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TDA 2822 compatibility

post #1 of 17
Thread Starter 
Hi guys,

I have just constructed an amp that works with the TDA2822, I would like to check (as I am not good at the spec-sheet for opamps), if the opamp can be directly replaceable with the more popular lm4562, ad823, ad826, and opa 2134.

Rgds,
Marcus
post #2 of 17
the tda2822 is not an opamp, it's an integrated power amp. and it's not compatible with any opamp. (opamp: 8 pins, tda2822: 16 pins)
post #3 of 17
Thread Starter 
hi balou,

mine is 8 pins, its a power amp build to supply 1w to 8 ohms at 9v powersupply.

however the amp is giving a soft hiss and i tot perhaps a opamp change could work out something. you have any idea how i can over come this or improve the amp with a better chip.
post #4 of 17
okay... the sources on the net i found always showed a 16-pin amp.
do you have any datasheet with the pinout?
but I don't think there's much to do. the datasheet of the 16-pin version showed that it's a chip which requires huge electrolytics, indicating that it's a rather cheap and low quality dc-coupled amp. you could try a resistor at the output of both channels, this might lower the hiss.

but in the end, building another amp (cmoy, pimeta, etc.) might be the only option to overcome sonical shortcomings
post #5 of 17
Thread Starter 
hi balou this is where the chip i am refering to.
and my circuit is similar to figure 1 except for the r3 and r4 being a 10ohm resistor
post #6 of 17
You have to do some hardwiring. Everything's possible. Tell us what amp this is and show us some pictures. If you're going to use it as a headphone amp, maybe all you have to do is lower the gain to get lower noise, if noise is your only problem and not bad SQ in general.
post #7 of 17
Thread Starter 
its a simple kitset and i dun have camera with me now. SQ, there is nothing u can say at that price point. I just got it up yesterday and the hiss is terrible. when nothing is playing there is this background his going on.

The kitset also mentioned that it can drive 8 ohms at 1w, thats abt all the info i have. its more like a school project sort of kitset, for the fun of it i even bought a small speaker driver to see if it works.
post #8 of 17
Do you have a link to the schematic? What are the resistor values? Try to lower the gain. You don't need more than a gain of 2 - 4 in a headphone amp.
post #9 of 17
Thread Starter 
TDA2822M Datasheet pdf - DUAL LOW-VOLTAGE POWER AMPLIFIER - SGS Thomson Microelectronics
the second link and circuit 1 of the pdf doc. my R3 and R4 is 10ohm.
post #10 of 17
doesn't look moddable. first it hasn't got any external feedback loop, so no gain adjustments are possible. and the 8-pin version is also dc coupled (the 470uF electrolytics at the output).

have you got this amp on a etched board, or on a protoboard? you can surely reuse the jacks and the pot, maybe with some creative air-wiring you could transform the board into a cmoy. but I think ordering some protoboard, an opamp and some resistors would be better than modding this circuit which is quite far away from a standard opamp amplifier

btw, I'm completely dumbfounded by C1 and C2. What do these caps do? shouldn't the "-" pin somehow be referenced to ground?
post #11 of 17
Look at this, here it's used like a common opamp.
1 W Home Stereo Amplifier Constructional Project
It's explained how you alter the gain. A gain of 11 is way too much. The S/N ratio is claimed to be >80 dB wich isn't good but not a disaster either.

If the noise really bothers you, and lowering the gain doesn't help, you can add some resistors in series with the output. I think 100 Ohms will be fine. This will alter the tonality though depending on your phones impedance curve.
post #12 of 17
Thread Starter 
i see i will try adding some 100ohms on the output, it more for common heaphones, I got a kitset from the store and thought this might make some interesting christmas gifts to my frd. in fact i also got another 2w kit to play ard with.
post #13 of 17
Thread Starter 
As a update,

I have gotten some 150ohm at the output and i am still getting the slight hiss, the interesting thing is using it to drive the k240m(600ohm) no hiss was noted.
post #14 of 17
Thread Starter 
not sure if anyone can help me with the hiss problem though, and also if the opamps can be directly replace with the more common ones like opa2134, lm 4562 etc.

here are some pics of the amp
The first build, cased up in a hammond box


The uncased one with a volume pot wired in


post #15 of 17
I don't understand the circuit. Is it the "test circuit 1"? I see 9 caps and 2 resistors on your board but 7 caps and 4 resistors in the schematic, or are the grey cubes resistors. Is this amp amplifying the signal? Is the noise the same independent of the volume? What pot do you use, and where in the schematic is it?

If you want to use LM4562 or some other high quality opamp, it's better to build a new amp, like a CMOY on a stripboard. If you want something better, I'll recommend Mini3. You can use the board and populate it with the opamps of your choice if you don't find the AD8397 attractive, but AD8397 is very low noise. Mini3 as a whole is very quiet.
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