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L20.5  AP SYS  Test data My design
L20.5  AP SYS  Test data My design
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Old 16th June 2018, 03:04 AM   #1
ljm_ljm is offline ljm_ljm  China
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Smile L20.5 AP SYS Test data My design

I designed this amplifier. The original page is lost.
There are a lot of people asking for the parameters of my design. I re - update the web page.
To facilitate their acquisition
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Old 16th June 2018, 03:07 AM   #2
ljm_ljm is offline ljm_ljm  China
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I designed this amplifier. The original page is lost.
There are a lot of people asking for the parameters of my design. I re - update the web page.
To facilitate their acquisition
Attached Images
File Type: jpg L20-5频率响应.jpg (95.7 KB, 1066 views)
File Type: jpg L205-2017.jpg (182.5 KB, 1017 views)
File Type: jpg IMD-.jpg (112.2 KB, 645 views)
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Old 16th June 2018, 03:25 AM   #3
ljm_ljm is offline ljm_ljm  China
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It's very low distortion. The main reason is because it uses a CFP output structure.
CFP can refer to DOUGLAS SELF.
Can be applied to other general circuit structure. But note that CFP is easy to self oscillation.
To ensure the stability of the instrument for measuring strictly.
Because CFP almost no crossover distortion, so L20.5 very low quiescent current. No heat.
But it's smaller than CLASS A amplifier distortion.
The distortion of 50 watts is about 0.001-0.002%.
It was more than I made LME49810 amplifier. Of course also includes many I have been making the amplifier.
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Old 30th July 2018, 12:28 PM   #4
tupoi33 is offline tupoi33
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Hi, LJM! What is the best quiescent current for this amplifier? Earlier you wrote about 20 mA. But hou do you measure it? Is it collector current common for four pairs of output transistors or is it emitter current of each transistor?
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Old 16th September 2018, 06:36 AM   #5
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by tupoi33 View Post
Hi, LJM! What is the best quiescent current for this amplifier? Earlier you wrote about 20 mA. But hou do you measure it? Is it collector current common for four pairs of output transistors or is it emitter current of each transistor?
hello
About the static current. I think 1-50 ma don't have too big effect.
The SELF is introduced in the book. Not suitable for large static current.

Because it can increase the distortion.

But I found in practical measurement, the influence of the static current did not too big.

Whether it is a 0 or 100 ma. There is almost no difference.

So I set about 20 ma. Is about 3 * 8 = 24 ma ma
May have some different actually. Even different temperatures will have some changes.

But in fact will not bring any influence.


I think my test is also suitable for other amplifier.

Of course L20.5 adopted CFP output. It of the distortion, voltage is the smallest.
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Old 23rd September 2018, 06:57 AM   #6
jvhb is offline jvhb  Europe
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Location: Countryside Zealand, DK
LJM, can you confirm that you are using DMMT5401 in the input section?

- If not, what are the SOT26 devices?


Thanks.
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Old 14th January 2019, 04:02 PM   #7
DAZER is offline DAZER
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Is it AB class?
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Old 5th April 2019, 03:47 PM   #8
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by DAZER View Post
Is it AB class?
yes

IQ= about 15 MA
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Old 12th June 2019, 07:45 AM   #9
maty tinman is offline maty tinman  Spain
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Default LJM L20.5 and very simple MODification (feedback)

Review and Measurements of L20.5 Loudspeaker Amp

Review and Measurements of L20.5 Loudspeaker Amp | Audio Science Review (ASR) Forum

by YMY

Quote:
SO..the mother board must be MODification, finally can be use, Warning!! Must remember don't use switching power supply at any time& Please don't use pre-amplifier

“science datasheel”

8Ω 200 W 4Ω 400 W CLASS-AB
frequency response 20-25 Khz -0.15 DB 20 Khz-0.05 DB 10 Hz -0.7 DB
AP TEST (8Ω)1-50 W
THD+N 50 HZ 10 W(9 Vrms) <0.0007
THD+N 1 Khz 10 W(9 Vrms) <0.001
THD+N 10 Khz&20 Khz 10 W(9 Vrms) <0.0008
THD+N 50 W(20 V rms) 1 Khz <0.0015
Quote:
Unfortunately, the seller himself demostrated a very wrong way to use AP.. which led to the master design error and insisted on the wrong AP test method, we have different views, so we could not communicate with each other, fortunately, my friend is an experienced university professor who is very interested in this product and makes a simple MODification (feedback) I'll show you how to MOD the motherboard later.
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Last edited by maty tinman; 12th June 2019 at 07:50 AM.
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