I bought 2 small speakers at a garage sale (6W 8Ohms)
I'd like to build a 2 speaker cigar box amp using the 2.5W Artec amp circuit from CBGitty.
Would that power both speakers with one 9V battery?
would I be able to wire them in parallel or in series? (i.e. would wiring them in series be 'dangerous')
How would I figure this out for myself? For example what if I wanted to find out the maximum amount of speakers I could have in cigar box amp. (just for my own edification) How would I do that.
Is there a formula or something?
I've never understood volts, watts, ohms when I was in school. I've been reading up on it today and nothing has changed, it still just confuses me for some reason
Thanks
Replies
Take a magnifying glass and find the number on the back of the chip.
Post that here and I'll show you how to work the data sheet to determine what to expect from the amp with different speaker configurations.
To Robert Jones---The numbers on the back (assuming I'm looking at what you're referring) is
2073D
JRC
6514B
To everyone--Thank you for all the responses. I don't mind the experimenting part, and I have wired a few CBG's, because I had the directions with picture diagrams. But if I try to do something 'not in the directions' I get worried cause I don't fully understand it, so I'm afraid it'll blow up or electrocute myself or something. lol
That's exactly what I was talking about, the JRC2073D is the amp chip.
When you put that number into search box at alldatasheet.com it pulls up the NJM2073 data, not to worry, same chip. The pdf even has the JRC logo in the upper left corner.
The 2073d is a dual audio amp that will operate from 1.8-15v supply. This is a good thing when it comes to battery powered amps. It means that the amp will continue working, at a reduced output, down to 2v.
"No turn on noise" means the amp doesn't POP when switched on. This is protects your speakers.
The Artec amp is BTL this is only of concern for reading the data from the appropriate section.
Note the highlighted line.
You'll see that at 9v and 16ohms resistance you get 2w of power.
This means that if you connect your two 8ohm speakers in series it'll be loud with 10% THD and the amp won't clip.
(Yep this also means that the 8ohm speakers packaged with this amp board in most instances won't deliver the full power of the amp.)
If you wire the speakers in parallel you'll have 4ohms resistance and at 9v supply the amp will clip pretty quick. You don't want that to happen.
I know these are advertised as 2.5watt amps but these are really only 2watt max.
Thanks!!
You're welcome.
The reason for looking at the datasheet is that some amp ICs are designed for one output resistance. Those chips behave as Scott aka Farmer Ted described.
Now if you ever get feeling froggy and want to build an amp from scratch contact me. ;-)
Experimentation is how many of us here learn, discover, and create these moments of genius.
One thing to consider about the speakers: when you make the speaker perform outside of its rated parameters, it will cause the speaker(s) to sound different than they were intended or designed. This is not all bad...it is simply trying a new sound.
If wired in series, as noted by Smokin elFish, (i.e. into the + & out the - on speaker #1, then into the + on speaker #2 and out the - to your common ground...it will double the resistance (ohms) to 16, and "choke" the speakers full potential. If wired in parallel (positives to positives, negatives to negatives) it will cut resistance (ohms) to 4, and make the speakers "loose" and lose much of their tone.
Try both ways and see what works for you.
As for fitting them into a cigar box, that just requires the right box...or a shoe horn.
Good luck.
wiring in series is safer for the amp. Series you can count the impedance resistance. 8ohm's will be 16ohm then. ( more resistance = less amps so less heat the amp will make) Don't know much about the gitty amp but if you put the speakers parallel then the total resistance is going to be 4 ohm. Since 4 ohm is a normal resistance for a single car speaker i would asume that the amp can take it.