Hello all!

I'm interested in putting together a basic portable speaker system, but my knowledge of circuitry is only pretty rudimentary.

I wanted to use a mini amp in combination with some bookshelf speakers, and my question is if it is possible to run this: http://www.amazon.com/LP-2020A-Lepa...6OTI/ref=sr_1_1?ie=UTF8&qid=1360165681&sr=8-1 on a DC battery such as this one: http://www.amazon.com/UPG-Security-...SCWI/ref=sr_1_5?ie=UTF8&qid=1360166194&sr=8-5

The rear of the amp looks like this: http://ecx.images-amazon.com/images/I/61zBx9b5cJL.png and is powered by a 12V2A adapter.

Is it that simple to bypass the AC/DC adapter and power it directly from a battery? Or is additional circuitry involved?

Thanks!

 

It should be no problem as long as you are VERY SURE to observe polarity when making the connection. How do you plan to recharge the battery?

 

Thanks for the reply.

I was just going to use a regular SLA battery charger like this one: http://www.amazon.com/Sealed-Lead-Battery-Charger-D1724/dp/B001G8AIMU/ref=pd_bxgy_e_img_y

Another question: how could I calculate the theoretical maximum time I could run the amp off of that battery?

Logically I figured it would math out like this:

Amplifer: 12V * 2A = 24 W
Battery: 12V * 7.2Ah = 86.4 Wh

86.4 Wh / 24 W = 3.6 hours

 

The run time would depend upon how loud you play your music. The louder you play, the shorter the run time. You may be able to find discharge curves for your specific battery from the manufacturer. You do realize the battery voltage will drop as it discharges. The amplifier may or may not like running at reduced voltage.

 

Is there any way to build an external circuit that will boost the voltage?

 

Is there any way to build an external circuit that will boost the voltage?[/QUOT]

Yes, but more amps will be drawn from the battery. Have you read the reviews on Amazon for the amplifier?

 

I have read a few, but I'm not ready to make a purchase yet by any means.

Is there something that I should know about?

 

Just curious as to whether you had seen some of the problems mentioned in the reviews such as needing more than a 2 amp supply. Not saying it wouldn't run on 2A, but some found it deficient.

 

The ICs used are from Tripath who are bankrupt because the ICs could not produce their rated output and maybe because the ICs fail soon.

The amplifier is no-name-brand so it will probably fail soon and the replacement IC is not available anymore. Don't buy it.

I can't remember its output power but it might be 5W per channel into 4 ohms or 3W into 8 ohms. Look at its datasheet to see the REAL power before there is a lot of distortion.

You do not play continuous tones at full blast so the current will not be very high.
Oh, acid rock is almost continuous noise so the current will be very high.

 

I noticed that. I figured it might be a good idea to switch to this amplifier or one similar:
http://www.amazon.com/Pyle-PFA300-S...?s=electronics&ie=UTF8&qid=1360188629&sr=1-16
According to the spec sheet it will run on 9-14.4V.

They should be enough to drive these speakers http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-652 which are rated at 8 ohms, 40 W RMS.

 

I noticed that. I figured it might be a good idea to switch to this amplifier or one similar:
http://www.amazon.com/Pyle-PFA300-S...?s=electronics&ie=UTF8&qid=1360188629&sr=1-16
According to the spec sheet it will run on 9-14.4V.

Nobody (NOT EVEN THE IMPORTER, Pyle) knows which Tripath ICs it uses.
Its spec's are not detailed.
It might produce 14W per channel into 4 ohms with a 13.2V supply or 11.5W with a 12V supply. It might produce 21W per channel into 2 ohms with a 12V supply. It might produce 45W per channel into 2 ohms with a 14.4V supply and a momentary saturated square-wave input (not music).

The output is probably 6W per channel into 8 ohms with a 12V supply.
Beware, it uses obsolete Tripath ICs.

They should be enough to drive these speakers http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-652 which are rated at 8 ohms, 40 W RMS.

The little speakers will work fine with that amp but will produce hardly any bass.

 

I see.
Do you have any suggestions for an inexpensive amp that will drive these speakers?

 

It is difficult to find an inexpensive amplifier because they lie about the amount of output power. Select a name-brand.

The power must be spec'd for each channel, the speaker you will use (8 ohms), with a certain supply voltage and with a specified low distortion.

45W into 8 ohms is 54V peak-to-peak and the amplifier will use a 60V power supply voltage or plus and minus 30V.