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Old 22nd July 2012, 03:55 PM   #1
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Question LJM MX50 kit amp

Please help us and someone could clarify the differences between the various versions of the LJM MX50 amp kit - we've seen for sale versions 6.1 and 6.3. More recently the SE version. Does the transistors 5401, 5551, 1815 and with 2SB649 & 2SD669 plus power Sanken 2SA1186 and 2SC2837 as an amplifier providing good fidelity music reproduction?
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Old 23rd July 2012, 12:15 PM   #2
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Quote:
Originally Posted by augustoriodosul View Post
Please help us and someone could clarify the differences between the various versions of the LJM MX50 amp kit - we've seen for sale versions 6.1 and 6.3. More recently the SE version. Does the transistors 5401, 5551, 1815 and with 2SB649 & 2SD669 plus power Sanken 2SA1186 and 2SC2837 as an amplifier providing good fidelity music reproduction?
That depends on the circuit design and transistors used, for starters the 2sb649/669 hasnt been manufactured for many years so will probably be either fakes or second source which implies they wont be as good. As for the others they are good parts if not fakes.
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Old 23rd July 2012, 02:20 PM   #3
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Originally Posted by homemodder View Post
...As for the others they are good parts if not fakes.
+1 regarding fakes on those kits but why not use the search button to read threads like this one which may already address your concerns.
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Old 23rd July 2012, 03:19 PM   #4
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For study purposes, and to express opinion, publishing the scheme available in electronics stores Ebay. Warning do not encourage copying and be respectful of intellectual property of the device.
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Old 12th April 2013, 09:56 AM   #5
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Originally Posted by augustoriodosul View Post
For study purposes, and to express opinion, publishing the scheme available in electronics stores Ebay. Warning do not encourage copying and be respectful of intellectual property of the device.
Your schematic seems to be the LJM MX50 the SE only has 2 output pairs. Am I wrong in noticing a similarity to the APEX AX14?

http://www.diyaudio.com/forums/attac...chematic-2.jpg
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Old 12th April 2013, 11:41 AM   #6
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C14 is incorrectly shown, otherwise it looks OK. I would probably change R6 to something like 470Ω.
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Old 12th April 2013, 02:31 PM   #7
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This schematic is distributed in stores Ebay, as usual, the amplifier must be for sale.

I did the assembly and operating two units MX50-SE with output Sanken A1186 and C2343. The result was surprising, tested on multi amplification, mid and treble bands. The voice is very natural and treble, like breaking glass, percussion dishes are outstanding. I can say that is very close to my F5 running.

A small mod is change the cap MKP of 3.3 uF the input circuit was replaced by Nichicon BP-S of 2.2 uF. Very good indeed, considering the price of the kit.

Sorry for my bad English.
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File Type: jpg 20130325_145758.jpg (438.0 KB, 1660 views)
File Type: jpg 20130325_145644.jpg (472.5 KB, 1575 views)
File Type: jpg 20130326_003914.jpg (304.8 KB, 1492 views)
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Old 12th April 2013, 04:13 PM   #8
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Thanks for your report augustoriodosul. I've bought 2 of these kits for US17$ each from ebay and I am intending to use them to repair an old Sony amp with burnt out power amp section.

Building an amp like this, the largest cost is the power supply and the case/heatsink and hardware.

Reusing old junk amps is a cost effective way for a beginner to build a nice sounding system.

What rail voltage did you use? Do you think this kit can really take 50+/-?
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Old 12th April 2013, 05:27 PM   #9
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What rail voltage did you use? Do you think this kit can really take 50+/ -?

I use a multi amplified with 6 way. Then mid and treble amplifiers are low power as class A. My MX50-SE run with 36 VDC power which would give an approximate 50 to 60W. Do not heat up, just get warm.

Do not forget that transistors output are important, had read good reviews about Sanken 2SA1186 and 2SC2837 with fT 60 and 70 MHz, are very good and fast. Other little mod, change MKP input for Nichicon BP-S 2,2 uF, also increase quality.
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Old 21st July 2013, 10:07 AM   #10
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Hi guys i've built this amp and it is great!!!
I want to ask can i use a pair of 1943 5200 instead, and if yes am i going to get more watt from this amp?
My tranformer is 2*34v ac.
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