I couldn't resist whipping up Pavel's idea in the simulator, made it into a full bridge for better efficiency and set the output for 80W/8R. The numbers I got aren't in the least bit disappointing, here's the THD20K at 80W/8R:
Fourier components of I(r38)
DC component:1.88071e-006
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 2.000e+04 3.171e+00 1.000e+00 -0.28° 0.00°
2 4.000e+04 3.375e-06 1.064e-06 -55.67° -55.39°
3 6.000e+04 5.025e-06 1.585e-06 -118.35° -118.07°
4 8.000e+04 2.325e-06 7.333e-07 157.09° 157.37°
5 1.000e+05 1.683e-06 5.308e-07 77.54° 77.82°
6 1.200e+05 9.958e-07 3.141e-07 0.57° 0.85°
7 1.400e+05 4.393e-07 1.386e-07 -107.32° -107.04°
8 1.600e+05 4.818e-07 1.520e-07 101.26° 101.54°
9 1.800e+05 8.989e-07 2.835e-07 7.13° 7.41°
Total Harmonic Distortion: 0.000216%(0.008551%)
Fourier components of I(r38)
DC component:1.88071e-006
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 2.000e+04 3.171e+00 1.000e+00 -0.28° 0.00°
2 4.000e+04 3.375e-06 1.064e-06 -55.67° -55.39°
3 6.000e+04 5.025e-06 1.585e-06 -118.35° -118.07°
4 8.000e+04 2.325e-06 7.333e-07 157.09° 157.37°
5 1.000e+05 1.683e-06 5.308e-07 77.54° 77.82°
6 1.200e+05 9.958e-07 3.141e-07 0.57° 0.85°
7 1.400e+05 4.393e-07 1.386e-07 -107.32° -107.04°
8 1.600e+05 4.818e-07 1.520e-07 101.26° 101.54°
9 1.800e+05 8.989e-07 2.835e-07 7.13° 7.41°
Total Harmonic Distortion: 0.000216%(0.008551%)
Alright, simulated efficiency is 186W in, 80W out, that's 80/186 > 43%, not bad considering this is class-A.
Try to run asc file
http://www.diyaudio.com/forums/solid-state/96853-extrema-class-strikes-back-30.html#post4120514
Fourier components of I(r40)
DC component:0.000407211
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 2.669e+00 1.000e+00 178.12° 0.00°
2 2.000e+04 5.812e-08 2.178e-08 3.00° -175.12°
3 3.000e+04 5.652e-06 2.118e-06 -124.58° -302.70°
4 4.000e+04 3.135e-08 1.174e-08 -0.20° -178.32°
5 5.000e+04 3.423e-07 1.282e-07 67.10° -111.03°
6 6.000e+04 2.038e-08 7.636e-09 0.03° -178.09°
7 7.000e+04 2.216e-08 8.303e-09 -60.47° -238.59°
8 8.000e+04 1.510e-08 5.659e-09 -0.11° -178.23°
9 9.000e+04 1.385e-08 5.188e-09 5.15° -172.97°
Total Harmonic Distortion: 0.000212%
http://www.diyaudio.com/forums/solid-state/96853-extrema-class-strikes-back-30.html#post4120514
Fourier components of I(r40)
DC component:0.000407211
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 2.669e+00 1.000e+00 178.12° 0.00°
2 2.000e+04 5.812e-08 2.178e-08 3.00° -175.12°
3 3.000e+04 5.652e-06 2.118e-06 -124.58° -302.70°
4 4.000e+04 3.135e-08 1.174e-08 -0.20° -178.32°
5 5.000e+04 3.423e-07 1.282e-07 67.10° -111.03°
6 6.000e+04 2.038e-08 7.636e-09 0.03° -178.09°
7 7.000e+04 2.216e-08 8.303e-09 -60.47° -238.59°
8 8.000e+04 1.510e-08 5.659e-09 -0.11° -178.23°
9 9.000e+04 1.385e-08 5.188e-09 5.15° -172.97°
Total Harmonic Distortion: 0.000212%
Correct, with 20V per rail for the output stage there's a bit of headroom left still and efficiency goes up. Simulated efficiency is 152W in 80W out, which is 80/152 > 53%.
So try it, simply edit 10kHz to 20kHz..
Fourier components of I(r40)
DC component:0.000265904
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 2.000e+04 3.465e+00 1.000e+00 176.23° 0.00°
2 4.000e+04 8.835e-09 2.550e-09 28.75° -147.48°
3 6.000e+04 4.338e-06 1.252e-06 -138.55° -314.78°
4 8.000e+04 1.114e-08 3.216e-09 -8.34° -184.57°
5 1.000e+05 3.114e-06 8.989e-07 63.60° -112.63°
6 1.200e+05 5.183e-09 1.496e-09 -7.20° -183.43°
7 1.400e+05 3.595e-07 1.037e-07 -119.38° -295.61°
8 1.600e+05 3.816e-09 1.101e-09 -12.84° -189.07°
9 1.800e+05 4.946e-08 1.427e-08 61.28° -114.96°
Total Harmonic Distortion: 0.000154%
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@BV,
You're referring to your post #298 correct? If you can forward me the .asc I can have a closer look, I can be reached at ssassen(at)hardwareanalysis(dot)com, feel free to email the .asc to that address.
You're referring to your post #298 correct? If you can forward me the .asc I can have a closer look, I can be reached at ssassen(at)hardwareanalysis(dot)com, feel free to email the .asc to that address.
Sine source is defined this way, "SINE(0 1.3 {freq} 0 0 0 10)", and parameter {freq} is defined in schematic as spice directive line ".param Freq=20k". So it is enough to edit 10kHz to 20kHz in this line...
And .asc file is in post 298 .
And .asc file is in post 298 .
With 2 x 18V for the opamp, you need at least 2 x 22V for the output stage (ccs and triple junction margin), otherwise distortion gets higher).
😎🙂 Nice idea.
Kinda reminds me of driving a OPS bias pair with ref to the output. Conceptually, wasnt that done in a former life with a diode-resistor from output to bias (spreader)? (NPass). But this is a nice balanced circuit refinement.... like a comparitor, too.
Opamp input now then one of the many good discrete front end, later?
THx-RNMarsh
Kinda reminds me of driving a OPS bias pair with ref to the output. Conceptually, wasnt that done in a former life with a diode-resistor from output to bias (spreader)? (NPass). But this is a nice balanced circuit refinement.... like a comparitor, too.
Opamp input now then one of the many good discrete front end, later?
THx-RNMarsh
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This OPS input current is, hopefully, only in microamperes, as long as the output stage remains in class A. That's all the magic - it almost does not load opamp output.
Attachments
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No load on the opamp is great as that was the last area of concern (OPS loading) for using opamps. How much current does the sim say the opamp must supply (max) when the amp goes out of class A?
THx-RNMarsh
THx-RNMarsh
Not nice, then. Starts quite mild, as attached, but continues to milliamps and tens of milliamps.
The image is for stepped load 8, 6, 4 ohms. You can see input current and ouput current through one output device.
added an image for 2 ohm load
Attachments
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You have to specify idle current first. Otherwise there is no good answer.
Class A for 8 ohms only, or for 4 ohms as well, or for 2 ohms as well? Idle current is half peak current to stay in class A.
Class A for 8 ohms only, or for 4 ohms as well, or for 2 ohms as well? Idle current is half peak current to stay in class A.
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