Beginner in audio, need guidance on amps and other parts.

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JoFroMo2013
 
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Beginner in audio, need guidance on amps and other parts.

Post by JoFroMo2013 »

Hello, I am completely new to electronic engineering, but I want to make a portable Speaker/Radio system.
Features:
  • Bluetooth Audio Compatibility
  • FM Radio Receiving / Scanning (if it is to hard to implement this than it doesn't need to be done)
  • 3.5mm Audio In Jack
  • Able to run on a rechargeable battery. (If possible, built in charging)(Also I don't know what kind of capacity I'd need. Maybe 12V will work?)
Currently I have a X64CP45-01F 6 Ohm 5W speaker just laying around that id like to use in the project. I'd like to know what amp would be best compatible with this speaker and other parts that I can buy that would help please. If more information is needed, please let me know and I will update it.

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adafruit_support_mike
 
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Re: Beginner in audio, need guidance on amps and other parts

Post by adafruit_support_mike »

We have amplifiers that will drive that speaker, and this tutorial shows how to set up a mobile sound system for a bike:

https://learn.adafruit.com/ride-rock-di ... r/overview

The only FM receiver we have is part of the FONA embedded cell phone though (https://www.adafruit.com/product/1963), and we don't have any Bluetooth devices that transmit data fast enough to work for music.

To run a 6-ohm 5W speaker at capacity, you'd need about 5-1/2v across it, and the class-D amplifiers we carry need about 2v of headroom beyond what reaches the speaker. That means you'd need about a 7.5v supply to get everything the speaker can put out. Running it at a lower voltage and power level won't hurt anything, but you won't be able to blast it as hard as the speaker will stand.

We have LiPo cells and chargers for them, but only the 3.7v kind. For a battery with higher voltage you'd need to check somewhere like Pololu.com (they do robots: http://www.pololu.com/category/54/batteries) or diydrones.com (airframes: http://store.3drobotics.com/t/parts/rc- ... /batteries).

Choose a battery, then find the right charger for it. Different battery chemistries need to be charged in different ways, and using the wrong charger is dangerous.

markofthebeast
 
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Re: Beginner in audio, need guidance on amps and other parts

Post by markofthebeast »

Why couldn't the OP run a powerboost 500 or 1000 to bump the voltage up to 5V? I know it isn't the full 7.5V, but it's better than 3.7V. Right?

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adafruit_support_mike
 
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Re: Beginner in audio, need guidance on amps and other parts

Post by adafruit_support_mike »

That would work with one of our smaller class-D amps, but I was thinking about the MAX9477 20W amp:

https://www.adafruit.com/product/1752

The 3.7W MAX98306 can only drive a 6 ohm speaker at about 1W to 1.2W, depending on how much distortion you're willing to accept. The MAX9477 running from an 11v LiPo pack should be able to drive a 6 ohm speaker at 5W with minimal distortion and still have a bit of power to spare.

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JoFroMo2013
 
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Re: Beginner in audio, need guidance on amps and other parts

Post by JoFroMo2013 »

Alright, sorry for the late response, but I finally was able to get a hold of a breadboard/LM358N/Raspberry Pi w/ cobbler. Would the LM358N be an ok amp? It came with a pack I bought that had 60+ pieces of equipment.

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adafruit_support_bill
 
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Re: Beginner in audio, need guidance on amps and other parts

Post by adafruit_support_bill »

It's OK for driving headphones and such. But you won't be able to get much volume out of your speaker with it.

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