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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
twl OP
3,251 posts
 
Thanks, Zaikesman. I agree that with the low bearing friction, there may be some movement allowed with the mass system. I cannot say that absolutely no lateral movement is present over the groove. But I can definitely say that it is much reduced, because of the results of greater dynamics, crisper detail, and bass I got with it. I may not even have the best ratio, because I did not try a bunch of different weights. But by luck, I got a pretty good result on my first try.

I have thought of making the weight on a threaded shaft, so it could be adjusted for distance from the pivot. This would complicate the prototype, but production would be just as easy. You may have caused a price increase :^). It would certainly be more applicable to a wider range of cartridges with a system like that. But the spread would have to be equal on both sides, or you'll be changing the anti-skate force.

What type of arm are you using, Zaikesman? If you have a way to fix these weights onto your arm, I could send you a set for evaluation on your TT. I know that they easily go onto a Rega arm. I would like to get some feedback on this. I am already sending a set to Nrchy, who has a Rega RB900. And if Basement wants some to try out on his RB300, he can have some too. They don't cost much, I just get them at the fishing store. If you think you could somehow get them onto whatever type of arm you've got, just email me your address, and I'll send a set to you.

By the way, I think that there is a sort of "mass threshold". As an example, if I am lifting weights, and I keep increasing the weight, at some point I won't be able to lift it. The static moment of inertia will be too high for me to overcome. That is the "threshold" that I am looking for with this system. If the mass is higher than the cartridge can overcome with its suspension, then the theoretical infinite mass can be approximated. As long as the arm can still move freely to track the groove spiral. Since the spiral tracking occurs over a long arc, the low friction of the bearing should allow this to occur, but on the quick dynamic spikes of the groove info, this mass should be sufficient to virtually eliminate arm deflection, if the mass is calculated correctly. Do you agree with this hypothesis?
twl OP
3,251 posts
 
Basement, I wish my eyes were as good as yours. Now that I'm over 45, I can't see up close anymore.

About the off-center records, I don't really see this as a problem, because the mass increase is easily moved during the long arc of an off-center record. The shortest arc that it could have to navigate would be 180 degrees, because the hole is only off-center in one direction from the center. That means that the record will start to move one way for 180 degrees, and start moving back for 180 degrees. On the outside of the LP, if there was 1/8" off-center, the stylus would have to adjust only 1/8" over 19 inches of groove travel(the circumference of a record is about 38 inches). This could hardly be called a rapid movement. The low bearing friction could easily handle this. And 1/8" off-center is a hell of a lot. I personally would not even play a record that bad. None of my records are even close to that far off. I do have some warps though.

Adressing your statement about the "speed of the cantilever", the cantilever is designed to operate at the speeds and distances it will encounter in the RIAA curve that is encoded into the groove. These parameters are known and designed-for by the cartridge makers. I see no way that a well-designed cartridge will be caused to mis-track by the proper orientation of the arm over the groove. If you are saying that the damping or horizontal mass increase will cause the arm not to properly track the off-center record, I have already covered that topic. It can track the off-center record. If the record is so far off-center that a damped arm cannot track it, then that record is junk. I cannot consider items like that in my design. A high-performance Ferrari suspension is not made for going "off road". We have to assume at least a decent level of record quality. I will accept the loss of some defective records, in the pursuit of improving the sound of 99.9% of my collection. The slightly off-center records are not affected by this design.

On the next issue, I agree with all 3 of your points regarding increased mass on tonearms. The problem with cantilever breakage on ET arms is generally attributed to the TT not being level. With the low friction air bearing and the lack of anti-skate on linear arms, leveling is crucial on these arms. The other cause of breakage was the "Groove guard" ridge, that caused a rapid accelleration of the stylus into the lead-in groove, as it slid down the side of the "Groove guard" ridge. This is why many recommended the starting of play after the first groove into the first song, with these arms. Fluid damping reduced these hazards. These are cases of "runaway, out of control mass" as we talked about in the previous posts. On pivot arms, this is less problematic since there is usually higher bearing friction in these, as well as an anti-skating mechanism. However the "Groove guard" can be a pain in the ass, at times.

Continuing to address your points. The use of fluid damping in addition to horizontal mass increase is not out of the question. It may be a good combination for reasons previously stated. I have not tried it yet. I have already addressed that I don't think that there is any possibility of damaging the cantilever with any of these systems. We want the cantilever to move as much as needed to retrieve the info off the record, and no more. If the cantilever is stiff enough to not bend under these stresses(no cantilever should bend), then these methods of keeping the cartridge centered should only help matters. It is the mass of the arm moving away from groove-center that may damage the cantilever. None of these systems allow the cartridge to move off groove center, even on off-center records, as previously stated. The entire purpose of these mods is to keep the cartridge groove-centered in all circumstances. I really don't follow your point of saying that these mods will cause/allow the opposite of their intended purpose. They do not impede the long slow movement of the arm during tracing of the groove spiral, or even off-center records. They only stablize the cart/arm during quick movements of the stylus, particularly during dynamic bass activity. If you are seeing your cantilever moving sideways because of an off-center record, then your cartridge is too high compliance for your arm. Or your records are really bad. What kind of cartridge are you using? This may be the reason why you had dead sound when you increased the mass. If you have a med-high compliance cart, your arm may already have enough mass to provide stabilization. If you can see your cantilever moving off groove-center, then something is drastically wrong.

Regarding your last sentence, I am not promoting the idea of preventing the arm from moving with the groove spiral. I want it to move with the groove spiral. I just want the arm/cart to remain centered over the groove while it is moving with the groove spiral. This is the aim and purpose of my mod. Remaining centered with the groove, and still being able to move enough to trace the spiral, is not a mutually exclusive combination. It can do both, and do it quite well. And it does not carry with it any greater danger of breaking the cantilever.

I wanted to offer you some of my weights to put on your RB300, but now I'm not sure if your cartridge can handle them with the records you are playing. Tell us what cartridge you have. If I think you can benefit from these, you are welcome to them. I am a little concerned right now that you might be over-weighted as it is now.
zaikesman
3,017 posts
 
Time to go watch "The Sopranos", so I'm being brief. Basement & Twl, my TT/arm was mentioned above (OK, way above), but it is a garden variety Technics SL-1200 with its stock arm. Also as mentioned before, the damper will be from KAB, and it is specifically designed for the Technics (the KAB website has some interesting stuff - check it out). FWIW, the arm is about 11-12g, I believe, which is supposed to mate fine with my B-M Glider M2. If you are familiar with this design, Twl (and who isn't?), you will know that there is no way a weight could be attached to the left side of the horizontal axle, because the sideways-U shaped bracket that fixes the upper vertical bearing is in the way. I'll have to get back to you on the other stuff after the show. :-)
twl OP
3,251 posts
 
KAB is a pretty cool site. That fluid damper rig looks like it will work fine, and it looks real "factory" like. Very clean and professional. It seems to me that they are primarily promoting a vertical damping, but it appears from the photo that the paddle can be rotated to provide a lateral damping effect. I expect that this will make an improvement in sound quality on your 1200. Let us know. I am sending a set of these weights to Nrchy tomorrow, so we can get some feedback on how they work on his Sota/RB900 system. He's got a Benz Glider with a 15cu compliance, so we'll see how this works with a medium compliance cartridge on a Rega arm.
zaikesman
3,017 posts
 
You know, it's been so long since I took a look at the KAB site, I guess I forgot which plane the damping operates in. Considering that the grooves are actually cut at a 45 degree angle, I would suppose that a little of both horizontal and vertical damping would be a good idea (which ties in well with my idealized theoretical above). I'll make a point of asking Kevin at KAB about this aspect.

As far as the threshold hypothesis goes, I can't agree with your analogy about lifting a weight. Weight is not the issue here, mass is. If the weight you couldn't lift was floating in space, and you attempted to push it away from you, you would move both move in opposite directions, according to your respective masses. In theory, when you or I jump up in the air, our push-off sends Earth moving infitesimally in the other direction; there is no real threshold - a practical one, yes, but no absolute one. Or to put another spin (sorry again) on it, if the arm was really so massive that the cantilever's suspension couldn't overcome its mass to move it when transcribing a groove modulation, then it also couldn't move it across the record as it played - the suspension would just keep deflecting until something gave way. If a force applied at the stylus can move the arm at all, then it can move the arm period.
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