i haven't left to go home, but i built this file so folks could keep playing.
after making sure you include the correct location for the Cordell-Models.txt file, i think this will run with no errors.
i don't have any of the models that OS (or whoever made the OPS file originally) used, so I changed all semis to something from the cordell models list.
good luck
(heh, heh)
mlloyd1
after making sure you include the correct location for the Cordell-Models.txt file, i think this will run with no errors.
i don't have any of the models that OS (or whoever made the OPS file originally) used, so I changed all semis to something from the cordell models list.
good luck
(heh, heh)
mlloyd1
It could just as easily be said that a cold, clinical representation is another form of 'coloration'. Any graphic artist will tell you an over sharpened or 'etched out' image looks unnatural and so it goes with sound. A straight wire with gain is more elusive than the words indicate. Defined does not necessarily mean accurate and sometimes we need more THD to make the sound more 'real'.
That is a choice you have to make for yourself. To my knowledge, that is not what this task was about. Sounds like you are looking for ASKA. They are all about coloring the tone. The goal with the Slewmaster was speed, low THD and accuracy. Reproducing what the recording engineer produced. They use as accurate an amp as they can find.
I cleaned it up a it and got it to run. Not great but it runs. Here is the error message.
Starting Gmin stepping
Gmin = 10
Gmin = 1.07374
Gmin = 0.115292
Gmin = 0.0123794
Gmin = 0.00132923
Gmin = 0.000142725
Gmin = 1.5325e-005
Gmin = 1.6455e-006
Gmin = 1.76685e-007
Gmin = 1.89714e-008
Gmin = 2.03704e-009
Gmin = 2.18725e-010
Gmin = 2.34854e-011
Gmin = 2.52173e-012
Gmin = 2.70769e-013
Gmin = 0
Gmin stepping succeeded in finding the operating point.
N-Period=8
Fourier components of V(vout)
DC component:0.00522343
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 2.484e+01 1.000e+00 -0.90° 0.00°
2 2.000e+04 6.271e-04 2.525e-05 86.12° 87.02°
3 3.000e+04 8.410e-04 3.386e-05 106.35° 107.24°
4 4.000e+04 4.795e-04 1.931e-05 72.45° 73.35°
5 5.000e+04 5.802e-04 2.336e-05 110.94° 111.84°
6 6.000e+04 4.173e-04 1.680e-05 116.42° 117.31°
7 7.000e+04 7.192e-04 2.895e-05 109.47° 110.36°
8 8.000e+04 4.532e-04 1.825e-05 103.43° 104.32°
9 9.000e+04 7.617e-04 3.067e-05 118.99° 119.88°
10 1.000e+05 4.580e-04 1.844e-05 107.90° 108.79°
11 1.100e+05 9.043e-04 3.641e-05 120.30° 121.20°
12 1.200e+05 4.142e-04 1.668e-05 118.87° 119.76°
13 1.300e+05 8.299e-04 3.341e-05 123.81° 124.71°
14 1.400e+05 3.063e-04 1.233e-05 105.70° 106.60°
15 1.500e+05 8.228e-04 3.313e-05 131.69° 132.58°
16 1.600e+05 3.663e-04 1.475e-05 96.18° 97.08°
17 1.700e+05 8.023e-04 3.230e-05 122.38° 123.28°
18 1.800e+05 5.014e-04 2.019e-05 107.01° 107.91°
19 1.900e+05 8.338e-04 3.357e-05 123.09° 123.99°
Total Harmonic Distortion: 0.011045%
Date: Thu Aug 14 16:18:48 2014
Total elapsed time: 56.726 seconds.
tnom = 27
temp = 27
method = modified trap
totiter = 475044
traniter = 474549
tranpoints = 132400
accept = 91456
rejected = 40944
matrix size = 172
fillins = 290
solver = Normal
Thread vector: 76.2/35.6[3] 27.4/18.4[3] 7.0/4.7[3] 2.9/2.8[1] 2592/500
Matrix Compiler1: 31.5 KB object code size 17.7/9.3/[6.3]
Matrix Compiler2: 21.0 KB object code size 36.1/8.6/[5.0]
That's something the musicians and their instruments should take care of, not an amplifier. Please, stay on topic and don't try to redefine the task of an amplifier.
Edmond Stuart
I don't see how a broader discussion on what we perceive as accurate is off-topic. You can 'sharpen' a generated tone or group of tones past their wave in nature so that the sharpening itself becomes the inaccuracy. We are making some possibly faulty assumptions when we only use tone generators and the reproduction of those images as our standard. Electrical slew is a very dubious predictor of good PRAT. The linearity of the slew effect or more specifically, the curve of the slew effect seems to be more important in reproducing 'accurate' PRAT. If you accept this premise, it is not hard to imagine a musical playback introducing accents and emotions that were not in the original piece. These accents may be pleasing and possibly deemed to be 'better', even by the musicians who played the piece but may not be accurate. I'm just trying to better define what we accept as accurate when we compare.
I don't see how a broader discussion on what we perceive as accurate is off-topic. You can 'sharpen' a generated tone or group of tones past their wave in nature so that the sharpening itself becomes the inaccuracy. We are making some possibly faulty assumptions when we only use tone generators and the reproduction of those images as our standard. Electrical slew is a very dubious predictor of good PRAT. The linearity of the slew effect or more specifically, the curve of the slew effect seems to be more important in reproducing 'accurate' PRAT. If you accept this premise, it is not hard to imagine a musical playback introducing accents and emotions that were not in the original piece. These accents may be pleasing and possibly deemed to be 'better', even by the musicians who played the piece but may not be accurate. I'm just trying to better define what we accept as accurate when we compare.
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Try to think about what mean "playback", real sense of this word. To add "something" is not playback.
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At slewing all the transistors in an amp are jammed in an anarchic mayhem that often only slightly correlates with the amp's behavior at audio. IE an amp that slews badly can behave during normal use the same as one that slews well. An amp that slews well can even have a bad actual step response.
If step response correlates to sound then why overdo it by jamming the transistors into operating points far away from what they're in when you're actually listening?
To measure the most relevant step response you need to do a small-signal step response, IE 100mVpp or less at the output of the amplifier. This will reflect how the amplifier actually responds to audio signals. A more advanced test is to add this test tone to a LF sine wave so you can zoom in on the step response at different output voltages - you will see that it can change alarmingly at excursions.
Also, consider that in cases where designers entirely neglect the small-signal step response, the large-signal step response can show a smooth square wave even if the small-signal step response shows overshoot or ringing on the edge! Yes, slewing can actually hide bad behavior. So it's important to use a test that's relevant for the conditions in which the circuit will be used.
If step response correlates to sound then why overdo it by jamming the transistors into operating points far away from what they're in when you're actually listening?
To measure the most relevant step response you need to do a small-signal step response, IE 100mVpp or less at the output of the amplifier. This will reflect how the amplifier actually responds to audio signals. A more advanced test is to add this test tone to a LF sine wave so you can zoom in on the step response at different output voltages - you will see that it can change alarmingly at excursions.
Also, consider that in cases where designers entirely neglect the small-signal step response, the large-signal step response can show a smooth square wave even if the small-signal step response shows overshoot or ringing on the edge! Yes, slewing can actually hide bad behavior. So it's important to use a test that's relevant for the conditions in which the circuit will be used.
Edmond Stuart, BV
Agreed. The problem is how we recognize and measure the spectral content and that is what prompted my initial post.
keantoken
Thank you. Too many people neglect what goes on behind what they measure.
Agreed. The problem is how we recognize and measure the spectral content and that is what prompted my initial post.
keantoken
Thank you. Too many people neglect what goes on behind what they measure.
Fully agree. An amplifier must be as "transparent" as possible. Maintaining this transparency despite "unwanted" external factors - like "difficult" complex loads, for example. Taking low power at the input, giving high power at the output. Nothing more than that.
Some people like "colored" sound - I'm not one of them.
2-nd harmonic, at the level up to -70db, in some cases sounds cool. This is the only exception I can allow 🙂
All the other unwanted spectral components - especially odd ones and especially higher order ones - must be as low as possible. Including inter-modulation "products"...
All the rest must be taken care of by the audio engineers, producing the recording 😉
P.S. Wrote it at the same time with the previous post 🙂
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Unless you have a perfect acoustic space and perfect reproduction chain including perfect speakers I say bring back tone controls. Something to simply correct for imbalances in the system, not to change the music. A parametric equalizer could be used by someone who has the knowledge to use that without causing a worsening of the sound field. I would never consider a 1/3 octave device due to the known phase shift that any of those units are shown to create. I don't think we should be looking for our amplifiers to add tone by themselves whether that is from a SS or Tube amplifier producing euphonic second harmonic distortion or any other type of sound shaping.
I think that most on this site have far superior speakers than I have.
Given the complete audio chain from source to ears,
How can transparency of an amplifier equate to transparency of the audio from source to your ears in your listening environment?
btw, I'm looking for a stereo tone control with volume preamp 🙂
Reagrds
Given the complete audio chain from source to ears,
How can transparency of an amplifier equate to transparency of the audio from source to your ears in your listening environment?
btw, I'm looking for a stereo tone control with volume preamp 🙂
Reagrds
It does not equate, but ensures that at least this link of the chain (amplifier) does not bring in too many unwanted parasitic spectra components 😉
Hi,
The above affect can also be shown in comparing a 1W and a full power freq response test. usually - if no input filtering is used during the test of the amp-- you will often see the full power FR (Freq Response) BW is less. This leads to the affect you see with SQ waves.
If you limit the BW at the input to that of the full power BW, there will be no change seen in SQ Waves at different levels. [You will also be hard pressed to drive the amp into slew rate limiting]
THx-RNMarsh
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I just gave your file a spin (changed the OPS VBE BD139's for the Cordell models) and it went through its simulation in a few seconds. Didn't seem slow to me, nor were there any errors in the log. Mind you the OPS bias is some absurd value like 700+mA per pair! Likely because the output of the front end is about double the current the SM OPS expects to see.
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