LJM amps or other sugestions for basic amp build

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PatAllen

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Joined 2023
#1
Hi, i would like to build a basic amplifier using readily available kits.
what i read about LJM kits vary a lot from one thread to another. Some say they are great kit and some other simply burn them.

i already have a psu with 42v rails at 500VA so this is my main starting point.
i would like to have at least a modest 50wrs into 8 ohm, more is welcome.
MX50X2 seems a good candidate.
MX50SE seems on the edge for 42v mains.

The amp will be used in a bi amped system, running the upper range (not bass).

any suggestions is welcome, links to trusted sellers too.
thanks.
 
#2
Calvin

Post in thread 'L12-2 CFP Output amp 120W*2 8R'

Hi,

these small modules were one of the biggest surprises I came across yet.
I didn´t expect much, but the parts alone could have been worth a shot.
The Hitachi drivers and Sanken LAPTs belong to the best Sand You can use for audio amplification. So I ordered the completed modules, since the price difference renders self soldering obsolete.
As they came straight out of the box the modules looked fine. Ok, optically a few components could have been soldered in more carefully, but functionally everything was ok.
The schematics in #6 contain several failures. Besides the output transistors...
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You're on the right track with an LJM L12-2 and taking @Calvin 's advice.
 
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#3
I have an old PA amplifier with a ring transformer with +/- 51v, +/- 12v, and +/- 15v rails and is a 1000va. Would that be a good transformer to power 2 Ljm L12s? The rectifier circuit is on a PCB integrated with other circuitry for the amp so I'd just buy a new seperate rectifier as well as speaker protection board.
 
#5
https://de.aliexpress.com/item/32847643038.html?spm=a2g0o.detail.pcDetailBottomMoreOtherSeller.54.55ceKkVaKkVa8H&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.40050.354490.0&scm_id=1007.40050.354490.0&scm-url=1007.40050.354490.0&pvid=a319422d-5a24-4b50-ab57-a8306dcaa808&_t=gps-id😛cDetailBottomMoreOtherSeller,scm-url:1007.40050.354490.0,pvid:a319422d-5a24-4b50-ab57-a8306dcaa808,tpp_buckets:668#2846#8109#1935&pdp_npi=4@dis!EUR!45.69!39.19!!!46.29!39.71!@2103867617374807072372058e7930!12000027809831222!rec!DE!!ABXZ&utparam-url=scene😛cDetailBottomMoreOtherSeller|query_from:

I have build such an blameless amp and it sounds great. Later i put 2µH coils /10 Ohm 5 Watt in. The amp does work without too, only for more safety.
My amp is powerd with a connex 500r +-45 Volt. Bias 65mA, more is not necessary in my oppinion.
Anyway..better than a MX50/MX50SE. I own a MX50X2 the oldest version.

Peter
 

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#8
Hello PatAllen. I have made and currently use the L20 V 9.2 boards. They sound so clean and transparent; I cannot believe any amp could sound much better. If you see the reply I got here from the very man himself, you will see that this is the board he recommends:
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#10
I buy all my Chinese Electronics from AliExpress. They have a better choice and usually cheaper too. Look out for "Genuine LJM" items...They are usually a glossy blue coloured board with the brand symbol quite near to the board type name. Also, the photos will often have a large LJM "watermark" written over them...FOR EXAMPLE: If you wanted the L20 click on the link, go down to "specifications" Then "VIEW MORE" and see the photos ...These are genuine LJM boards (I believe). Look out for similar type ads for any of your chosen LJM amplifier boards https://www.aliexpress.com/item/1005002382904828.html?
 
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#12
Yes, not easy, but what makes it even harder is that each type has multiple VERSIONS, and what makes choosing even more difficult, is that some later versions are quite different in design and not always better! One has to really dig into details and reports, which is where DIYAudio helps so much..
 
#13
availlyrics said:
Some L12/2 version 5 design problems pointed by Michael Beeny-
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This is only the version 5 that stinks. If you buy a version 4 or older they're good. Michael has a version 4 he put into a very nice enclosure and listens to daily. If he says it's good than it's more than good enough for me. I've read a lot of mixed reviews on the mx50 amps. I think they are sold with 2 or 3 different types of transistors and some were good some would blow up.
 
#14
sonicles said:
I buy all my Chinese Electronics from AliExpress. They have a better choice and usually cheaper too. Look out for "Genuine LJM" items...They are usually a glossy blue coloured board with the brand symbol quite near to the board type name. Also, the photos will often have a large LJM "watermark" written over them...FOR EXAMPLE: If you wanted the L20 click on the link, go down to "specifications" Then "VIEW MORE" and see the photos ...These are genuine LJM boards (I believe). Look out for similar type ads for any of your chosen LJM amplifier boards https://www.aliexpress.com/item/1005002382904828.html?
Click to expand...
I agree 100%. If your going to buy an LJM board I would recommend only buying one from AliExpress. Im pretty sure LJM has a store on there where your guaranteed to get an original board right from him. Ebay I've only seen fakes or genuine ones but double to tripple the cost and they ship from China anyways.
 
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