Contact Mics

Just a request for knowledge/recommendations on contact mics & preamps. DIY or reasonably-priced both interesting! Any meaningful difference between the standard ‘piezo benders’ available on digikey potted into a bottle cap and more fancy ‘instrument pickups’?

I’m guessing for a pedal-board-factor preamp, just pick any JFET-input op-amp & wire up in noninverting configuration with a gain knob? Anyone ever try it?

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I made some contact mics recently. Just some random piezos plus jacks and electrical tape. I used a DIY opamp module as a preamp but found that I got a lot of 50Hz hum. Adding a bit of load resistance for the piezo to drive helped some but I didn’t debug it too seriously.

I default to Tim Prebble’s knowledge on this: http://www.musicofsound.co.nz/blog/the-first-rule-of-contact-mic-club. There’s some stuff in there about carefully matched preamps being important.

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agreed that the Tim Prebble post is really helpful. A few more links:

Attachment methods -

Making contact mics -

http://www.nicolascollins.com/hackingtutorial05.htm

Buying contact mics -

This is an interesting post about a different kind of piezo. I’ve looked before and found them in Australia but they may be available on ebay in the U.S. if you search:

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hmm - yea ok so on second thoughts, very high input impedance inst. amp would probably be a better choice, with balanced XLR wiring like any other mic. I suspect adding any load impedance whatsoever will drastically degrade the low-frequency performance. Will share my circuit design here when I have something tested/working (or something that looks like it should work, but doesn’t!).

Yea I got inspired by Tim Prebble’s site, but not super-stoked to shell out 250USD-odd for the barcus berry he mentions without trying some DIY first. I’m thinking more in terms of installing a suitable piezo inside a more ‘designed’ percussion device (partly inspired by the daxophone), rather than recording sound-effects from a workshop full of found objects, so the demands are a little different…

Plenty of food for thought, thanks for those!

I have quite a few contact mics ranging from cheap DIY ones, to my workhorse K&Ks to a fancy-pants Schertler.

In general I use the K&Ks as they are cheap, compact, and relatively sturdy. I have several ‘hot spots’ and a ‘double hot spot’. These are quite quiet (very little noise/hum) and have good frequency response (bass is still there, and they are really bright).

The Schertler is deathly quiet when it comes to noise/hiss. Like night and day difference from any other contact mic I’ve used. It sounds great as well, though significantly less bright than the K&Ks (surprisingly). For this reason I would rarely use it completely on its own, since it lacks that sparkle.

For DIY things I’ve made mics out of all different sizes/types of ceramic piezo discs, and even made several using piezo film, which is supposed to sound fantastic in certain contexts (double bass bridges etc…). Unless you shield these really well the noise is often prohibitive.

So given how cheap K&Ks are, I’d go that route, if you’re going for a Daxophone type thing.

In general they all sound a lot better with a buffer in-line, at minimum. I’ve got a few of these I’ve built:
http://www.scotthelmke.com/Mint-box-buffer.html

I also have a stripboard layout that I had someone work out for a Barcus Berry 3000A preamp/buffer that fits in an altoids tin (along with a 9V battery). It sounds fantastic and has bass/treble/volume controls, so super useful/flexible. I’d post it here but I got the schematic for the BB preamp off some random webpage, so I’m unsure of the copyright situation on it, but if anyone PMs I’d gladly share the stripboard layout of the circuit.

I also can’t recommend this book highly enough:
http://windworld.com/products-page/books-cds/getting-a-bigger-sound/

Lots of great info about contact mics in there, but also covers all kinds of pickups and approaches to amplification.

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awesome! That seems like a sane level of investment for this experiment. I’m pretty sure those gold coin thingies must ring like a bell - tempted to get a couple for comparison anyway!

Ha - someone else does copper-less perfboard builds - love it! Bet that FET circuit would overdrive somewhat more gracefully than an inst-amp… According to K&K website the right input impedance for the hot spots is 1M, so no problem tuning to that:
http://kksound.com/support/pickups101/piezoinfo.php
but… on the other hand I bet it will be murder to get that circuit hum-free on a 9V guitarpedal daisychain! maybe worth a try - 7V reg followed by a stack of gradually smaller caps might do it. Might try adding a ground-lift for output 1/4 inch jack…

OTOH I already had some success using the INA217 (of 5 dollar mic preamp fame) for various jobs round the lab at work, learnt it’s quirks. will probably order the bits for both preamp designs then see what works best. There’s also this inst amp:
http://www.digikey.ca/product-detail/en/analog-devices-inc/AD623ANZ/AD623ANZ-ND/750974
whose input impedance is astronomical! Kind of wondering whether that would produce interesting results combined with one of the matchstick bimorph elements on @bassling’s blog glued to a wooden ruler - the objective being tuning the bass cuttoff low enough to be useful as a gestural thing, rather than making a crappy daxophone.

E.g one hand bending the ruler to modulate the cutoff of a near-oscillating filter, the other whacking an wooden ‘attack generator’ with various beaters…

heard of beatboxers & gamers using throat-mounted microphones - kind of intrigued by the idea…

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the secret is simple, and horrifying

plasti-dip: it Just Sounds Better On Contact Mics

also yea a FET buffer!

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Out of curiosity, which model Schertler mic and pre do you have?

And if running that combo, do you still feel you need the buffer?

great info. I second plastidip. Here’s a picture of my design. I’ve been trying to build a super robust one
https://f4.bcbits.com/img/0007072601_10.jpg

The output is a lot lower than a disc piezo, so preamping is definitely a must there. I bought a bunch of different sizes from windworld.com back in the day, but it looks like this company handles that now:
http://www.pinpegpickups.com/category-s/1818.htm

I was looking for it when I was making my post, but they’ve changed all the models/look since I bought one. I guess the closest is this:
https://secure.schertler.com/en_IT/shop/pickups/dyn-uni

It’s the ‘expensive’ universal one.

edit: I have the A-DYN model.

It’s still desirable but often I don’t to be honest, I just try to use the shortest cable possible.

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yep. yepyepyep. and it makes them sorta-waterproof, too.

I received this a few days ago, the new Mogees Play. I got it for about 29 pounds on Kickstarter. It’s a contact mic and it can be used without iOS and the Mogees apps (according to the manufacturer). It sticks on many surfaces. Well, after a few not very satisfying diy experiments with contact mics, i will plug this readymade device to a regular interface and I’ll let you know if it’s worth trying if you want :slight_smile:

While different piezos get slightly different results, much like with microphones a lot of the result comes from the preamp with contact mics.

I’ve used homemade piezo sensors and discs soldered onto to RCA cables then plugged into a Zoom H4 with the Hi-z setting for input of guitars. It can have grounding issues, which can often been overcome by holding onto the Zoom with a finger resting on an input.

A Fishman preamp goes a long way in improving the quality of the sound, even when using the cheap clamp-style piezo designed for instrument tuners. Been meaning to explore using guitar EQ pedals to see if they’re useful in the field.

opened my multimeter to change the battery, realised there was a piezo buzzer in there! No shortage of bottlecaps at my place…

Plastidip may well sound better, but shoegoo will do!

Have you ever heard of Crank Sturgeon?

He has made a name for himself in New England as a contact-mic enthusiast and retailer.
He also does crazy noise performance art.

http://cranksturgeon.com/

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Thanks for the heads up. All those will pair nicely with the koma field kit

Also got myself a Koma Field Kit, hopefully that will put an end to my struggles with getting contact mics to work. I also have a handful of Music Thing Mikrophonies and the Mutable Version of it Ears and they work ok with most of my cheap crap DIY piezo things.

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I’ve got a 1U (Pulp/Erthenvar) port of Ears in my rack now - just the amp, not the follower. Works very nicely, takes up very little space, makes little old contact mics sound lots better. At some point once I’ve finished my first round of tiles, I should probably get on with releasing this…

his pocket gamelan looks interesting! Was messing around with contact mic taped to a blank 19" rack panel - surprising variety sounds can be coaxed out of that. Eventually hoping to build a tiny percussion instrument emitting broader range of thumps, clicks, whacks, clangs, scrapes… fun stuff!

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