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Class D Switching Power Amplifiers and Power D/A conversion

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Old 30th December 2017, 11:31 AM   #11
FauxFrench is offline FauxFrench  France
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Fully right that the decoupling proposed by me relates to unregulated 50z/10ms (double rectified) power supplies. And, if you use a good (fast) SMPS or a good quality laboratory power supply they can regulate in less than 10ms. But, with the (probably simple) SMPS shown (likely to be intended for LED lights) or power adapters intended to charge laptops, they may have a slow regulation loop. Both LED lights and laptop batteries are very static loads and a slow regulation loop is cheaper to implement and remains stable with an increased range of loads.
You can try the actual power supply out with an oscilloscope and load-switching but then the work becomes more cumbersome.

This is why I normally use 4700uF-20000uF to be sure, for the moderate costs (compared to the amplifier).

When you have a solid bass transient (like a prominent bass drum) you need the charge to be available for the amplifier, either by charge available in the decoupling capacitors or charge quickly made available by the regulated power supply.

Last edited by FauxFrench; 30th December 2017 at 11:36 AM.
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Old 30th December 2017, 06:07 PM   #12
ICG is offline ICG  Germany
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Quote:
Originally Posted by taita View Post
I didn't use this power supply for the first failing amplifier. I tested this one using a 12V battery. I think the first amplifier was already failing when I received it (buyed it second hand).

The power supply did it very well even on the highest levels before the second amplifier failed on a low level. I'm in doubt amortizing this power supply and buying a new one.
That's not impossible but not likely and I doubt with that description it's the fault of the power supply. I'm really sorry if I start that again and might annoy you with it - but are you absolutely sure you did not connect the - of the amp with the enclosure or ground? A friend wanted to measure his amp and it failed while measuring it with a scope. He was so adamant he did not short the output, I had then a look onto his setup. He was using one channel of the scope on the input, the second on the output, to compare them. What happened? The short was completed with the ground/negative of the probe, it connected the bridged output with the shielding, which in turn, was connected on the board to the - of the power supply. Another time he connected the - to the enclosure, ofcourse with the same result.
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Old 30th December 2017, 10:57 PM   #13
FauxFrench is offline FauxFrench  France
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To taita:
Your first amplifier seems to be real TK2050, thus, genuine Tripath with TP2050 bridges. Very low THD (if it worked).
If there are no screws holding the heatsink, it is likely to be glued to the ICs with thermal glue and then very difficult to remove. It is perhaps possible, as described in the article, but with a risk that the copper tracks on the PCB will be damaged.
Did you do the 10 Ohm test on this board?
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Old 31st December 2017, 10:21 AM   #14
taita is offline taita  Netherlands
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Quote:
Originally Posted by ICG View Post
That's not impossible but not likely and I doubt with that description it's the fault of the power supply. I'm really sorry if I start that again and might annoy you with it - but are you absolutely sure you did not connect the - of the amp with the enclosure or ground? A friend wanted to measure his amp and it failed while measuring it with a scope. He was so adamant he did not short the output, I had then a look onto his setup. He was using one channel of the scope on the input, the second on the output, to compare them. What happened? The short was completed with the ground/negative of the probe, it connected the bridged output with the shielding, which in turn, was connected on the board to the - of the power supply. Another time he connected the - to the enclosure, ofcourse with the same result.
Thanks for helping to find the root cause. I didn't shorted the outputs of the amplifier, I use an additional terminal to connect the speaker cables to the small amplifier terminals and changed nothing on this when the second amplifier failed. But I am thinking of another experiment I did. I have problems with a Zero DAC that is buzzing and I thought this might be a grounding issue. So I connected the ground of the DAC (the RCA plug outside) with the ground (the metal housing) of the power supply. Nothing happened, de DAC keeps buzzing and the amplifier kept playing, so I disconnected this. A day later one of the amplifier channels failed.

To come back to the power supplies. I examined some of Meanwell but found no specific audio smps. Alle power supplies are for general purpose (LED and electronic equipment) the same as the one I have. Do you recommend a specific type?
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Old 31st December 2017, 01:19 PM   #15
taita is offline taita  Netherlands
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Quote:
Originally Posted by FauxFrench View Post
To taita:
Your first amplifier seems to be real TK2050, thus, genuine Tripath with TP2050 bridges. Very low THD (if it worked).
If there are no screws holding the heatsink, it is likely to be glued to the ICs with thermal glue and then very difficult to remove. It is perhaps possible, as described in the article, but with a risk that the copper tracks on the PCB will be damaged.
Did you do the 10 Ohm test on this board?
I did the 10 ohm test on this board: everything was high.
I succeeded in removing the heatsink by turning it a little. I found two PCB's that look fine. To be honest I think the problem with this board is not the PCB, but an errouneous design of the activation of the amplifier.
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Old 2nd January 2018, 11:20 PM   #16
FauxFrench is offline FauxFrench  France
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On the power supply: Finding one explicitly for audio use is difficult. Therefore, I use an ordinary (standard) power adapter (outline as a laptop charger) and connect the 10000uF at the output. Only in few cases did I have a bit of hum in the speakers, probably due to the combination with other power adapters for my DAC and headphone amplifier (being used as pre-amplifier with volume control).

Last edited by FauxFrench; 2nd January 2018 at 11:22 PM.
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Old 3rd January 2018, 04:43 PM   #17
ICG is offline ICG  Germany
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Location: I had a Déjà Moo - I've seen that BS before!
Quote:
Originally Posted by taita View Post
Thanks for helping to find the root cause. I didn't shorted the outputs of the amplifier, I use an additional terminal to connect the speaker cables to the small amplifier terminals and changed nothing on this when the second amplifier failed. But I am thinking of another experiment I did. I have problems with a Zero DAC that is buzzing and I thought this might be a grounding issue. So I connected the ground of the DAC (the RCA plug outside) with the ground (the metal housing) of the power supply. Nothing happened, de DAC keeps buzzing and the amplifier kept playing, so I disconnected this. A day later one of the amplifier channels failed.
For how long did the buzzing of the DAC play? Did you let the amp on but idle for an extended period of time? If it went to standby, the power consumption is very low, not every power supply likes that, I've seen some which got voltage spikes without or with extremely low loads.

Quote:
Originally Posted by taita View Post
To come back to the power supplies. I examined some of Meanwell but found no specific audio smps. Alle power supplies are for general purpose (LED and electronic equipment) the same as the one I have. Do you recommend a specific type?
I would recommend the LRS-150-24 (24V) or another of the series for the smaller amps (<75W), they got short circuit, overload, over voltage and over temperature protection and they are pretty cheap too. These PSs need ventilation openings in the enclosure, like almost all PSs.
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Old 25th February 2018, 09:50 AM   #18
taita is offline taita  Netherlands
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Quote:
Originally Posted by FauxFrench View Post
To taita:
Your first amplifier seems to be real TK2050, thus, genuine Tripath with TP2050 bridges. Very low THD (if it worked).
If there are no screws holding the heatsink, it is likely to be glued to the ICs with thermal glue and then very difficult to remove. It is perhaps possible, as described in the article, but with a risk that the copper tracks on the PCB will be damaged.
Did you do the 10 Ohm test on this board?
It's some time ago, but I spend some time now on the Tripath amplifier. I removed the heatsink and discoverd a Tripath TC2000 chip. All channels measure an impedance of kilo-ohms, no low values. So I think the amplifier is fine but I have to solve the annoying hmute issue. I enclosed some pictures of the amplifier. There is a mute port and I have shorted this with the 5V port and the ground but the hmute led keeps blue. Any ideas how to solve this?
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Old 25th February 2018, 06:47 PM   #19
FauxFrench is offline FauxFrench  France
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Let's give it a try.

The TC2000 chip you found is the modulator. The two chips with thermal grease are probably TP2050 or STA505. Will you please check? They all have mute/disable pins and fault indication pins.

What is your supply voltage?

I had to check the datasheets for the interesting pins:

TC2000:
Pin 8 (output): Logic high means muted or fault discovered.
Pin 18 (output): Low indicates input to be out of range.
Pin 19 (input): Over-/under-voltage setting resistor.
Pin 24 (input): High or floating leaves outputs muted. Only low ensures operation.

TP2050
Pin 24 (input): Must be high for parallel operation.
Pin 25 (input): Stand-by, must be high for operation.
Pin 26 (input): Tri-state, must be high for operation.
Pin 27 (output): Fault, must be high, indication of fault if pulled low .
Pin 28 (output): Thermal warning output, low if overheated.

Please do all your tests with power using dummy resistors at the output. An unloaded output may destroy the TP2050 chips!

Will you please check if the pin voltages are as shown above?

The question is if the “mute” lamp on your board is turned on by an output pin on the TC2000 (probably pin 8) or an output pin on a TP2050 (probably pin 27) or something else.
Can you figure out by what that lamp is controlled?
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Old 25th February 2018, 08:28 PM   #20
taita is offline taita  Netherlands
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Quote:
Originally Posted by FauxFrench View Post
Let's give it a try.

The TC2000 chip you found is the modulator. The two chips with thermal grease are probably TP2050 or STA505. Will you please check? They all have mute/disable pins and fault indication pins.

What is your supply voltage?

I had to check the datasheets for the interesting pins:

TC2000:
Pin 8 (output): Logic high means muted or fault discovered.
Pin 18 (output): Low indicates input to be out of range.
Pin 19 (input): Over-/under-voltage setting resistor.
Pin 24 (input): High or floating leaves outputs muted. Only low ensures operation.

TP2050
Pin 24 (input): Must be high for parallel operation.
Pin 25 (input): Stand-by, must be high for operation.
Pin 26 (input): Tri-state, must be high for operation.
Pin 27 (output): Fault, must be high, indication of fault if pulled low .
Pin 28 (output): Thermal warning output, low if overheated.

Please do all your tests with power using dummy resistors at the output. An unloaded output may destroy the TP2050 chips!

Will you please check if the pin voltages are as shown above?

The question is if the “mute” lamp on your board is turned on by an output pin on the TC2000 (probably pin 8) or an output pin on a TP2050 (probably pin 27) or something else.
Can you figure out by what that lamp is controlled?
Thanks for your answer. On your questions:
- The power supply is a 12V battery
- The thermal grease has completely been backed on the surface of the chip. I can't remove it to read the type of chip

Before I read your answer I did some experiments myself. I found the datasheet of the chip TC2000 datasheet(3/9 Pages) TRIPATH | STEREO CLASS-T™ AUDIO CONTROLLER USING DIGITAL POWER PROCESSING (DPP™) TECHNOLOGY and found that pin 24 of the chip has to be grounded to operate. So I did this with a thin wire and the hmute LED went off. Then I made a soldered connection. But when I turned the amplifier on the LED went off but then went on again. And now the hmute LED is on independent if pin 24 is grounded or not. Unfortunately I didn't loaded the output of the amplifier. So probably I repaired it but it is destroyed? I tested the impedance of the output but no low levels there until so far.
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