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Old 3rd April 2013, 09:27 PM   #221
prezden is offline prezden  Canada
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I tried several different mods to the boards- especially the 3122. By replacing some caps then others until I found what sounded the best to me. On the first 3122 I tried I put some big caps on the rails and instantly blew the chip. I guess that comes with not really knowing what your doing The nice thing about mucking about with these things is that the are so cheep to by if you screw it up it's not such a big deal
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Old 3rd April 2013, 10:09 PM   #222
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Quote:
Originally Posted by zerokelvin99 View Post
radiosmuck, have you got a link to the board?
They may have sold out, you might need to check around.
2x50 w Stereo Class D Audio Power Amplifier Circuit Board TI TPA3123 | eBay
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Old 3rd April 2013, 11:16 PM   #223
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carefull on the input caps on the 3110.

The board calls for .13uF making a pole (if 20db gain setting) of 20hz. I for the life of me can't understand people put 1uF there. Poly caps, yes, that I get. Especially the feedback one........

Norman
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Old 13th April 2013, 04:30 AM   #224
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after much thinking (wow smokey?) and playing with mine, I think I need to try a beefier supply than the 8 AA's I'm using now.

Also the great sound (when it's not making me angry, lol) may be due to the output not going through output coils, but then it should use only a few inchs of twisted spkr wire, unlike my 6' of parallel junk.

Isn't a 3122 basicaslly half of a 3110 ?
based on page 6 (on texas instruments data), you can't bridge a bridge amp............
http://www.ti.com/lit/ds/symlink/tpa3110d2.pdf

at 12v and 8ohms, I should be able to get 7 watts, and 4 ohms I should get 11.
(page 9 of the above pdf).
I ain't getting 11w, no way, no how, even 4.5 watts (we are not driving a resistor here folks).

I think 8 AA's can put out what, an amp? And that's not enough for 11 watts into 4ohms.....
12v into 4ohm = 3amps, 8v (subtract for .707) into 4ohms still would be 2amps (that 8 AA's can't deliver).

Am I off base ?
I am pretty new at this class D stuff..........

Norman
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Old 13th April 2013, 05:31 AM   #225
prezden is offline prezden  Canada
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Norman- regarding the 3110 input caps. Am I running the risk of damaging the amp or is it just plain overkill to use the larger size caps
The 3122 I built is running off a 24v meanwell. I tried using a 12v supply and the difference is huge

cheers- prezden
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Old 13th April 2013, 06:51 AM   #226
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http://www.ti.com/lit/ds/symlink/tpa3110d2.pdf
page 25, bottom

the numbers do crunch out (20db gain, 60k Zin), to a 20hz pole.
If you put a 1uF there, do you want an input pole that low ?

So 24v meanwell, I'll look it up.
Or a 12v Sla battery, how many amps ? 3 or more?

Norman
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Old 15th August 2013, 10:16 PM   #227
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The TPA3110D2 is just screaming out for input transformers. Both + & - inputs for each channel are biased at +3V, so an input transformer could be connected directly without any coupling caps. You also don't need to trade off LF extension against charging time to keep pops away. I suspect that the transformer would also reduce any RFI interference on the input signal by acting as a low pass filter (very relevant if you use an SMPS in the same chassis). I've ordered two boards and have plenty of 600:600 transformers that will do for testing the theory :-)
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Old 16th August 2013, 12:19 AM   #228
rsavas is offline rsavas  Canada
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Default The TPA3110D2 is just screaming out for input transformers?

I guess things depend on your design, when you say this part needs a I/P transformer. I believe that it is an unnecessary expense.
I have been using this part capacitor coupled, SE, for 2 years now and it is a very well behaved part.
I would not be hooking up my best speakers to it until I was sure that this part would not fry them or had annoying pops.
These pops you speak of, could be coming from ckts up the signal chain and the transformer will do nothing to prevent it.
I use the enable pin as well, since I shut it down when I am powered from USB.
I have tried transformer and SM external supplies and have no issues.
I use a 1uF/50V/X7R/1210 coupling cap. You could get silly and use a film cap but it I doubt that you would hear the diff in a listening test or with the analyzers.
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Old 16th August 2013, 03:47 AM   #229
DUG is offline DUG  Canada
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I use a 10uF on my 3116.

No compromise on the bass.

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Old 16th August 2013, 06:52 AM   #230
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Quote:
Originally Posted by rsavas View Post
I guess things depend on your design, when you say this part needs a I/P transformer. I believe that it is an unnecessary expense.
I can see that perspective. The amp is so cheap and an no doubt function well without. Decent transformers would increase costs substantially.

I am less concerned about budget sanity, as I have spare transformers and this approach appeals to me (for some reason!).

A nice solution may be to pair the amp with a Vout dac with transformer output stage (there are many solutions of this kind described in the forum). As long as the secondaries were isolated from ground the amp could be connected directly without coupling caps. Of course this may necessitate digital volume control, which raises its own issues.

Looking forward to playing with the board.
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