Portable audio

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Kevinm11

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Joined 2015
#1
Hi all,
I am building a portable audio system that will be ran off of a 3.7v 5000mah battery. I am having trouble figuring out the best way of getting the voltage up high enough to power a good amp. Most of the amps I am considering require 12v. The amps that I have tried that run on 5v just don't get loud enough. This amp will be powering 2, 5 watt speakers. I would just make a battery pack out of several 3.7v batteries but this is a space limited project. So I have been considering some boost converters but most of them can't put out enough output power. Any suggestions would be great on getting the 12V or a better amplifier that runs on 5v.

Thanks!
 
#3
Kevin,

I've had good results using the Cincon DC to DC converters (available from Mouser) to provide bipolar 15VDC (they make bi/unipolar outputs up to 10 watts, isolated and regulated - around $20) from a 12V DC battery for op-amp preamplifier/driver applications.

Unfortunately it looks like your 3.7V (Lithium?) battery is below their minimum input of 4.5V. Might check out other vendors/manufacturers. Could you go to, say 6V worth of NIMH cells (6)? - you can get 3000mah in AA size.

Charles
 
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#5
It's not gonna run long onna 5000mAh battery after the voltage conversion. Double yer voltage, double yer current (mAh.) demand from the battery..

I've had good results usin' one of the amps magnus h suggested and a common 5 volt bank battery. Git some sensitive speakers and that little amp will put out plenty of sound.. (Enuff to suit me, anyhow)
 
#6
Thanks for all of your response! As you can tell I am new to audio. I guess from your response it seems to be best to just stick to an amp that will operate on 5v. My schematic already has a chip that will boost to 5v from the battery voltage. I bought this little amp from adafruit and tried it out. https://learn.adafruit.com/stereo-3-7w-class-d-audio-amplifier/overview
I made a makeshift tupperware speaker box that I put 2 5W speakers in that are about 2.5". This sounded ok I just didnt feel like I got the sound output necessary for my project. Would having these speakers completely sealed in a small enclosure greatly improve their sound output? I also bought and tried this amp Sure Electronics 2x8W at 4 Ohm TPA3110 Class-D Audio Amplifier Board and with the same speakers in the same enclosure it sounded much better. So now my problem is it needs atleast 10v for power and I was using 12v in my testing. Anyone have any suggestions on maybe some better speakers? Looking for something in the 2 inch range.

Thanks!
 
#7
"I made a makeshift tupperware speaker box that I put 2 5W speakers in that are about 2.5". This sounded ok I just didnt feel like I got the sound output necessary for my project."

The sound from the plastic flappin' around will null out the sound comin' from the speaker. Cardboard would be better if ya wanna try sumptin' before sawin' up any wood..

Git yerself a stiff cardboard box about the rite size to fit the speakers and mount them in there. (hot glue makes it easy!) Steal the womans pillow and "borrow" some of the stuffin' out of it and put it in the box behind the speakers. Duct tape it up and put the power to it. I'll betchya they sound like different speakers.. 😉

Just remember, when you use a lower voltage battery and convert to a higher voltage, the current (Amp) demand can double to the battery.. (Eats 'um up a lot faster)
 
#8
Just remember, when you use a lower voltage battery and convert to a higher voltage, the current (Amp) demand can double to the battery.. (Eats 'um up a lot faster)
Click to expand...
right it is the watt hours not the mAH that count. To the battery a boost converter looks as constant wattage load, plus the conversion losses. IMO a good tradeoff for audio amps which are very voltage sensitive to direct connected drooping batteries.
 
#9
Twice as loud is 10 times the power. The intended use dictates the PSU
requirements. Perhaps you need a different PSU?
My small portable speaker provides ~2W from a BTL amp running from a 6VDC wall wart or 7.2V 4000mAh lithium battery. Enough SPL to fill a room or patio.
The battery was manufactured as an add-on aux source for a portable DVD player. It has integrated charge controller and pushbutton LED bargraph charge status meter. The wall wart, without the DIY 6V regulator, is the OEM recharge source.
 
#10
It's better to step down from a higher voltage to a lower voltage. 12 volt batteries and power supplies are more common than most it seems..

These things are neat and very flexible. They can be used to regulate voltage for runnin' an amp or chargin' a battery from a D.C. supply..

10pcs Mini 3A DC DC Adjustable Step Down Converter Standard Power Module LM2596 | eBay

I use um' to regulate voltage from my 12 volt lipos to operate those little 5 volt wonder amps and to regulate the charge voltage to the batteries from my solar power.. (The A.C. chargers are paperweights to me..)

Free lithium battery backup power supply of 12V 6800mA 12 volt 6500 mA DC12680 6 sets/pack-in Camera Battery from Consumer Electronics on Aliexpress.com | Alibaba Group

One of those 5 volt wonder amps and a USB powered Bluetooth adaptor will run for a loooong time before needin' a charge. Gotta be a little crafty and solder savvy but well worth the effort..
 
#11
Thanks for all of your replies!

So The reason I was even considering boosting the voltage is because I cant find anywhere a battery that is small enough and provides a higher voltage. Does any one have a clue what batteries are used in a portable blue tooth speaker? because essentially that is what I am making. I imagine they use a 7.2v lipo so maybe I should explore that route. It just needs to be small like 3" x 2" x .5".
 
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