Ok thanks, how i can calculate the gain with the value of the resistor ?
@ LJM: It's possible to have the schematic in PM ?
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Same question here, any simple and clear webpage with all kits and specs? There's info on LJM's stuff everywhere, more or less accurate, more or less "official" sellers and such.
I'm looking for 150W clean (no 20%THD), an "audio" SMPS and really reliable (pro?) serviceable boards (have been a victim of 41Hz's crooks). And the info of the input Z, but I guess my OpAmp output stage (OPA1632) can drive it with ease. Hence the need of clear infos.
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I don't have a link for his Chinese site anymore. I just remember that I opened it once few years ago.
İ have 2x24v 300vac toroidal transformer for poweramp ljm mx 50se and 2x12v 30vac for preamp. İ measure ac voltage difference between grounds of two transformer. As a result i cannot use the preamp... There is a phase difference between two transformer i think but this is not make sense to me.
Any idea to overcome this situation??
Any idea to overcome this situation??
If
If you measure open ends of transformers, you get funny readings, as they should isolate from the AC power grid. To find useable measurements, do it like this: First connect two wire ends of the first transformer, in a way that you measure twice the single voltage over the free ends. This is the "middle" and ground for a +- configuration. If you only see the nominal voltage, you have twice the amps and a single voltage, the other ends connected. But dont mess this up or you get a short cut.
Then the ground (or middle) of both transformers must be connected, thats all. Off course, you have to add rectifiers and some condensors to make a useable +- power supply. You will measure about 17 volt dc at the 12 v ac end, 34 volts over both ends.
With the 24 volt ac 34v dc and 68v dc should be seen. The voltages are a coarse estimate and will be higher without load, depending on the transformer. Under load they drop.
That should solve your phase problem.
If you measure open ends of transformers, you get funny readings, as they should isolate from the AC power grid. To find useable measurements, do it like this: First connect two wire ends of the first transformer, in a way that you measure twice the single voltage over the free ends. This is the "middle" and ground for a +- configuration. If you only see the nominal voltage, you have twice the amps and a single voltage, the other ends connected. But dont mess this up or you get a short cut.
Then the ground (or middle) of both transformers must be connected, thats all. Off course, you have to add rectifiers and some condensors to make a useable +- power supply. You will measure about 17 volt dc at the 12 v ac end, 34 volts over both ends.
With the 24 volt ac 34v dc and 68v dc should be seen. The voltages are a coarse estimate and will be higher without load, depending on the transformer. Under load they drop.
That should solve your phase problem.
For those here trying to connect to LJM,because of technical problems with his products: A reliable source from somewhere in China told me, he gave up on designing audio products with the help of diyaudio.com and has started a new business.
His new enterprise is recycling blown up amplifier circuits, as he has best connections to unlimited supply of raw materials.
His new enterprise is recycling blown up amplifier circuits, as he has best connections to unlimited supply of raw materials.
ljmaudio.cn
[Chinese] 北京赛车走势图_北京赛车pk10走势图分析_PK10走势图网页版
Bing works better there than Google: Bing Microsoft Translator
[Chinese] 北京赛车走势图_北京赛车pk10走势图分析_PK10走势图网页版
Bing works better there than Google: Bing Microsoft Translator
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On the linked chinese home page is a lottery game. So, if you win, you might get a working amplifier? That is nothing new with LJM products...
Maybe I should not make fun of LJM, but his products are offered anywhere, without a manual, schematics or effective support.
If there where schematics, others could give help to buyers of this badly designed stuff, that is a only a open OEM design with cost reducing and problem producing shortcuts made, China style. Sell and forget...
But LJM does not even offer these, what makes me really upset. He claims to not be responsible, because he does not sell these boards with his name on, but refuses to give basic information. Someone could "steal his design"... which is made in thousands without his permission and license, as he told us? Really?
Maybe in China he is considered a smart, honorable guy with this practice.
If there where schematics, others could give help to buyers of this badly designed stuff, that is a only a open OEM design with cost reducing and problem producing shortcuts made, China style. Sell and forget...
But LJM does not even offer these, what makes me really upset. He claims to not be responsible, because he does not sell these boards with his name on, but refuses to give basic information. Someone could "steal his design"... which is made in thousands without his permission and license, as he told us? Really?
Maybe in China he is considered a smart, honorable guy with this practice.
I have finally listen for few hours my L20.5 with "ebay low cost SMPS500W" (one of therm blast during the first minutes = surely a defect one)
Without any tweak, just wiring the module, put a Alps RK27 for passive volume control an play musik with my phone (Meizu Pro 7, CS43130) ... the result is over my expectation !
Already, there is no "breath" in the speakers once the power is turned on, total silence, and the dynamic is very impressive for class AB, it look like a class D !
They are also very transparent without being aggressive, I can find any defaults for the moment ... hurry to test some tweak see if I can still improved it ... but we start on a very good basis !
(In addition the heating is very moderate, the original sink is enough I guess)
PS: anyone have the schematic of the L20.5 ?
Without any tweak, just wiring the module, put a Alps RK27 for passive volume control an play musik with my phone (Meizu Pro 7, CS43130) ... the result is over my expectation !
Already, there is no "breath" in the speakers once the power is turned on, total silence, and the dynamic is very impressive for class AB, it look like a class D !
They are also very transparent without being aggressive, I can find any defaults for the moment ... hurry to test some tweak see if I can still improved it ... but we start on a very good basis !
(In addition the heating is very moderate, the original sink is enough I guess)
PS: anyone have the schematic of the L20.5 ?