2. analog
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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
 
Doug, I thought about making the weights threaded for adjustability, but finally decided that it left too much to chance. Also, any threaded pieces will set up resonance points at the joints, unless very securely locked, and even then they could still have some(ie. removeable headshell joint). They are right on the axle, so resonance could be a problem. Also, that would raise the cost noticeably. It would be worth a try for an experienced user who knows what he's doing with cartridge compliance matching.

I'd be willing to make some units with adjustability for someone, but the machining costs and labor might make them quite expensive on a small scale manufacturing basis. I've talked with the guys at Starsound about making this item in a more professional(and possibly adjustable)form, but so far it is on the back burner.

This plain model that I'm making has a pretty good working range for most cartridges(5cu-15cu), and is simple and cheap.
twl OP
3,251 posts
 
Alex, as you mention, the actual lateral mass is the combined mass of the tonearm, cartridge, counterweight, bearing housing, AND my added weights. All arms, of course, have some amount of lateral mass built-in as part of the basic components. Usually it is similar to the vertical mass. But some tonearms have designed-in some additional lateral mass to give similar benefits as the HiFi mod has, notably the OL Encounter and Illustrious which do not need my mods.

Regarding your multiple resonance point theories, I think it has merit. By distributing the 2 resonance points over a wider range, it will have less additive effects resulting in lower amplitudes, but over a wider range. By keeping this range small and in the "ideal" range between 8Hz and 12Hz, the additive amplitudes can be minimized and still not have adverse audible effects. In Doug's case(Shelter cartridges) the 11Hz vertical and 9Hz horizontal both fall in the "ideal" range, and are wide enough apart to reduce additive amplitudes. This will result in significantly less mass/resonance amplitudes compared to having both(vert.& horiz.) resonating at the same freq. and causing a doubling of the resonating amplitude. In an ideal world, we could try to produce these amplitudes at the exact same point, but 180 degrees out-of-phase, thus causing cancellation of the resonance altogether. I haven't figured out how to do that yet. So this narrowly distributed resonance may be the best way to go so far.

As far as the idea you had about the counterweight with side-weights, the weights must be located exactly at the pivot axle, or else you are adding mass to the vertical component. My weights are small-diameter, and concentric with the center of the rotating bearing axle, so they have minimal(if any) effect on vertical mass. All of the HiFi mod effect is on the horizontal mass, so as to keep vertical mass unchanged, for good warp tracking. In addition, having the weights made of lead will damp any resonances that might adversely affect the performance, and the extra weight attached to the axle actually makes the axle itself less likely to become excited or chatter in the bearing clearances.

In some cases, a very simple idea or device can address a wide range of problems effectively, as long as it is well thought-out. I have resisted doing any big changes to it, since it is working so well as it is.

I think this thread is turning out to be a lot of fun.
twl OP
3,251 posts
 
Basement, I agree that placement of mass, as well as the amount of mass in various planes, is very important to the overall success of a tonearm design. This is still an evolving art/science, even after all these years. A natural inquisitive nature is needed to spend time thinking and testing new ideas. Maybe some people will be spurred into making the next leap forward to a totally new tonearm design, or just the next evolutionary discovery, after reading some of our posts here. In any case, I think this thread has become one of the real reasons why forums can be so good for the development of the hobby.

I really appreciate all of the posts and ideas that have been presented here on this thread, in a most genuine way. Maybe all of us "tonearm geeks" needed someplace to converse. I'm glad it is working out the way it is.
zaikesman
3,017 posts
 
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.
dougdeacon
3,338 posts
 
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!
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