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Looking for Elektor AXL V2 Boards

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Strong Believer

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Joined 2023
#1
HerrFlick said:
More then 30 years ago (1985) I build the Elektor AXL class A/AB amplifier, time to upgrade this amplifier using new (= better)components.
My main goal was to replace the power mosfets 2SK134/2SJ49 with Exicon ECF10N20/ECF10P20. Also the medium power transistor BF469/BF470 changed to MJE340G/MJE350G.
Extra power supply filter capacitors where used and placed on the PCB.
The two capacitors for the 15V zener diodes where increased to 100uF 25V
and the capacitor parallel to the quiescent current potentiometer (1k) is increased to 220 µF (Single-Ended Conductive Polymer Aluminum Solid Electrolytic Capacitors)plus extra 47nF WIMA MKP.
The two source resistors (0,22 Ohm) are no longer needed.
The input capacitor (C1,C2,C3-820 nF) is replaced by a high end capacitor 2,7 uF Clarity Cap ESA.
The Exicon Application notes told me to decrease the inductance in the output line to 1µH (1mm Cu wire inner diameter 8 mm, 15 windings). Due to different gate input capacitance of the mosfets the gate resistors are also different, 330 Ohm for ECF10N20 and 220 Ohm for ECF10P20.
The power supply for each channel (2x25V AC 2,4A 120 VA) is filtered by 4 x 10.000 µF rectifier (Ebay) so that results in 2 x 38V DC output voltage.
It is still very important to set the quiescent current potentiometer to zero Ohm before switching on the amplifier for the first time.
I tried to use the same component labels but did not 100 percent succeed.
On my old (same as me) but still working oscilloscope (Philips PM3226) I saw a maximum error free waveform of about 60 Volt peak-peak with a 8 Ohm resistor load.
No oscillation what so ever, 60 Volt peak to peak over 8 Ohm i.e. 30 : 1,4 = 22 Watt output power with a quiescent current 0,1 A.
The calculated damping factor is more then 200.
I am using a Rasberry Pi in combination with the HiFiBerry DAC plus and a home made power supply (5V 3A), controlled by Volumio software, NAS. The loudspeakers: Acoustic Energy AE1.
Click to expand...
Are the pcb's of this AXL V2 version available somewere ?
Eagerly want to build this amp . Thx
 
#5
If you dont find any gerber or pcb let me know i can draw for us. And please check the lang amp on forum. I would like to try both amp and definitely i will draw pcb for them. I am busy little my jfet class a buffered composite tda7293
 
#6
sercan85 said:
Could you use any pcb drawiing programs? It looks not difficult for drawing. did you check the lang amp? The same generation and looks better...
Click to expand...
Hello,
I have both AXL ( elektor ) and Lang PCBs and gerbers of sprint layout 6.0. I built them both 5 years ago and sound really good. My PCBs had been ordered by JLCPCB in China. I can post some photos if you want to see what I am talking about.
 
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#8
If HerrFlick schematic is identical to the elektor one but the TO3 only, you can use my gerbers or the PCB using your exicon mosfets. The old mosfets must be matched. I don't know about EXICON. BC550C and BC560C must be matched too. The quiescent current must be adjusted to less than 750mA for good results. Have a look at the PCBs.
axl.JPG
LANG 20W.JPG
 
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