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, 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.
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.
The problems with the design of the Dynavector tonearm are twofold. First, the short end of the arm that is attatched to the vertical bearing causes a much greater change in VTA/SRA when tracking less than flat records. The other problem is the seperate resonance points in the vertical and horizontal planes. The vertical resonance, in particular, is somewhat higher than in a conventional arm due to the reduced mass of the vertically moving part of the arm. With certain cartridges this can cause resonance problems within the audible range.
Viridian, I agree. They were onto something, but the execution, while being a complex beautifully made machine, lacks certain important things and includes problems, that were not needed. I am sure that my mod is not perfect, but it is a simpler solution than the Dynavector, and does not introduce as many problems as the 507 does. As of this time, I am not noticing any audible problems with the horizontal mass/resonance change. In fact, the sound overall is just great.
Twl, your inquisitive and experimental interest in the hobby is so reminiscent of the 1960s and 70s. The gear was not so well made back then; more art than science, or, some might say, the perfect balance of art and science. All audiophiles had to constantly experiment with intriguing ideas like your own. The sport was much more participatory back then. We even built kits on occasion. The hands-on aspect of the hobby has been largely lost. Computer, home theatre, work, kids, all vying for time. The manufacturers producing the product-of-the-month. Squeezing the soul out of the gear. No wonder we are having a hard time attracting more enthusiasts. I am glad that we still have people like you in the game. It makes it all worthwhile.
Marty