Do you have a question? Post it now! No Registration Necessary. Now with pictures!
- Posted on
- Home Built Speakers for iPod
February 17, 2008, 12:32 am
rate this thread
Re: Home Built Speakers for iPod
If the delivery truck has a cigarette lighter socket, that gives a
source of 12V. In my car, I think that has a fuse on it, of somewhere
around 20 amps, so you can get quite a few watts of power there if
If you have to run your amp on batteries, then running all day,
at a high volume, might be a problem.
As an example of one extreme, for the wealthy, Apple made this "ipodhifi".
It apparently runs on D-cell batteries. The link on the Apple site today,
doesn't show this item, so it may have been discontinued. At $349.00, you can
do better anyway. (The unit appears to consist of two treble speakers,
and one bass speaker, inside the same "cabinet". Power in watts not stated.)
An old fashioned ghetto blaster, would be another option.
Or, if you like to hack, then this is another approach.
This is a 2 x 5W stereo amplifier kit. These are available in both
unassembled, and assembled and tested versions. The UK154 is
assembled and tested. (I almost bought one of these kits from
a local electronics store, until they told me it wasn't a
stock item, and I'd be slapped with shipping charges when
it arrived.) Note that this kit is available from American
shops as well, and the origins of these kits is probably
China or Taiwan. I don't think they are locally designed.
Use the part number (UK154) and "amplifier" and you may be
able to find more sources for the product.
Now, why did I pick one with such wimpy output ? The problem
is, as the sound power in watts goes up, so does the DC
input voltage spec. That particular one runs from 12 to 16
volts DC at 1 amp. The lighter socket in the delivery van
would deliver 12.6 to 14.4V or thereabouts (going by my
measurements on my dying and replacement car batteries
a couple days ago). The only thing I don't like about
the lighter socket, is the possibility of transients on
the 12V rail. I understand up to 70V spikes can
appear on the 12V rail in a vehicle, and then you'd
want to see the amplifier fitted with protection
against that. This kit may not have provision to
protect against "dirty" automotive power, and I'm not
an expert on such things.
If you want to run that thing from batteries, no problem.
Purchase ten NiMH D-cells, which are nominal 1.2V each,
and put them in series. (As long as the cabin temperature
inside the delivery vehicle stays above freezing, the
NiMH are OK. For sub-zero performance, nickel cadmium
is recommended, but they also typically hold fewer
For example, purchase 5 kits of this two battery product.
5 * $17 = $85 for a total of 12V @ 4.5 amp/hours. You
could run the above stereo at full volume for 4.5 hours,
or squeeze out an 8 hour day, by turning it down a bit.
The kicker, is you'll need to buy a charger as well.
I'd look somewhere other than RadioShack for a charger. This
is the first one I could find, which might do the job. To
charge your ten batteries, would take two charging cycles on
this thing. Charging time would be somewhere around 2-3 hours,
and with eight slots, you could charge in two groups of five.
For battery holders, Radio Shack has those. You'll need to
solder wires to this, to build your 10 (or more) cell battery.
http://www.radioshack.com/product/index.jsp?productId=2062245 (holds 4 D)
http://www.radioshack.com/product/index.jsp?productId=2062241 (holds 2 D)
I would also place a fuse in series with the battery, to prevent
accidents. For example, maybe the 3 amp fuse from this kit.
You can also get fuse holders for these. The fuse and fuse holder,
goes in series with the battery. If the battery wires get shorted
by accident, the fuse opens before the batteries burst or
Other examples of amp kits. Note the use of heatsinks here, and
if you put an aluminum box around this unit, you'd want to
leave the heatsinks exposed for cooling. The heatsinks may not
be insulated, and could be at battery potential (if using the
cigarette lighter socket). You can check for that, by using a
multimeter, and probing the heat sink to see if it is "hot" with
respect to ground. This unit is a single channel, so
you need two of these for stereo. The "UK" in the part number,
means assembled and tested (but still needs a box to hold it).
The next model (UK194), puts the two channels on the same PCB.
This is the equivalent of two UK193. Now, note that while you get a
max of about 22W per channel, it takes a total of 3 to 4 amps
from the power source. And the output power specification,
depends on the level of DC voltage you can deliver to it.
So you won't be getting the full 22W max, unless the DC
rail powering it is close to the max allowed value.
The UK193 and UK194 would only be practical for running
from the cigarette lighter. The UK154 (2x5W) could be run from
the ten NiMH cells, battery holders, and fuse. Otherwise, those
puny NiMH cells wouldn't have a very long run time. The batteries
also have a maximum continuous current level they can safely
This is the overview page, so you can see some of the other kits.
Finally, one more example. Take this kit. This kit uses a
hybrid amp (the big blob). The blob is stereo, and gives
2 x 35W into 4 ohms. It has no volume control! (More hacking
to do, to add it.) For power, it uses 30 to 45VDC at 2 amps. This
is well out of the range of practical or safe D-cell usage.
The D-cells would cost a fortune, and you'd spend all day
on the charger, doing recharges.
To power something like that, you can get DC-DC converters.
For example, the company here makes one with a 36 volt output.
It can put out 19 amps peak, on the 36 volt output. Now, if
you plugged that into the cigarette lighter of the delivery truck,
and then overloaded the output of the DC-DC converter, the
fuse on the cigarette socket would blow. But since the UK250
draws only 2 amps, then there wouldn't be a problem with the
fuse. So running the amp at full volume, is still within
the limits of both the power converter box and the cigarette
lighter socket. You could also stick a fuse in line with the
amplifier power input, to protect against accidents of one
sort or another (say a 5 amp fuse).
So, there are some wacky ideas for you. I did the last one,
to show how you might power something that needed well more
I didn't include any mention of speakers, but I presume you can
find those at an automotive stereo place. I picked up some
6x9 oval speakers years ago, for just such a project. I don't
recommend perfectly circular speakers, because I had trouble
with those (coils rubbed against magnet). The 6x9's still work
today, but they're pretty grubby. Just stick with the impedance
spec of the amplifier (4 ohms or 8 ohms or whatever), when
Happy motoring, and don't get too carried away :-)
Re: Home Built Speakers for iPod
Why not just buy a cheap FM transmitter from Ebay then you can use the
radio in the truck?
As a Brit I'd like to thank the Americans for their help in the war
against terror because if they'd not funded the IRA for 30 years, we
wouldn't know how to deal with terrorists.