scott wurcer said:
Of course. But then think how many other things can affect an amp phase/amplitude response before reaching the DA level. A 1% variation in a frequency compensation capacitor is four orders of magnitude over what (maybe!) DA can do. Is this common sense, or what?
Hi,
This is off topic. So sorry.. but..
Theres a lot of really good analogue guys participating in this thread now (you know who you are 😉 ), I try and follow some of the concepts but most of its over my head.
Where do you pick up such good understanding of analogue principals? I know that degree level is not a scratch on the knowledge being exchanged here.
I ask because im doing an MSc in analogue and digital IC design soon with the hope I can begin to design amplifiers afterwards but if im missing somthing id like to know!
Sorry again for the off topic question, please continue with the excellent banter 🙂 .
This is off topic. So sorry.. but..
Theres a lot of really good analogue guys participating in this thread now (you know who you are 😉 ), I try and follow some of the concepts but most of its over my head.
Where do you pick up such good understanding of analogue principals? I know that degree level is not a scratch on the knowledge being exchanged here.
I ask because im doing an MSc in analogue and digital IC design soon with the hope I can begin to design amplifiers afterwards but if im missing somthing id like to know!
Sorry again for the off topic question, please continue with the excellent banter 🙂 .
Capacitor test you can do at home.
I mentioned this before but here’s a little picture as an example. The trick is to use the two outputs of a soundcard 90 degrees out of phase to drive an RC network. If you do the complex math you will see that the fundamental nulls. At the bottom I show a portion of a frequency sweep using a 1.21K resistor and a .1uF cap showing the null point. Then putting in a sinewave at the null frequency you can gain up the residual quite a bit. The distortion shown is a comparison between a .1uF EAO film cap and a bad ceramic cap. This test maximizes (guessing here a little) the distortion since it is at the RC time constant. You would have to do a little work to calibrate the actual levels and THD.
MJL21193 – Does this explain it?
I mentioned this before but here’s a little picture as an example. The trick is to use the two outputs of a soundcard 90 degrees out of phase to drive an RC network. If you do the complex math you will see that the fundamental nulls. At the bottom I show a portion of a frequency sweep using a 1.21K resistor and a .1uF cap showing the null point. Then putting in a sinewave at the null frequency you can gain up the residual quite a bit. The distortion shown is a comparison between a .1uF EAO film cap and a bad ceramic cap. This test maximizes (guessing here a little) the distortion since it is at the RC time constant. You would have to do a little work to calibrate the actual levels and THD.
MJL21193 – Does this explain it?
Attachments
As they say: 'You can lead an engineer to the references, but you can't make him see the connection' or some such. 
IF one looks at the asymmetrical waveform example in the link provided on asymmetric voices and their modification, one sees a test waveform that looks almost entirely like the waveform that we use for testing caps for DA. Why do we use such a waveform? Because it brings out the EFFECTS of DA to the maximum, AND it also resembles human speech, at least on occasion.
Please remember that we test only ONE CAP at a time, yet .1-10% deviation is possible. Think what 10 caps of the same DA might do to effect the signal! Even the all-pass filters used for fixing asymmetry for broadcast contain a series of caps. What happens if those caps are made of high DA material?
Nonlinearity is actually a slightly different matter. Random speculation and hearsay will give inconclusive answers. We have already done the work, decades ago (as usual) [on our own personal time, I might add] and published it somewhere in one of these tedious papers that we keep referring to.
For example, adding DC bias to tantalum (electrolytic) caps IMPROVES their non-linear distortion, big-time. However, adding DC bias to aluminum electrolytic caps doesn't change much, usually. Hi K ceramics are ALWAYS lousy. From the get-go! Why waste your time trying to 'improve' them? There are generally better alternatives.
Maybe, for a rocket to Mars, ceramic might be necessary, but your home hi fi? No, I don't think so.
IF one looks at the asymmetrical waveform example in the link provided on asymmetric voices and their modification, one sees a test waveform that looks almost entirely like the waveform that we use for testing caps for DA. Why do we use such a waveform? Because it brings out the EFFECTS of DA to the maximum, AND it also resembles human speech, at least on occasion.
Please remember that we test only ONE CAP at a time, yet .1-10% deviation is possible. Think what 10 caps of the same DA might do to effect the signal! Even the all-pass filters used for fixing asymmetry for broadcast contain a series of caps. What happens if those caps are made of high DA material?
Nonlinearity is actually a slightly different matter. Random speculation and hearsay will give inconclusive answers. We have already done the work, decades ago (as usual) [on our own personal time, I might add] and published it somewhere in one of these tedious papers that we keep referring to.
For example, adding DC bias to tantalum (electrolytic) caps IMPROVES their non-linear distortion, big-time. However, adding DC bias to aluminum electrolytic caps doesn't change much, usually. Hi K ceramics are ALWAYS lousy. From the get-go! Why waste your time trying to 'improve' them? There are generally better alternatives.
Maybe, for a rocket to Mars, ceramic might be necessary, but your home hi fi? No, I don't think so.
FrankWW said:
FrankWWW;
without mechanical deformations they would not exis at all. Nor audiophiles.
john curl said:
Should I ignore being contacted directly, John? Should I start from an elementary physics?
Or do you mean my comment about DC and asymmetry?
Please clarify.
Please don't take it personally, just keep to the subject, and if you have a question that only I can answer, why not call me? Rather than guess my intention.
john curl said:
Don't take it personally, but your comment about my sloppy comment sounds sloppy that's why I've asked you to clarify. Instead of sloppy comments you could call me and ask what did I mean commenting "sloppy". I don't understand which comment was sloppy, and what do you want me to explain in details what I may see as an obvious thing. I don't guess your intentions, I ask to clarify directly. May I?
OK, Wavebourn. First, the reason that we use asymmetrical test signals is because they are generated by the human voice and other musical sources, and pass through the electronics that precedes the loudspeakers. Each time an otherwise 'perfect cap' except for DA, passes a signal, there is a tendency to modify the path of the electronic signal from .1 to 10% for EACH CAP in series with the signal. The loudspeaker not passing DC has nothing to do with it. This confuses others.
I have been asked to PROVE that asymmetry exists in music and speech. I think that this has been proven successfully, because it is addressed by the communications industry as important.
Next, Walt Jung, Scott Wurcer, and I have measured the effect of what happens when you put a single high DA cap in the audio path.
This has NOTHING to do with diffraction, DC in speakers, or anything else, except what we have measured. Going off on those tangents, strays from the target of why we are concerned about DA in CAPACITORS when making the best high fidelity equipment that we can possibly make.
Personally, I have removed MOST series caps from the audio path in my designs. That is practical and useful, in the last few decades. Before, in the past, it was not so easy, for a number of reasons. I will leave it to the readers to figure this out.
In any case I would like the debate to come to some sort of completion, if possible.
I have been asked to PROVE that asymmetry exists in music and speech. I think that this has been proven successfully, because it is addressed by the communications industry as important.
Next, Walt Jung, Scott Wurcer, and I have measured the effect of what happens when you put a single high DA cap in the audio path.
This has NOTHING to do with diffraction, DC in speakers, or anything else, except what we have measured. Going off on those tangents, strays from the target of why we are concerned about DA in CAPACITORS when making the best high fidelity equipment that we can possibly make.
Personally, I have removed MOST series caps from the audio path in my designs. That is practical and useful, in the last few decades. Before, in the past, it was not so easy, for a number of reasons. I will leave it to the readers to figure this out.
In any case I would like the debate to come to some sort of completion, if possible.
Asymmetry of musical signals means required headroom. Effective and peak powers are very different. We need low distortions on all signal levels of all frequencies we amplify, even if it seems to be insane to have minimal distortions on full power for 30 KHz. That's the point in assymmetry.
RC - networks are acting like filters, RC networks with capacitors that have DA are acting like more complex filter networks, but if the cap has high DA, but low dependence of capacitance on voltage, current, and frequency, it does not cause more of non-linear distortions than an equal capacitor with less DA. But DA often indicates also high non-linearities of capacitor, this is another story. Filtering alters shape of the signal on oscilloscope, but it does not mean non-linear distortions.
For me personally big DA is suspicious because I did not investigate all available on market capacitors, so stick with what works for me well, and use them accordingly.
However, if some boss strictly commands me to use the certain topology only selecting best parts for it I will conduct such an investigation, but while I am my own boss and free in topology variations I don't care too much about capacitors: the best available transistors are potentially more harmful than caps, so topology matters for me much more.
RC - networks are acting like filters, RC networks with capacitors that have DA are acting like more complex filter networks, but if the cap has high DA, but low dependence of capacitance on voltage, current, and frequency, it does not cause more of non-linear distortions than an equal capacitor with less DA. But DA often indicates also high non-linearities of capacitor, this is another story. Filtering alters shape of the signal on oscilloscope, but it does not mean non-linear distortions.
For me personally big DA is suspicious because I did not investigate all available on market capacitors, so stick with what works for me well, and use them accordingly.
However, if some boss strictly commands me to use the certain topology only selecting best parts for it I will conduct such an investigation, but while I am my own boss and free in topology variations I don't care too much about capacitors: the best available transistors are potentially more harmful than caps, so topology matters for me much more.
Actually, high DA in caps might be WHY your electronics sounds so GOOD to you. DA in caps creates a 'forgiving' sound. Unfortunately, I like to make an 'accurate' sound, except for TV reproduction.
Iron, Fe, magnetic metal
Horror!
I found that the pins who sits at the bottom on tubes are M A G N E T I C, they are made of iron, can it be possible that the small tiny signals from a magnetic pick up have to stand this.
It is really Ok! a small virgin flute signal in IRON, many tubes and a lot of iron pins in a amplifier.
I have read a lot in this thread and understand that iron is totaly forbidden in the art of making audio electronics.
Or can it be so that iron is good for audio
😱
Horror!
I found that the pins who sits at the bottom on tubes are M A G N E T I C, they are made of iron, can it be possible that the small tiny signals from a magnetic pick up have to stand this.
It is really Ok! a small virgin flute signal in IRON, many tubes and a lot of iron pins in a amplifier.
I have read a lot in this thread and understand that iron is totaly forbidden in the art of making audio electronics.
Or can it be so that iron is good for audio
😱
Iron seems to be an issue, when magnetics are involved.
I recently had an eye opener in this regard.
When placed next to a hefty air-core inductor, long steel legs of resistors seems to pick up just about anything besides radio Moscow.
Magura 🙂
I recently had an eye opener in this regard.
When placed next to a hefty air-core inductor, long steel legs of resistors seems to pick up just about anything besides radio Moscow.
Magura 🙂
john curl said:
My electronic sound so GOOD to me and to those who heard it because I am free to optimize everything, from topology to construction, without religious following by beliefs what and how should be used.
I don't understand what "forgiving sound" means; I understand "forgiving listeners" who believes that "PA have to sound like any PA".
My PA systems tend to sound as if they don't exist, this is my goal. When after concerts sitting around the table I switch on the record people often get confused, where the singer is speaking, sitting here with us, or staying there on the stage, so close it sounds. Or, does somebody play piano right now, or is it the record.
Craig405 said:
Hi Craig
Sorry to see that none of the “big shots”😉 are answering your post.
Cut to the bone, it takes a lot of years and practise to learn these things.
I’m sure that a lot of people in here are willing to share their knowledge if you contact them by email.
Craig405 said:
This is a really tough one. One suggestion is to try to find someone local and offer to do some light tech work in exchange for an explaination of the circuits. Make sure you respect their work and what they have accomplished.
Even the top universities are giving traditional analog design short schriff.
stinius said:
The real BS is when for magazine reviews people conduct double blind tests so no comparisons with the real sound are available, only personal preferences matter.
Another BS is, when some performers say, "I can't sing because I don't hear myself". That means, they don't want to satisfy listeners, they want to satisfy themselves hearing their own voice distorted by PA like they used to. If I can't convince them I give them a personal dynamic microphone and a stage monitor, for self-satisfaction. In such case I can't tell that my system sounds good: it sounds as if a microphone distorts, proximity effect presents, and monitor's distortions go around.
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