Any love for the TDA2822?

[Mark Hammer]

I dropped by the local Pirincess Auto store today (the Canadian equivalent of Harbour Freight, both of them inexpensive hardware/machinery/auto repair supply outlets), and picked up a half dozen little powered plastic speaker units for plugging into one's iPod or other portable music player, from the "surplus" section.  They were 23 cents each, and came with some nice little molded mini-phone patch cables.  Those were actually the reason I bought them (I can't make 3ft cables myself for that price).  In any event, I pulled them apart immediately, and found they contained an 8-pin TDA2822 2-channel power-amp chip on a cute little board.  I'm not savvy enbough to know what the important differences between this chip and an LM386 are, but I do note that there are a surfeit of LM386-based distortions, some of them (like the Frantone Peachfuzz) using two cascaded such units.

So, is the TDA2822 the sort of thing one might repurpose for such a purpose, or is it best to use them for teeny amplifiers, as SGS-Thomson and Contek intended?

[Gurner]

I personally like this little chip....in my tests I reckoned it had one of the the cleanest output signals of many low power audio ICs I scoped. It is particularly useful for low supply voltage where there was little observable/objectionable distortion way down  to 4V  supply (I didn't go lower as I have no need for going below that supply level. The kicker for me was the lack of shutdown pin....which like the LM386 rules it out for most of the battery 'conservative' circuits I typically try to design.

[Earthscum]

I love these, as well. Tayda carries them really cheap... however, I dig them for headphone drivers, and mini-amps. I did drive one into distortion, and it sounded about like the 386 does to me. Not sure if it's friendly with long term abuse or not, but I would certainly think it's worth a shot, for how cheap they are. BTW, for reference... 386 and 358 sound identical to me, never have tried them side-by-side. NE5532 has the same kind of distortion, as well, so my point of reference is probably not very good, lol.

I discovered these little guys the exact same way... bought a pair of "Computer" speakers to make a little stereo/mono amp out of, figuring I'd need a simple preamp at most, and everything from the "master volume" on out is taken care of, including PSU, and the bonus Headphone out.

[DavenPaget]

I love these, as well. Tayda carries them really cheap... however, I dig them for headphone drivers, and mini-amps. I did drive one into distortion, and it sounded about like the 386 does to me. Not sure if it's friendly with long term abuse or not, but I would certainly think it's worth a shot, for how cheap they are. BTW, for reference... 386 and 358 sound identical to me, never have tried them side-by-side. NE5532 has the same kind of distortion, as well, so my point of reference is probably not very good, lol.

I discovered these little guys the exact same way... bought a pair of "Computer" speakers to make a little stereo/mono amp out of, figuring I'd need a simple preamp at most, and everything from the "master volume" on out is taken care of, including PSU, and the bonus Headphone out.

That is , dave , if you think 386 is an opamp too .
Seems like 386's aren't bad at all , unlike what some 'philes think .
Actually they're pretty awesome , the last one i did didn't go well since the chip was buzzing . Damn shop had to cheat me .

[Earthscum]

I got a bunch of 386's that are fizzy sounding, and I'm just not in that mood right now, and it dawned on me I have the TDA's.

These actually sound really nice, once you put a buffer in front. I discovered that the input resistance is only 100k, and I used a 10k to ground at the input as per datasheet. I put a simple jfet buffer in front, used a 1u and a .22u cap to split the signal between the 2 inputs. One side cleans up the bass (.22u) for guitar, and the other side is nice and thick. It doesn't really get muddy on the bottom end... seems to handle it quite well, actually. At the output I used a 47u and dumped that into a 1n4148/1N60P (schottky) parallel to the 100k volume pot. I haven't integrated both outputs together in any way yet...

I need to drop a 1k before the diodes... the chip didn't even giggle at me, but my power supply was groaning a bit. But, initially, without clippers, just a hair on the top end, sounds pretty nice through a 5W SS. With the clippers, it is really smooth sounding.

Quiescent current, though, is a bit under 7mA... 386 is showing about 4.5 (@9V). You actually save about 2mA with the TDA over a pair of 386's, which (with the LED's we're getting nowadays) easily covers the power of the LED. I'll get back with more later, just figured I'd make note of my initial findings... which are very pleasing, except needing a buffer.

Another note, these have 40dB, or about 100x gain. It's about half of the 386, and it's not adjustable. If you want something closer to 386, you'll need a 2x gain stage and a voltage divider to the TDA. Simple stuff, really.

[Earthscum]

Somebody wanna give this a try and see what you think? I'm digging on it. I'm sure I'll have a couple more schems to add tonight. This seems to be a very forgiving chip, so far. I left power on while screwing around... pop crack hummmmmm..... BRRRRRRRRRRRMMMMMMMGH... strum... smile. 

[Earthscum]

So, yeah... this thing is kind of an odd beast, in ways. Notice the cap... it's kind of reverse of what you would think. You put it in for high gain, and remove it for lower gain. Funky, right? So, here's a distortion...



I'm not finished exploring this thing, yet... and these are more or less just starting points... they work, and could probably benefit from tone stacks or input filtering or other tweaks, but as is they are most definitely usable... especially the distortion. The octave up was just a way for me to "bridge" the output, and the input is thusly ran just as the bridged mode in the datasheet example.