How could in-line attenuator like the Shure A14AS work with condenser microphone?

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Dantheman06

New member
On some forum I was told that I could build an attenuator using 3 resistors in an H configuration. One resistor will be between lines 2 and 3 and the 2 others (2 identical ones) will be on line 2 and 3. This is how I understand the H configuration. I have 2 questions:

1- How could it work with condensers mic? I think that it will drop the phantom voltage, especially if the condenser mic draws a significant current.

2- According to the user guide for the Shure A15AS in-line attenuator, the input impedance is much higher than the output impedance. How is this possible if it is built using only resistors???

From the user guide:
Impedance: Input (XLR Female): 1,000 Ohm; Output (XLR Male): 150 Ohm
Attenuation (switch selectable) 15 dB, 20 dB, or 25 dB
NOTE: The equivalent single series simplex-powering resistance
is 215 Ohm; this resistance should be considered in addition to any
existing circuit resistance when using the attenuator.

see: http://cdn.shure.com/user_guide/upload/611/us_pro_a15as_ug.pdf

Thank you for your help,
 
Dantheman06 said:
From the user guide:
Impedance: Input (XLR Female): 1,000 Ohm; Output (XLR Male): 150 Ohm
Attenuation (switch selectable) 15 dB, 20 dB, or 25 dB
NOTE: The equivalent single series simplex-powering resistance
is 215 Ohm; this resistance should be considered in addition to any
existing circuit resistance when using the attenuator.
Click to expand...

Just the fact that it mentions impedance means it isn't built using only resistors. In fact, there may not be any resistors in it at all. It is probably a transformer.

Most condensor mics do not draw much current. Very very little. Just enough to polarize the diagphram and power the FET circuits if any. (FETs work off of capacitance and don't draw much current.)

I don't know about any H circuit, but I wouldn't be putting in line with phantom power.

Why do yuo feel you need to attenuate the signal? Can't you just turn down the gain?
 
In the pics I found of the A15as they're careful not to show the diagram on the side of the barrel. What I can see of it, I'm guessing something like below.

att.jpg

Maybe start with 330 ohm resistors like the diagram on the right in the link below. The 330 ohms may minimize loss of the phantom depending on the current draw of the mic.
Attenuator
 
Chili said:
Why do yuo feel you need to attenuate the signal? Can't you just turn down the gain?
Click to expand...

Hot microphone, very loud and dynamic opera singer. Difficult to adjust the gain and prevent distortion. The singer could be more far but then I get more room and my studio acoustic is not 100%.
 
Ah right. You posted about your opera singer in another thread. Good luck with that. :rolleyes:
 
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