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It's been a long time but could this be the result of the anti-skating or lack there of on the turntable?
As we know, a pivoted tonearm is drawn by inertia or pressure toward the center of the record. If the inertia is strong enough the arm would have a tendency to jump grooves and skate toward the center. Anti-skate devices were incorporated into tonearms to counter this physical force and keep the needle in the center of the groove as it travels. They work by applying a small amount of back-pressure on the arm to pull it slightly toward the edge of the record. Rarely are anti-skate devices accurate. The space between grooves on a record, are not universal. The wider the spacing, the faster the arm travels toward the center of the record(more inertia) and the more anti-skate is needed to counter balance this extra pull. While it is acknowledged that these devices are not accurate, anti-skate devices are completely necessary in order for most arms to work “properly”. Knowing that tonearms are full of compromises on perfection, a little error in anti-skate is acceptable and probably seen as a necessary evil.When a pivoted bearing arm (most arms are of this type, REGA for example) is used with no anti-skate, the needle of the cartridge rides on the inner side of the groove due to inertia’s pull (or push) . Because the arm is held steady in the vertical plane at two pivot points, its azimuth is not affected. The top of the tonearm is still parallel to the platter or record (at least it should be). What is affected is where the needle rides in the groove. If you could see the needle riding in the groove you would notice that the tip of the stylus is not at the lowest possible point in the groove but is rather riding up on the side of the inner groove of the record. Not only will you get a mismatch in volume left to right but you will also get more distortion from the inner groove and decreased response, because the stylus is no longer seated properly in the groove.When a uni-pivot tonearm is used without anti skate, the physical reaction of the arm is VERY different. Because the arm is not rigidly held in the vertical plane, it’s azimuth is greatly affected by this inertia. (Remember, a pivoted/bearing tonearm’s azimuth cannot be affected unless manually changed). When the needle on a uni-pivot arm rides the inner groove of the record, the simple mechanics of the arm causes it to pivot to one side thus causing the needle to sit at an angle in the groove. Of course you get all kinds of distortion and balance problems when this happens. Most answers to this problem is to use a little fishing line with weight attached and drape it over the arm. This presents a host of problems involving the arms affect to this extra weight which rarely sits in the same place on the arm , the line used to connect the weight is not frictionless and thus has negative affects as the arm travels toward the center, the line needs to move to specific points on the arm as it travels toward center to work correctly, etc…etc…By using an off axis counter weight, the azimuth of the arm is controlled by what position the weight is in. You can have a gram of weight on the arm and have it pivoted to the left OR to the right depending on what position the counter weight sits. If you position the counter weight so that at no point on the record the arms azimuth changes, then you know that the arm is “correctly” riding in the center of the groove thus needing no “anti-skating” compensation. If it is NOT riding in the center of the groove, then, by the very nature of how a uni-pivot arm works, the azimuth would be incorrect. One edge of the headshell would be tilted up. If we know that the shape of the needle rarely matches the groove exactly, any constant contact of the needle with EITHER side of the groove will reveal itself as an incorrect azimuth! Simply setting the azimuth correctly on a unipivot arm (and of course making sure VTA and counterbalance weight are correctly set) controls the “anti-skate”. When all these are set correctly, the needle rides in the center of the groove at its deepest point possible and no anti-skate mechanism is needed.
than all the others?....it seems that the upper frequencies are more distorted than the tracks before it. My buddies say I'm nuts...but I noticed that years ago with a total different set-up...what do you think?Peace, Pogue
Sounds like your cart is out of alignment. You’ll need an alignment protractor to do the job. The price range is from free to several hundred dollars. You get what you pay for in terms of precision and ease of use. If you cart is way out of line, one of the free protractors should get you back in the ballpark.
... I don't think there is such a thing as a unipivot cutting lathe as far as I know. ...
If the cutting arm is a "tangential" arm then the "normal" arm must be a "radial" arm. In a radial arm, you can have two sorts of pivots ... a "unipivot" (like the Graham - ie. a needle) or a "gimbal" pivot (like the SME).Regards, Andy
Quote from: andyrIf the cutting arm is a "tangential" arm then the "normal" arm must be a "radial" arm. In a radial arm, you can have two sorts of pivots ... a "unipivot" (like the Graham - ie. a needle) or a "gimbal" pivot (like the SME).Regards, Andy Yes, I know...but I'm not sure what you're getting at. The idea is that if the record was cut in a straight line (as I assume all records are) a playback arm that also moves in a straight line gains an advantage over a playback arm that moves in a slight arc, right?
