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Class D Switching Power Amplifiers and Power D/A conversion

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Old 7th September 2011, 02:21 AM   #91
dewardh is offline dewardh  United States
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Two arrived today, will be re-working for lower gain and lower (42V) supply. Yep, no thermal paste at all . . . will be treating like semi-populated "project board" . . .
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Old 7th September 2011, 02:43 AM   #92
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by cOz View Post
How can we be sure that the board we purchase is not pirated and is to spec of the original design? Does ljm_ljm sell them officially somewhere? If there are differing designs where are the differences described in detail?

L20D I have more strict production material requirements.

Including military level of materials of the PCB, plating.
Low temperature wave metal resistance, and use of Japanese make capacitors.

No matter what the time these are not change.
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Old 7th September 2011, 02:51 AM   #93
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by petegt View Post
Thanks for this information. The 2k2 1W has definitely changed colour on my working board.

I am struggling to find these values though.

1W 6K2 - Would 1W 5K6 be suitable?

1W 3K - Would 1W 3K3 be suitable?

my board does not have 80V 150UF it has 63V 100UF.

was 2200UF a type error? Did you mean 220UF? 100v

YES。

Increase 1 W to 1 W6K2 5 K1, 5 K6 can also.
Increase 1 W to 1 W 3 2 K2 erp


Electrolytic use 100 V 100 UF-220 UF. In the radiator to the right of the two.
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Old 7th September 2011, 02:59 AM   #94
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by alkasar View Post
Hello,
I would like to use L20D board for a 4ohms subwoofer. This sub is controlled by a servo and will really use close to 300W at the lower frequencies.
To achieve 300W in 4ohms, +-52V rail powersupply should be sufficient.

as trevmar mentioned, the iraudamp7s reference design pdf, fig5, shows reasonnable THD measures up to 300W with +-50V supply. This is with 4019H. 4020H should behave even better.

ljm confirmed 4020H is limited to about 9A continuus, leading to 9*4=324W max in 4 ohms. Looks good

L20D board specs is 60 to 80V. Will it work well with +-52V ?


+ -52V 4ohms。
I suggest you to change only 8 resistance.
130K 1/4W - 120K 1/4W
5K1 1W - 3K3 1W (2PCS)
2K2 1W - 1K 1W
20K 1/4W - 15K 1/4W
5K1 1/4W - 7K5 1/4W
8K2 1/4W - 9K1 1/4W
75K 1/4W - 47K 1/4W

Do not need to change the IRFI4020.

Or, you can consider to use L15D, L15DX2.

They are IRAUDAMP7S -150
Use the +-50 V, 250 W * 2, 4 OHM

Last edited by ljm_ljm; 7th September 2011 at 03:06 AM.
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Old 7th September 2011, 03:29 AM   #95
cOz is offline cOz  United States
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Quote:
Originally Posted by ljm_ljm View Post
L20D I have more strict production material requirements.

Including military level of materials of the PCB, plating.
Low temperature wave metal resistance, and use of Japanese make capacitors.

No matter what the time these are not change.
Where do you sell your pcb modules?
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Old 7th September 2011, 07:18 AM   #96
Bernie7 is offline Bernie7  Singapore
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Just received my L20D modules.

Is a cap used to decouple DC at the input, or is there no decoupling cap?

If so which cap? I may want to replace with a better quality film cap.
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Old 7th September 2011, 10:42 AM   #97
dewardh is offline dewardh  United States
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Quote:
Originally Posted by Bernie7 View Post
Is a cap used to decouple DC at the input
22 mfd electrolytic. Probably not the best choice.
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Old 7th September 2011, 12:51 PM   #98
Bernie7 is offline Bernie7  Singapore
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What's the input impedance of L20D? Need this to determine blocking cap value.
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Old 7th September 2011, 01:19 PM   #99
dewardh is offline dewardh  United States
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Quote:
Originally Posted by Bernie7 View Post
What's the input impedance of L20D? Need this to determine blocking cap value.
About 3.4k. You can get all the answers you need from:

http://www.irf.com/technical-info/re...iraudamp7s.pdf

and

http://www.irf.com/technical-info/appnotes/an-1138.pdf

You may not need input blocking, depending on your application . . . if your pre-amp/crossover has either AC coupled output or servo control of its output offset. Much depends on how you're actually using the L20D . . .
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Old 7th September 2011, 01:33 PM   #100
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by cOz View Post
Where do you sell your pcb modules?

In EABY there should be sold in China, there are some dealers in doing international trade.

If has the question to the original confirmation. Can send photos to me

ljm_ljm@foxmail.com.

I found no L20D have temporarily of piracy.
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