Optimize audio amplifier for safe opening

[pickmonger2]

Several amplifiers are sold to help safe openers by using audio frequency filters that try to isolate the sound of contact points setting.

I am trying to do a DIY amp but I need to know what frequencies to emphasize and what to try and filter out.

Perhaps some one with a bought amplifier has a manual that outlines the frequencies

[grit1]

In my non-lock life I am an audio/visual production engineer...part of that is audio engineering. I don't know the frequencies specifically, but you could reverse engineer the frequencies that work the best by adding a 31 band (1/3 octave) graphic equalizer in the signal chain between the transducer and the amplifier. You could then go through and boost or cut frequencies one at a time to see what is most helpful while you dial a lock with either known or unknown contact points. This could also be done with a parametric equalizer, which had adjustable bandwidth (Q) to "dial" it in even closer (pun intended).

My hunch is that optimizing for this sort of thing would involve more cutting out of distracting "noise" than boosting the actual frequencies that you're listening for. I could be wrong, I don't have a lot of experience manipulating by sound.

[capt-dunc]

not used it for combo manipulation but i've made up a piezo mic for opening la gard 2200's, i run it into a crate taxi tx15, and adjust as required. it's a balance between boosting noise signals and reducing background sounds. why not make up your mic and run it to see what works for you before making the amp?

[pickmonger2]

Thanks Grit1.

I showed it to a friend who now knows what I want to do. He has a lot of gear
to do something like this.

His main hobby is recording birds and wildlife found in the city.

He has a parabolic microphone and showed me how he can filter noise so that
you can hear conversations in noisy traffic.

[Squelchtone]

Thanks Grit1.

I showed it to a friend who now knows what I want to do. He has a lot of gear
to do something like this.

His main hobby is recording birds and wildlife found in the city.

He has a parabolic microphone and showed me how he can filter noise so that
you can hear conversations in noisy traffic.

You should watch the movie The Conversation. I think you'll like it.

[cajunshooter]

Guys, I use a Humbucker guitar pickup as my "mic"; it is engineered to pick up metallic sounds and does an awesome job. I use a 6 band graphic equalizer and an inexpensive guitar amp that I picked up from Goodwill. Cheap and very sensitive. I use gorilla tape to attach the guitar pickup to the safe door, just tape it face down on the door and you can hear every little tick and scrape that those elusive wheels are making.

Thanks Ron