Do 45 RPM records need higher anti-skate setting?

While science is a good objective parameter, I suggest that trying out the skating force is the best way to determine the answer. I do not see a consensus among the posters of exactly what the science is. If one assumption is incorrect, all conclusions from that are wrong. Or you could conclude that one of the explanations of skating force is correct, and procede accordingly.

When there is a groove, the inside face restrains the stylus, so there is effectively no such force, because the arm is rotating only minimally (at less than 0.01 rpm), and the stylus has such a tiny mass, that any forces are negligible, and totally overwhelmed by the friction forces by many orders of magnitude.
J
John_gordon (Answers | This Thread)

As a layman, this would most closely resembles my experiences. Well put J.

Mmakshak,
There is actually a logical default position: namely, that given there is a skating force (which is old, proven, science, well documented, though commonly misunderstood) and which leads to VTF being different on each channel, it should be counteracted.

it is approximately between a fifth and a third of the VTF, depending on stylus profile and other factors.

Now, while it may vary subtly to some debatable extent across the record and with platter rpm, it is, as Omsed stated, always there and always towards the centre. Applying anti-skate may or may not be audible, but it is designed to compensate for something which could result in record or stylus damage, which is why 99.9% of arms have it in some form.

Users seldom use VTF below cartridge makers recommendations, because the cartridge will mistrack and even if you can't hear that mistracking it is acknowledged as being a bad thing.

However, without anti-skate, the chances are that your cartridge is running below recommended VTF on the right channel.

John

Timeltel
you said:

A pivoted arm with overhang will seek the center of a blank (ungroved) LP. Would it not move towards the spindle more rapidly if the disc were spun at 78 or 45 rpm than at 33.3?

That depends on the friction generated. All things equal, the friction would be more or less the same, as once the stylus is moving the friction (dynamic as opposed to static) is constant if nothing changes. It is is like when you try to push a heavy box. Static friction makes it hard to get started, but once it is moving it takes more or less the same effort whether it is moving slowly or quickly ). And it is the friction which supplies the force to rotate the arm.

However in any particular modulated groove, the friction changes with velocity (due to the modulation). So in the case of the OP, there may have been a particularly loud passage which indicated that the the existing anti-skate setting was inadequate.

John

1. The difference in sound between 33 and 45 has nothing to do with the amount of energy being put into the stylus or the energy in the system. It has to do with less information density on the groove. There is greater length groove per second of musical signal. Lower information density, which is storing the same information in a greater storage area/length/volume (depending on the technology) gives greater fidelity. This is true in records, tape (30ips instead of 15ips, for instance), photography (a 4" x 5" negative compared to 35mm, which is 1" x 1.5", movie film....any analog medium.

This is a huge thing, and it is why more tape run by the head, more groove length under the stylus, and greater info on a negative enlarged to the same size all yield great improvements. The record does not play louder with a 45, which it would with higher modulation, the tape does not play louder.

2. As for energy, you are mixing energies. Energy put into moving the cantiliver is the same or volume would be louder. Kinetic energy of the platter is higher, yes, but that has nothing to do with playback and has nothing to do with more energy put into the cartridge, which is not done.

But, there is more kinetic energy in the platter. You are wondering about it. Well, where it came from is the energy put into it by the motor. That kinetic energy came from the torque required to get it up to speed over the period of time of acceleration. That energy is = i(w x w) where w (omega) = rotational velocity and i is the moment of the inertia of the platter. That energy stays constant, and when the switch is turned off the energy gets bled off, turning into heat, in the bearings and motor "off torque". That amount of energy during deceleration = the amount of acceleration = the kinetic energy while the platter was turning. Thus, energy is neither created nor destroyed, but is conserved, only changing forms. Newton is satisfied. Or at least his laws are, I trust he is dis-satisfied about how much physics is twisted and mutilated in this industry!

And finally, here is the bit of wrong information on the forum John sent us to, written by a "John" on that forum.

There is no centripetal force involved, as the arm is not rotating with the record. Now, if we put the whole turntable and tonearm mechanism on a rotating sub table and rotated the subtable then the cartridge would indeed try to fly outward.

But I know of nobody spinning their ENTIRE turntable setup while playing a record, so there is not such force.

It is a great optical illusion: stylus on a rotating record, so it must fly outward! False illusion. Spin the platter faster and faster and faster and there still is no centripetal force: only the platter is spinning! There can be no such force as the velocity of the stylus/cartridge/headshell in the tangential direction is essentially zero.

Don't worry about getting this wrong, most first year physics students would. A lifetime studying and working in physics and engineering: there's no substitute for that plus the education beforehand. Nobody should feel bad about that, I do not feel bad about not knowing as much about their respective fields as my doctor and lawyer do!