I have ordered this 3W amplifier from eBay for a Halloween prop.
http://cgi.ebay.com/MINI-digital-Amplifier-board-3W-3W-MP3-MP4-CD-DIY-/120589672648?pt=LH_DefaultDomain_0&hash=item1c13b460c8
I haven't received it yet but was wondering about this note;
3:left and right speakers can not be connected with the negative, that is to say Speaker of the four lines are completely independent, and does not allow total access!
Does anyone know what this means?
Thanks for the explanation
I saw that they had removed the markings on the chip. It’s probably crap but I’m only playing of a 8bit mono file so hopefully it will work for that. After all its only $5
Oh I hope this board works…
I just bought one.
Any idea what the "OFF"
Any idea what the “OFF” connection is for?
In your hands yet?
Well, have you got it yet? --I mean plugged in…
How does it sound? Loud?
It’s hard to judge the
It’s hard to judge the sound quality as I’m streaming an 8bit mono sound but it seems ok. And yes it’s loud, so loud actually that I need to turn the volume down. I’m running it through a 5W 4 ohm speaker.
So how do I turn the volume down? Can I just add a trim pot, and if so on the input or the speaker side?
pot yes, trim no
I would try putting a potmeter between source and input pin(s). Stereo potmeter, so you can control L and R separately, if you would have two channels. Logarithmic “taper” was designed for audio purposes. It looks like there already is a 1 KOhm resistor in series at the inputs. So I would use a potmeter that was approx. 10 times that value or higher. Whatever the junk box has on sale. If you go a lot higher than, say, 100 KOhm, you will not hurt your circuit, but you may find yourself using only the first 40 degrees of the turn or so. That’s a waste of available control space.
Some circuits have the potmeter set up as a voltage divider. Dividing input signal against ground level. The slider pin connects to the input. Others only use two of the three connections on the pot and use them as a variable series resistor. Basically the same pins, without the ground.
I choose the input side because that’s a teeny weeny current to limit. Disadvantage (in theory) would be that any noise created by the slider inside the pot would also get amplified.
A “Trimpot ®” is a multi-turn potmeter, used for very fine adjustments, often using a screw driver. It would work, but a normal 270 degree pot is just more convenient in use.
Thank you for your response Rik
I added a 10k pot and that allows me to somewhat control the volume.
But I also have this low level pulsing noise when it should be no sound. It’s like low level white noise pulsing like mores code. I’m working on this setup http://www.microframeworkprojects.com/index.php?title=FEZ_Audio_OUT and I can’t remember having that issue when I used my PC speakers.
Do you have any suggestions?
