Amplirider - radio headphone amplifier

Upgrading the headphone circuit. My previous attempt had a lot of noise, interference buzz/noise, at speed, probably because it needed to use the car chassis as the common ground.

The new approach is using a little headphone amplifier from a Canadian firm - the Amplirider. It's designed for motorcycles; takes a 12v feed, draws less than 0.2Amps with up to 3 line level inputs and one output.

All the reviews I have seen on various motoring and other forums on this, and its brother PA2V2, are positive with great support from the guy that builds them; so thought I'd give it a try.

Wiring

My Blaupunkt Melbourne head unit drives its line out pins as a pre-amp still controlled by its own volume knob. All accessible from the Mini-ISO C connector: it has a 12v feed, common ground alongside the stereo line levels. So relatively simple wiring on the input side - the Amp will simply piggy back on this port.

Doing a little reading on ground loops - This amplifier seems to have built in isolation on the power lines, so no issues.

The Amplirider will act as power-amp to drive headphones/helmet speaker levels. It's volume will be left somewhere around 3/4 to max.

Installation

The plan is to glue the amp in place on top of the head unit with a double sided sticky pad, no need for access to its volume knob in normal use which will be hidden somewhere around the side out of sight.

Headphone jacks

The amp output is wired to the existing jack panel between the seats.
The rear speakers retain their switch to isolate them when using only using headphones.

Much nicer sound and higher distortion free volume in static tests with and without the engine running; actually got carried away testing  & listening to various tracks/radio...