Upgrade from TW Acustic Raven AC-3 to what?

Dover, what are the specifics of the motor and speed control? Low or high torque? AC or DC?

Dertonarm, Lewm, Dover,

I have been pondering the technical aspects behind TT speed stability in a qualitative way. I think there might be situations where mass plays an important role. I tend to think about this as AC vs DC, low vs high torque, low vs high platter Inertia (driven by mass). I tend to bracket in the following fashion:

1) Optimum

a) low torque, high platter inertia, AC
b) low torque, high platter inertia, DC

2) Moderately optimum
a) high torque, high platter inertia, AC
b) high torque, high platter inertia, DC

3) Not so optimum

c) high torque, low platter inertia, AC
d) high torque, low platter inertia, DC
e) low torque, low platter inertia, AC
f) low torque, low platter inertia, DC

What I’m basically trying to say is that a high mass platter may be able to “ride out” or sustain small speed instabilities introduced by either the motor or drag from the stylus/record interface.

I wonder if a high torque motor combined with a low enough platter mass begins to dominate speed instability in case there are speed instabilities in the motor. In other words, the platter inertia may not be high enough to dampen this effect if the motor torque is the dominant factor.

I would think that the low or high torque options with low mass option may be the worst.

I also wonder about AC vs DC motors. I heard that while AC motors are constant speed, DC motors are actually constant torque.

Any thoughts on these questions?

Dertonarm

You make a very interesting point which may help explain some observations I had with a previous system.

In a way I was thinking about low torque as a way of minimizing a motor speed instability on the platter. I think you are right that some wanted belt slippage would accomplish the same thing. Possibly better.

Couple of comments. Would the belt slippage concept work the same with a DC motor? If these are constant tourque, would the motor try try to compensate for slippage and therefore lose speed? Whereas an AC motor being constant speed would not change pulley speed if the friction changed due to slippage.

Any thoughts?

The recent threads suggest that maybe the way to segment this better might be in the following camps:

1) Strong coupling to platter and strong control of plater speed

The direct drives would fall into this camp. As would most belt drives that have strong connection to the platter.

I would think that either low or high mass platters can fall into this category with high mass being better.

Either low or high torque with higher torque being better when trying to control a high mass platter with belt.

Either DC or AC with speed stability playing the more important parameter independent of motor type.

I would also think platters with purpisely hgiher friction bearings or eddy-brakes would have to fall into this category.

2) Loose-coupling to platter, use of platter inertia to maintain stability

This would need to be a string-based drive with enough slippage. Obviosuly, direct drives would not be present since there is direct motor coupling to platter.

I would think you would need to use an AC motor or the like since it is a constant speed device and would not change spindel speed if there is slippage.

I'm not sure if torque would matter for an AC motor.

I think one would defintely need the high platter mass in this case to maximize platter inertia.

I would think that a more freely spinning, "friction-less" platter would be better than something that is helb back by a large bearing friction or eddy-brake. But then maybe a certain amount would be okay?

Anyway, would seem that the number of turntables in camp two is smaller. Forsell? Acoustic Signature? Platine? Custom units?

Andrew

Allectiong

The Raven-AC-1 that i have been using over the last few years is an incredibly engaging TT.this is a result of its neutrality and ability to manifest the micro and macrodynamics of the music. it really is a neutral table and chances are you are hearing something that is not optimum.

Try relooking at your cartridge vtf and vta, vtf being a huge factor. Sounds like you may on the high side. Your tonearm may be to low. Try playing with vta.

Try placing record directly on the platter. You may be hearing resonances introduced by a mat. Make sure you compensate for vta if the thixkness of the mat is large.

As dgad mentions, optimize azimuth and anti skate.

Try experimenting with all these parameters. These have major impacts on the sound.

I was lsitening to my system friday and was amazed at how easily the Raven AC allows the music to come through once everything is as optimum as possible. Lightnin hopkins, john lee hooker,sonny/brownie, muddy where right there. The energy they were puttin down was NOT lost by the Raven ac-1.

You will get a lot of suggestions. Start with the basics. Make broad adjustments to understand the ramifications of the range of settings. Then fine tune. I dont think the table is the issue; however you may want to try one motor. Also, make sure you have the new motor controller. Big improvement.

Pardon me if you are seasoned in these matters and you have tried all of this.

Andrew

Another way to look at this is the following. If the
table did really have the signature you are describing, then you would tend to hear that to a large extent independent of changing some of the other tonearm/cartridge and system parameters. Well you might say that through "system synergy" you might be able to strike the right balance. In this case, if you were correct in the TW signature (which I don't think you are) you would have to get an oppositely colored piece of equipment to compensate for this. I don't think that would be wise.

The table is a lot more neutral than you think.

Based on some of Raul's points, I have been experimenting with platter mat. in fact, no mat at all. Try this and you will be surpirsed. also try lowering your VTF. My guess is you are too high.

I get very dynamic, open sound with detailed and extended bass without any overhang or sluggishness. I can easily get what you're hearing by using a mat, too high VTF and tow low SRA.

Happy experimenting.

Not sure if there is a specific recommendation on mat type or need for it in the first place. I have tried the millenium mat extensively as well as the boston audio. My ears tell me no mat is better than either of these two.

I am now wondering if increasing the copper platter thickness by using one of those copper mats would be even better.

Andrew