Hi Doug,
I found for my purposes that the audio output level from the Pi 2B isn't loud enough ( though my kids ARE saying I need a hearing Aid!). I wanted to combine the audio output of my tablet with PAW to then feed to the aux input of the integral intercom of our Becker 8.33khz radio. The little mixer I made up was passive and so effectively reduced the PAW level even further. The radio aux input sensitivity was set to max.
I had noticed that PAW didn't remember the audio volume setting in the Configuration page, that Jeremy refers to. Extremely useful that "PilotAware" is spoken every time the volume controls are pressed.
So I ended up making an amplifier to put inside the mixer, one based on the Texas Instrument LM 386 8-pin chip. I priced out the components from RS Components but because you have to buy in multiples it was working out pricey for a couple of resistors, capacitors, the chip and some Vero Board.
Maplin was the saviour! They have a range of little project kits. They had two different amplifiers using this chip and include a small PCB and all components. I opted for the 1Watt Output version that can be connected to 12v DC power. It worked out half the cost of buying components individually from RS and features a preset gain control that I can access through a hole drilled in the case of the mixer unit.
When powered up in our Eurostar, I noticed a faint audible clicking interference through the headset, but reducing the sensitivity of the radio aux input to near minimum effectively suppressed this. In the air I was satisfied with the audio levels and was able to pre-set them close to what I was receiving from the Tower via RTF. If I need to mute either the PAW or navigation audio from the IPad this is easily achieved by turning down the appropriate volume pot on the mixer which I have velcro'd to the bottom edge of the panel adjacent to the central throttle control.
