Hi Klaus,
Do you mean to attach the lead to resistors r4,r12, r44,r48 in the evm? Those i believe are 0ohm jumpers not 100ohms?
I am also curious if the sound could be improved by bypassing the opamps which are ne5532s. How much gain/db is decreased by bypassing?
Assuming you're talking about evm, I tried once with direct input from the audio interface board (J28 pin nos 11,13,15,17), which according to the schematic is also a direct way to connect differential input, but got no sound. Could be my jumper wire connections too. Or maybe the opamps needs to be grounded or such.
One thing I did which to me sounds better is I changed the series input capacitors al el 10uf (8 of them C20,C62,C66, C71, C17,C28,C55,C63) to Vishay film caps.
Regards,
Kay.
I tried my own board for TPA3255 and no matter what i do i cannot get pass 20watts from my board. All the drawing is same as in datasheet. Using 3.3 volt on board. Gate supply is 11.7volts. main supply is 33volts.
The problem is when i increase input gain it just goes off. Fault pin goes low and i have to reset it again. Don't know what is causing problem.
The problem is when i increase input gain it just goes off. Fault pin goes low and i have to reset it again. Don't know what is causing problem.
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Sweetperfume,
Nice work making your own board!
There are a couple of things that may be causing this.
1. Are you running without a heatsink? If so, it gets hot when more than a few watts output and thermal protection kicks in.
2. Did you set the max current limit programming resistor correctly? If too low or not set, current limit kicks in around 20w. I bet that’s what you have. Read data sheet to select proper value.
Nice work making your own board!
There are a couple of things that may be causing this.
1. Are you running without a heatsink? If so, it gets hot when more than a few watts output and thermal protection kicks in.
2. Did you set the max current limit programming resistor correctly? If too low or not set, current limit kicks in around 20w. I bet that’s what you have. Read data sheet to select proper value.
Thanks for your reply man. I am running without any heatsink but this happens on startup so no heat issues.
I am using 22k resistor as specified in TI datasheet. And to check i used 20k to 100k but still same issue persists.
Don't know what went wrong. I made another board to see if there were minor shorts on previous board but same issue was on new one.
And one more thing, sometimes it wont start and will remain in fault from start and while increasing input channel AB shuts down first then Channel CD.
For test i am using it on single ended btl mode.
Your board is wrong. There are no wonders in electronics. There are bad contacts and short circuits.
See error in your PCB.
Show board file?
That statement about board is wrong was a hard one. Broke my heart. I don't have board file with me. Laptop is away now. But no shorts as i checked every pin. I never used anything like TPA3255. I am using tpa3116 commercially. Never faced issue like this one.
Only thing bothers me is reset and fault pin. I did not make any arrangements on board for 3.3v supply so i supplied reset n fault pin from AVDD pin. Can this cause any issue? If yes what should i do?
Yes it is in air. But when i tested it i added 4k7 resistor through avdd pin
Sorry my bad. I used dvdd not avdd. I rechecked after your message.and on reset and fault pin i get 3.2volts but sometimes on fault pin it drops to 2.8v before shutting down.
I rashly tried to change my 3e-audio TPA3251's 12V rail to an external linear supply, similar to what forum member greinedo did here -
https://www.diyaudio.com/forums/class-d/309813-wrong-tpa3255-41.html#post5561124
I cut the output pin of the amp's 7812 regulator chip, then fed in my external 12V supply - a TPS7A4700 regulator - to the amp at this point.
But when I turn on the amp, all I hear is a regular beating noise from the speakers. (Of course the speakers I used are old test units!)
Can anyone please suggest what's going wrong?
https://www.diyaudio.com/forums/class-d/309813-wrong-tpa3255-41.html#post5561124
I cut the output pin of the amp's 7812 regulator chip, then fed in my external 12V supply - a TPS7A4700 regulator - to the amp at this point.
But when I turn on the amp, all I hear is a regular beating noise from the speakers. (Of course the speakers I used are old test units!)
Can anyone please suggest what's going wrong?
Yes, 12.3V. At my first attempt earlier today, I used a transformer which had too-low AC voltage output, and the regulator was only outputting 10V. Iin this case the amplifier was silent, no output at all.
The main power supply (Connex SMPS300RS @ 32V) and transformer/TPS7A4700 are connected to the same AC power switch.
Mmm, I see that my Connex SMPS has 2 big caps at its input and 2 big caps at its output. The TPS7A4700 has a single 5600uF cap between rectifier and regulator, and just a 47uF cap at the output - so I'm guessing that the 12V supply is up before the Connex 32V supply?
Maybe this is why in the link I mentioned previously that greinedo mentioned using a regulator + 1000µF FM + 3xFKP1 0.1µF - is he adding capacitance to delay the startup?
Hi linuxfan,
Logically, the 12V should be available very short after the main supply voltage.
If nothing works, can you reestablish the 7812 just temporarily to see that there is no damage on the TPA3255 chip?
If the TPA3255 chip is still OK, you can try again. I managed to put in a cascade of two LM317, the first (down to 24V for the input buffer-OPAmps) feed from the main supply voltage, the second LM317 (12V out) feed from the output of the first LM317 (aux voltage for the TPA3255). In my case the timing was inherent.
Logically, the 12V should be available very short after the main supply voltage.
If nothing works, can you reestablish the 7812 just temporarily to see that there is no damage on the TPA3255 chip?
If the TPA3255 chip is still OK, you can try again. I managed to put in a cascade of two LM317, the first (down to 24V for the input buffer-OPAmps) feed from the main supply voltage, the second LM317 (12V out) feed from the output of the first LM317 (aux voltage for the TPA3255). In my case the timing was inherent.
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