pop up noise on Arjen's Mk2 t2020 - diyAudio
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Old 31st January 2013, 08:16 PM   #1
msj965 is offline msj965  United States
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Default pop up noise on Arjen's Mk2 t2020

Hello

Just wanna ask this problem. Since I bought a t amp s from Arjens a long time ago, I just got a chance to assemble it by my own.but the out come is not good. If you turn the power on you can hear this pop up noise from the speakers.I don't wanna ruin my bookshelf speakers. Is there any solution for this? I know how to solder,understand diagrams and make a circuit connection.

Thanks and more power,
ps: t-amps MKII 2020, I dont know if Arjens still selling this on ebay.
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Old 31st January 2013, 08:23 PM   #2
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You could build a soft start circuit which has a relay to the speaker.
You hold off the relay activating for a few seconds to let the amp settle.
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Old 31st January 2013, 08:43 PM   #3
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Yes. The solution is simple. Change the "audiograde" input caps to class D appropriate caps. For example, 1uF Wima or Epcos MKP/MKT cap.

Large high voltage caps with large antenna area and high parasitic inductance have no place in the input of a class D amp.
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Old 31st January 2013, 08:51 PM   #4
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I had a similar problem with an IRs2092 class d amp.
It clicked, made a loud crack and sometimes sounded like a siren !

Turned out the 2092 doesn't like large smoothing capacitors.
They make the power supply come up slowly and go down slowly.
I found the simplest fix was to add an 8 pin PIC with analogue to digital converter to monitor the power supply and hold off the 2092's reset if the voltage was out of range.
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Old 2nd February 2013, 07:42 PM   #5
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Quote:
Originally Posted by msj965 View Post
Hello
If you turn the power on you can hear this pop up noise from the speakers.I don't wanna ruin my bookshelf speakers. Is there any solution for this?
Adjust bias voltage to 0mV (using those blue potentiometers).
You can use these same instructions for Arjens TA2020:
6moons audio reviews: Trends Audio TA-10


from trends ta 10 manual:
"4.1 Offset the DC bias voltage of the speaker terminals
There are two blue adjustable potentiometers (Rt) for offsetting the DC bias voltage between the positive (+ve) and negative (-ve) terminals of each channel. Offset this DC bias voltage can enhance the purity of the sound and minimize the “pop" sound when power on and off. The DC bias has been pre-set in factory. But after run-in for a period, it would be slightly changed that the fine-tuning is needed."

Last edited by tamphist; 2nd February 2013 at 08:00 PM.
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Old 3rd February 2013, 05:10 AM   #6
msj965 is offline msj965  United States
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Default Hi:)

Quote:
Originally Posted by tamphist View Post
Adjust bias voltage to 0mV (using those blue potentiometers).
You can use these same instructions for Arjens TA2020:
6moons audio reviews: Trends Audio TA-10


from trends ta 10 manual:
"4.1 Offset the DC bias voltage of the speaker terminals
There are two blue adjustable potentiometers (Rt) for offsetting the DC bias voltage between the positive (+ve) and negative (-ve) terminals of each channel. Offset this DC bias voltage can enhance the purity of the sound and minimize the “pop" sound when power on and off. The DC bias has been pre-set in factory. But after run-in for a period, it would be slightly changed that the fine-tuning is needed."
Got yah, But this MkII pcb board doesn't have an Offset bias adjustment. Ill try to check the voltage output and let you know what is the outcome.
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Old 3rd February 2013, 12:31 PM   #7
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Quote:
Originally Posted by msj965 View Post
Got yah, But this MkII pcb board doesn't have an Offset bias adjustment. Ill try to check the voltage output and let you know what is the outcome.
Found instructions for adding those trim pots
Lepai T-Amp with TA2020

But I would rather buy new board with speaker protections relays
and bias adjustment pots. http://www.ebay.com/itm/170955692451
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