EL34 Baby Huey Amplifier

[zintolo]

Originally Posted by Francois G

Thank you also for your reminder about CFB transformers - I forgot about the additional drive requirements with them. I will have to learn LTSpice to play with and balance these things and devise a proper drive circuit for those Toroidy TTG-CFB6600PP transformers in the closet.

LTSpice is an useful tool, but it's really only part of it. I use it during the week, when I cannot push the amp to its limits and hear how it sounds. Then details must be defined by hear IMO.

Originally Posted by Francois G

I don’t know if it is a simulation artifact, or some other cause, but I am dubious about the “optimal CCS current” result of >6 ma for two 12AX7 triodes. See the chart below.

I was probably not clear in my explanation, but the current I was talking about is through the leds of the CCS, not through the NPN (so not passing through the PI). It is clear that a current flowing through the triode would change its working point and so its harmonics, but here I'm talking about the current through the leds.

[zintolo]

This is again a cascoded version of the BH with KT88.

In attachment there's the schematic in image and LTSpice format, here below the THD at 70 Wrms with no gnfb:

Harmonic	Frequency	 Fourier 	Normalized	 Phase  	Normalized
 Number 	  [Hz]   	Component	 Component	[degree]	Phase [deg]
    1   	1.000e+03	3.341e+01	1.000e+00	   -3.54°	    0.00°
    2   	2.000e+03	9.127e-03	2.732e-04	  -93.13°	  -89.59°
    3   	3.000e+03	2.083e-01	6.237e-03	 -146.94°	 -143.40°
    4   	4.000e+03	9.812e-04	2.937e-05	  -90.02°	  -86.48°
    5   	5.000e+03	2.459e-01	7.362e-03	 -177.65°	 -174.11°
    6   	6.000e+03	6.152e-04	1.842e-05	  -86.21°	  -82.67°
    7   	7.000e+03	2.082e-02	6.231e-04	  162.87°	  166.41°
    8   	8.000e+03	5.356e-04	1.603e-05	  -82.22°	  -78.68°
    9   	9.000e+03	3.107e-02	9.300e-04	  174.51°	  178.06°
Total Harmonic Distortion: 0.971709%(0.971996%)

[zintolo]

Another trial of the cascoded version of the BH, this time with KT120.

In attachment there's the schematic in image and LTSpice format, here below the THD at 110 Wrms with no gnfb:

Harmonic	Frequency	 Fourier 	Normalized	 Phase  	Normalized
 Number 	  [Hz]   	Component	 Component	[degree]	Phase [deg]
    1   	1.000e+03	4.177e+01	1.000e+00	   -2.91°	    0.00°
    2   	2.000e+03	1.047e-02	2.507e-04	  -91.83°	  -88.92°
    3   	3.000e+03	1.350e-01	3.232e-03	  -71.34°	  -68.43°
    4   	4.000e+03	5.792e-04	1.387e-05	  -71.50°	  -68.59°
    5   	5.000e+03	2.946e-01	7.053e-03	 -168.55°	 -165.65°
    6   	6.000e+03	2.006e-04	4.803e-06	  -76.50°	  -73.59°
    7   	7.000e+03	1.674e-03	4.007e-05	 -112.26°	 -109.35°
    8   	8.000e+03	1.510e-04	3.615e-06	  -79.49°	  -76.59°
    9   	9.000e+03	2.552e-02	6.109e-04	  175.67°	  178.58°
Total Harmonic Distortion: 0.778626%(0.778689%)