[ARC5] Audio Booster Part 2

[Brian Clarke]

Hello Wayne,

 

What you have bought is a stereo, bridged-push-pull audio amplifier. I have
exactly the same device to listen to TV sound on my stereo headphones that
have separate, two-wire feeds for each earpiece. There is no way of wiring a
bridged stereo output to feed mono aircraft headphones. The two audio
outputs from each of the stereo channels need to be fed directly to your two
earpieces SEPARATELY. Your use of an audio transformer will achieve nothing
except further attenuation.

I suggest you pull your headphones apart and feed two twin-line wires, one
to each earpiece, and one to each output of the audio amplifier. You may
have to make this headset dedicated to that audio amplifier.

 

A far simpler way to achieve increased loudness in your aircraft is to use a
mono, non-bridged-output audio amplifier, perhaps as little as 1 W. Then,
all the grounds will be common and you will not need to modify your
expensive Clark aircraft headphones.

 

73 de Brian, VK2GCE

 

From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of Robert Eleazer
Sent: Tuesday, 23 March 2021 8:18 AM
To: arc5 at mailman.qth.net
Subject: [ARC5] Audio Booster Part 2

 

As y'all might recall, I wanted an audio booster I could plug into my
airplane radio and get a little more volume for weaker signals.  I found a
little 3W audio amp at All Electronics and put it in a small aluminum box,
powered by 3 AAA cells.

 

Eventually I found out that the little amp uses three different grounds, one
for each side of the stereo output and one that is the same for both the
audio input and the power input.  The audio output and the audio input
cannot use the same ground; the circuit does not work if you tie those two
together. And since the airplane uses a common ground for everything that
means not only that you cannot use a metal faceplate to mount the imput and
output jacks, but you also need an isolation transformer on the input.  I
made a plastic faceplate out of Lexan and used a Radio Shack 1000 ohm CT to
8 ohm secondary transformer that I happened to have on hand.

 

It looks like it is going to work in the airplane, the only question being
if it provides enough audio boost to do some good.  And since I have a
couple of discarded plastic cased stereo speakers on hand I plan to buy a
couple more of those little amps and install them in the speaker cases for
use with boatanchors.

 

Wayne

WB5WSV            

 


 
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