L12-2 CFP Output amp 120W*2 8R

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#402
Thanks for your replies.

Here is a picture (I know, this is ugly and i do not have any speaker protection ; for now).

20/28/axlm.jpg - Visionneuse Zupimages

As you can see, I have capacitors between my SMPS and my amplifier boards. This little board is very usefull with a SMPS (great results).

Website infos here :

LPS212A | Connex Electronic


I think i missed something (wrong wiring certainly). This is my first DIY board amplifier in AB class. Most of the time i'm with class D board amps and this is way easier to understand (and yes, this connex electronic SMPS is grounded)
 
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#403
Linear Power Supplies / LPS212A - SMPS may start poorly on capacitive loads. Need a soft start with current limitation on the exit side.
Due to a grounded case, there may be a short circuit of the output SMPS.
 
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#405
1) Disconnect L12-2.
2) Disconnect the ground from (- 45 V) to SMPS No. 2 - it will be (-45 V) bus.
3) Connect SMPS No. 1 (-45 V to the ground) with No. 2 (+45 ) - this will be "0" ground. SMPS No. 1 will be a bus (+45 ) in. SMPS No. 2 will be a bus (-45 ) in
4) At the inputs No. 1 and No. 2, turn on the fuse 1-2 a. On the bus (+45 V) and (-45 V), turn on the fuse 4 a.
5) Connect the load to each bus (100 W lamp) and check the voltage.
I myself did not do that (((At your own peril and risk.
If everything is OK, you can connect an amplifier)))
 
#406
OldDIY said:
1) Disconnect L12-2.
2) Disconnect the ground from (- 45 V) to SMPS No. 2 - it will be (-45 V) bus.
3) Connect SMPS No. 1 (-45 V to the ground) with No. 2 (+45 ) - this will be "0" ground. SMPS No. 1 will be a bus (+45 ) in. SMPS No. 2 will be a bus (-45 ) in
4) At the inputs No. 1 and No. 2, turn on the fuse 1-2 a. On the bus (+45 V) and (-45 V), turn on the fuse 4 a.
5) Connect the load to each bus (100 W lamp) and check the voltage.
I myself did not do that (((At your own peril and risk.
If everything is OK, you can connect an amplifier)))
Click to expand...


According to the Connex website - he has a +/-45Vdc SMPS.
Make sure you have +45 to the correct lug on the board.
Then verify the -45 is to the correct lug on the board.
Then make sure to “0” of the SMPS voltage output goes to the “0” or main Ground lug on the board.

This is where a grounding scheme has multiple ways. I take the input to the board (+ and - from RCA plug) then take positive “out” to your speaker and then take the negative speaker to - either the ground on your amp board (same as your main voltage lug went to) or take it back to the “0” on the SMPS.
I would go to the amp board, but if you get noise try taking it to the SMPS.
 
#408
bullittstang said:
According to the Connex website - he has a +/-45Vdc SMPS.
Make sure you have +45 to the correct lug on the board.
Then verify the -45 is to the correct lug on the board.
Then make sure to “0” of the SMPS voltage output goes to the “0” or main Ground lug on the board.
Click to expand...

Exactly. Smps from Connex are +/- DC power supply. I'm using it right now with another
Amplifier module without any problem.

On my previous post, if you look at the picture you can see that everything is okay ; with only one exception : 0 (or GND) on my power supply is not connected to the GND on amplifier boards. The reason is simple : I had to connect the black speaker cable on it because there is only one speaker "out" (OUT +) on Ljm L12-2 board. This is the first time in my life i see this. On my other class D amplifier modules i have 2 speaker outputs (+ and -).

So, if i'm right, I need to try to connect speaker - (black cable) AND smps GND at the same spot (GND on the amplifier board).
 
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#409
Peterwitkin said:
So, if i'm right, I need to try to connect speaker - (black cable) AND smps GND at the same spot (GND on the amplifier board).
Click to expand...

Yes, you will have 2 wires going to ground lug on the amp board.
One from the SMPS “0/GND” connection and the other wire from the negative speaker terminal.

If it’s easier, you could double the wires at your SMPS - should be the same end result
 
#412
Rallyfinnen said:
Only mod so far is 'HBR:s'. Drilled out the trough-plating from ground plane to signal ground and put a 10ohm resistor between them on the solder side on the pcb.
.
Click to expand...
@ Rallyfinnen sorry but what do you mean by "HBR:s" mentioned in post #327?

I got a pair of L12-2 ver 4 yesterday and going to implement it into Grundig V303 amplifier. The modifications I want to do are: replace C5 with film capacitor located off the plate and add 100nF capacitors + bias control as Calvin suggested. Also will put clamps on transistors packed with silicon covers.

Only don't know what to do with C8 feedback capacitor. Now it is 1000uF but I think that 470uF bipolar would be better

Any suggestion from your experience is welcome
 
#420
@ljm_ljm I have finally assembled the L12-2 amplifier boards from kits. They were version 4 so ( among others) with connected input ground with overall ground. In my project, as I had one general ground coming both from preamp and power supply - I have connected it to input ground socket and that overall groung connector I didn't soldered in at all. When powered those amplifiers with ca 2x47V DC there was nothing heard in headphones, but when I just connected the volume plate a hum ( or small brum) appeared (with no signal/music connected). Don't know if I had to do as was described in post #327 (quoted in my post #412) so drill out a connection between signal ground and overal ground connector and connect them with 10 ohm reistor ? Generally the hum is not so big and hardly heard in loudspeakers so I just left amplifier boards as they are but knowing that hum breaking resistor (or maybe a ferrite bead) would help I could dismantle L12-2s to implement that change. Please advise !
 
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