic. And that means I can’t get that great hand-wah sound. With a volume control at the mic, I simply set the PA up hot enough for my harp playing, and reduce the volume a little when I sing so I can get close. Voila!

Some things you should know:

This control is designed for “balanced” low impedance wiring, which is the standard for low impedance microphones. Please read the information below for important caveats:

The control will not work properly with cables designed for hi-impedance microphones like the Hohner Blues Blaster or the Shaker microphone. Those cables have an XLR connector at one end and a 1/4″ phone (“guitar”) connector at the other, and they are wired “unbalanced”, with either pin 2 or pin 3 hot, and the signal return connected to ground. If you are plugging your low impedance mic directly into a guitar/harp amplifier with one of these cables, the control will not work well for you. Perhaps more importantly, you are only getting 1/2 of your mic’s potential output! You should always match the impedance of your mic to the impedance of the first active device to which it is connected – i.e., amp or effects pedal. The proper way is to use an XLR-to-XLR cable and an impedance matching transformer at the amp end of the cable as shown to the right.

I can make you a custom control that incorporates an impedance matching transformer right into the control itself. This eliminates the need for an impedance matching transformer at the amp. However it adds weight and length to your mic. Usually it is preferable to use a traditional impedance matching transformer at the amp end of your cable.

Got a high impedance mic with an XLR connector?

Some JT30’s, Hohner Blues Blasters and other mics are high impedance mics, but have an XLR connector. These are a different animal and the low impedance control will not work well for you. However I can build you a custom control that does what you want – even changing the cable connection to 1/4″ or Switchcraft if you prefer. Here, the mic, control and cable all have to match; either “Pin 2 Hot” or “Pin 3 Hot”. There is more information on my custom controls and other customization services on the Mods page. And if this kind of stuff confuses you, just ask me. I will help you sort it out.

Photo shows proper setup using XLR cable with impedance matching transformer.

The control has been tested successfully by hundreds of customers with a variety of PA systems, effects processors, impedance matching transformers and microphones. It does not work with microphones requiring phantom power – however I have an alternate design that does.  Greg Heumann


Additional information

Weight 120 g