Sennheiser HMEC 25-KA modification?
 

Hi. I use the above headset on an Airbus 320 and find the volume too loud with the radio vol at minimum. This headset is not fitted with its own volume control.

It should be a simple enough mod to fit a suitable potentiometer or even a fixed value resistor to the headset to rectify this. Can anyone suggest if;

a) this is the correct way to resolve the problem.
b) an appropriate value for that resistor.

Unless anyone has done this before I'll figure out the mod itself, it's the spec of the resistor that I need.

Power supply
 

Hi,
Would you be able to tell me if the A320 provides the power for the NoiseGuard ANR on the hmec 25-ka headset through the XLR5 connector or do you need a separate battery box?

I'm not suggesting a do-it-yourself solution would be appropriate:=, but ....

Not quite. An LPAD is commonly used to attenuate amplifier outputs. Here is a tutorial:

L-pad Attenuator Tutorial for Passive Attenuators

Referencing the above web page, here are some values for R1 and R2 (ohms) for a few attenuation levels:

3db ... R1 = 75, R2 = 150
6db ... R1 = 110, R2 = 50
10db .. R1 = 130, R2 = 16

Use 5% carbon resistors (avoid wirewound), rated at 1/2 watt.

You will need one LPAD for each headphone channel (left, right). I would suggest building this in its own box with appropriate plugs and jacks so it can be removed if necessary. Don't hack a perfectly good headset.

Better yet, check around for a TSO approved in-line attenuator. Better to CYA if found plugged into an aircraft circuit.
:8