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Topic: 3 watt audio amp (Read 726 times) previous topic - next topic

ScottG

I am building an alarm clock and for the sound I'm using Sparkfun breakout board for a WTV020SD.  It has a built in 1/2 watt 8 ohm amp, but I am thinking of using an external amp.  The breakout board has a dedicated 16-bit DAC/PWM audio output to use with an external amplifier.  My speaker is just a little 3W 4 ohm - Digikey 668-1234-ND.  I'm thinking of using either an ISSI IS31AP2005 or Analog Devices SSM2305 audio amplifier.  They seem to be the same thing to me, except ISSI is about $0.35, Analog Devices is $1.55.  Is this a good choice for my application?  In the example circuit (attached) from the data sheet's I wasn't sure how I should control the volume (I can't do it with the WTV020SD breakout board).  Would I put an audio potentiometer in for Rext?  If so, do I need  dual gang one?  I'd like to just have a little trimmer pot for the volume.

cjdelphi

In the real world, better the speaker, better the quality...

For example, i happily drive a 20watt (generic) satellite speaker from a 5.1 setup and avoid all the little cheapy speakers, those speakers are generally heaps better sounding regardless of your driver it's just a thought, I use a cheap amplifier with a decent speaker rather than a cheap speaker (they sound tinny)

But you know if you don't mind the power loss you can build a Class A? (the crappiest of all of them) using a half decent power transistor and 3 resistors practically but is a waste, it's better to amplify it in stages and give a feed back , but literally a tip31 a voltage divider gives a killer amplifier circuit if you don't mind wasting the power that is....

cjdelphi

"Would I put an audio potentiometer in for Rext?"

Sure, a 1 - 5k? potentiometer, it should not matter be it before or after the filtering cap (to block DC)

ScottG


In the real world, better the speaker, better the quality...

For example, i happily drive a 20watt (generic) satellite speaker from a 5.1 setup and avoid all the little cheapy speakers, those speakers are generally heaps better sounding regardless of your driver it's just a thought, I use a cheap amplifier with a decent speaker rather than a cheap speaker (they sound tinny)

But you know if you don't mind the power loss you can build a Class A? (the crappiest of all of them) using a half decent power transistor and 3 resistors practically but is a waste, it's better to amplify it in stages and give a feed back , but literally a tip31 a voltage divider gives a killer amplifier circuit if you don't mind wasting the power that is....


The alarm clock will be in a Doctor Who Tardis (my daughter is a big fan); so I don't have much room for a speaker. Sound quality for this project isn't very important. 


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