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Class D Switching Power Amplifiers and Power D/A conversion

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Old 22nd December 2011, 02:25 PM   #11
ljm_ljm is offline ljm_ljm  China
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Originally Posted by activexp View Post
Hi ljm_ljm,

I have recently received the TA2022 kit from Zoe_Tsang and the board is marked V1.1 with 2 resistors and 1 diode already soldered to the board.

One of the resistors replaces diode 12U but IC power source is LM7805, not LM7810.

Do I need LM7810 for the board to work correctly?

Regards,
Steve
The blue version will exist 7805,7810.

The green version is only 7805.

Carefully observe the PCB above printing.
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Old 22nd December 2011, 05:48 PM   #12
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OK, mine is Green so 7805. Many thanks for your help LJM
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Old 5th January 2012, 12:16 PM   #13
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Hi ljm_ljm, I have now finished the board and it is working

7805 gets very hot, is this normal?

There is some low level hum and noise but this is probably caused by my signal input wiring being to near to the power supply section.

Regards,
Steve
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Old 23rd January 2012, 04:55 AM   #14
ljm_ljm is offline ljm_ljm  China
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7805 current = 35MA
Its voltage = VCC-10V-5V
10V is the concatenation of the voltage divider resistors above.
7805 power consumption is about 15 * 0.035 = 0.52W. It is quite hot, but not dangerous.
Short out the input signal IN INGND. If there is no noise, it means the noise is caused by the input signal. Such things are more common.

Pay attention to the generation of the input signal interference. And ground handling.
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Old 23rd January 2012, 11:54 AM   #15
activexp is offline activexp  United Kingdom
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Thanks ljm_ljm,

So 7805 is OK without heat sink?

Yes, the low frequency buzz is from input source, DIY pre-amp which I think is caused by the switch mode power supply I am using.
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Old 25th January 2012, 12:14 PM   #16
ljm_ljm is offline ljm_ljm  China
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Originally Posted by activexp View Post
Thanks ljm_ljm,

So 7805 is OK without heat sink?

Yes, the low frequency buzz is from input source, DIY pre-amp which I think is caused by the switch mode power supply I am using.
Yes. No heat sink. Of course, there is a version of the radiator. They have no problem.
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Old 9th February 2012, 05:48 PM   #17
jonfrason is offline jonfrason
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Default Problem with TA2022 board

Quote:
Originally Posted by ljm_ljm View Post
Yes. No heat sink. Of course, there is a version of the radiator. They have no problem.
I have the green board version as well (v. 1.1)
My 7805 and 7812 also get very hot to the touch, but my main concern is the inductors.
They get so hot it hurts to touch them.
The values are 22uH and are rated some 2A or around.
The board came pre-fitted with one resistor and a diode.

The DC offset is fine, voltage supply is 22.5-0-22.5 direct from a transformer.

Lately the relay does not switch on mute, so a loud clicking noise sounds when put out of mute.

Anybody have an idea what this could be?

Regards Jon
(first post ever on diyaudio)
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Old 15th February 2012, 07:52 PM   #18
activexp is offline activexp  United Kingdom
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I'm running mine at 24V dual rail. I haven't checked the inductors but other than the temperature of the voltage regulators as already mentioned in this thread, I've noticed that the 4700uF/35V smoothing caps get quite hot too. In fact one of them is showing signs of bulging

Apparently this is caused by 'Bus Pumping'.

Expanation: "A switching amplifier that is single ended (IE not a bridge) will cause what is known as "bus pumping". Energy that is stored in the output inductor has to go somewhere when the output stage switches & as it can't run in a continual loop like the current could in a bridge amp it over charges the main reservoir capacitors."

I'm going to replace them with 6800uF/50V ones.

Despite all this, the amp itself is working fine and sounds OK.
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Old 16th February 2012, 03:27 PM   #19
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by jonfrason View Post
I have the green board version as well (v. 1.1)
My 7805 and 7812 also get very hot to the touch, but my main concern is the inductors.
They get so hot it hurts to touch them.
The values are 22uH and are rated some 2A or around.
The board came pre-fitted with one resistor and a diode.

The DC offset is fine, voltage supply is 22.5-0-22.5 direct from a transformer.

Lately the relay does not switch on mute, so a loud clicking noise sounds when put out of mute.

Anybody have an idea what this could be?

Regards Jon
(first post ever on diyaudio)
Yes, the regulator IC is indeed quite hot, but not damage.You can ignore it.

Because TA2022 frequency is high. PWM has 620KHZ. Therefore inductance fever. You can also do not care.
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Old 16th February 2012, 09:23 PM   #20
jonfrason is offline jonfrason
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Ok, thank you.
After reading the TA2022 datasheet, tripath recomends minimum a 10A rated toroid inductor to prevent saturation. The zobel network seems fine. I have now swapped in new 10uH iductors and hence, change the LC filter to 107kHz, as specified by tripath. They are also rated to low. About 3 amps. Still very hot! Can i replace the current limiting resistor for the lm7805 with a 12v zener diode like 1n4742?
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