2stageEF high performance class AB power amp / 200W8R / 400W4R

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chat72

Member
Joined 2012
One channel is ready, waiting for your instruction.
20220823_101840.jpg
 
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chat72

Member
Joined 2012
Both channels are singing now. Sound great so far, sound quite accurate. Bass a little bit overwhelming, but I have small room. I think position of speakers need adjusting.

I use 30vac, it is 40Vdc, 40000uf for both channels. Bias is 18mv across 0.12 Ohms.
Bias is stable but offset is a bit high. I have around -58mv (red probe is on speaker output) on both channels. I match hfe but not vbe. Is there anywhere I can adjust this without pull out transistors? Can it be done by adjusting r10 and r18?
 
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DavidK

Member
Joined 2005
Hi Toni,

Having spent some time reading through the thread, I am hoping to construct a MOSFET version of your impressive amplifier. I tend to favour the Lateral MOSFET version E1) SA2016 L-MOSFET using approx 50V supply rails unless you feel that C1) SA2015 V-MOSFET offers any advantage in terms of performance or stability?

I would be grateful if you could let me know your view.

I have also sent you an email to sa2016 (at) aws-it.at enquiring about the availability of PCBs.

Thank you and best wishes
David
 
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DavidK

Member
Joined 2005
Hi Toni,

I am putting together the BOM for the small PSU but am struggling to find film capacitors with a pitch of 7.5/10mm for C1 and C2. These are specified as 1uF/250V. I would be grateful if you could let me know the series and value of the blue film capacitors (Epcos/TDK?) that you have used in the images in post #2071? I assume C7/C8 C17/C18 are also from the same series?

Thank you
David
 
Agus sugiono

Agus sugiono

Member
Joined 2018
astx said:
... pikir Anda mengacu pada file simulasi ltspice karena penomoran bagian dari gambar skema terlampir berbeda:
Mungkin Anda benar bahwa 2N5401 bukanlah BJT terbaik untuk mirror saat ini.
Menggunakan BC560C bukannya mengurangi simulasi THD memang sekitar 3ppm.
BTW transistor yang digunakan untuk Q1/Q2 dipilih dengan tangan dari sejumlah besar perangkat yang diukur dan memiliki hfe> 220. Mungkin inilah alasannya, bahwa angka THD amplifier dunia nyata lebih baik daripada yang disimulasikan ...
Akan mencoba tip BJT Anda di hari-hari berikutnya di dunia nyata.

Terima kasih,

Toni
Click to expand...
bagaimana menjalankan 2 stageEF_class_AB asc?
astx said:
Dear keantoken, manso, AndrewT

interesting discussion about current mirrors. During learning LTSPice I have simulated "simple current mirror", "EFA current mirror", "wilson current mirror" and "4 transistor improved current mirror". Douglas Self has made a comparison between these 4 CM types (APAD Handbook, Fifth Edition, page 85) .
One of the conclusion I made, that if using bjt's with beta > 200 the error of the simple current mirror between current in/out is very low in comparison to the "better CM" variants. So I decided to use a simple current mirror as the simulation showed only a few ppm THD difference.
As there are many empty input stage pcb's left (got it cheap from overproduction) I will try to test different bjt's and degeneration values during the next days and will give a feedback

  • if 2N5401 is really a mistake in this case or
  • more or less degeneration will improve or worsen distortion measurements
  • produces more or less harmonics. (currently only H2 and H3 are visible above 100dB / measurement noise floor of HP3585A)
Keep on going to discuss the 2stageEF amplifier so one day an improved schematic/pcb revision will see the real world.
Btw.: the same input/vas stage exists assembled with matched 2SK170 and about 150R degeneration. Will add ltspice asc file the next days.

Note: one can never have enough good amplifiers!

BR,

Toni
Click to expand...
how to run 2 stageEF_class_AB asc?
 
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