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3e Audio SY-DAPx002 TPA3250/TPA3255 DSP Amplifier

zachery2006

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Actually after your tests I'm more oriented to say it's a defect because it's strange that the amplifier isn't properly grounded to the chassis. Can you check with a voltmeter if there is continuity between the rca shields and the chassis? Be sure to check on a point where the chassis painting has been scraped or on a metal screw that goes through the chassis. If there is none, you can try running a wire from one of the rca shields to the chassis and check if the hum disappears.
I don’t have a voltmemter at hand, so I directly linked rca shields to the screw hole. No changes, the noise of speaker is still there. But I tried to move the OP, then the noise disappeared. Insights?
 

zachery2006

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You have to remove it with your fingers, it is important to remove it gently and evenly, so as not to catch the OP's legs. Change to the new one, make sure that the OP is in the right direction, leg number 1 must be on the same side as the existing OP. But I highly doubt the hum is from an OP. Do you have another SMPS to verify that this is not the cause?

I removed the OP, then the noise disappeared! So what does this mean?
 

daftcombo

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After connecting power, dac and speaker, when I turned on the amp, there is hiss noise coming from speaker, loud enough that I can hear it from 2 meters away. My other amps don’t have this hiss noise, speakers are pretty quiet, I can only hear a small amount of hiss when my ear touches to the speaker. The hiss volume is consistent and doesn’t change with volume knob turn. I bought a pair of opa1612a, hoping to alleviate this hiss problem.

I noticed that hiss issue with my DIY speakers 1m50 away and @renaudrenaud and I noticed it also 3m away from the ELAC DBR62. Pretty annoying it was in the former case.
 

Toku

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I removed the OP, then the noise disappeared! So what does this mean?
From the result, it was confirmed that the power amplifier part of TPA 3255 is normal.
Also, it is unlikely that two OP amplifiers will be defective at the same time, so the OP amplifier will be normal.
If you have another op amp, try replacing it and testing it. If the noise disappears after replacing the OP amplifier, the cause is a defective OP amplifier. But that's unlikely.

The most suspected part of the results is the DSP circuit. However, this part requires a dedicated interface and control app to be installed on the PC.

Also, since the noise is constant regardless of the volume operation, it is judged to be normal between the RCA terminal and the input of the DSP chip.

The power supply is probably normal.
 

Toku

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But I tried to move the OP, then the noise disappeared. Insights?
I am very interested in this word from you.

Does that mean that the noise may disappear if you shake the OP amplifier inserted in the socket of the PC board by hand?
If so, observe a little more about the changes when you touch, hold, or shake the op amp with your fingers.
 

molexey

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@molexey
i suggest if you are able please swap the position of these 2 small
desoldered capasitor.jpg

Done. But it was not easy. It is especially difficult to remove the cap near the USBi connector. Can I get compensation for this? ;)

Time for DIY fun. Since the device has already been disassembled.

caps.jpg


I decided to change the 470 uF SMT caps to Panasonic polymer hybrid caps and 2200 uF ChengX to Panasonic FM. I also replaced a ceramic disk capacitor in a snubber. This capacitor made an annoying sound when the power supply was in burst mode (standby or quiet music).

PFFB.jpg


I tried to realize PFFB. The Rv1.0 is prepared for feedback. But I have failed, the amp can not start. It looks like the STM32 is receiving a fault signal. When I removed 18K R_fb resistors the amp starts without PFFB.

@3eaudio please give me some advice. How to implement PFFB for Rev1.0?
 

zachery2006

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I am very interested in this word from you.

Does that mean that the noise may disappear if you shake the OP amplifier inserted in the socket of the PC board by hand?
If so, observe a little more about the changes when you touch, hold, or shake the op amp with your fingers.

Sorry, typo, “moved”=“removed”
 

zachery2006

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My friend got a SY-DA1002 Rev1.1 amp and he noticed exactly the same noise. He tried to bypass the opamp (input pins shorted with out pins) and the noise disappeared.

Does this mean the noise come from the OP amp?
 

zachery2006

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From the result, it was confirmed that the power amplifier part of TPA 3255 is normal.
Also, it is unlikely that two OP amplifiers will be defective at the same time, so the OP amplifier will be normal.
If you have another op amp, try replacing it and testing it. If the noise disappears after replacing the OP amplifier, the cause is a defective OP amplifier. But that's unlikely.

The most suspected part of the results is the DSP circuit. However, this part requires a dedicated interface and control app to be installed on the PC.

Also, since the noise is constant regardless of the volume operation, it is judged to be normal between the RCA terminal and the input of the DSP chip.

The power supply is probably normal.

I purchased opa1612a, but not arrived yet. I think that’s my last try
 

Tangband

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As it was said above, a defective OP is possible, but 2 broken, I don't believe it. The problem comes from elsewhere in my opinion.
probably from the dsp .
 

daftcombo

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Pardon my ignorance: if the amp works fine wiithout the noisy op-amps, why replace them and not remove them purely and simply?
 

ModDIY

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Yes, it does.
I'm not sure if this is a fake or a wrong operation mode.

If it is a fake or a bad operation, in this case it is possible.

I was assuming that this is not fake.
 

somebodyelse

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hi @3eaudio I'm tempted to buy one of your TPA3255 integrated Amplifiers but I realized reading specs you suggest it is for 8ohm speakers while the 3151 is for 4ohm. can you pls clarify? now I'm successfully using your TPA3255 stereo version in a DIY final Amp with 48V 17 Ampere peak with 4ohm speakers. it's very good, coils become pretty hot. ok to drive it at 48V?
thanks
L.
Discussed earlier in the thread - I think there are other relevant posts before and after.
 
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