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Chip Amps Amplifiers based on integrated circuits

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Old 3rd January 2014, 06:33 PM   #11
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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.
Nope, lm3886 has typical 50dB @ 20kHz, see page 16 of the data sheet. (here) http://www.ti.com/lit/ds/symlink/lm3886.pdf
The data sheet for the TDA8566 claims 60 dB without any frequency specification. (here) http://media.digikey.com/pdf/Data%20.../TDA8566_6.pdf

Mike
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Old 3rd January 2014, 07:09 PM   #12
paulb is offline paulb  Canada
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Originally Posted by shlshh View Post
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.
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Old 3rd January 2014, 07:27 PM   #13
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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).
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Old 4th January 2014, 12:17 AM   #14
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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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Old 4th January 2014, 12:23 AM   #15
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P.S. I love the quad amplifier you built! Really neat wiring and compact. Nice work.

Dale P.
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Old 4th January 2014, 01:15 AM   #16
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Originally Posted by ibuildstuff4u View Post
P.S. I love the quad amplifier you built! Really neat wiring and compact. Nice work.

Dale P.
Thanks. I wish I'd built 2 of them. I need another one for my bi-amp'd computer system. Finding the heatsinks turns out to be the hardest part. Those were surplus.
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Old 4th January 2014, 01:37 AM   #17
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Quote:
Originally Posted by Michael Bean View Post
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.

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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.
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Old 4th January 2014, 06:25 AM   #18
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Oh yeah?...My amp can beat up your amp!

Mike
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Old 4th January 2014, 10:15 AM   #19
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Originally Posted by abraxalito View Post
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.
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Old 4th January 2014, 02:03 PM   #20
shlshh is offline shlshh  United States
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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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