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LJM Audio

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M

mslim

Member
Joined 2020
Saarmichel said:
Sorry: second try

Hello

:wiz: This is my LJM-Audio L20.5 Amplifier.

I let pictures speak first.

https://www.diyaudio.com/forums/att...aar/835638d1587311061-ljm-audio-l20-5-amp-jpg

https://www.diyaudio.com/forums/att...87311061-ljm-audio-l20-5-amp-innenansicht-jpg

https://www.diyaudio.com/forums/attachments/vendor-s-bazaar/835640d1587311061-ljm-audio-4-ohm-jpg

https://www.diyaudio.com/forums/attachments/vendor-s-bazaar/835641d1587311061-ljm-audio-8-ohm-jpg

https://www.diyaudio.com/forums/att...r/835642d1587311061-ljm-audio-vg-m2-l20-5-jpg

@LJM Congratulations, with this Amplifier board you didn't promise too much :c_flag::king:

This is by far the best Amplifier I've ever built.


Thank you very much for that :wave:

Michael
Click to expand...


Looks good. I’m a novice so.....

1) May I have the link for the SMPS?

2) Is there a THD vs noise chart?

3) How about SINAD?
 
H

Hakuo

Member
Joined 2019
H

Hakuo

Member
Joined 2019
Yes, I know.
But with changing a few components it should be a real subwoofer amplifier.
And it should have a voltage gain of 68 in stead of 34.
So if a know what components I have to change and what value they must be, it is an easy job.
 

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L

ljm_ljm

Member
Joined 2006
Hakuo said:
Hello,

I have a problem:
I bought 2 L20SE bass amplifiers on Aliexpress. Bass Gun L20 SE A1943 C5200 200W 8R Mono Assembled AMP Amplifier Finished Board|Amplifier| - AliExpress
I have now put them into use.
However, they are not bass amplifiers.
The frequency response is straight up to 20 kHz.
I have asked the seller for an electronic diagram of the bass amplifier, but I have not received an answer.
Does anyone have a diagram or know where I can find it?

Thank!
Click to expand...

You can upload your photos. I can have a look.
Because of the l20se and l20se subwoofer versions. The appearance is the same.
I don't know if the purchasing agent is wrong. However, it can be easily modified to a bass version.
 
L

ljm_ljm

Member
Joined 2006
ekremy18 said:
what is the gain of the board? the supplier said that 32 times (30dB) and i noticed a 330 ohm and 10kohm Ri and Rf so Ri/Rf=32, i think he is correct.. but i wonder which resistor or resistor are responsible for gain adjusment? can you show them for me on the pcb with their values so i want to increase the gain
Click to expand...

33000/1000+1=34 GAIN.
If you don't know. You can take a picture and I'll tell you.
Because there are two versions of L7.
I'm not sure which version you are.
 
L

ljm_ljm

Member
Joined 2006
The latest version of the photo.
Because I found that the OSCON capacitor is in a relatively hot position. It may be damaged after working for a long time.
And it can't be seen from the outside.
So in some places. I replaced the electrolytic capacitor with a higher voltage. 50V-63V。
They are used for filtering capacitors. More capacity. Higher withstand voltage. So performance doesn't degrade. It will be improved.
The input signal capacitor has a very low working temperature. So the OSCON capacitor is still used.
PCB adopts two layers.
 

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