Contact mics with real sound

posted in: news | 0

Its been a while since I’ve been using contact microphones, but they never really performed very well. I knew there were ways of making simple piezo elements sound better but could never be bothered investing too much energy into it. Until recently when I found myself in a situation when I needed detailed high quality percussive sounds without picking up any other sounds. Lavalieres or contact mics, you’d say. Former being too expensive and still audio range, I went the piezo way. They’re cheap and… well, they reall are “cheap”.

As I soon discovered, what makes them sound crappy is the resistance mismatch (impedance) between the mic and signal receiver (mixer, audio unit, recorder…). That basically creates high-pass filter and successfully eliminates most of the bassy sounds. Plus it is not really that sensitive, so the tiny sounds I was going for were to be missed. Doing a bit of research, I discovered many have tackled this problem ahead of me, so all I needed to do was to follow their example. So I ordered JLC Schenzen to manufacture quite some pcbs (printed circuit board) for me (as it isn’t really cost-effective to design a whole plate just to print 5 pcbs). I had them over in less than two weeks. And in two different variations – one phantom powered and one powered by 9v battery (you’ll remember me when you run out of 48v inputs;)


These pcbs basically pre-amplify the sound (not sure how many db it adds but the difference in volume between just piezo and piezo with this circuit is several classes apart) and match the impedance (so you get full scale of sounds, not just mids and highs). I set out to build the phantom powered ones as they’re small enough to fit on top of the piezo element itself. And I’ll be needing them in a couple of days at Baschet strctures. After spending quite some time sourcing obsolete components, and figuring how to fit equivalents’ pins in, I came up with two blobs like this 🙂

Beautiful, isn’t it? #Gluegun_everything!

…they really should have had built the national library blob in Prague as they originally intended