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Hello,

I need help from more experienced sound recording gear users.

If I want to use this microphone: dacs-audio.com/product_details.php?product_id=512
with this sound recorder: www.zoom.co.jp/products/h1 do I need any pre-amplifier?

I've not used contact mics, but it's on my list of things to explore. So my answer is more from a theoretical point of view.

First, those contact mics look vastly over-priced. If you have any facility at all with a soldering iron, you could probably rig something similar for much, much less. Someone else may be able to offer insight in to why backing a mic head with "glittery silver or gold polyethylene" makes any difference to the sound. I can't think of any...

You don't actually need a preamp - you should get useable sound without one. However you will have a significant impedance mismatch between your mics and your recording device input, which is why many people choose to use one. A simple one transistor FET buffer - literally a handful of cheap components and a battery - should produce really nice results. In theory, using just the mics will produce a tinnier (and quieter) sound. Having said that, lots of people seem to produce surprisingly good results without a preamp. I'm planning on building one simply because I'm diy minded and it's my idea of fun, but I suspect it's not strictly necessary. Try it without and see what results you get.

Simple cicuit here http://www.megalithia.com/sounds/tech/piezo/fetamp.html For someone who wants to get in to electronics, this would make a nice first project - simple and cheap. Other possible circuits would be the single stage Fet amps that people build for their guitars - it's all the same really.

Hope that helps.

Speedenza wrote:

First, those contact mics look vastly over-priced.

This is the type of piezo I use: EPZ-27MS44W
Price ca $ € 0,37

Some recordings search: klankbeeld piezo

success

Any electronics shop will sell piezo speakers or piezo transducers, plus everything else you will need (cable, 3.5mm plugs, etc)
You want the ones that look like a flat disk with two wires already soldered on. (it is also possible to buy just the disk with no wires soldered, but soldering onto the disks is quite difficult, so avoid these. There are also other products where the disk is mounted inside a plastic housing of some sort. You also want to avoid these because you would need to break the housing to get to the disk and risk damagind it when you do this. Also they are more expensive)

You should apply a coat or two of of enameil paint over the whole disk. I use a product called "plasti dip" but you would be able to use other similar products if you have difficulty buying this particular one.
There re 2 big advantages from applying this coating:
1) The solderpoints in the disks are very fragile and they will break easily as you manipulate the disks. You can solder tham back on but, as I mentioned above, soldering onto the disks is very difficult. The paint protects the solderpoints from breakage.
2) Once coated with paint, the disks are water proof. So you can use them to make recordings under water, in very moist environments, etc.

I do not recommend you apply more than 2 coats of paint, as then you can start to loose sensitivity.
With plasti dip, this is very easy to apply: I just dip the piezo into it, then pull it out and let it dry. Then repeat the process for a second coat.

Contact mics need to be in good contact with a solid object in order to record something.
I use various means of attaching them to objects, depending on the object, whethre they will be subject to motion or vibration and how permanent I want the attachment to be.
USually a clip or a clothes peg can be a good option. Sometimes even an elastic band will do.
Sticky tape and bluetack are also very useful.
On occasion I have got useable recordings just pressing them adainst an object with my finger - although you are very likely to get handling noise if you do this.

The sounds produced are usually faint, so you may need to boost the recording volume.
Also, please note that the piezo mics are very efficient at picking up noise from objects they are fisically connected to: this includes the wires connecting back to the recorder! - so make sure you fix those in place (sticky tape is useful here!) rather than kick them or leave them hanging. The wind rattling these wires or your own inadverted motions can ruin an otherwise excellent recorsing.

Have fun!...

Gentlemen, thank you for your excellent tips!

AlienXXX wrote:
Any electronics shop will sell piezo speakers or piezo transducers ...

You can also salvage them from electronic devices which bleep/speak/buzz ,
e.g. watches* toys alarms ...

http://upload.wikimedia.org/wikipedia/commons/thumb/6/60/Electronic_component_piezo.jpg/320px-Electronic_component_piezo.jpg
http://en.wikipedia.org/wiki/Piezoelectric_sensor

[ *Maybe even retain the wrist-watch case to protect the transducer from damage ]

I have also sucessfully used an impedance matching box (a DI box) - the kind of thing that you would use t oconnect a guitar or bass to a low impedance input.
However, since my Zoom can work with the piezo mics without it, I find it is not worth the additional bulk and weight when I am setting up to record. To be honest, I have not bothered to check if I get better level or sound quality when using the DI box. I have found the recordings without it perfectly suitable - you can find them on the packs stating "piezo" or "contact mics" under my profile.

I have read somewhere that larger piezos are supposed to give you a better response to low frequences. I have not tested this myself.

Speaking of frequencies... Piezos can generate frequencies high up into ultra-sounds. Conversely, they can also receive those frequencies and convert them to electric signals.
Your recorder may or may not sucessfully record these (may have input filters), but my guess woud be that it does not.
If you want to experiment with this, I suggest you record at the highest possible rate (96kHz I believe is ths highest supported by the Zoom H1) Then playback the recordings at low speed, so the ultra-sounds now play at audible frequencies.
A quick simple maths would determine that if you can play these sounds in your DAW 4 octaves below their original pitch, 20kHz (the highest frequency the human ear can detect) would convert to 5kHz. Setup a high pass filter in the signal chain cutting anything below 5kHz and anything you hear then was originaly ultra-sounds when the recording was made.