SERFE - a Single Ended Rush Pair Front End

I have a few Sony small SIT 2SK63 and 2SK79, Mu ~30 and 120V Max Vds. Combined with a 2SJ103 GR to form Rush pair we have a non inverting gain stage. 5dB feedback allows for gain of ~20dB. Predicted THD of ~0.23%, negative phase H2 dominant with H2/H3 ~33.9dB.
I call it SERFE K79 to serve a need for spooky presentation. 🙂
Code:
N-Period=1
Fourier components of V(out)
DC component:-0.0112158

Harmonic	Frequency	 Fourier 	Normalized	 Phase  	Normalized
 Number 	  [Hz]   	Component	 Component	[degree]	Phase [deg]
    1   	1.000e+03	4.000e+00	1.000e+00	   -0.06°	    0.00°
    2   	2.000e+03	9.232e-03	2.308e-03	   90.59°	   90.66°
    3   	3.000e+03	1.850e-04	4.624e-05	    0.81°	    0.88°
    4   	4.000e+03	6.786e-06	1.697e-06	 -134.34°	 -134.28°
    5   	5.000e+03	3.998e-06	9.996e-07	 -179.84°	 -179.78°
    6   	6.000e+03	3.215e-06	8.037e-07	 -180.00°	 -179.94°
    7   	7.000e+03	2.755e-06	6.887e-07	 -179.91°	 -179.85°
    8   	8.000e+03	2.411e-06	6.027e-07	 -179.94°	 -179.88°
    9   	9.000e+03	2.144e-06	5.359e-07	 -179.91°	 -179.85°
Total Harmonic Distortion: 0.230840%(0.230840%)
Pic 2 - FFT spectra at 8Vpp output.
Pic 3 - Frequency Response.

The topology also works for other Jfets, Mosfets, Triodes and Pentodes.

Pic 4 - SERFE ECC88
Pic 5 - FFT of SERFE ECC88 with THD ~0.23%, good H2/H3 ~45.3dB
Pic 6 - Mated to M2 output stage to make 25W class A
Pic 7 - Mated to a 50W class AB composite power buffer.
Pic 8 - 14dB (5x) gain headphone amp version with ECC88
 

Attachments

  • SERFE K79.gif
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  • SERFE K79 FFT.gif
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  • SERFE K79 FR.gif
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  • SERFE ECC88.gif
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  • SERFE ECC88 FFT.gif
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  • SERHA ECC88.gif
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  • SERAB50 K79.gif
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  • SERA25 K79.gif
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Pic 9 - SERFE LND150 Lateral DMOS version
Pic 10 - FFT of LND150 version
Pic 11 - SERFE K117 - Cascoded 2SK117 (or 2SK209) version
Pic 12 - FFT of K117 version
 

Attachments

  • SERFE LND150.gif
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  • SERFE LND150 FFT.gif
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  • SERFE K117.gif
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  • SERFE K117 FFT.gif
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me likee,Mighty Indra!

you need intervention there , to comply with name - toss "pair" from thread title

(years ago, I was so bloody smart, so I invented Rush cascode/diff pair ...... was so proud for a day; not first, not last time .......... :rofl: )

have plans to put proto ?
 
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