Ageev S. Should the amplifier have a low output impedance? (ABOUT REDUCING INTERMODULATION DISTORTION AND SOUNDS IN SPEAKERS)
- Radio, 1997 Должен ли УМЗЧ иметь малое выходное сопротивление?
- Radio, 1997 Должен ли УМЗЧ иметь малое выходное сопротивление?
Radio Magazine 12 issue 2002 ?????? ????? 12 ????? 2002 ???. ????????????
amplifier (UMZCH) WITH ADJUSTABLE OUTPUT RESISTANCE
A. MASLOV, Zhukovsky, Moscow Region
I am more and more convinced by my own amateur radio experience of the correctness of the provisions of article [1] on the dependence of the nature of sound ("tube" or "transistor") on the operation of the UMZCH - loudspeaker system. The sound features of the speakers are not connected at all with the UMZCH element base and not with the presence or absence of the OOS, but to a large extent with its (UMZCH) output impedance, so I will share the results of my research.
After many experiments with transistor UMZCH (with various feedback [2] and without it at all), each time comparing the sound with the "standard" in the form of UMZCH tube radio "VEF-Radio" (one-touch, pentode, with an ultra-linear lamp on and shallow overall environmental protection), I came to the following conclusion. The generally accepted opinion about the favorable low (preferably "zero" or even negative) output impedance of the UMZCH for reproducing low frequencies is not always true. If the output impedance of the amplifier (UMZCH) is approximately 20 ... 50% of the speaker impedance (you can’t talk about deep damping), the soft sound of double bass in jazz is more pleasant (of course, purely subjective). On the other hand, listening to rock, modern electronic music with up-and-coming bass requires stronger loudspeaker damping. There is a funny situation when for each style of music it is desirable to have its own UMZCH: for jazz - tube and without general OOS are better, for rock - transistor with deep OOS in voltage (OOSN), which provides low output impedance.
In this regard, I propose a device tested on a model that "reconciles" this contradiction. The adjustable output impedance of the UMZCH allows you to smoothly transform the transistor amplifier into a “tube triode” or “pentode” amplifier without OOS, but without a characteristic third harmonic coefficient for pentodes. This conversion of UMZCH is possible with the help of variable resistors, which convert the OOS by voltage to OOS by current through the load at a constant transmission coefficient of the device.
The layout of the UMZCH is shown in Fig. 1. Adjustment of the output resistance is as follows: in the lowest extreme position of the engines of the dual variable resistors R4.1, R4.2, only OOSH occurs, the depth of which is determined by the ratio of the resistors R3, R1 and the initial gain DA1 without OOS. In the other extreme position of the motors, the variable resistors create only OOS for current (OOS). At the same time, depending on the load resistance (4 or 8 Ohms), the switch SA1, which changes the resistance of the current sensor (R5, R6), closes or opens.
amplifier (UMZCH) WITH ADJUSTABLE OUTPUT RESISTANCE
A. MASLOV, Zhukovsky, Moscow Region
I am more and more convinced by my own amateur radio experience of the correctness of the provisions of article [1] on the dependence of the nature of sound ("tube" or "transistor") on the operation of the UMZCH - loudspeaker system. The sound features of the speakers are not connected at all with the UMZCH element base and not with the presence or absence of the OOS, but to a large extent with its (UMZCH) output impedance, so I will share the results of my research.
After many experiments with transistor UMZCH (with various feedback [2] and without it at all), each time comparing the sound with the "standard" in the form of UMZCH tube radio "VEF-Radio" (one-touch, pentode, with an ultra-linear lamp on and shallow overall environmental protection), I came to the following conclusion. The generally accepted opinion about the favorable low (preferably "zero" or even negative) output impedance of the UMZCH for reproducing low frequencies is not always true. If the output impedance of the amplifier (UMZCH) is approximately 20 ... 50% of the speaker impedance (you can’t talk about deep damping), the soft sound of double bass in jazz is more pleasant (of course, purely subjective). On the other hand, listening to rock, modern electronic music with up-and-coming bass requires stronger loudspeaker damping. There is a funny situation when for each style of music it is desirable to have its own UMZCH: for jazz - tube and without general OOS are better, for rock - transistor with deep OOS in voltage (OOSN), which provides low output impedance.
In this regard, I propose a device tested on a model that "reconciles" this contradiction. The adjustable output impedance of the UMZCH allows you to smoothly transform the transistor amplifier into a “tube triode” or “pentode” amplifier without OOS, but without a characteristic third harmonic coefficient for pentodes. This conversion of UMZCH is possible with the help of variable resistors, which convert the OOS by voltage to OOS by current through the load at a constant transmission coefficient of the device.
The layout of the UMZCH is shown in Fig. 1. Adjustment of the output resistance is as follows: in the lowest extreme position of the engines of the dual variable resistors R4.1, R4.2, only OOSH occurs, the depth of which is determined by the ratio of the resistors R3, R1 and the initial gain DA1 without OOS. In the other extreme position of the motors, the variable resistors create only OOS for current (OOS). At the same time, depending on the load resistance (4 or 8 Ohms), the switch SA1, which changes the resistance of the current sensor (R5, R6), closes or opens.
It seems that you are not aware of the fact that the speaker impedance is in series with the cable impedance.
Being rude and just denying everything doesn’t change this.
Hans
Stop talking nonsense about me, think about yourself. You reported an eardrum rupture with amplifiers and speakers.
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I saw a funny quote the other day:
"Knowledge is like butter - the less you have the more you spread" 😀
"Knowledge is like butter - the less you have the more you spread" 😀
Regardless of the merits of this analysis, we already had measured results where the distortion figures at both ends of the various cables were dependent on the cables if the load was an actual moving coil speaker, while the influence of the cables was mainly insignificant for a resistive load:
https://www.eetimes.com/loudspeakers-effects-of-amplifiers-and-cables-part-5/
It seems that rudeness is your trademark, isn’t it.
You won’t convince the world with your far fetched opinions that way.
Hans
Nothing here to eliminate simple R/L/C effects and EMI incursion all known engineering. I also didn't see any measurements of the amplifiers with the speakers as close as possible.
What is being claimed here is the cable makes the distortion rather than the amplifier and the speaker. There are plenty of amplifiers that are poorer in driving complex loads and rejecting EMI. If a certain cable makes an amplifier oscillate which one is the cause?
In the discussion here as far as I can tell the amplifier has been depicted by the little triangle in the figure, an ideal voltage source. By that I mean the original figure explaining the Aurex circuit, the amplifier is ideal and the cable is depicted by a resistor. The speaker creates the non-linearity the non-linear current does not make the resistor non-linear nor does it change the non-linearity. Maybe there is some language barrier but this basic statement is wrong (certainly at the 0.01 Ohm level).
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At least it was not from me. Please show me a quote.
Even non-linear current through a line resistor always causes a voltage drop. And according to Ohm's law, this voltage drop will be non-linear. From this Japanese scheme, everything has long been clear since the 80s. Therefore, I did not understand all kinds of strange explanations that cables never affect anything. Like my friends, I and those who work in a studio in California are obviously just a deaf and Russian mafia. By the way, one of them, the Russian mafioso, worked for the U.S. Navy, the other published several books about amplifiers back in 1975, including on tubes, and the third is constantly published in specialized magazines and shows his audio equipment at exhibitions. ,
What I read fully confirms my conclusion and opinion, even that it is necessary to use shielded speaker cables. And Mr. Van den Hoole is of the same opinion.
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I was responding to your assertion:
"....The distortion measured at the output of the amplifier remains 0.03%..."
as it seems to be contradicted by the measurement Newell & Holland are writing about.
The measurements at the output (i.e. the amplifier end of the cable) showed different IMD products if the load wasn't a (mainly) resistive load but a moving coil loudspeaker load instead.
The distortion products are different not only in dependence of the load but of the cables used as well.
Of course additional experiments are needed to sort out the effects.
Sure, but must be placed in the proper context. When the back-emf current is nonlinear then the speaker is already distorting heavily and then the microscopic additional contribution of the cable I-V transformation is irrelevant. Actually, higher impedance (of cable+amp) help reducing current distortion and most often this reduces acoustical distortion.
I think that there is a very complicated mutual relationship, and no one has said anything about the inductance of the cable and its capacity.
I agree, that’s what I tried to say in #3977 that the contribution of the cable for this I/V effect is insignificant.
However I’m not saying that cables can’t make a difference, but most if not all explanations given so far are just BS.
Hans
You see what’s the matter when people have an audio system for $ 10,000 or more and it still doesn’t sound right ....😉
As I said I was speaking to the provided example where there is no assumption that the amplifier's performance varies with load. The possibility exists that there are amplifiers that are not effected, the article did not survey enough amplifiers to make any conclusions.
And in the studios too. Some branded amplifiers and speakers are too expensive to throw away. better buy a cable.
Hi guys. I don't post often, but I try to read as much as I can. So, I have no doubt that various cables can sound different. The various variables are very varied. Connector quality, connector-to-conductor quality, conductors, conductor spacing and style, on and on.
What I'd like to bring to the table is this: Even though they may sound different, which one is more accurate? There is clearly a mindset which says that more expensive cables don't just sound different (and different from each other), they sound "better" than less expensive cables. Obviously, this "more $=better" is a common theme across most products and services in virtually every aspect of our lives.
So, which one(s) more accurately conducts the signal from point A to point B? How can we determine this? Does it make a difference as to what pieces of equipment are at each end of the cable?
Now we get into the original signal. What is that signal supposed to sound like? Take a trumpet sound for example. What room was it recorded in? What microphone was used? what electronics were in the recording chain? What speakers were used to master the recording? Let's not even get into the playback chain! And, let's not worry about minutiae about the differences in sound from one trumpet brand or model or player's mouthpiece to another - they all sound the same - LOL.
So, this raises an important, if not critical, question: How do we know if cable A is "better" or "worse" than cable B?
If cable A costs $20, and cable B costs $3,000, and they sound different, which one is more accurate?
What I'd like to bring to the table is this: Even though they may sound different, which one is more accurate? There is clearly a mindset which says that more expensive cables don't just sound different (and different from each other), they sound "better" than less expensive cables. Obviously, this "more $=better" is a common theme across most products and services in virtually every aspect of our lives.
So, which one(s) more accurately conducts the signal from point A to point B? How can we determine this? Does it make a difference as to what pieces of equipment are at each end of the cable?
Now we get into the original signal. What is that signal supposed to sound like? Take a trumpet sound for example. What room was it recorded in? What microphone was used? what electronics were in the recording chain? What speakers were used to master the recording? Let's not even get into the playback chain! And, let's not worry about minutiae about the differences in sound from one trumpet brand or model or player's mouthpiece to another - they all sound the same - LOL.
So, this raises an important, if not critical, question: How do we know if cable A is "better" or "worse" than cable B?
If cable A costs $20, and cable B costs $3,000, and they sound different, which one is more accurate?