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Month: May 2015

Ground Control: Sun 31st May 2015

Maplin's Bone Conductor Transducer

This little critter is Maplin’s Bone Conductor Transducer offering for not so cheap at £9.99! [ Maplin ] It is a small, sturdy and relatively weighty device, due to a metal body housing two coils and a metal actuator. The metal plate photographed above in between the screws is a moving actuator, which induces vibration into any surface the device is pressed against or adhered to.

This device is essentially an incredibly tiny speaker rated at 1 Watt of Power. This power limits how much we can drive the speaker from the amplifier, and it means the transducer induces relatively tiny force into the surface it is pressed against. Depending on the surface of your choice, the transducer seems to be more effective when stuck against the jaw or ear bone, as it is advertised. But this doesn’t stop us from sticking it on any surface imaginable, and experimenting how effectively it conducts the sound into metal objects, wood, plastic or even glass.

It’s easy to drive this too hard as it requires little power. So some care is needed with the amount of amplification applied.

 

Using the Transducer as a Pickup

What’s more interesting though, is to use this transducer as a microphone instead of a speaker. By soldering the transducer to a Male XLR connector, I can plug this into the Mixer’s microphone input and put the Gain right up.

transducer pickup

This turns the little speaker into a microphone which pickups any vibrations from the surface it is stuck onto! I’ll put some recordings done using this method very soon. Although in contrast to a proper Guitar pickup, this has much lower sensitivity to the vibrations of a string or instrument body.

 

Verdict 

The Bone Conductor Transducer is much more rewarding perhaps to use as a movable pickup, in close proximity to a vibrating string or body. Otherwise, acquiring another unit of those to turn into headphones you can stick on your ear bones would definitely be an interesting endeavor; for any of the wild ones out there who want to try this crazy idea.

 

Ground Control 

At Hackoustic, we love Piezo discs. We use them in the Frame Project.  As Piezo discs are incredibly sensitive, high impedance components, it is important to provide adequate shielding from any external interference that may happen, as the signal goes from the piezo discs to the amplifier inputs. Hum noise is a big issue in the Audio world, especially when using Piezo discs and Guitar pickups.

This great PDF written by Bill Whitlock [ link ] sheds some light on the mysteries of the Hum, and how to get rid of it. This is especially useful when making your own DIY guitar or Piezo pickups. The first step is to use high performance shielded audio cables such as Belden’s 9259 Coaxial Cable. [ Farnell ] This will ensure no hum noise is picked up from the cable going from source to destination.

It is recommended to read the PDF to get an idea of this whole situation. Other solutions is to steer away from using mains power, and using batteries only at the amplification stage. Active DI boxes such as Behringer’s Ultra DI is an example.

 

Thank you for reading, and Good Luck in Your Projects! 

I hope this post has been some help. We’ll continue rummaging through Maplin’s goodies and Kits at the next meetups. For now, stay tuned, and get in touch.

 

In the true Tradition of Hackoustic, We leave you with is basically a Gigantic Industrial Sawblade, the Mother of All other Sawblades. (saving this one for a summer project, stay tuned in)