View Full Version : BOSE A20 & THE EC135
DOUBLE BOGEY
6th Sep 2021, 13:31
Hi All,
Does anybody know for certain if the EC135 intercom system is LOW or HIGH impendence? We are looking to pruchase some Bose A20 headsets for the machines.
I have a A20 that I used in the EC225 and it does not work in the EC135. I seem to remember that the EC225 was LOW impendence and therefore am assuming the the EC135 is HIGH.
I would appreciate anyone's experience of this issue.
FloaterNorthWest
6th Sep 2021, 16:18
DB,
Most EC 135 are high impedance but newer Helionix aircraft are configurable so could be either. The only way to be sure on an individual aircraft is try both and see which works.
if you have an A20 already, just swap out the mic and lead for a high impedance one and see if it works.
https://www.gps.co.uk/product/bose-a20-headset-replacement-downleads-2/
You will also need to know which plug you need!!!
FNW
Our Helionix H135 is low impedance Bose A20's, as is our EC155.
We have tried the high impedance from our AS355 and they do not work in either the 135 or 155.
aa777888
6th Sep 2021, 17:53
For low impedance mic-to-high impedance aircraft, another option would be the impedance adapter from Pilot Communications USA. They have them in various connectorizations. Example: https://www.pilot-usa.com/adapters/helicopter-adapters/pa-88h.html
They also have high-to-low, which I've personally used with a DC ONE X on a UH-60, but high-to-low requires a battery and you will go through a 9V battery every day.
Take a look in your Avionic Manual which is part of your maintenance documentation specific to your aircraft serial number as well as eyeballing your Audio Panels.
Pretty sure Becker DVCS which is fairly common on most models can be switched between electret and dynamic with reconfig through software.
Which way they are configured when they leave the factory seems to be connected with which way the wind is blowing on that day!!
Be aware that I think with a "dynamic" version of the A20 you cannot get "bluetooth" capability. Sometimes handy for phone calls - on the ground of course!!
Strange, I used my A20 Bose in both our EC135T2 and the EC225LP without any issue?