LJM Audio

[camargo]

I will do that Kozard, I have a reasonable knowledge of electronics, it will not be difficult for me. Then post the results. Much obliged.

 

[datrumole]

can someone give me a hand picking a power switch?



i'm putting together a (2) L20.5 amplifier


using (2) of these power supplies: 600W Class D Digital Amplifier Switching Power Supply Board Auto DC+-58V | eBay


if i'm reading the meter correctly at the top, he's pulling about 3.2A at full bore


since i'm running two, do i need a switch rated for >6.4A?



i see a lot of power switches max out around 5A on audiophonics


thanks!

 

[Erlend Sæterdal]

Does IT have a soft start?

LCD TV Mains Power On Off Rocker Switch 4 Pin-240V 10A DPST Technika LG etc | eBay

 

[datrumole]

not sure, it doesn't have a great description



I was hoping for one of those nice round ones with the led halo like they have on audiophonics that would look nice on the front of a case

 

[Erlend Sæterdal]

10 A

Metal button 19mm Red LED Power symbol 220V Self-locking Switch High Current | eBay

 

[datrumole]

nice find, thanks!



if I can hopefully find a US seller that would be great


but also, is there anyway to know my actual current pull for this power supply? perhaps I could be using a 5A switch?

 

[Erlend Sæterdal]

Class D

It's a class D and I am sure 5 A will be enough for that.

 

[datrumole]

i dont believe the L20.5 is class D

 

[Erlend Sæterdal]

Correction "If it is class D" 😁

 

[Peterwitkin]

Hello there.

Can somebody give me some little help with something?

I have two LJM L20SE in a DIY amplifier and I got an issue : I think some transistors are dead (the one you can see on the picture was really hot with bad smell).

Everything was running with a very good SMPS : connex electronic SMPS500RXE
and with CLC filter from connex electronic (with almost 10 000uf per rail).

The sound was fantastic. Last morning I tried to turn on the amplifier and the sound was harsh. One minute later everything was dead, with my SMPS safety activated. I tried to use other amplifier boards with my poser supply + filter and everything is ok.

Do you think this can come from SMPS use? I cannot find the info.

Thanks

 

[Puffin]

Hi there, do you still have any of the L12 stereo amp boards? I blew one of mine up and I was bi-amping with another one. If you do can you let me know how much one would be with shipping to UK. Thanks

 

[diyAchim]

L20.5 gain

Hi - what is the best way to reduce gain on this amp model?

 

[DaveFred]

I have been looking three different amps from LJM,

L20 V10

LJM -L20 power amplifier board finished board dual channel two boards 200W8RVER 10-AP2 test

L20.5

L20.5 two-channel kit HIEND ultra-low distortion 0.0015% AP actual measurement

L25

L25 front and rear combined power amplifier finished board dual-channel 250W 8R

Of the three, any opinions on which one is the better one and works out of the box without having to make modifications?

Thank you,

David.

 

[kozard]

I think both the L20 and L20.5 are good out of the box. However in my case I bought the L20.5 without the heatsink and if I did it again I would have bought it with the heatsink due to the peculiar mounting of the power transistors.

I don't know about the L25.

The L20 is easier to mount inside a salvaged receiver, for example. But I think the L20.5 performance is a little better. But both are quite high performance.

 

[kozard]

Hi - what is the best way to reduce gain on this amp model?

There are two resistors which divide the output to provide the negative feedback.

They might be values like 10k (upper resistor in the divider) and 330 (or 470) for the lower resistor in the divider. If you raise the lower resistor the gain will be reduced. If you lower the upper resistor the gain will also be reduced. I lowered the upper resistor to suit my application. I have also reduced the gain in some of the pre-amplifiers I have bought. You need to consider where it is best to reduce the gain, if needed.

For the L20, MX50SE and L12-2 I have marked the resistors on the enclosed schematics. Unfortunately I don't have the full L20.5 schematic. Perhaps someone can post that.

However all the designs are related as you can see. I believe the L12-2 is most closely related to the L20.5 (being an upgrade).

 

[diyAchim]

Thank you, kozard - only just saw your reply!

 

[martinr1604]

GAN Mosfet class-d Amplifier

Hi LJM,

did you already developed an gan-mosfet class-d amplifier or plan to do so?
GAN-Mosfet seem to be superior to silicon-mosfet especially for audio applications. Have a look at

Class-D Audio Amplifiers

I am very interested in a reasonable priced gan class-d amplifier and I am for sure not alone.

 

[turion64]

Hi LJM,

did you already developed an gan-mosfet class-d amplifier or plan to do so?
GAN-Mosfet seem to be superior to silicon-mosfet especially for audio applications. Have a look at

Class-D Audio Amplifiers

I am very interested in a reasonable priced gan class-d amplifier and I am for sure not alone.

If Lester is not working on one, or is not pursuing that idea, drMordor is developing one. Its only conceptual at this point (I think).



Pete

 

[kozard]

Hello LJM,

I recently bought an LJM Power Supply Filter (Capacitance Multiplier).

Is this a genuine LJM product? Or is it a fake? Are the capacitors real or are they fake? Especially the Nichicon KG 6800 uF 63V?

 

[datrumole]

is his logo on the bottom?