It's very, very difficult to make a interconnect cable that has a constant impedance across the audio range.
Probably the only company that might try is Dynaudio.
Dynaudio - Authentic Fidelity
While the link is for speaker cable, the whole idea is even more complicated for an interconnect.
Probably the only company that might try is Dynaudio.
Dynaudio - Authentic Fidelity
While the link is for speaker cable, the whole idea is even more complicated for an interconnect.
I have had fun and very good results with this project. Used both copper magnet wire and solid super fine silver. It's nice to be able fabricate to the exact minimum needed.
SoundStage! Synergizing - An Under $20 Home Brew KILLER Interconnect! (02/1998)
SoundStage! Synergizing - An Under $20 Home Brew KILLER Interconnect! (02/1998)
Actually, I was initially motivated by the OCOS report originally published by ZUMIKO. Since Alpha Core made speaker cables I was satisfied with, and compared favorably against many speaker cables, I did not find it necessary to put effort in that area.
The reason why these work is exactly due to impedance characteristics, lots of people find balanced interface better for the same reason. But lets try to keep cable discussion in the cable threads, if any is still open; these normally get too heated up.
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soongsc, I'm a little confused. My reference to the particular interconnect project is/was based on your comments about the unpredictability of impedance when considering C12 & R12.
From post #3560
"Most interconnects causes a drop like this which is why I designed my own interconnects. I doubt that anyone will hear an improvement unless the interconnect has constant impedance across the audio range even though they changed C12 & R12."
What I was suggesting - though not clearly - was having a couple of known and stable elements (The RS magnet wire due to it's availability around the globe, and the super-thin high purity silver for it's consistency) could act as a standard to use when making choices/revisions for other components. The simplicity of the tape approach eliminates a whole bucket of variables on the test bench. One's eventual choice of interconnects for their own system is of course a personal preference thing.
Does that make any sense to you?
From post #3560
"Most interconnects causes a drop like this which is why I designed my own interconnects. I doubt that anyone will hear an improvement unless the interconnect has constant impedance across the audio range even though they changed C12 & R12."
What I was suggesting - though not clearly - was having a couple of known and stable elements (The RS magnet wire due to it's availability around the globe, and the super-thin high purity silver for it's consistency) could act as a standard to use when making choices/revisions for other components. The simplicity of the tape approach eliminates a whole bucket of variables on the test bench. One's eventual choice of interconnects for their own system is of course a personal preference thing.
Does that make any sense to you?
When the impedance is not flat, the sound stage is not as precise. So whatever you do is making it sound better by blindly trying things out. Sure, it is possible to hear differences with each change, but what you end up with is just change where we think improved in certain areas, but when we start listening to a variety of music, we find that we also have degradation in some areas. My point is, regardless whether you have the interconnects fixed or not, unless you have a method of compensating the effects of such varying impedance, there will be a point where you will start going into endless variation without going anywhere. That was what I was getting into until I did a simulation that shed light on the input impedance issue. Now I am happy that is taken care of so I can move on.
Twin lines without shielding generally provides pretty little effect in input impedance shaping, that is also why the balanced interface generally is more accurate in reproduction. For unbalanced interface, the capacitance contributes to the drop of impedance at higher frequencies, generally starting around 2KHz. Now, since the MyRef input impedance also starts dropping around 2KHz, I could not maintain a flat impedance with my interconnects even if they do not contribute to the drop.
I am not saying that I am right, but it's just saying it from personal experience.
Twin lines without shielding generally provides pretty little effect in input impedance shaping, that is also why the balanced interface generally is more accurate in reproduction. For unbalanced interface, the capacitance contributes to the drop of impedance at higher frequencies, generally starting around 2KHz. Now, since the MyRef input impedance also starts dropping around 2KHz, I could not maintain a flat impedance with my interconnects even if they do not contribute to the drop.
I am not saying that I am right, but it's just saying it from personal experience.
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soongsc,
I sincerely hope you are not interpreting my comments as either a challenge or a disagreement. I don't have the technical savvy, test equipment or experience to do that. My intent is simply an attempt to understand a few baselines within your prolific and useful suggestions. My questions relate to a desire to understand which mods/changes prove to be reliable and repeatable from a development view, and those (not just yours) that are valid, though personal preferences.
No doubt the interplay between you Dario and other experimenters is interesting, fun to watch and will lead to a better sounding MyRef.
I sincerely hope you are not interpreting my comments as either a challenge or a disagreement. I don't have the technical savvy, test equipment or experience to do that. My intent is simply an attempt to understand a few baselines within your prolific and useful suggestions. My questions relate to a desire to understand which mods/changes prove to be reliable and repeatable from a development view, and those (not just yours) that are valid, though personal preferences.
No doubt the interplay between you Dario and other experimenters is interesting, fun to watch and will lead to a better sounding MyRef.
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The whole idea is to freely share experiences. I cannot say whether others experience the same with these mods, but I hope some new ideas pop up. It would be encouraging to hear whether others have the same or different experience with the same mods.
Now I have to take into consideration polarity when I listen. Some brands like Decca, EMI, DG, etc. have to be played with inverted polarity to make a more accurate evaluation for me.
I can say, that this current pump concept was what I had my mind on as a good implementation, it will beat lots of amps in the same power category.
Now I have to take into consideration polarity when I listen. Some brands like Decca, EMI, DG, etc. have to be played with inverted polarity to make a more accurate evaluation for me.
I can say, that this current pump concept was what I had my mind on as a good implementation, it will beat lots of amps in the same power category.
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How did you found this possible problem?
Measures?
According to Mauro's documentation that net limit input bandwith to 220kHz and filters hf.
He also states that this net is related with compensation network but he don't say much more.
I first discovered using simulation exploring some "what if" scenarios. When I looked at the input impedance I saw the drop. So I looked at the circuit again, and sure enough, we find that the filter to ground path impedance is dominated by the filter in the higher frequencies. I removed the C12, with C13 already removed, now the amp sounds beautiful!!! Holographic.
Currently, I am not sure what the risks are, but I have not ran into any problems. Maybe there is a way to test sensitivity to external noise?
Interesting, I'll give it a try too but I fear that C12 is necessary...
If the fc is 220kHz how can be that impedance drops in audio band?
Dario
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I'm not at all sure way interconnects are in a chip-amp thread but.
On an unbalanced interconnect rating scale of 0 to 10 these rate:
a] Heavy signal return they get a 0.
b] Interference shielding they get a 0 plus another 0 for not being a twisted pair.
c] Low capacitance they get a 10 plus.
post 3560Keven, Please see post 3560 in this thread.
Okay, I found a problem. The combination of C12 and R12 causes the input impedance to drop to less than one third of the assumed value at 20KHz. Whether you think this is a problem for you or not, please make your own judgement. In my opinion, the impedance should be as flat as possible across the audio frequency. Most interconnects causes a drop like this which is why I designed my own interconnects. I doubt that anyone will hear an improvement unless the interconnect has constant impedance across the audio range even though they changed C12 & R12.
This does not have any relevance to the above linked interconnects, as they do not have a constant impedance (or characteristic impedance) across the audio range. And even if you did manage to make interconnects with constant impedance, you still would not have a well behaved transmission line system.
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Sorry, not going into cable discussion here. But the input should have constant input impedance, or it should be designed to match whatever cables the owner uses which varies with cable make and length.
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It's easy to use an on line calculator to calculate the impedance of 220pF @ 20KHz (or whatever frequency you wish). @20KHz you get a value of something like 36K Ohm, plus 3K of R12 is 39K Ohm, parallel with 100KOhm you get even less. At low frequency, the impedance is something like 96K Ohm I believe.