I’m building a small project box with some basic components (LEDs, pots, switches, etc.) that will be used to learn microcontroller programming. It currently lacks any decent audio functionality, so I’d like to remedy that. I picked up the K8066 3W Mono Amplifier kit a while back … just trying to figure out what’s a suitable speaker to use. I’ve got two that came out of grab bags - they are both labeled 8 ohm - one says .5W … the other .1W. They are 2" and 1" in diameter.
I’m not entirely sure what that wattage rating means… But here’s my main question: Is this 3W mono amp going to put out too much power to use with either of these two speakers?
@laserguy - thanks for the advice; however, do you have any knowledge that would help answer my actual question or help me understand the math behind the figure you came up with?
From this answer, I might infer that if I use 6V DC, the larger of my two speakers would be acceptable to use. Would the smaller speaker rated at 8 ohms / .1 W be damaged if it were used? I’ll admit to being completely ignorant and confused regarding this speaker Wattage rating. How is it determined?
Since posting this question and receiving very little information (and ZERO information from the company that produces the products I’ve purchased), I done some additional research that has me leaning towards going with a 741/386 amp solution. It seems to be more suitable for the smaller speakers I intend on using.
Does anyone have experience with these ICs they would mind sharing? Am I correct in believing that the K8066 is overkill for small speakers and that a 386 circuit would be better?
Sorry Perry, about speakers and power complete books are written. I really can’t write this all here. A speakersystem is a combination of electricity, mechanics, electrodynamics and thermodynamics (compression and expansion), … If you want to know more, look for a good PA-forum (NOT HiFi-forum as these guys have too much fantasy sometimes) and start reading ;).
Yes, the one with the highest power is the best choice, no, you won’t kill the one of 0.1 Watt as long as you make sure the output of the amplifier is below 0.1 Watt continuous (depends on the “music” you want to play and so on … read about crest factor/clipping/ … on the professional audio forums).
A 741 is an opamp, and can’t deliver much power, also because its fairly high internal resistance. That is why indeed we have something like the LM386.
As said: on only 6 Volts: the K8066 is perfect for speakers of 0.5 Watts. What is overkill? The K8066 is not extremely expensive and is not extremely powerful.
@laserguy - once again, thanks for taking the time to post helpful information. In response to a couple of your latest comments … You mention that the 741 opamp doesn’t deliver much power - that makes sense now when I look at the circuit I’ll probably be going with. It comes from one of those Forrest Mims Radio Shack books, “Engineer’s Mini-Notebook - Op Amp IC Circuits” and is simply titled “Audio Amplifier.” Mr. Mims uses the 741 as a preamplifier which then pumps the signal into the LM386 for the power amplification stage. Both stages contain a variable resistor for controlling gain.
Hopefully I didn’t come across in my first two posts as someone who expects to sit on my lazy ass while others spoon-feed me info that they themselves worked hard to learn! Like the best things in life, electronics is about the journey - not the destination. I recently picked up a nice used copy of “Circuit Analysis: Theory and Practice - 4th ed.” for $6.49 shipped. If anyone else is looking for such a book, I HIGHLY suggest this one. It’s full color - has answers to the odd questions in the back - and comes with a disc that has Multisim/PSpice files for most example circuits. There’s also a companion lab manual - this one cost me a bit more than the book at $28.53.
I’ve checked through all the books I have that might contain good info on speakers, or to be technically correct, transducers … and I’m coming up blank. So if anyone reading this cares to share the title of a book that might go into any sort of detail on transducers or transduction, I’d highly appreciate it!
Finally, regarding the term “overkill” I sometimes forget that although English is commonly spoken on boards like this, it’s not everyone’s first language. Overkill basically means “excessively more than necessary” … um … like when people use SPF 100 sunscreen You could say … anything over SPF 45 is overkill! So even though K8066 is ~ $15, I can build the 741/386 circuit for a few bucks.
That makes sense indeed: first a 741 (but use TL071 of TL081 to minimise noise) followed by the “power”-amp LM386.
Where did you find that book of Mr. Mims? These are already about half a century out of print? Did you rob a museum? Were very good small books: simple and effective circuits! Surely keep it for further reference!
No, you didn’t: you gave us the full story and a full explanation. This shows already some efforts, which everyone normally appreciates.
Circuit analysis is not that simple! You will learn A LOT of it!! Succes!
If you did understand Dutch or Deutsch, I could recommend you a good book. In English this one seems to be very good also: Loudspeaker handbook of John Eargle. Again: this is also not simple! Make sure you like maths before starting to read it.
I understand overkill but where is the limit between normal and overkill? I think this is a matter of personal opinion. The K8066 can deliver 3 Watts but powered with 6 Volts it’s only 0.5 Watts so this is not much overkill. And of course: you can build this cheaper with other components but you will never have an almost perfect PCB like Velleman delivers. But of course: this is completely a matter of personal choice. If you are asking me the same question with a 25 Watts amplifier I suspect some overkill, if you are going to try this with an 100 Watts amplifier it definitely is overkill ;).
You could say … anything over SPF 45 is overkill! So even though K8066 is ~ $15, I can build the 741/386 circuit for a few bucks.
Were very good small books: simple and effective circuits! Surely keep it for further reference!