Hi Jason,
Thanks, I didn't notice those were wrong. Yes it runs fine now. So now I have a few questions.
1) How do you lower the output of this IPS?
2) Now that we know it runs, what changes need to be made to replace those "independent current sources" with real parts?
3) Does this look like an interesting IPS to consider for the Slewmaster?
Thanks, Terry
Thanks, I didn't notice those were wrong. Yes it runs fine now. So now I have a few questions.
1) How do you lower the output of this IPS?
2) Now that we know it runs, what changes need to be made to replace those "independent current sources" with real parts?
3) Does this look like an interesting IPS to consider for the Slewmaster?
Thanks, Terry
One of the things I'm also noticing about the IPSs is that a few things like gain, input filter corner frequency, input impedance and NFB corner frequencies are often different, even if just a little, from one another. This will make meaningful comparisons difficult. My thoughts are that so long as stability isn't compromised we standardize the gain, input filter corner frequencies, input impedances and NFB corner frequencies amongst the various IPSs.
Any thoughts or opinions for / against / indifferent?
Any thoughts or opinions for / against / indifferent?
Looks like R41 might be the place to start, though altering operational currents is likely to set off a chain of other changes in values to accommodate a lower VAS current.
There are a few options for 'real' CCSs, likely any of them will work. Which type of CCS works best for a given application may differ depending on the requirements of the circuit. I am not familiar with this circuit and so can't offer an educated opinion on the subject.
It certainly looks interesting. I'm sure we could find the unbalanced input version, I don't think we need the added complexity of a balanced input since I think most domestic users still use unbalanced sources.
Jason,
You are one of the people here that seem to have the knowledge to work out any of the problems with each of the implementations of input and output sections. I on the other hand am just observing but I am wondering since the original premise here was to compare the ultimate differences and compare the CFA and VFA against each other why you would want to try to standardize all the different versions? I would think you would want to optimize each configuration to see the real differences between the circuits. Then the real differences in bandwidth and frequency response and even final usable output could be compared. Am I wrong in my thinking or is there some reasoning that I am missing that you would want to try to match the input impedance and output? I imagine there are probably ideal conditions to match the output section but doesn't this also have to do with the feedback ratios and such that each input section requires? Just questions from a novice here so take no offense as none is meant.
You are one of the people here that seem to have the knowledge to work out any of the problems with each of the implementations of input and output sections. I on the other hand am just observing but I am wondering since the original premise here was to compare the ultimate differences and compare the CFA and VFA against each other why you would want to try to standardize all the different versions? I would think you would want to optimize each configuration to see the real differences between the circuits. Then the real differences in bandwidth and frequency response and even final usable output could be compared. Am I wrong in my thinking or is there some reasoning that I am missing that you would want to try to match the input impedance and output? I imagine there are probably ideal conditions to match the output section but doesn't this also have to do with the feedback ratios and such that each input section requires? Just questions from a novice here so take no offense as none is meant.
As for the question earlier by the poster wanting some harmonic addition to an amplifier, not something I agree with personally, couldn't the circuit with the tube hybrid input section be used to create some extra second harmonic distortion if that is something someone desired. that single ended tube distortion sound? I don't know how you do that besides driving the tube into some sort of overdriven state but perhaps one of you gurus would know how to do just that even if you agree with me that it is not something most of use want to do?
Makes sense to standardize the LP filter and input impedance. Instead of standardizing the NFB corner frequency I would standardize the phase margin - that way you are comparing the stages as they would be used normally.
Of course once you make the comparison and find the results, someone is always going to point out an improvement that will reverse the result. There's just so much you can do with any given IPS. So can we really say any one is "the" winner?
I suggest some measure of complexity also be considered. A measure of complexity may be transistor count. Add to this a penalty for each trimmer. Another measure of complexity may be labor, for instance the number of pins needing to be soldered (trimming would be considered a labor penalty).
As far as technical specs, a simulation test jig could be thrown together which would analyze many different performance indicators for the stage and combine them to make a score, as well as showing the strengths and weaknesses of each circuit. Such an overview would be more useful and less subjective than simple comparisons which tend to leave a lot of subtle aspects out.
Of course once you make the comparison and find the results, someone is always going to point out an improvement that will reverse the result. There's just so much you can do with any given IPS. So can we really say any one is "the" winner?
I suggest some measure of complexity also be considered. A measure of complexity may be transistor count. Add to this a penalty for each trimmer. Another measure of complexity may be labor, for instance the number of pins needing to be soldered (trimming would be considered a labor penalty).
As far as technical specs, a simulation test jig could be thrown together which would analyze many different performance indicators for the stage and combine them to make a score, as well as showing the strengths and weaknesses of each circuit. Such an overview would be more useful and less subjective than simple comparisons which tend to leave a lot of subtle aspects out.
The big problem with comparing these stages is that everyone disagrees on what determines the winning circuit.
One person may decide based on THD. Another person may decide based on speed regardless of THD. No one knows for sure what is the relative importance between THD and speed.
So the idea of standardizing tests in this way is flawed from the outset. It is impossible to make a standard that will be widely accepted.
That said, whether the input impedance is standardized depends on what aspect of the stages is being compared. For instance, if one stage allows a greater input impedance, that is an advantage. However if you are comparing by listening, then you want to have standardized input impedance, so that the source behaves the same for each circuit being tested. If not, then you're testing the source rather than the prototype.
So, it is really important to think about what exact test each situation requires. Before you can make any comparison, you must know what you are trying to compare. You can compare harmonic distortion, bandwidth, etc easily. Can we compare sound quality? Highly unlikely that we can widely agree on how to do that, because one has an exact electronic definition of sound quality.
One person may decide based on THD. Another person may decide based on speed regardless of THD. No one knows for sure what is the relative importance between THD and speed.
So the idea of standardizing tests in this way is flawed from the outset. It is impossible to make a standard that will be widely accepted.
That said, whether the input impedance is standardized depends on what aspect of the stages is being compared. For instance, if one stage allows a greater input impedance, that is an advantage. However if you are comparing by listening, then you want to have standardized input impedance, so that the source behaves the same for each circuit being tested. If not, then you're testing the source rather than the prototype.
So, it is really important to think about what exact test each situation requires. Before you can make any comparison, you must know what you are trying to compare. You can compare harmonic distortion, bandwidth, etc easily. Can we compare sound quality? Highly unlikely that we can widely agree on how to do that, because one has an exact electronic definition of sound quality.
Keantoken,
Because of all the differences you have just described that is one of the reasons it is so hard to understand how all these different versions can sound the same hooked up to the same source equipment. If it is indeed true that you can't hear a difference with many different sources and even different speakers then I would have to conclude that we have gone below the threshold of audibility of the human ear at some level and the discussion becomes moot. Who cares about the measured distortion at that point, it becomes just an exercise with no real meaning besides just that. At what point chasing distortion numbers becomes irrelevant I surely couldn't say. the same goes for speakers, at what point have we reached our capabilities to discern the difference? I do know I can easily hear the differences between speakers, not saying which is the best, but that they are different.
Because of all the differences you have just described that is one of the reasons it is so hard to understand how all these different versions can sound the same hooked up to the same source equipment. If it is indeed true that you can't hear a difference with many different sources and even different speakers then I would have to conclude that we have gone below the threshold of audibility of the human ear at some level and the discussion becomes moot. Who cares about the measured distortion at that point, it becomes just an exercise with no real meaning besides just that. At what point chasing distortion numbers becomes irrelevant I surely couldn't say. the same goes for speakers, at what point have we reached our capabilities to discern the difference? I do know I can easily hear the differences between speakers, not saying which is the best, but that they are different.
I think that when excellent imaging comes at no expense to practical tone, then that is an epic clue. Well it is something to strive for. Otherwise, I'd wonder what the device is for.
Hi yldouright,
You obviously have an agenda, You have been posting the same rhetoric all over the forum. Have you found anyone to agree with you yet? Maybe you should stick with guitar amps. Colorization is very acceptable there.
You obviously have an agenda, You have been posting the same rhetoric all over the forum. Have you found anyone to agree with you yet? Maybe you should stick with guitar amps. Colorization is very acceptable there.
still4given
I do have an agenda and it has a beneficial outcome for all who accept it but I am currently experiencing resistance to it. This is not necessarily a bad thing. I'd rather have my ideas emerge from the onslaught of critique than to never have them questioned. Please be aware that what you assume to be linear and colorless may be otherwise. Forced sterility is another kind of coloration.
I do have an agenda and it has a beneficial outcome for all who accept it but I am currently experiencing resistance to it. This is not necessarily a bad thing. I'd rather have my ideas emerge from the onslaught of critique than to never have them questioned. Please be aware that what you assume to be linear and colorless may be otherwise. Forced sterility is another kind of coloration.
To my thinking you can not compare in any meaningful way the original production of music to the reproduction of that same music. What I mean is that distortion such as over-driven tube amps, specific microphones with certain tonal characteristics and even effects pedals are used to make particular sounds, but you can not equate this with replaying those same sounds, you would be changing the sound reproduction following that premise. Adding any harmonic content that is not in the final finished recording is counter to everything I think we are attempting to do with SOTA electronic devices.
I'm suggesting standardization of the interface. My thoughts are if the input impedances are different between IPSs then you might derive a difference in the response depending on the source. Also, things like LP corner frequency needs to be the same to make the differences in topology show themselves, assuming they exist. I advocating a level playing field.
Thanks Jason for your explanation. Wouldn't setting the LP corner frequency the same on all the different versions do just the opposite and limit the max bandwidth that you are looking at on any that would have a wider bandwidth.
The BW on all these are absurdly high anyways, but I simply suggest making the topology the only difference. If a difference exist then it be the result of the topo and nothing else.
Okay Jason,
I was thinking that the LP filter could affect the audio bandwidth at the 20-24khz region. I guess that isn't a problem then.
I was thinking that the LP filter could affect the audio bandwidth at the 20-24khz region. I guess that isn't a problem then.
Hello,
I found this in post #29:
"On to the technical side , this EF3 is a wonderful candidate for
MJL21193/4 OP's or the insane Semitech MG9410/6330 BJT's.
IMAGINE 400-500 watts with just 3 pairs - this board was designed for it !"
Just woundering what about 5 pairs? What can you expect from this?
Thank`s
Gisle
I found this in post #29:
"On to the technical side , this EF3 is a wonderful candidate for
MJL21193/4 OP's or the insane Semitech MG9410/6330 BJT's.
IMAGINE 400-500 watts with just 3 pairs - this board was designed for it !"
Just woundering what about 5 pairs? What can you expect from this?
Thank`s
Gisle
I tried with MJL21193/4 and had some oscillation issues. I replace them with MJL4281/4302 and they work great. I haven't tried them with the +-90V that I intend to use yet. I have more boards coming and will give the MJL21193/4 another go with different compensation. I've never even see the Semitechs yet. I'd like to try them some day.
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