Jameco Electronic has these amplifier kits one of which should work
fine for our purposes. All you need be able to do is solder a printed
circuit board. My guess is the last one down would work the best.

http://www.jameco.com


Paul Lamar

Paul the price looks nice. Panel mount would be smart. Volume and on/off
switch makes things tiny. But perhaps I have been over here to long. I
should be asking how BIG it should be:)

Anyone can solder this up easily.  Would the output be soldered to the
headphone  jack.  Or would it be better to have a combination male/female
adapter that would plug into the audio input and the headphone line would
then plug into the female backside of the adapter.

The panel could contain a LED with a "ON" status only but could blink if the
output signal reached a certain threshold. Your thoughts.

Doug in Japan

All you really need on the front panel is a mini jack for the ear phones,
perhaps
a red power LED and an on and off switch. A lot of guys have panel space
limitations. I think any kind of visual indication of knock is not going
to work well. It may not attract your attention in time to back off.
Second; it is real hard to program a signal processor to tell the
difference between normal engine noises and knock IMHO. Your brain does a good
job of that just from the sound. MSD did both but it took a much larger
and more expensive printed circuit board and case. Here are a few shots
of the inside of the MSD unit. On the other hand backing off could be
done automatically with a signal processor. That in and of itself
is somewhat controversial as in; do you want the engine to back off when you
are heading for the trees? Something like that happened to an Airbus at
least one time. Perhaps a quick throw of the on and off switch would
prevent that.


Paul Lamar

Paul

I understand the  mini Walkman size audio jack. How is that going to
interface with my aviation headphones?  It will become background noise but
we can adjust the gain.

Doug in Japan

I envision this as a development system only. I guess with some experiments
it could be integrated into the intercom system but then you would have to
listen to amplified engine noise all of the time. The knock sensor is like 
a microphone. It picks up all noise. Only the pitch and amplitude changes 
when knock occurs. With some development you might be able to design
a filter that passes only knock signals. First you might want to record
the knock sound to determine the pitch amplitude and attack. Then use 
the playback as a development tool. I have not used the MSD system yet 
to see if it is entirely quiet in the absence of knock.

Paul Lamar
 
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