Offset voltage in Lang 20W class A mosfet amplifier

because it was a commercial arrangement with Selectronic and Selectronic did not respect its commitment, so I went through Jean Marc who sent me his files under Proteus and the address of the person who made the PCBs (very old school).
It's been twenty years since I assembled it
 
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You got a nice set of PC boards for this project. :)
The only reason I will use my layout because I already has the plastic case power mosfets from Hitachi.
My layout is 100% finished, very soon I will have to etch PCB-s for other projects, a the same time I will do this one to.
Plan to test it with 24-25V DC rail voltage. I have some 20 VAC 650 VA toroidals at home.
3 pair power mosfet 1.5A biased to Class A it is plen

It will be a great satisfaction for you to build your own amplifier from step one to the last. Go for it. I wish you all the success in your effort.
 
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Offset comes from resistance tolerances. I use resistors with 1% and 0.6W metal film and I have never had an offset over 3mV. And I see another anomaly that increases the offset. R4 + R5 = R1.
Building Elektor's AXL class A 2 x 16W some years ago, the editor have written clearly that if there is an offset voltage more than +-50mV, increase or decrease the resistors values of the differential amplifiers . That has been very boring to me, so When I matched the BC550 and BC560 in that circuit, the offset fell to 9mV. In all my projects i use 1% metal film resistors 1/2W from Vishay or dale. The offset voltage is not a matter of tolerance at all.
 
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Yes I like to do that, total DIY. From PCB to the finish product!:cool:

I mentioned this to you, the Zenotron is the DIY version of the ProFet.

https://www.gods69.com/download/AUDIO/7480MM.pdf

I built my based on the original but I used only 17.5VDC rail voltage bias-ed into Class A . 1 A total bias.

It sounded great in a smaller room but in my living room it came out her weakness. The original can be bridged.

I gave up on her, perhaps too soon. My friend built it with 20V transformer and was happy with her.

Still have 4 stuffed PCB without the power mosfets. One day I may try it with a different PS (with a higher rail voltage).

One amplifier similar topology I strongly advise to take a look! I believe this is better that the ProFet or Zenotron.

https://www.diyaudio.com/community/threads/f5-meets-buzquito.162042/
 
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Yes I like to do that, total DIY. From PCB to the finish product!:cool:

I mentioned this to you, the Zenotron is the DIY version of the ProFet.

https://www.gods69.com/download/AUDIO/7480MM.pdf

I built my based on the original but I used only 17.5VDC rail voltage bias-ed into Class A . 1 A total bias.

It sounded great in a smaller room but in my living room it came out her weakness. The original can be bridged.

I gave up on her, perhaps too soon. My friend built it with 20V transformer and was happy with her.

Still have 4 stuffed PCB without the power mosfets. One day I may try it with a different PS (with a higher rail voltage).

One amplifier similar topology I strongly advise to take a look! I believe this is better that the ProFet or Zenotron.

https://www.diyaudio.com/community/threads/f5-meets-buzquito.162042/
Thanks a lot for your recommendation. Good luck with your project.
 
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sercan85

Having built both I can declare that Lang is slightly better and more powerful than AXL.
They have a very good sound both. There are surely some other amps that play better.
If you want to use the exicon mosfets, you must make a couple of modifications on the output circuit.
HerrFlick is the guy to ask as he has used them in his amps.
Cheers
 
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Lang ampifier works on simulator perfect.
ac sweep test are showed, there are better phase line with 10uf input cap. I need to compare them on listening test.

resim_2024-03-16_114334869.png
 

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