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Old 21st February 2011, 02:04 PM   #11
49 - for the 18th time
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Nice work dadod

Ahhhh - Nice work bench!!! Looks like mine!!!
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Old 21st February 2011, 02:47 PM   #12
dadod is offline dadod  Croatia
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Quote:
Originally Posted by homemodder View Post
I think your LTP degeneration resistors are too large for Jfets, the noise contribution from there will probably be higher than the THD. You shoulnt go higher than 22 ohms and that is pushing it.
You quite right.
I simulated now with 100, 47 and 22ohm for LTP degeneration resistors at 20kHz.


Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 2.000e+04 2.663e+01 1.000e+00 -2.61 0.00
2 4.000e+04 2.516e-05 9.446e-07 94.06 96.67
3 6.000e+04 1.830e-05 6.872e-07 51.00 53.61
4 8.000e+04 2.071e-05 7.777e-07 -140.51 -137.90
5 1.000e+05 2.371e-05 8.903e-07 4.00 6.61
6 1.200e+05 2.488e-05 9.343e-07 -139.66 -137.05
7 1.400e+05 1.931e-05 7.251e-07 137.76 140.36
8 1.600e+05 2.865e-05 1.076e-06 -134.64 -132.03
9 1.800e+05 4.145e-05 1.556e-06 152.18 154.79
Total Harmonic Distortion: 0.000278% 100ohm

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 2.000e+04 2.664e+01 1.000e+00 -2.12 0.00
2 4.000e+04 1.766e-05 6.628e-07 89.11 91.23
3 6.000e+04 1.115e-05 4.185e-07 52.87 54.99
4 8.000e+04 1.317e-05 4.942e-07 -136.29 -134.17
5 1.000e+05 1.512e-05 5.677e-07 9.02 11.14
6 1.200e+05 1.587e-05 5.956e-07 -133.50 -131.38
7 1.400e+05 1.233e-05 4.628e-07 144.74 146.86
8 1.600e+05 1.835e-05 6.889e-07 -126.55 -124.43
9 1.800e+05 2.664e-05 1.000e-06 161.12 163.24
Total Harmonic Distortion: 0.000180% 47ohm

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 2.000e+04 2.664e+01 1.000e+00 -1.89 0.00
2 4.000e+04 1.426e-05 5.353e-07 84.29 86.18
3 6.000e+04 7.765e-06 2.915e-07 53.04 54.93
4 8.000e+04 9.577e-06 3.595e-07 -134.13 -132.24
5 1.000e+05 1.103e-05 4.139e-07 11.50 13.39
6 1.200e+05 1.156e-05 4.339e-07 -130.34 -128.45
7 1.400e+05 8.975e-06 3.369e-07 148.25 150.14
8 1.600e+05 1.339e-05 5.027e-07 -122.41 -120.52
9 1.800e+05 1.946e-05 7.304e-07 165.66 167.54
Total Harmonic Distortion: 0.000133% 22ohm

With 22ohm open loop phase margin is to small 55degree at 0dB.
With 47ohm it is 61degree, so I'll go for 47ohm.
dado
With 47ohm
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Old 21st February 2011, 03:00 PM   #13
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To get back to the same phase margin just increase your miller cap. I doubt whether there will be much change in THD performance between the 100 and the 22 ohm degeneration if the phase margin is kept the same. 61 degree is close call, you might get in trouble with some speakers but its your call, it could work but its safer aiming for around 80.
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Old 21st February 2011, 04:14 PM   #14
dadod is offline dadod  Croatia
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If I increase Miller cap (in this case two) Iam back with the same OLG at 20kHz. What do I gain in that case.
I do my own loudspeaker and try to have easy load for amp.
This project was intended for ORION loudspeker, an easy load.
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Old 10th July 2011, 05:03 PM   #15
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Now when I finished simple amp in other thread bootstrapsCCS+T-TMC I am going back to this amp with triple TT OPS.
I changed a bit in a mintime and here is a new circuit diagram.
Input stage up to predriver will be powered from separate voltage higher by 5V then output valtage. Now I can use simple clamp(D4 and D5) to prevant clipping in OPS.
I apreciate commentcs before to start practical implamentation.

This one shows simulated distortion of 0.000014% at 1W and 10kHz.
dado
Attached Images
File Type: jpg DADO-TT-TMC-3-1_015-triple-fina-sch.jpg (145.4 KB, 1053 views)
File Type: jpg DADO-TT-TMC-3-1_015-triple-FFT.jpg (210.5 KB, 990 views)
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Old 10th July 2011, 05:09 PM   #16
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Do D7 & D8 reduce the driver bias current, as the outputs warm up? Or do they increase the driver bias current?
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Old 10th July 2011, 06:05 PM   #17
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Quote:
Originally Posted by AndrewT View Post
Do D7 & D8 reduce the driver bias current, as the outputs warm up? Or do they increase the driver bias current?
I am not sure. I think that this influence is minor, but I have to simulate it, as I have not yet.
More about this diodes look at Biasing/thermal compensation of Thermal Trak transistors
dado
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Old 11th July 2011, 03:02 AM   #18
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Try this (below) , . For a EF2 -only 3 diodes (4 for triple). If over compensated , try 3 diodes , adjust the 330R. I simmed with mur320's - just about equivalant to the TT's. The 3503 is NOT thermally coupled.
PS - playin' around , I ran this just to see .... as it is a MJE/NJW OP stage is biased at exactly 75ma/.22Re with what you see. The NJL(TT), might be slightly different.

OS
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Old 11th July 2011, 07:37 AM   #19
dadod is offline dadod  Croatia
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Quote:
Originally Posted by ostripper View Post
Try this (below) , . For a EF2 -only 3 diodes (4 for triple). If over compensated , try 3 diodes , adjust the 330R. I simmed with mur320's - just about equivalant to the TT's. The 3503 is NOT thermally coupled.
PS - playin' around , I ran this just to see .... as it is a MJE/NJW OP stage is biased at exactly 75ma/.22Re with what you see. The NJL(TT), might be slightly different.

OS
Thanks OS, I tried this configuration as used in Leach amp. I bought Cordell book and after that decided to use his recommendation for bias spreader. In this case I use two TT diodes to stabilize the bias and other two to keep the impedance between drivers emitter very small. In this amp I use two TT pairs as that is more than enough for my project(amps for Orion loudspeakers).
dado
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Old 11th July 2011, 02:10 PM   #20
dadod is offline dadod  Croatia
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Why not to use convenience of the higher voltage for the imput part and not to use cascoded VAS.
Here is circuit diagram with Hawksford cascode for the VAS.
Simulated distortion:

.step level=0.088
Fourier components of V(vout)
DC component:-0.0109679

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 2.775e+00 1.000e+00 -0.75 0.00
2 2.000e+04 4.674e-08 1.684e-08 131.39 132.14
3 3.000e+04 1.078e-07 3.884e-08 111.54 112.29
4 4.000e+04 6.440e-09 2.321e-09 7.71 8.46
5 5.000e+04 2.205e-09 7.948e-10 38.68 39.42
6 6.000e+04 6.127e-09 2.208e-09 -4.10 -3.35
7 7.000e+04 6.956e-09 2.507e-09 -6.21 -5.46
8 8.000e+04 7.828e-09 2.821e-09 -4.59 -3.84
9 9.000e+04 8.796e-09 3.170e-09 -3.38 -2.63
Total Harmonic Distortion: 0.000004%

.step level=0.5
Fourier components of V(vout)
DC component:-0.0109674

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 1.577e+01 1.000e+00 -0.75 0.00
2 2.000e+04 9.157e-07 5.808e-08 53.27 54.02
3 3.000e+04 1.722e-06 1.092e-07 110.31 111.06
4 4.000e+04 8.287e-07 5.257e-08 -152.95 -152.20
5 5.000e+04 2.511e-06 1.593e-07 141.56 142.31
6 6.000e+04 5.673e-07 3.598e-08 -124.60 -123.86
7 7.000e+04 2.376e-06 1.507e-07 154.46 155.20
8 8.000e+04 1.740e-07 1.104e-08 -80.98 -80.23
9 9.000e+04 1.428e-06 9.057e-08 161.87 162.62
Total Harmonic Distortion: 0.000028%

.step level=1.3
Fourier components of V(vout)
DC component:-0.0109574

Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 4.099e+01 1.000e+00 -0.75 0.00
2 2.000e+04 1.297e-05 3.165e-07 7.47 8.22
3 3.000e+04 3.698e-05 9.022e-07 110.09 110.84
4 4.000e+04 7.739e-06 1.888e-07 -151.51 -150.77
5 5.000e+04 2.625e-05 6.404e-07 -42.79 -42.04
6 6.000e+04 2.595e-06 6.332e-08 74.68 75.43
7 7.000e+04 1.305e-05 3.184e-07 144.61 145.36
8 8.000e+04 3.457e-06 8.433e-08 -140.42 -139.67
9 9.000e+04 7.925e-07 1.933e-08 -68.20 -67.45
Total Harmonic Distortion: 0.000121%

dado
Attached Images
File Type: jpg DADO-TT-TMC-3-cascVAS-015-tripl.sch.jpg (131.8 KB, 772 views)
File Type: jpg DADO-TT-TMC-3-cassVAS-015-tripl-V.jpg (254.8 KB, 389 views)
File Type: jpg DADO-TT-TMC-3-cassVAS-015-tripl-FFT.jpg (256.2 KB, 171 views)
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