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
Tom, just to clarify, what I wrote was intended to describe a tonearm having *not only* a conventional counterweight, but *also* side-weights mounted as you specify (I included the detail about bearing-axle concentricity, for instance) - *not* a counterweight with side-weights added to *it*, as it seems you may have aprehended.

Doug, thanks for making clear that you posted earlier about the idea (which I'm sure Tom must have also had from near the beginning) of making the side-weights adjustable. I've thought about this a little more, and come to the conclusion that a production tonearm with this feature would probably need both a provision for threaded-post fine adjustability, plus a small assortment - maybe three different mass values - of exchangable side-weights, to yield a practical working range of variability that's broadly compatible with cartridges of differing compliance. As far as the potential sore point of resonance at the threaded (or whatever) junction goes, I don't think this looks too bad: you already have an adjustable counterweight that's affixed to the tonearm proper, so doing something similar that's on the bearing axle - rather than directly in the tonearm 'mechanical path', such as a detachable headshell - doesn't seem overly daunting to me.
Alex,
You're right with all those ideas I think. That would make an arm very broadly compatible, especially if a couple different counterweights were also included. Then one could really tune in both vertical and lateral moving mass. Whether resonances at the threads would be a problem I don't know, but quality machining and very fine theads would help, and they'd give finer adjustability too. Maybe a Delrin female thread insert to prevent metal-to-metal contact?

Another idea I'd like to see is a VTF fine-tuning adjustment screw that threads into the back of a locked down counterweight. You could quickly add or subract a few 100ths of a gram by moving the screw in or out without having to move the C/W and remeasure. Big benefit for VTF-sensitive cartridges like Shelters. We change VTF every time the weather shifts: 1.95g in January, 1.70g now, who knows in July. The screw would be quite tiny, we do small VTF adjustments on our modded Silver with a rotating paper clip mounted on the HIFI weights.

Of course I'm never retreating from my main position: Kuzma Air Line or bust!
Speaking of what goes on behind the counterweight, that's where I would work on putting the fluid damping trough, to get the paddle farther from the pivot point than is normally possible on the platter side of things. (The Townsend trough-at-the-headshell-over-top-of-the-spinning-record design notwithstanding, which makes me nervous and seems like it would be a bit of a pain in the butt when it comes to actually playing a bunch of records, although I'm sure that it is the most effective implementation possible from a damping standpoint). So instead of having a relatively massive counterweight very close to the pivot, I'm imagining an extension of the tonearm continuing to the rear, terminating in the damping paddle, with only a relatively light counterweight needed.

I just had an intriguing thought: mightn't Tom's idea be somehow translatable to and beneficial with the Well Tempered tonearm suspension design?
Twl:
I've just looked over my OL RB 250 tonearm and I don't see where one would "press fit" the weights. There aren't any real "nuts" to press them onto. Did you remove something else on the tonearm?
Hi,
The standard RB250 has end caps which are pressed into the bearing yoke on both sides. Sometimes these are already removed. If they are still there on your arm, and you don't want to mess around with taking them out, then just apply these same principles to your application by grinding a depression in each fishing weight that approximates the curve of the brass end caps. Then glue or Blu-tac the weights right to the brass end caps, and you are ready.

Be careful to choose a fishing weight which is shaped such that it will not interfere with your cueing lever.