That is unfortunate. I welcome your input here. I do think Andy will be totally objective. We are getting different results and are trying to establish why. I don't feel like I am being picked on by either you or Andy.
No worries, I'm leaving tomorrow for a while anyway. I would like to see some convergence of results too.
I am trying to be cooperative this time around. I very much want to know where the discrepancies occur. I am open to the possibility (some here would say certainty) that I am wrong about this. If that turns out to be the case, then it has been a learning experience for me. Is it possible that my simulation package could be that incorrect even at DC? If that is the case, then this will be great advertising for Intusoft.
It's more likely that no one is "wrong" and there is some out of bounds quirk handled in two different ways. That is where real human intervention is needed.
Here is the output stage only. I simply deleted the VGS. Some of the node numbers were changed by the program when I did this. I have always used a higher voltage regulated supply on everything but the drivers and outputs, so I have left the 40V supplies in. If you choose to use only the 34V supplies, you will need to add the connections so the front of the OPS gets voltage. This will change the measurements I posted earlier, but not much. The DC on the input is to adjust the output offset. This was done before in the VGS. The 277 ohm resistor in series with the input represents the output impedance of the VGS. I put it there to be complete, it is not needed.
Has any consensus yet been reached on this output stage or convergence of opinion yet taken place?
Andy hasn't reported back yet, if that is what you are asking. I assume he is being thorough.
Steve,
I'm having issues getting emails through to you - so, could I ask a question?
Your stage either softens the landing of output devices as they switch, OR, prevents them switching altogether, Andy's simulations may give some sort of resolution on this one. Either way, will it account for the reported lovely sound of this topology?
Have you thought much about the large, compressive non-linearities due to Vbe creep and emitter resistor losses in the formation of odd order harmonics? If these could be reduced, presumably with error correction, would not the spray of odd, high order harmonics found in almost all Class AB output stages be drastically reduced?
Hugh
I'm having issues getting emails through to you - so, could I ask a question?
Your stage either softens the landing of output devices as they switch, OR, prevents them switching altogether, Andy's simulations may give some sort of resolution on this one. Either way, will it account for the reported lovely sound of this topology?
Have you thought much about the large, compressive non-linearities due to Vbe creep and emitter resistor losses in the formation of odd order harmonics? If these could be reduced, presumably with error correction, would not the spray of odd, high order harmonics found in almost all Class AB output stages be drastically reduced?
Hugh
Hi Hugh,
First, I don't understand why you are having problems getting E-mail to me. I seem to be receiving E-mails from every one else, including those in other countries.
The difference in the perceived sound quality of my amps changed very much for the better when I changed over from the standard method of setting output bias to the method I use now. Distortion figures also improved. I think if I say more than that right now it would just be speculation on my part. Hopefully Andy will provide some answers.
Error correction, such as feedback, can (and does) reduce distortion in my amps. I built amps both ways. I prefer the NGFB sound. I did use feedback in my pro amps, and they sounded very good also. I'm not really driven to the pursuit of ever lower distortion numbers. I am happy that what I like sound wise also happens to measure fairly good. Here is the distortion numbers on the amp Andy is working on.I am content with numbers like these.
Fourier analysis for v(47):
No. Harmonics: 10, THD: 0.00248421 %, Gridsize: 200, Interpolation Degree: 1
Harmonic Frequency Magnitude Phase Norm. Mag Norm. Phase
-------- --------- --------- ----- --------- -----------
0 0 -0.12172 0 0 0
1 1000 28.2861 -0.0092264 1 0
2 2000 0.000657583 71.3428 2.32476e-005 71.3521
3 3000 0.000128306 -151.08 4.53601e-006 -151.08
4 4000 8.10099e-005 100.802 2.86395e-006 100.811
5 5000 0.000170485 -0.65197 6.02717e-006 -0.64275
6 6000 4.31291e-005 83.065 1.52474e-006 83.0742
7 7000 6.33176e-005 43.2346 2.23847e-006 43.2439
8 8000 4.00605e-005 85.5068 1.41626e-006 85.516
9 9000 4.22854e-005 76.0533 1.49492e-006 76.0625
First, I don't understand why you are having problems getting E-mail to me. I seem to be receiving E-mails from every one else, including those in other countries.
The difference in the perceived sound quality of my amps changed very much for the better when I changed over from the standard method of setting output bias to the method I use now. Distortion figures also improved. I think if I say more than that right now it would just be speculation on my part. Hopefully Andy will provide some answers.
Error correction, such as feedback, can (and does) reduce distortion in my amps. I built amps both ways. I prefer the NGFB sound. I did use feedback in my pro amps, and they sounded very good also. I'm not really driven to the pursuit of ever lower distortion numbers. I am happy that what I like sound wise also happens to measure fairly good. Here is the distortion numbers on the amp Andy is working on.I am content with numbers like these.
Fourier analysis for v(47):
No. Harmonics: 10, THD: 0.00248421 %, Gridsize: 200, Interpolation Degree: 1
Harmonic Frequency Magnitude Phase Norm. Mag Norm. Phase
-------- --------- --------- ----- --------- -----------
0 0 -0.12172 0 0 0
1 1000 28.2861 -0.0092264 1 0
2 2000 0.000657583 71.3428 2.32476e-005 71.3521
3 3000 0.000128306 -151.08 4.53601e-006 -151.08
4 4000 8.10099e-005 100.802 2.86395e-006 100.811
5 5000 0.000170485 -0.65197 6.02717e-006 -0.64275
6 6000 4.31291e-005 83.065 1.52474e-006 83.0742
7 7000 6.33176e-005 43.2346 2.23847e-006 43.2439
8 8000 4.00605e-005 85.5068 1.41626e-006 85.516
9 9000 4.22854e-005 76.0533 1.49492e-006 76.0625
Steve,
I'm confident he hasn't; he's either busy or still working on it. Andy is dedicated, I give him that.....
Hugh
I'm confident he hasn't; he's either busy or still working on it. Andy is dedicated, I give him that.....
Hugh
Hi Steve
It seems like Andy is busy with other things, so if somebody else would like to simulate the circuit I’m posting the models you are using.
Maybe you could confirm that these are the right models?
Cheers
I’m not using LTspice, so I don’t know if they will work in LTspice, but most of the simulator programs are based on the same algorithms so I see no reason why they shouldn’t work.
These are the models I’m getting when I open the”Export to Andy” file in Pspice.
BTW I have seen a lot of different models for the components you are using.
Cheers
I looked them over and they seem to be correct. Maybe someone else can give it a try. It will be interesting to see the results. I trust they will use the schematic in the screen shot I attached in post 127.
Hi stinius,
It has been 28 days since I posted the requested files. It looks like no one is going to use the models you posted, so I learned enough about LTspice to run the file Andy_C posted earlier. I have attached my results. I ran the file as posted by Andy, then just for fun, I ran it again with the bias resistor changed from Rbias to 4200 ohms. That is what the text in the lower left indicates the value Rbias is. I was not the least bit surprised to see that if you zoom in on the wave form and do the math, it appears the transistors do not turn off. That is what I have claimed all along. What does surprise me is that changing the bias resistor from Rbias to 4200 ohm changed the results. Does anyone have an explanation for why this happens?
Next I will edit Andy's schematic to the one I posted and try again. It may take me a while to do that. Please be patient.
Interesting, Steve, something of an epiphany.
Your contention all along was correct, then? The outputs never turn off?
Could it be that the simulator has problems with driving the collector of a transistor?
Hugh
Your contention all along was correct, then? The outputs never turn off?
Could it be that the simulator has problems with driving the collector of a transistor?
Hugh
That didn't take as long as I had expected. The attached file is the same schematic I posted in post 127. All resistor values are the same as in my posted schematic. I used the models that Andy included with the file he posted. The results are somewhat different from what I get with my sim program, but seem to be in my favor.
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