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Topic: Small Amplifier along with a Sound to Light board (Kits by Velleman) (Read 1 time) previous topic - next topic

thomas3120

Jun 20, 2012, 09:28 am Last Edit: Jun 20, 2012, 11:38 am by thomas3120 Reason: 1
I've been trying out different ways to amplify the sound for a small speaker (1W, 8ohms) for the 'mouth' of my robot.  Tried building my own from scratch but was having a bit of trouble with the volume levels.  Also tried some cheap DC desktop speakers at a thrift store but didn't sound that great.

I went ahead and bought the 3W mono amplifier kit from Velleman K8066:
http://www.vellemanusa.com/products/view/?id=521723
Works great with my 1W, 8ohm speaker (volume and clarity).

I also bought the Sound to Light kit also from Velleman MK103:
http://www.vellemanusa.com/products/view/?id=350678
Also works well.  I did not install the small condenser microphone (M300) that came with the kit, instead I hooked my speaker (that's connected to the 3W amp kit) to flash the LEDs according to the sound from the speaker.
There is a small trimmer pot (RV1), which I'm guessing is for the sensitivity level of the input.
Only problem I'm having is that the LEDs stay dimly lit even with no sound.  When there is sound they work fine.
Guessing that maybe (even with the trim pot turned down), the speaker is providing a stronger signal (or a barely audible background hiss or noise) that's setting off the LEDs.  Was thinking of possibly adding a resistor to the sound input on the Sound to Light board?
Here are some schematics of both kits.  I'm powering the small amp board with 12VDC and the output signal to the speaker is shared/hooked up to the + & - of where the small mic was on the Sound to Light kit board.




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