SS Power amp chip using 9 to 12v

[javacody]

I'm looking for something I can almost drop into RunoffGroove's Ruby project and get higher wattage, say 5 to 10 watts.

[The Tone God]

hmm...you could use something like say a LM383/TDA2002/TDA2003/NTE1232 which is not a DIP power amp its TO-220 but will work with 9v single supply.

Remember that just dropping in a bigger power amp won't make things louder. You need the amperage to back it up. You won't get 5-10w out of a battery.

Andrew

[javacody]

How much amperage are we talking about? I'm using my Ruby with a wall wart that does up to 300mA.

[The Tone God]

Good ole' Power law.

P = E x I

E = 9v
I = 300ma = .3A

P = 9 x .3

P = 2.7w

Thats not including any loss in the amplifier which if I were to estimate at 60%

.6 x 2.7 = 1.62w.

So with what you got you can do roughly 1.62 watts.

To do 5w with 9v you would need rougly 560ma. Thats not including any loss in the amplifier. Check the spec sheets. They should give you the answers to how much power you will need.

I recently built a mini-amp that fits in a 1590B that spits out roughly 5w. I used a 15V 800ma transformer to have lots of power availible.

Andrew

[javacody]

Well the wall wart says it puts out 12v, but you know how that goes, it may actually be putting out higher, and it may have been 600mA or 650mA, I'm not sure.

That would give us:

E = 12v
I = 600mA = .6A

P = 12 x .6

P = 7.2

So 60% of that would be 4.32 watts, correct?

Does that sound feasible for a LM383/TDA2002/TDA2003/NTE1232?

This amp also has a JFET buffer in front of it (unity gain MPF102), how many mA will that use up?

[Ansil]

lm384 5watts each..

free as a sample from national semiconductor.

[javacody]

Ansil, that sounds like a good avenue to explore, but I wasn't happy with my experience with the Rat Shack lm386 1. The JRC386 stomped all over it tone wise. Is there a JRC/NJM version of the chip you mentioned?

[The Tone God]

The LM384 is a neat little IC but there are a few things to be aware of. Its a 14 pin DIP package which means if you plan on using it at a higher wattage it will need a heat sink. There are not many DIP heat sinks out there. The heat sinks only fit one side of the IC which means that half the heat is go through the other side which you can not attach a heat sink too. You could put a big copper layer on the board for heat sinking but that spreads the heat to surrounding componets. If the board material is thin it could warp or burn.

You also have to tweak the circuit to fit it in to the Ruby. It sometimes doesn't play nice with certain circuits and can kick up alot of noise into the power supply almost as bad as a 555. Interestingly enough there is a circuit in the app notes that uses a fet on the input much like the Ruby.

The LM384 is also alittle more efficiant then other low power amps so you can get a fair bang for your power.

The mini-amp in the 1590B that I mentioned earlier uses a LM384.

The TDA2003 is a TO-220 which is the package similar to voltage regulators. I find the TDA2003 kicks out more heat then the LM384 but there are lots of heat sinks to choose from. You can even be lazy like me and just mount the device to the inside of the enclosure using the box as the heat sink. It also requires a bit of circuit tweaking to make it work like the LM384.

There is also the LM4871 which is a 3w amp but I haven't played with those.

To answer your question about the power if those figures are correct then you can put out that wattage. Once again check the spec sheets for the answers. There should be some kind of power output vs. voltage supply graph that will give you an idea what the amp can put out.

Make sure thats loaded regulated DC. The 15V adapter I used is rated at 15VDC regulated but the adapter provides unregulated DC so its about 18VDC coming out. I have to regulated it down to 15V to get clean power. I would recommend doing that anyways to make sure you power is ultra clean. Any dirty power can make things noise.

Andrew

[Ansil]

hey javacody,  you had the ratshack lm386n-1. which is crap compared to the n-3.  for some reason according to the manufactur the n-1 (although it will run above an below 9v) thrives at 6V  when i changed my circuit to thisi was stunned. as it sounded much better.

i use the n-3 i haveused a couple of jrc386's  and i do prefer them to the ratshack ones but the n-3's i got walk all over them  a ton of punch compared to the jrc at the same voltage.

they actually make a nifty little heatsink made just for chips.. it is this little v shaped thing you put the chip down into.. so that its heatsink pins in the middle of the circuit. connect to it.  really great little thing.  of course in the spirit of diy you can also use a skinny hose clamp.. one that doesn't touch the legs  and attach a regualr heatsink with that using the thermal compound stuff they sell at ratshack.

then the easiest way is to go down to your local hardware store and get the stuff in the big copper tube, that not only conducts heat it is a HIGH HEAT ADHESIVE.. :)  costs about 5 bucks for a whole tube of it.  works great my chips don't hardly even get warm after you apply this stuff let it set for like 45 seconds and apply your standard heatsink to the chip hold for about 30 seconds..  or you can put a rubber band around it if you can get one in there

and last but not least the heatsinks used by craig anderton in his book. for the miniamp. are available.  ratshak carried them at one time. but most electronics supppliers carry them in on version or another,  there are like 5 different ones at my local parts distributor

http://www.shieldselectronics.com/

[javacody]

Thanks for the heatsink info. I've built several computers over the years and I have some big ass, beefy, cpu heatsinks. In the true diy spirit, I think I will hack one of those up.     It'll be cool to see a one inch high heatsink on a tiny chip. Or I could put a peltier device on the sucker.  :lol:   Nothing like a little overkill. Ooh, how about watercooled?

The idea about the copper plate is interesting, but folks in the computer biz, have actually heatsinked the bottom of their cpu sockets (under the motherboard), I could cut out the bottom of the board under the chip, and heatsink it from both sides.

I jest, but you see stuff like this with people who overclock their computer cpu's. Warranty schmarranty.

You guys have given me some great ideas. Ansil the idea about the hose clamp is good, but even better would be a plastic zip tie, and I have actually used this to hold an oversized fan on a mother of a cpu heatsink.

[Mark Hammer]

Get yourself a couple of LM386-4 chips and use them with 12v in a bridged (BTL) mode.  You'll get lots of oomph.

Do your layout right and you can line up the chips and bolt a hunk of aluminum to the board right over them with a dab of thermal goop to help matters out.  The dash-4's can dissipate more power but the 12v will tax them enough that a bit of help from a heatsink is a good idea.  Even if they don't burn up, I can't imagine they adhere to spec when hot.

[The Tone God]

For the LM384 amp I built I did use an actual DIP heat sink. The one that is suggested in the spec sheet is hard to get and too tall to fit in a 1590B case. Mine cost less then a buck and fits quite nicely. I attached it using themal tape which is good enough for this purpose.

A computer heaksink might be overkill. I do bask in the days of taking a P166 and OCing it to 266 or a Mal. Celeron 300s to 450 without water cooling or peltiers although I did have one mother of a huge heatsink for that. Four fans on it too to go with the other 10 fans in my system.

I run my LM384 amp at the 15v. Its pretty loud for a little thing. I built a better front end for it too so I'm much happier with it. I still have a couple lying around. Maybe a bridge version would be fun to build especially to see if I can fit it in a 1590B. hehehe

Andrew

[Nasse]

I have posted these links before bur here they go once more, for those who might want little more power

http://www.electronics-lab.com/projects/audio/013/index.html

http://www.kolumbus.fi/mikko.esala/lista.htm#Vahvistin18

The first one might be illegal copy of a commercial kit, if you live somewhere where the original kit is available it might be cheap to purchase original kit. I have two almost similar amps made along Elektor project (I think it is more or less some semiconductor manufacturers straight application. Nothing sexy and interesting but even I got this amp workin, and it is happy with less voltage and amperes, just drop supply voltage or put 8 or 16 ohms speakers and current consumption and output power drops quickly :wink:

The second one is some finnish collection of amp projects at about 12 volts and thereabouts, pcbs and all. I have had success (?worked without hassle) with similar TDA7370 2x22 watts amp