What's your power transformer specifications in secondary volts and current?
It's a Amplimo toroidal transformer 2 x 25V 2,4 A = 120VA
https://www.amplimo.nl/images/downloads/ds standardrange/48016.pdf
https://www.amplimo.nl/images/downloads/ds standardrange/48016.pdf
Try the class A operation- 1A current wit no load. You will be amazed by the sonic impression! I work it to its limits with +- 39VDC 5A power supply. My capacitors are 40000Uf/63VDC and i have built 2 separate boxes for power supply and amplifier. Yesterday I finished the 3 pcbs, 2 for the amp and 1 for the DC stabilization. I have ordered my spare parts from mouser and I will start rebuilding the project under the knowledge and experience of today. 15 years ago I came to your country working for a military project of my company( Hellenic Aerospace Industry).I stayed for 1 month in Wintersvijk and I had a really good time with the local fellows.
Try the class A operation- 1A current wit no load. You will be amazed by the sonic impression! I work it to its limits with +- 39VDC 5A power supply. My capacitors are 40000Uf/63VDC and i have built 2 separate boxes for power supply and amplifier. Yesterday I finished the 3 pcbs, 2 for the amp and 1 for the DC stabilization. I have ordered my spare parts from mouser and I will start rebuilding the project under the knowledge and experience of today. 15 years ago I came to your country working for a military project of my company( Hellenic Aerospace Industry).I stayed for 1 month in Wintersvijk and I had a really good time with the local fellows.I would appreciate it If you could inform me about the exact dimensions of the old AXL pcb because scanning the image from the magazine is a little bit tricky.
Thanks a lot
Did you manage to build the old AXL, if so how does it sounds? Any large deviations from the original design?
Currently I use 2 AXL amps daily, connected to a laptop usb to a high quality dac. With Seas Excel homebuild speakers. Sound is truly amazing.
I have finally opened the old AXL case and measured the pcb dimensions. I have designed the pcb with print layout 6.0 and sent the gerber files to a pcb manufacturer in China and everything has been under control. When you had built your 2 AXLs, did you match the output mosfets? I have noticed that If you don't match them, there is a problem in adjusting the quiescent current around 1A for both channels for class A operation! In my case the 1st channel could reach at 980mA and the 2nd just 800mA maximum. That was a big problem for the sonic performance of the amplifier. So I have adjusted 800mA for both. My second AXL construction (2 months ago) is running perfectly because I purchased 2 pairs of matching mosfets( 2SJ49 - 2SK134) and the quiescent current was easily adjusted at 1A. Its sonic perfomance is increadible. Its power supply is consisted of 40.000uF + 40.000uF and there is a voltage stabilization circuit with 2N6287 and 2N6284 darlington transistors for +-30volts - 10Amperes. The measured ripple is less than 100microVolts.I can post some images if you want.Thanks for your reply.
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I have constructed just 2 AXL amps and this one(Lang 20W class A) will be my 3rd. All of these 3 aps use the same hitachi mosfets 2SJ49-2Sk134. I haven't tried any other brand of mosfets. These hitachi mosfets have got a great reputation through the time and I trust them.Herr Flick had made a modification to the old AXL circuit using lateral mosfet of Exicon. He said that their sonic performance was great, eventhough it operates in class AB.
Thanks. Yes I heard the newer mosfet is better sounding. And AXL had a good reputation too in the past, just like the Crescendo. But today we have more options that I found almost no one favor the amps anymore.
Actually, in the past many people didn't like the sound of mosfet amps when side by side compared to BJT amps. It's like comparing TDA7294 with LM1875 you will see that the majority will lean towards the latest.
I have always wanted to build this AXL just to know how it would sound like but I knew it would be a waste of time. I guess the positive feedback will have a positive effect on damping hence better bass (e.g. than Crescendo), but I don't know in reality. What I want to know is the quality in other area other than bass.
BTW, I will google the Lang 20W.
A class A amplifier has the best sonic performance from any other transistor ampifier thanks to its principals of operation. There are surely better class A amplifiers than AXL. When I built my 1st AXL back in 1988, I was astonished by its performance. I had compared that to my friends' expensive BJT ones and mine was far better. Give it a try and it won't let you down! I mean it !!
Thx for the encouragement hehe. Wait, is AXL class-A? Or did you mean it can be biased more into class-A?
Have you heard the VSSA? Many people like the sound of VSSA but my bipolar amp is much better. But I know that better class-B amp can be made with latfet so I kind of desperate searching for basic latfet amp that I can improve to better my bipolar one.
By adjusting the quiescent current potentiometer you can adjust the class of the amplifier. At 350mA you will get a class AB amplifier. At 1A you get pure class A. You may choose 750-800mA for a mixed class A till 10Watts and class AB for the rest. It's up to you.
If you need the full article from elektor I can send you a pdf. To my opinion, the AXL is a much better amplifier than any BJT amplifier. If you can afford of an about 500 euros expense you mut give it a try!!!
If you need the full article from elektor I can send you a pdf. To my opinion, the AXL is a much better amplifier than any BJT amplifier. If you can afford of an about 500 euros expense you mut give it a try!!!
Ok thank you, I will give it a try. And yes I want the article, thanks...
I wont need 500 euros as I have all the parts. For testing I will use TO3P. When it has to be TO3, creating the holes on the heatsink and cutting the aluminium are things I don't really like
I will compare it side by side with the NRDS by J.M. Plantefeve...
Thank you, metanastis! So the AXL was intended for class-A with 350mA as the compromise between heat and quality. This is interesting because increasing bias in Crescendo didn't make it sound better (at least to my ears).