antcollinet
Grand Contributor
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3e Audio TPA3255 Amplifier Kit 480-1-29A Review
- Thread starter amirm
- Start date
Hi! I wrote to the seller in the official 3Eaudio store. The seller sent a "recommendation from engineers" - to replace 2 capacitors. (look pics.1)
Before replacing these capacitors, I checked them on both boards. (look pics.2,3)
All 4 capacitors are serviceable. They have a capacity of 9.10mF - 9.90mF. It doesn't make sense to change them.
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antcollinet
Grand Contributor
You can't measure them while they are in circuit - everything else connected to the circuit will influence the measurement.
What is the value shown on the capacitor body? (It's uF BTW, not mF).
Here the advice was not just to change the capacitors. They are in good condition. But their capacity needs to be changed. The default capacity on the board is 10 uF. 3E advises replacing the capacitors with 1 uF capacity where the pop is. I have a similar problem when turning off on one channel on my stereo board. 3E gave me the same advice.The purpose of the replacement is to reduce the capacity.
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Unfortunately, pop noise when powered off is more difficult to deal with than pop noise when powered on.
Changing the coupling capacitor from 10uF to 1uF according to 3e audio suggestions may reduce the pop noise slightly, but it does not disappear completely.
A solution is to instantly disconnect the speaker connection immediately after the AC power line is turned off, or reset the TPA3255 and stop the amplifier from running. However, this requires the addition of additional external circuitry.
Changing the coupling capacitor from 10uF to 1uF according to 3e audio suggestions may reduce the pop noise slightly, but it does not disappear completely.
A solution is to instantly disconnect the speaker connection immediately after the AC power line is turned off, or reset the TPA3255 and stop the amplifier from running. However, this requires the addition of additional external circuitry.
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I put a relais in the + of the speaker and another switch. First amp on an then relais on, then relais off and amp of.
You can do it also the opposite way with a small 9V batterie. When the relais is on the + is off. First relais on (+ is cut) then amp on and relais off. You need power from the batterie only for parts of a second so it will last very long. Switching off means first relais on (+ cut) and then amp off.
Both work fine. I have the first version installed because my amps run completely on batteries.
You can do it also the opposite way with a small 9V batterie. When the relais is on the + is off. First relais on (+ is cut) then amp on and relais off. You need power from the batterie only for parts of a second so it will last very long. Switching off means first relais on (+ cut) and then amp off.
Both work fine. I have the first version installed because my amps run completely on batteries.
Your first graphic of "Measured Spectra in Music" is showing averaged signal levels on the vertical axis. Clipping happens on signal peaks associated with high crests in the signal, and may be exacerbated by longer crests which may sag unregulated rail voltages.
In the digital domain, a maximum unclipped signal peak happens with a peak centered between maximum samples (an "intersample over") at a frequency that is exactly one quarter of the sample rate frequency. For Redbook CD, the sample rate Fs= 44.1_kHz, so the maximum unclipped signal peak may occur on an intersample over at 44.1_kHz/4= 11.025_kHz.
John Siau has posted some good information about intersample overs on his Benchmark Media website. One of the improvements that he made in his later DAC designs, including the current DAC3 family, was in accomodating +3.5_dB signal to fully accomodate intersample overs.
At 11.025_kHz a peak centered between maximum samples will be slightly more than +3.01_dB relative to any peak centered on a maximum sample.
+3.01_dB increase is square root of two, 1.414, so is 41.4% increase in signal voltage in the analog domain.
At lower frequencies, which correlate with longer wavelengths, the associated peaks are more broad, so at those lower frequencies a peak centered between maximum samples is not as much higher than peaks centered on maximum samples. Your first graphic of "Measured Spectra in Music" is showing highest magnitude at 80_Hz, where wavelengths are so very much longer than 11,025_Hz, and at that low frequency a peak centered between maximum samples is not significantly higher than a peak centered on a sample, such that the trivial difference may be ignored.
There is much more energy in music below 1_kz than there is above 1_kHz, but that is not so for the maximum signal peaks. Crest factor is a measure of peaks relative to average, and crest factor is highest in the top octave, where the average is clearly lower, but the maximum unclipped signal peaks are not lower, and may be a much as 41.4% higher.
Н! How to get rid of the clicking sound in the speaker system when the module is turned off. There are two methods.
First.
You do not need to turn off the primary alternating voltage going to the power supply. This is exactly when this clicking sound occurs. This is due to the attenuation of the constant voltage, which is incorrectly perceived by the module circuit ...
You need to turn off the secondary constant voltage going from the power supply to the module. There should be no clicks.
Try it. If it does not help, I will tell you about the second method. The circuit is very simple. But you will need to use one simple relay, with one contact.
First.
You do not need to turn off the primary alternating voltage going to the power supply. This is exactly when this clicking sound occurs. This is due to the attenuation of the constant voltage, which is incorrectly perceived by the module circuit ...
You need to turn off the secondary constant voltage going from the power supply to the module. There should be no clicks.
Try it. If it does not help, I will tell you about the second method. The circuit is very simple. But you will need to use one simple relay, with one contact.
This is very difficult. There is a simpler method (2), with one relay. In this case, the acoustic systems do not need to be disconnected.
Have you actually tried this method and confirmed that it eliminates the popping noise?
Checked. Unfortunately, this method does not work. The capacitors on the module itself are discharged. After 0.5 sec - a click (pop noise).
Then the second method. It will work, because this is a function of the module itself.
There is a comb with contacts on the module.
If you close the contacts PS_CTRL and GND (there are two of them on the comb), the board will turn off. Open - it will turn on. The shutdown is instantaneous, without clicks (pop noise).
This way you can install a switch, and use it to turn the module on and off. It is better to close and open through a 50 Ohm resistor, but not necessary.
The downside of this method is that the power supply is always under voltage.
But you can improve it and turn off the primary voltage. After the switch, you need to install a 220 volt relay. And connect its normally closed contact between PS_CTRL and GND. Then, after applying 220 volts, PS_CTRL and GND will open, and the amplifier will turn on. And when removing 220 volts, PS_CTRL and GND will instantly close, and the amplifier will turn off without a click (pop noise).
The relay can be like this HJQ-13F-220VAC-1Z
Then the second method. It will work, because this is a function of the module itself.
There is a comb with contacts on the module.
If you close the contacts PS_CTRL and GND (there are two of them on the comb), the board will turn off. Open - it will turn on. The shutdown is instantaneous, without clicks (pop noise).
This way you can install a switch, and use it to turn the module on and off. It is better to close and open through a 50 Ohm resistor, but not necessary.
The downside of this method is that the power supply is always under voltage.
But you can improve it and turn off the primary voltage. After the switch, you need to install a 220 volt relay. And connect its normally closed contact between PS_CTRL and GND. Then, after applying 220 volts, PS_CTRL and GND will open, and the amplifier will turn on. And when removing 220 volts, PS_CTRL and GND will instantly close, and the amplifier will turn off without a click (pop noise).
The relay can be like this HJQ-13F-220VAC-1Z
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There is no mention of "PS_CTRL" in the data sheet for TI's TPA3255. There is no such pin in the pinout of the IC chip.
I think "PS_CTRL" is probably an input created in the 3e audio amplifier circuit. Does it actually go into a sleep-like state?
What does the technical data sheet of TPA3255 have to do with this?
We are talking about the 3E Audio module here. He has his own data sheet. See the screenshot.
Take a jumper and try it yourself. It works flawlessly, as I wrote above:
- If you close the contacts PS_CTRL and GND (there are two of them on the comb), the board will turn off. Open - it will turn on. The shutdown is instantaneous, without clicks (pop noise).
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It is important to know the function of "PS_CTRL". I have looked at the table in the 3e audio manual many times, but there is no detailed explanation.
I think that even if the "PS_CTRL" terminal is connected to GND, half the power supply voltage remains applied between the speaker terminal and GND. This means that the amplifier is not completely shut down.
Sorry, I used to be a development engineer, so I have a habit of wanting to know the details.
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