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Old 19th April 2012, 04:28 PM   #31
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by johnr66 View Post
I'd have power supply decoupling film caps near each IC.
You can parallel the IC's pins below.


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Old 19th June 2012, 01:48 PM   #32
Pemo is offline Pemo  Mexico
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Quote:
Originally Posted by ljm_ljm View Post
Complete Reference style 47LAB 3875.

Reference 50 watts output power versions. Two 2200UF capacitor.

Integration by adding the protection circuit board .10 * 2 relay reliable.

Backside of the PCB, DC location, said the short here, the negative feedback using DC.
I've just seen your kit and I have a question. What is this DC jumper in the backside of the board? What does it do? Is it important?

Thanks

RGDS
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Old 30th June 2012, 06:58 PM   #33
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Hi LJM,

Nice design!

Do you have an LM3886 Option?

Will you make this design available on ebay?

Thanks,
Chris
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Old 29th March 2013, 09:52 PM   #34
Pemo is offline Pemo  Mexico
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Default DC / Capacitive coupling switch possible?

According to ljm_ljm schematic (ljm lm3875 gainclone.jpg), is it possible to add a switch to these points (3875-3.jpg) to "SWITCH" between DC coupling and Capacitive coupling?

Thanks, Pemo
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Old 1st August 2013, 01:18 AM   #35
lsheng is offline lsheng  United States
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This was a very good design, better ones I saw were often for one channel only. But after combining two boards into stereo amplifier, most are not better design any more.

I wish I can find LM3886 board having better design, so far none. But LM3875s are more expensive and have less output power.
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Old 18th August 2013, 01:59 AM   #36
Pemo is offline Pemo  Mexico
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Smile Finished building, and listening impression of LJM_LJM gainclone kit

After almost a year after buying this kit, I finally found the time to build it (this afternoon). It was EASY to assemble, using 4% silver resin core solder. It took me arround 30 min to finish it. Attached a CPU heatsink to both IC's, and connected an Antek AS 2224 transformer.
Connected a mini USB DAC with no potentiometer, and my old faithful 8 ohm speakers.
Surprise, this amplifier really sound FANTASTIC!!!
Cristal clear highs, warm mids, and hard tight bass.
I'll like to say that I like it more than my old XY LM3886.
Played Jazz, Bosanova (Ana Caram), Led Zeppellin, 70's, 80's, classical, opera, Al di Meola guitar, etc at both low and high levels and there is absolutely no distortion nor clipping at all.
My 16 years old listened to it from his room (a Little apt. in the garden in the back of the house) and came running asking me what amp I was using. He was amazed!!. Now I've lost my new amplifier, but I'ts OK. I'll build another one. At $15 on ebay plus $35 Antek transformer I have to say it is one of the best buys ever. Really.
Congratulations LJM_LJM whoever you are.
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Old 18th August 2013, 02:40 AM   #37
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great! nice pcb...what equipment you wanna use them?
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Old 19th August 2013, 02:44 PM   #38
ljm_ljm is offline ljm_ljm  China
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Quote:
Originally Posted by Pemo View Post
According to ljm_ljm schematic (Attachment 339310), is it possible to add a switch to these points (Attachment 339311) to "SWITCH" between DC coupling and Capacitive coupling?

Thanks, Pemo
Is a convenient shortened C1 C2 way.

I think the tin, will be more stable than pin.

Don't be in general.

It will bring higher DC output.

Although the voltage is still very low.
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Old 3rd September 2013, 07:23 AM   #39
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Hi ljm!
I'm a newb and I have a couple of dumb questions. While I do understand some of the basic things in the circuit, I don't understand this:
1. Why would we need Q1, Q2 followed by a Darlington pair Q3, Q4 when the IC itself is quite capable of giving out several watts?
2. If there was nothing else (the transistor circuit part) to be used after the ICs, we would have outputs (L/R) right after R12 and R13, right? Then how do we get L/R channels after they have been shorted out and fed into Q1?

Again, I think my questions are kindergarten level stuff, so please point me in the right direction here. If there is anything I could read-up which in turn would help me figure out the things here, please let me know.

Thanks in advance!
Aashish
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Old 8th September 2013, 08:47 AM   #40
Gopher is offline Gopher  United Kingdom
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Good questions Aashish. I'd also like to know how the L/R channels are regenerated after being connected together after the 47k resistors. It seems a bit of an odd arrangement. Maybe someone can explain what going on for us mere mortals?

Last edited by Gopher; 8th September 2013 at 08:59 AM.
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