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Strange Tonearm Tweak. Long

As you all know, I am a little different. I like to read and study stuff like tonearm technology. I noticed that some of the better unipivot designs have employed "outrigger" style outboard weighting systems on their arms, that work like a tightrope-walker's balance pole. This not only balances azimuth, but also gives the arm better stability to lateral deflections from the cartridge suspension, so the arm is not moved when the stylus is pushed laterally by the groove information. I began to think on this, and I wondered why no gimbal-bearing arm makers are doing this. Surely since the vertical plane rides on a vertical axis bearing, there is still some chance for the arm to be laterally deflected by the stylus, when the stylus should be doing all of the moving, not the arm. I think that this is why they use heavy arms, but a heavy arm in the vertical movement plane is not good for tracking. A heavy arm in the horizontal movement plane is good for resisting sideways deflection that would impair pickup function.

So I decided to try increasing the mass of my tonearm in the lateral plane, while keeping it light in the vertical plane, by the use of "outrigger" weights, just like a unipivot does.

I bought lead fishing weights that looked like long rifle bullets(just the lead part) They were about an inch long and about 3/8" diameter, and weighed 12 grams each. I drilled into the bases about 1/4" and press-fitted them onto the nuts that hold the arm into the bearing yoke, so they stuck out straight sideways, like sideways spikes. This put the weight out pretty far to the sides as outriggers, and kept the weight centered exactly around the bearing pivot axis so it did not increase the vertical mass significantly, but it did very slightly. It did not influence the tracking force at all.

So now the arm had outrigger stabilizers on it in the horizontal plane of motion.

I put on a record and sat down to listen. Let me tell you, fellas, this was a mind blower. I have never heard this much information come out of a cartridge before. I heard sounds on records that I had listened to for 30 years, and never knew those sounds were on the record! And I have had some pretty good analog gear in my time. And what I didn't own, I heard at the audio store I worked at. This is the most astounding mod I have ever heard on a tonearm. And it cost me $1.49 for the fishing weights, and I got 3 extras.

The only slightly negative thing about it, is that it increases the anti-skating force, so you have to cut that back a little, and if you have some marginal scratches that might skip, they are more likely to skip with this mod, due to the resistance to sideways movement provided by the outriggers. I had this happen once last night, but I didn't consider it a problem.

But the increase in dynamics, and detail and overall sound quality is astronomical. It blew me away.

I have a DL103, which is a very stiff cartridge, and it may be that this is not needed for a higher compliance cart. But, I think that it would be good for anything that is medium or lower in compliance.

The key to it, is that it only increases the resistance to sideways movement, without interfering with the effective mass of the arm, or the vertical swing movement that needs to stay light to track warps. I played some warped records with this mod, and they played just as well as without the mod, except they sounded better.

I have a pretty good analog setup now, but I can say without reservation, that this mod made my rig sound better than any analog rig that I have ever heard in my life. I have never heard a Rockport.

Stabilizing the arm against unwanted lateral deflection increases the information retrieval and dynamics by a very large percentage. If your arm is not set up like a Rega style arm, then you can glue a 1 ounce long rod across the top of the bearing housing(sideways) like a tightrope-walker's balance pole. Use lead if you can, it won't ring. You don't have to do any permanent changes to your arm that might wreck its resale value to try this out. If it has anywhere near the effect on your system as it had on mine, you won't be taking it off.

It may come close to the movement of your cueing lever, so make sure you have clearance to use it. Mine was close, and I have to come in from the side now to use the lever, at the end of a record. That is fine with me! This was a major, major improvement in the sound of my rig. It is staying permanently. As in "forever".

If you are a little tweak-oriented, and not afraid to do stuff like this. You should try it. It will knock you over.
twl
zaikesman
3,017 posts
 
Basement, all tonearms already incorporate a greater vertical than horizontal resistance into their design (that is to say, beyond the biaxially uniform effective mass of the tonearm/cartridge combo itself) - the Vertical Tracking Force (VTF). Exactly how that tracking force should be calibrated is dictated by the cartridge's suspension compliance (and I would surmise cantilever length/effective tip mass), and is specified for all cart's. Correct VTF achieves the proper balancing act of allowing the stylus to accurately transcribe the vertical accelation of the grooves, while permitting the arm to respond to warps in the playing surface of the record. If you think about it, during set up of a typical tonearm, first the arm with installed cartridge is precisely balanced out by adjusting the counterweight to find the zero VTF calibration point, and then the tracking force is applied by moving the counterweight toward the pivot. Since gravity only affects the arm in the vertical plane, while the VTF is increasing, the amount of inertial mass resistance in the horizontal plane is actually slightly decreasing at the same time, as the counterweight is moved in toward the bearing center. Twl's idea adds back that leveraged mass and more, but keeps it out of the vertical plane of motion.

It would be interesting to know whether there is actually an optimum amount of resistance that should be applied in the horizontal plane, where performance would begin to suffer beyond that point, or whether more is always better up to the practical limits of the bearings, the anti-skating, the cantilever suspension, and the vinyl itself. One easy guess for a safe bet would be to add a calculated effective mass equivalent to 2X the tracking force (1X to bring the horizontal inertial resistance back up to what it was at the VTF zero point, 1X more to bring it up to equal the applied VTF point), since you already know the cart suspension can handle that. But looking at the massivity of the aforementioned Dynavector arm (the vast majority of which appears to pivot only in the horizontal plane), it seems as if it might be safe to add horizontal effective mass orders of magnitude greater than the VTF. (I suppose this is a determination that must be accounted for in linear tracking arm designs? I'm not personally familiar with any of these, but it seems to me that by the end of an LP's worth of play, a lot more mass will have been moved through a much greater distance than with a conventional tonearm.)
twl OP
3,251 posts
 
Zaikesman, I think you are on the right track for calculating the proper mass, but I would throw something else into the mix. The added weight in the case of my modification is at the pivot point. The stylus deflection is occuring about 9 1/2" away, out on the end of the tonearm. This distance causes the force vector to be increased dramatically by the leverage involved. Therefore the weight increase at the pivot must be far greater than equal to the lateral deflection at the stylus. This is the reason that I used long weights, that stick out an inch from each side. I am using the leverage factor to increase moment of inertia on my outriggers, just as the leverage factor increases the moment of inertia of the stylus, with respect to the pivot point. Since the tonearm is about 9 times longer than my outriggers, the outriggers must weigh more to compensate for this distance. In order to have a 1 to 1 ratio of outrigger weight to stylus force, you would have to have outriggers with a weight, in my case, of 2.75 grams(1.375 each)plus the effective mass of the tonearm. If the effective mass of these were the same as the tonearm (11 grams)+ the weight(1.375 grams x 2) then the total mass of each outrigger would be 6.875 grams, or a total weight of 13.75 grams. The lead weights are 12.25 grams each. About 90%. I didn't include the cartridge weight or equal the distance, but I did get the weight 1" outboard of the bearing yoke, so that helped alot, and used the materials at hand. And since there are 2 outriggers, my effective horizontal mass increase is at least 24.5 grams(plus the 1" width increase on each side). This is almost double(180%) the combined tonearm mass and stylus force. So when you add the existing tonearm mass(which also provides lateral stability), there is nearly an effective tripling(280%) of the horizontal stabilization. In addition, since the outriggers are equal weight and equidistant from the pivot, they are inherently counterbalanced. And they add no vertical mass. It may be possible to fine tune this even better, since I did no fine tuning at all. I just put them on, and voila! It worked so well that I didn't need/want to fuss around with it.
twl OP
3,251 posts
 
Basement, what Zaikesman said about the Vertical Tracking Force is true. However, increase in vertical resistance(mass/inertia) is also bad. The light weight of the arm in the vertical plane ensures good tracking on warped albums. If vertical mass is increased significantly, the arm will leave contact with the groove when it encounters a warp, due to the upward inertia imparted by the warp. Once the high mass is set into motion, it will continue to fly upward by momentum, and leave contact. This is bad. A small increase at the pivot area is not significant in this regard, though. In the case of my Origin Live Silver Tonearm, the bearings are relocated into the yoke, and the weights on my arm do rotate with the axle. This does make a very small increase in the vertical moving mass of my arm. Being that the weights are small diameter, the actual increase in vertical moment of inertia is small. If I had used large diameter discs instead of small shafts, the increase in vertical inertia would have been significant. This is not a good idea in the case of the OL arms. Use the bullet shaped shafts to minimize this. Also using discs would have ruined the advantage of moving the weight as far outboard as possible. The idea is to get the weight as wide as possible, since this increases the moment of inertia(resistance) by a multiplication factor. This allow the use of less weight, and gives a higher factor of resistance. If you make it too wide though, it gets in the way of everything and could get snagged off during use. This one inch long weight seemed like a good size.

You really need to start doing something with your arm. You have a diamond in-the-rough there and it would greatly reward you if you modded it. If you start with the OL end stub and the Heavyweight, you would really be getting somewhere. Be careful to not damage the bearings when you are removing and installing the end stubs. Don't apply any torque to the bearings! Isolate the bearings by holding the arm tube between the pivot and the end stub.
zaikesman
3,017 posts
 
Twl, what you figured out is what I was actually attempting to suggest - hence my description, "...calculated effective mass equivalent..." referenced to the tracking force itself, which is of course measured out at the stylus tip. I wasn't intending to include the arm's mass in the total increase, since it's already there, just to suppose that an increase in the horizontal plane inertial resistance equivalent at the stylus tip to that represented by the applied VTF in the vertical plane would be eminently safe. But again, as probably evidenced by the Dynavector design or a linear tracker, an increase far beyond this, such as you seem to have done, certainly appears to be OK.
twl OP
3,251 posts
 
I went to the Dynavector web page, and read the info on the 507, and it was very interesting. They had a very good description of why a tonearm should have high lateral mass and low vertical mass. It is notable that the way record grooves are recorded, the bass information is almost totally lateral in deflection, and are the largest movements for the stylus to trace. This makes the stylus more likely to move the arm laterally away from the center of the groove, thereby losing bass information and dynamics. The Dynavector web site describes the need for greatly increased mass in the lateral plane. This seems to be the major reason for their design of the 507. They called it "bi-axis" design. It appears that my mod gives similar results without having to change the tonearm. If the tonearm is already light enough in the vertical plane for good warp tracking, then all that is needed is to increase the lateral moment of inertia, through this weighted outrigger modification.
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