Chip for First Project

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Hi all,

I've been reading up on the forum quite a bit lately and am finally beginning work on my first project. My plan was to drive two Tang Band W3-1053 drivers, which are rated at 8 ohm impedance. I live in a pretty small place, I don't need blaring speakers, but would like something a little louder than my laptop :)

Two things -- I was hoping to build the circuit myself (I don't want to buy a PCB). Also, I know that these drivers aren't capable of much bass. The next addition to my project would be a subwoofer.

My question is: what chip do you recommend? This is what I've gathered from the forums so far.

LM386: can be powered off of 9V batteries (making a power supply might be too ambitious for me) but can only output 1W
LM3886: better power output, but would need to make a power supply (maybe future project)
TDA2030: supply voltage range 4.5~20V, so I could first power off batteries then later switch to transformer

Is this summary right? In that case, I think I'd go for a TDA20x0 amp, and first power it with a few batteries while I work on the subwoofer and power supply.

Thanks!
 
I really think you have kinda locked yourself in by selecting that little Tangband. As a point of reference, I have a 2822, 600mA amp pirated out of one of these cheapie "PC speakers".....those common stupid things everyone sees flanking a PC screen. Given that the drivers in those stupid white things are bad in all ways..... first & foremost efficiency, secondly frequency response (none).
In your case you have selected a driver that runs at 85Db...about as low as you can get. Looking up the 6.5" Visatron driver, it's rated at 93Db (in a 1.0 cubic foot enclosure) Can you have a 16" by 12" by 8"...or thereabouts sized enclosure? Point is, you are putting increased "pressure" on the amp side of the "equation" ...as far as designing the system as a whole.
My tiny clean 600mA worth of power is driving a pair of freebie two-way car 6X9s' in an open baffle.......& it's way loud enough, clean....& with them on 1.0M by 1.2M panels, they are "out of the way"..up against the walls, my computer in the corner, flanked by the two panels.


______________________________________________________Rick......
 
Interesting point. From the drivers I was considering it did have one of the higher sensitivities. This is probably because I locked myself into 3" diameter and less than $20/driver from Parts Express.

I've ordered the drivers but I can exchange them if it is going to have a very significant impact on the end result. A quick look shows this newly posted-driver (FaitalPRO 3FE25) should be an improvement at 91dB sensitivity
 
?Perhaps the LM4752 powered by a surplus laptop power supply?
http://www.ti.com/lit/ds/symlink/lm4752.pdf

Thanks for the suggestion paulb. Why do you recommend this chip? My concern -- from DigiKey and Mouser, it looks like there are only surface mount versions available. I was hoping to prototype with a breadboard. I'm new to electronics (if you couldn't tell!), so I don't know how I can make this work.

Easiest chip amp I ever built was TDA8566. Can run from a car battery or anything up to 18V (a laptop supply through a bridge rectifier to lose a volt or two works).

@abraxalito, same question -- why do you recommend this chip? From the datasheet it seems to be designed for 2ohm and 4ohm loads.

I'm also trying to learn, how are these different from what seems to be the more commonly used LM3886?

Thanks!
 
why do you recommend this chip? From the datasheet it seems to be designed for 2ohm and 4ohm loads.

First reason - I've built 3 or so and they've all sounded better than any LM3886 (or TDA7294 for that matter) I've ever built.

Second reason - its a very simple chip to put a low impedance supply behind because the pins are close together. Hence I use a lot of ceramic caps right between the pins.

Thirdly its got the gain resistors on the chip, it has separate signal and power grounds, it has differential input.

Yes its designed to drive down to 2ohms, that just means its really only loafing along with an 8ohm load, and that shows in the SQ.

I'm also trying to learn, how are these different from what seems to be the more commonly used LM3886?
LM3886 suffers from poor PSRR at higher freqs - perhaps its greatest weakness - about 24dB at 20kHz. The TDA8566 is at least 30dB better than this - a not insignificant margin.

<edit> Forgot to mention another major advantage - its a bridged chip, so grounding problems are eased considerably.
 
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The TDA8566 sounds like a chip to try out on my next build.

Here is a link to my chip amp that I just finished. The boards came from Chipamp.com and the power supply board was bought on E-bay, but you can also get that from chip amp. I went with a different power supply to save a few bucks.
http://www.diyaudio.com/forums/chip-amps/248524-my-new-chip-amp.html

Don't let the power supply thing scare you into limiting your options on an amp to build. The supply is quite easy to build.

Dale P.
 
Thanks for the suggestion paulb. Why do you recommend this chip? My concern -- from DigiKey and Mouser, it looks like there are only surface mount versions available.
...
I'm also trying to learn, how are these different from what seems to be the more commonly used LM3886?

Thanks!
Just that I've used it and had good results. It's designed specifically to run from a single supply voltage and requires very few external components. TI/formerly National also has a version with two amps in one package and very few parts required; I worked with a scout troop leader to create a project for the scouts with it.
Consider just whipping up a very simple amp and power supply or battery combination just to get started. While you're listening to this you can dream up what your next amp will be like.
 
I built a quad poweramp using the 3886 chip and am very happy with it. About 50 watts rms into 8 ohm loads, per channel. I figured that if it's good enough for Linkwitz (uses it in his Pluto system), it's probably good enough for me. My bench tests all look great, and it sounds great to me. Those who think it's not good enough have probably overlooked the many variables at play in any comparison test I've ever seen. Although I haven't personally bridged two of them for about 3 times the power output, Linkwitz has, and does in his Pluto system for the lower frequency band. I consider it the "go-to" chip for analog poweramps. If your experience is limited, I'd recommend researching kits. Phase margin is tricky, and all about lead lengths, and everything physical, as well as part values. A power supply is much easier to build, than a power amp with good phase margin.

You can see my 3886 amp at the following webpage (scroll down).
Soundbar Project
 
Does any one sell pre made circuit boards for the TDA8566? Im sure this chip is easy to work with and doesn't really need much of a circuit board, but if this is your first build it will be easier to work with a ready made circuit board that just needs the parts to be soldered to it. There are a ton of different 3886 amp kits on the market making it easy to build. I have even seen some boards on E bay that offer power supply circuits built right into the same circuit board so there would be less wires to run. Also web sites such as chipamp.com offer amplifier boards as well as power supply boards for them. You can even buy the amp as a whole kit which saves the headache of trying to figure out what parts to buy.

Any way there are a ton of options out there for a first amp build. I personally suggest going with the 3886 chip or similar since there are pre made circuit boards and kits on the market. Down the road you can easily change out the chip if you want to try different ones. The transformer and power supply will work for different chips, all you would have to do is swap out the amplifier circuit boards.

This is why I use screw terminals on my amp. I can very easily un screw the wires and try something different. Here is a picture of one of my chip amp boards. I have the input and output terminals mounted on the bottom of the board because they didn't fit on the top. The screw terminals were bought from my local Radio Shack and I always tin my wires with solder before screwing them down so the set screw has a better contact.

Good luck.

Dale P.
 

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Nope, lm3886 has typical 50dB @ 20kHz, see page 16 of the data sheet. (here)

I was giving the PSRR in a typical application circuit with gain=26dB. So from the 50dB figure (which is referred to the input) the closed loop gain needs to be subtracted. Hence my result of 24dB.

The data sheet for the TDA8566 claims 60 dB without any frequency specification.

If you look carefully you'll see its referred to the output, whereas for the LM3886 its referred to the input. That's why I gave the in-circuit PSRR so a meaningful comparison could be made between the two.
 
First reason - I've built 3 or so and they've all sounded better than any LM3886 (or TDA7294 for that matter) I've ever built.

Second reason - its a very simple chip to put a low impedance supply behind because the pins are close together. Hence I use a lot of ceramic caps right between the pins.

Thirdly its got the gain resistors on the chip, it has separate signal and power grounds, it has differential input.

Yes its designed to drive down to 2ohms, that just means its really only loafing along with an 8ohm load, and that shows in the SQ.

LM3886 suffers from poor PSRR at higher freqs - perhaps its greatest weakness - about 24dB at 20kHz. The TDA8566 is at least 30dB better than this - a not insignificant margin.

<edit> Forgot to mention another major advantage - its a bridged chip, so grounding problems are eased considerably.

Loafing along into 8ohms? With 18volts max voltage very little drive. Sure, add a transformer that costs more than the amplifier.
 
Thanks for your suggestions, everyone. I ended up ordering an LM4752 because it matched a DC adapter I had on hand, I understood its support documentation better, and it looked like it wouldn't take many extra components. I'm excited to put it all together, and am sure I'll have more questions when I do!
 
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