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
OK Tom, without going into every detail to the Nth degree, here's what's on my mind now:

First of all, I'm not sure I fully understand why or if it's necessarily desirable to decouple the counterweight. Or to go for lowest mass in general.

But if we assume that these are desirable goals, then why not get completely rid of the coupled mass of the counterweight? Hanging the weight off the end of the tonearm's rear extension seems like it would invite a swinging motion in response to energy inputs at the stylus, since the string can't perfectly decouple the weight. Additionally, the weight would be free to oscillate in response to spurious energy inputs to the plith as a whole, such as from loud bass notes or footfalls.

Today's post is a simpler design then in the post I deleted. End the tonearm at the pivot point, with no extension continuing behind it. Take a cue from the design of a conventional suspended-weight anti-skating arrangement. Hang a weight from a string, run it over a hanger positioned above the tonearm, and attach the string to the tonearm (moveable to fine-adjust VTF). The force of gravity pulling down on the weight now pulls up on the tonearm, offsetting the force of gravity pulling down on the tonearm/cartridge, minus the desired tracking force.

The hanger is mounted on the horizontal bearing housing, in order that there will be no lateral relative motion between the hanger and the tonearm. The hanger (and therefore the weight as well) must rotate along with the tonearm in the lateral plane so that it ignores the lateral component of the tonearm's movements. With the directly-hung counterweight described above, motions of the tonearm in both planes affect the motion of the counterweight. The counterweight 'sees' all the vectors and reacts accordingly. But with an intermediate hanger to run the string over, like is used for anti-skate, motions of the tonearm in both planes have only their vertical component transmitted to the counterweight. The counterweight 'sees' only vertical inputs, and accordingly moves strictly up and down, rather than like a pendulum.

But the counterweight might still move in response to spurious inputs. So, give it a streamlined shape and immerse it a dampening fluid bath. The trough, like the hanger and the weight, will have to ride on the horizontal bearing housing. But this might not be a bad thing, since we removed the mass of the tonearm's rear extension and attached counterweight, and we might want to bump up the tonearm's lateral mass in isolation, like you do with the HiFi mod.

Anyway, if decoupling the counterweight is what we want, then I can't think of many ways to decouple it further than this. I'm just not sure it would accomplish anything...
Hi Tom,
thanks a lot for your most clarifying post. It worked even for a dummy like myself :-). It seems I'll start looking for an available lead shaft. Thanks a lot.
Stefano
Alex, that sounds like a workable idea. Maybe you should try a mock-up of it and see how it sounds.

That's all I did. I had an idea, and tried it out to see if it worked to produce better sound for me. I'm sure that there are plenty of other improvements to be discovered, that none of us has thought of yet.

The stuff that I made is just another "stepping-stone" towards improved sound and improved design ideas in tonearms. There will be others who are spurred on to make further improvements on top of what I have done, or entirely different directions. I'm just glad to have been able to contribute something back to the hobby.

Regarding your particular design idea above, I think it is interesting to use a counterweight "lift" in front of the bearing, instead of a "see-saw" behind the bearing. This may have some interesting resonance effects, and possibly with careful implementation, could result in some resonance-reducing effects in the armtube. This would require experimentation.

I think it would be worthy of trying out to see just what you can get out of it. After all, tonearms aren't the most complex items in the world, and most of us could actually build a whole tonearm that sounds quite good, if we set our minds to it.

I enjoy seeing some other insights into the tonearm design issue, and love to see the seeds of innovations being brought to life.

Go for it.
Umm...mebbe, but I dunno. I think this one resides in the thought experiment file (along with most of my others :-) For one thing, it violates the KISS principle. For another, a string attached to the tonearm and pulled taut will have a very defined resonance, like a guitar string. But mostly, I just can't fathom why doing this would be beneficial. As opposed to your HiFi concept, which stemmed from an actual theory of its positive effect. I'd just be mucking around in the dark with no clear idea of why. This only occurred to me in response to your post about hanging counterweights, but taken to the max. If I have an opinion on this at all, it's that a conventional counterweight would probably be just as good or better in the real world. But if someone can explain to me why 'decoupling' the counterweight is ever attempted in the first place, maybe I'll change my mind and decide I could be on to something...