amplifier with 12v supply

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Sorry but none of these provides such power out with 12V supply.

I haven't looked but are you sure? Most Class D amps are bridged so you have effectively twice the voltage swing. Do we in fact have a figure for his load impedance anyway?

Incidentally, is there any reason that the Tripath amps, TA2020 etc, haven't been mentioned? They are surely among the easiest and best sounding things to meet this requirement - especially if you get them pre-built from Arjen Helder.
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
Like AndrewT said, car chip amps...

TA8225 (and even TA8210, which is the mostly used car chip amp for home mini hifi) has always amazed many listeners. It is rated for 45W but of course you don't need that highly distorted signal. At 4W/4R/1K it gives 0.015%, a very good number.
 
Do the sums.
for 12Vdc supply and assuming the maximum output voltage when driving the load gets to within 1V of the supply rails (+12Vdc and 0Vdc) then the output will be 5Vpk.

Into 4r0 this gives a maximum power of 5^2 / 4 /2 = 3.1W

Bridging a pair of these 12V amplifiers gives a maximum output of 6.2W into 8r0

If you design the chipamp to deliver maximum power into a 2ohms speaker and this requires an ability to deliver real power into a 1r0 resistor, then you can double those maximum power figures by halving the load impedance.

i.e. 6W into 2r0 for the single amp and 12W into 4r0 for the bridged pair of amplifiers.

When you do the sums you identify those retailers who tell the uninformed purchasers all the lies they want to believe.
 

wwenze

Member
2008-03-07 12:46 pm
Human ear is interesting, just to reconfirm my knowledge I went to clip the top 50% of the voltage of a track, it sounds just as loud as the original track and 20 times more likely to induce bleeding of the ear. 3rd harmonic distortion is definitely over 10%. But this is exactly how manufacturers claim to do 15-20W with 12V - @ 10% harmonic distortion.

Let me see TA2024's datasheet for example... into 8 ohm, low distortion up to until 5.5W, and then distortion just shoots straight up. About 11W @ 10% THD+N.
 
Human ear is interesting, just to reconfirm my knowledge I went to clip the top 50% of the voltage of a track, it sounds just as loud as the original track and 20 times more likely to induce bleeding of the ear. 3rd harmonic distortion is definitely over 10%. But this is exactly how manufacturers claim to do 15-20W with 12V - @ 10% harmonic distortion.

I congratulate you on making the actual experiment instead of just sitting in a chair and thinking.

I see people here (and in many other Forums) saying "XXX amp is *horrible*, over 0.5% distortion, for me maximum acceptable is 0.001%" ... while the program material they are listening to has already passed through tons of stuff, meaning microphones, preamps, mixer channel strips, equalizers, compressor/limiters, line amps, recorders (any type: Tape/Vinyl/Digital/Optical) before even getting to them.
Plus going through a mile of copper wire but *much* worse, going through metal *junctions* (audio connectors, terminal strips, PCB connectors, ***parts pins soldered to PCB or to each other***).
All that adds up to a lot more than what any individual amp can add on its own.
 

johnr66

Member
2009-03-05 1:55 pm
I congratulate you on making the actual experiment instead of just sitting in a chair and thinking.

I see people here (and in many other Forums) saying "XXX amp is *horrible*, over 0.5% distortion, for me maximum acceptable is 0.001%" ... while the program material they are listening to has already passed through tons of stuff, meaning microphones, preamps, mixer channel strips, equalizers, compressor/limiters, line amps, recorders (any type: Tape/Vinyl/Digital/Optical) before even getting to them.
Plus going through a mile of copper wire but *much* worse, going through metal *junctions* (audio connectors, terminal strips, PCB connectors, ***parts pins soldered to PCB or to each other***).
All that adds up to a lot more than what any individual amp can add on its own.

Good stuff, JMF. Just to add, in a test, it was found that when 2.5% THD was purposely added to the signal, the listeners were unable to distinguish from the "clean" signal. It took up to 4% THD before people were able to detect the distortion. Different types of music and instruments changed the level at which distortion was detected. For example, distortion in piano music was detected at 2%, pure sine waves well under 1%.

Dirty/oxidized contacts can be the worst offender as the response to a signal passing through can be nonlinear to voltage and polarity.

When performing listening tests on new amp builds I get concerned when I hear distortion in a passage. I replay the passage on separate gear only to find the distortion was in the source material. I'm surprised at how badly a lot of music is recorded.
 
so,with a 12 v supply we can't have a good 15+15 watt amplifier.
but
whit a +/-12v supply we can build a good amplifier whit pretty good power
anyone can help me to make a +/- 12 v(or +/-15v) supply from a 12v/7.2AH battery?whit minimum external components?

No, you can have what pretty much what you want with your 12V battery, just as long as it's a bridged amp (which gives you the equivalent power output to a split supply - or 4x the power) and you are using 4 ohm speakers or less. You certainly won't notice any deficiency even if you don't quite make 15W.

12V batteries generally charge to 13.5V or even 14.1V, so that gives you a bit more. And the voltage drop across the output transistors is pretty small. It should be plenty loud enough for what it is into any reasonably efficient 4 ohm speaker. If in doubt you can always check out the principle for very little money by buying a TA2020 board on eBay.
 

Arty

Member
2011-02-24 5:04 pm
http://www.datasheetcatalog.org/datasheet/philips/TDA1557Q.pdf
page 7.
13.2 V yields at 4 ohm 12 watt (0,5 % THD) .
I use that chip to drive a set of not too efficient 3 way 8 ohm rated speakers.
It is more than loud enough, so i have nothing to complain about.
These chips can take up to 18 volt as verry maximum.
If You have the option to go from 12v to something like 16 volts (regulated supply might be a good idea) then probably You can push some extra watts out.
for the above to be true we can ssume that the chip makes something close to 7 volts at the output when supply is 13.2 volt. means ~6,2 volt less than supply.
from 16.2 volt supply that would mean something close to 10 volt output swing-
so probably close to 25 watt at 4 ohm load and 0.5% THD.

but this would be verry crude logic. even so i think 20 watt would be more or less a number that could holds its own in real life.

Question comes why You need it to be a 12 volt device?
gona run it on a computer powersupply ?
 
http://www.datasheetcatalog.org/datasheet/philips/TDA1557Q.pdf
page 7.
13.2 V yields at 4 ohm 12 watt (0,5 % THD) .

Arty, it's not necessarily a good guide to pick power outputs off datasheets. Some of these designs are pretty old and have a Vbe drop or two that wouldn't be there nowadays. On modern chips the losses really are quite minor, especially when they know there is a genuine cap on the Vdd. I still hold that for all intents and purposes the OP can get what he wants with his battery.
 
Arty, it's not necessarily a good guide to pick power outputs off datasheets.
:eek:

Some of these designs are pretty old and have a Vbe drop or two that wouldn't be there nowadays.
Ok, suppose you have 1 less Vbe in the path (which is a great achievement).
This gives you extra 0.7V peak.
Not bad, every bit counts and doubly so when supply voltage is the limit, but that won't turn a 20W amplifier into a 40W one.
Gains will be modest.
 
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