ebay amp L20 power amplifier

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#44
so for the standart gain of it ,whats maximum ?
i have 5.1V from preamp,i can go higher up to 8V
and at 6V it was circa 150W in 6ohm with 64VDC supplies
--minimized the loss of Impedance matching ,LPF before Input amplifier is RCapacitance cable with resistor 56ohms
and then l20 10uF HPF + Inductor LPF
the declared is 35times gain if im not mistaken
 
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#46
swith to 48 volt AC>>DC 68 volt

Hi,

I will change when i get the time my 24VAC toroidals into 48VAC.

I had these still from my DX-AMP adventure and they needed 33 VDC.

My sum will be 48 volt. Power is oke now but i can do much better!

I will also need to change my both PSU which handle 50VDC max. I will go for 80V or 100V versions. Any tips for capacitators? Thanks,Marco
 
#47
How to get the full rated power out of these amps.
This is rated max +/- 70v dc, 40 amp and 350 watts @ 4 ohm.

I thought feeding it 70v and a 40 amp capacity with the wiring down stream from the transformer, and 27 amp transformer capacity would do it ? Would it ?

Cool.
Srinath.
 
#48
L20 project

rfj5106 said:
I just finished building an amp using the L20 boards with dual Plitron 40-0-40V @ 2.75 amps and 6 x 10K uF capacitors per channel in the power supply. I also used a soft start module and a speaker protection relay board for start-up. I had pipe dreams of using peltier devices which would allow me to get by with less heat sinks but my experiments with peltier devices were failures. So I have a thermal switch set to 85 degrees Celsius that will cut the AC if the temp by it reaches 85. So far the heat sinks have got quite warm but not too hot to touch. The maximum length of time I have had it on is 2 hours. I don't feel like tempting the fates by leaving it on.

How does it sound? So far quite good. It was built to replace an aging Yamaha M-70 that been in the shop 3 times in the last 2 years. My math says it was cheaper to build than repair. The L20 to my ears sounds slightly more detailed than the M-70 so I am a happy camper about this project although I should have had bigger heat sinks.

I am going to try to insert a picture of this project. My handy work is not so handy! I call this project the DB amp, DB stands for Dog's Breakfast in honour of ny chaotic wiring.
Click to expand...
Hi Richard,
Do U have the schematic drowing of this Power Amp LJM L20-V9 ??
Thks
 
#49
L20 V9 Power Amp

ljm_ljm said:
Thank you for your use me to design the amplifier.

. If you have any questions, you can mail. ljm_ljm@foxmail.com

L20 in constant updates, to the stability of the better version, and better performance.

The current version is VER 9. L20 USES blue PCB materials. Blue is genuine.

Notice that there is some other color is probably pirated products.
Click to expand...

Hi,
I am looking for the schematic about this version of LJM Poxer Amp?
Is it possible to have it ??

Thks
 
#53
183309-ebay-amp-l20-power-amplifier-5

I bought this module to make a replacement subwoofer amp for one that failed. It turned out to be a kit. I'm OK with that, DIY is fun, but there was no schematic and no instructions. So I re-drew the PCB and extracted the schematic using expressPCB.com. I figure the results may be of interest to others. Incidently, I do not recommend making copy boards, because the originals are good quality and low priced. But having the schematic is necessary for checking your work and troubleshooting if the result fails later on. Note these are not the official schematics or layout drawings. There could be residual errors. Use at your own risk, but if you do find mistakes, please do share them. This work applies to v9.2 of the board. There are PDF copies of the drawings for people who don't want to mess with electronic CAD software. The datasheets are representative of the semiconductors, not necessarily from the same manufacturers as the supplier ships.
 

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#57
Most of the mistakes in the schematic can be fixed by reversing the base and collector of the 2N5551 transistors. The 2N5551s supplied with the kits are non standard parts where the collectors are the middle leads. C9 should be reversed and the +ve side should go to 0v. Can someone explain why the collector load of the vas ( Q11 ) appears to be the constant current source formed by Q9 in parallel with the 33k resistor R23? The schematic is correct in this respect, as I have traced it out.
 
#60
the zips work fine here with 7zip on Windows

edit: If you're using a Mac (ugh), try Keka. Apple's standard "Unarchive Utility" is useless... for example, it creates non standard zip files when you add large (>2GB) files
 
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