The biggest disadvantage of supporting the shaft to fix the singing arm is that the stylus is always in the tracking error. Except that the stylus reaches a certain point in the middle of the record or two points on the outer ring (4.76 inches) and the inner ring (2.6 inches), whether one or two zero error points will be obtained depends on the design of the compensation angle of the singing arm. Contrary to the fixed singing arm supporting the shaft, the biggest advantage of the tangent singing arm is that there is no tracking error at all if it is properly adjusted.
Why is there a tracking error in the fixed arm of the support shaft?
In fact, this is not a question of adjustment. When engraving a record, the engraving machine just walks in sideways. In other words, its forward route is a tangent drawn along the axis passing through the turntable. The forward trajectory of the fixed singing arm supporting the shaft is to draw an arc. You can see what the problem is without my further explanation.
Since the tangent singing arm is similar to the engraving machine, why not produce the tangent singing arm from the beginning?
Tangent singing arm is ideal. However, the manufacturing technology of tangent singing arm is very high, which is not well done by ordinary factories. Therefore, everyone still walks in the direction of supporting the shaft to fix the singing arm, which is easy to produce.
What is the difficulty in the manufacturing technology of tangent singing arm?
First of all, how do you get the tangent singing arm to walk in sideways? Just use the spot. The question is how much force does the motor need to pull the singing arm? If you pull it faster than the stylus moves in the groove, the whole stylus arm will be crooked. What about pulling slowly? It is also crooked. As we all know, once it is crooked, it means that the needle tip is crooked in the groove. In this way, even the tangent singing arm is different from the fixed singing arm supporting the shaft? In addition, when the motor pulls the singing arm, there must be vibration transmitted to the singing arm. Vibration is the enemy of the singing arm, so it is better to fix the singing arm with a support shaft without power. Third, the tangent singing arm must be set on a "beam" (just like an overpass) and walk from the outside to the inside. How to solve the friction between this beam and the singing arm itself?
Is there no way to solve the above three problems?
Many problems can be solved as long as the singing arm is not in direct contact with the beam. Therefore, there will be an air-bearing tangent singing arm. Instead of any power, let the singing arm drive the singing arm by the self-propelled power of the stylus in the groove. Unfortunately, air flotation will also have problems such as uniform air pressure, air vibration and dust affecting air flotation. Moreover, Mr. Souther's unpowered tangent singing arm also has the friction problem between the slide rail and pulley on that crane (which looks like a small crane). In short, if there is one good thing, there will be no two good things.
So, isn't it wrong for everyone to choose this and that?
Before you make a choice, you must first understand the crux of the problems of these two kinds of singing arms, and then make a choice according to your own needs. If you are very concerned about the tracking error and think that there must be an error-free tangent to stand it, then of course you should choose the tangent singing arm. If you don't care so much about the tangent of the whole process, but pay attention to simplicity and easy tuning, you should choose the fixed singing arm of supporting shaft.
What's the difference between straight arm, S-arm and J-arm? Honestly, it makes no difference.
One moment the S-shape was popular, and the other moment it was all straight. After a while, J-type will be popular again. In fact, no matter what shape these arms are, the most important thing is the angle formed by the front end of the arms and the arms. This angle is called the offset angle. What exactly should we compensate? Compensate the tracking error caused by drawing an arc. If there is no proper compensation angle, the tracking error of the supporting shaft fixed singing arm will be greater. Because there must be a compensation angle, there will be S and J arm tubes. As for the straight arm tube? Its compensation angle is located on the top cover.
The shape of the arm tube has nothing to do with sound. What about the length of the arm tube?
The length of the arm tube is directly related to the sound quality. The longer the arm tube is, the slower the curvature of the arc will be and the smaller the tracking error will be. If the arm tube is infinitely long, in fact, the arc looks like a straight line if it takes a certain section. Of course, because the singing arm is mounted on the turntable, the length of the arm tube will be limited. Generally speaking, the standard arm is about 9 inches long (this is the origin of SME's famous 3009 series). There are also a few as long as 12 inch (30 12). If it is longer than 12 inch, I'm afraid there will be other problems.
Does the material of the arm tube affect the sound?
Yes! Generally, the arm tube is made of aluminum alloy. The more advanced arm tube is made of aluminum-magnesium alloy and even titanium alloy (Pluto singing arm). Previously, Japan's Audiocraft also introduced wooden and bamboo arm tubes. No matter what material the arm tube is made of, the key points are light and hard, high rigidity and low vibration influence. As long as these requirements can be met, it is a good arm tube.
Is there a difference between light and heavy singing arms?
Yes For example, SME3009S in Britain is the representative of light weight singing arm, and SAEC and FR in Japan are the representatives of heavy weight singing arm. The weight of the singing arm does not refer to the weight of the whole singing arm, but to the effective quality of the singing arm. What is the effective quality of singing arm? It's a long story, because it should be explained from the moment of inertia. Explain the moment of inertia, and non-mechanical readers may fall asleep. In a word, the effective mass of the singing arm is not used for weighing, but used to calculate the * * * vibration frequency of the whole singing arm after the singing head is connected to the singing arm together with the dynamic compliance of the singing head.
Why do you want to know the * * * vibration frequency?
This involves the collocation of singing head and singing arm. Simply put, if the head and arm are not properly matched, the vibration frequency of the whole arm will appear within the audible range of the human ear, which will seriously cause sound pollution. Generally speaking, at least the * * * vibration frequency of the singing arm should be suppressed below 15Hz. Of course, if the correct and effective mass of the singing arm and the dynamic amplitude of the singing head are known, the approximate vibration frequency can be calculated by mathematical formula. Generally speaking, the dynamic compliance of dynamic singing head is very low, so it is necessary to balance the quality of singing arm. However, the dynamic compliance of the moving head is very high, so it is necessary to match the lightweight singing arm.
Is the bearing of the singing arm important?
Very important. If the friction of the bearing is too large, it will hinder the tracking of the stylus. If the bearing is too loose, it is easily affected by vibration. In fact, friction and vibration have always been a big problem of singing arm bearings. You can imagine how tiny the vibration of the needle tip is in the groove. Once the bearing is affected by excessive friction and vibration, how much damage will be caused to the authenticity of the sound! In addition, the movement of the whole singing arm on the record can be regarded as a rotating object with axis. The most important thing for a rotating object is real balance, otherwise it will produce vibration. You might as well associate this rotation with the rotation of the car wheels, ceiling fans and engines, so that it is easy to understand the importance of this matter.
So, what kind of bearing will be better?
Theoretically speaking, precision ball bearing is the most commonly used bearing for fixing the singing arm in the supporting shaft. Because it can reach a compromise point with the closest and least friction at the same time. The contact area of unipolar bearing is small, but it is too loose. The double-knife bearing is too loose to be improved, but it is too heavy. Single point bearings (some oil seals) are flexible but unstable. There is also a needle-tip bearing that can resist in four directions. It can have the flexibility of a single-point bearing without instability, but there are still problems of friction and balance. Of course, the oil tank bearing singing arm is not a traditional bearing, but it still inevitably has problems of balance and vibration.
Is it important to avoid vibration between the singing arm and the turntable?
There are two theories here. There is a theory that there should be anti-vibration material between the singing arm seat and the turntable. There is also a theory that the arm seat and the turntable should be tightly locked together, and there should be no anti-vibration material inside. People who hold the first theory think that the less external vibration the singing arm receives, the better; People who hold the second view think that external vibration is inevitable, and vibration should be introduced into a heavier turntable by closely connecting the turntable. I also have my reasons. Where is my reason? I don't think the key point is whether it is shock-proof, but whether the singing arm can be locked on the turntable "flat and stable" You know, if the whole singing arm is locked unevenly during installation, it is useless for you to adjust it again. Furthermore, if the singing arm is locked on the soft anti-vibration material, it is equivalent to losing the stable support of the whole singing arm, and no one knows what it will be like.
Which is better, the integrated singing arm or the detachable singing arm?
It is a big project to disassemble and assemble the singing head every time the singing arm is integrally formed. Some cheaper integrated singing arms really don't know how to adjust their orientation. However, when it comes to detachable singing headgear, it is also full of complaints. At least readjust the orientation every time it is dismantled. Of course, from the perspective of "reliable" penetration, I would rather choose an integrated singing arm. If your requirements are not high, you'd better choose a detachable singer.
What about the static balance and dynamic balance of the singing arm?
The so-called static and dynamic refers to the way of giving pressure to the needle. Usually, a heavy hammer with a rotatable position at the end is used to balance the singing arm, and needle pressure is applied at the same time, which is called static balance. If the pressure at the tip of the singing arm is purely spring or magnetic, regardless of the balance at both ends of the supporting shaft, we call it dynamic balance. The problem of static balance is that when the singing arm meets an uneven record and swings up and down, its needle pressure changes at any time. The problem of dynamic balance lies in the accuracy and durability of acupuncture pressure. Later, someone put forward the idea of semi-dynamic. In other words, it is necessary to balance the two ends of the singing arm with a heavy hammer first, and then apply acupuncture pressure with a more precise spring or magnetic force. To be honest, I never thought about whether this really solved the problem. In my experience, although static balance often changes acupuncture pressure, it is still the most natural and stable way to apply acupuncture pressure.
Air bearing turntable and air bearing singing arm are popular. Does that make sense?
That makes sense! Let's start with friction. Because the turntable or singing arm is supported by air, there is basically no friction. Let's talk about shock absorption first. Because the air blocks the vibration from the floor, its vibration is much lower than that of the traditional singing arm and turntable. Basically, the problem with air flotation is: 1. How to maintain a stable air pressure? How to keep pores clean? Third, how to avoid the vibration of the turntable and the singing arm caused by the high-pressure airflow. Fortunately, these problems have been solved. To get a stable air pressure, we just need to design several air storage tanks and let them supply gas smoothly. Air holes should be clean and not blocked, and air filtering devices should be installed, which can also be solved by requiring users to be diligent in through holes. In order to avoid the vibration of airflow, some people use low pressure and large airflow to reduce the impact of airflow; Others increase the mass of the singing arm to resist the airflow. So far, I haven't seen any air-floating singing arm or air-floating turntable. They are all very expensive products. In other words, if you want to have a good voice, you have to spend money. In fact, I think there are many people who have the money to buy air-floating singing arms and discs, but not many people really know how to tune them. According to my experience, it is not the more expensive singing arm that will bring you a higher sense of accomplishment. On the contrary, sometimes you will feel depressed because you adapt to the problem. So when you buy a singing arm, don't pay too much attention to its design and manufacturing theory, because every designer will tell a great truth. You should first evaluate what kind of singing arm you really need. Such as easy to adjust? Still have to adjust the complexity; Is it tangent? Still need to be fixed on the support shaft. Is it cheap and good? Still have to represent identity. If you are a music pragmatist, I even think that the cheap Rega 300B is enough to impress you.