Plugging his overhang figure into a formula will be worthless at this point, without the ability to correct the figures for the error in his spindle to tonearm pivot distance. VE's formulas(like ANY given alignment protractor) assume a correct spindle to pivot distance for the tonearm's length. The existing error throws off the whole geometry of the process(and geometry is EVERYTHING, regarding tonearm/cartridge alignment).
How critical is alignment error??
I would appreciate advice regarding the following issue.
A tech recently installed a new tone arm on my old turntable base. The new arm has a spindle to pivot (S-P) distance of 222 MM. Upon return of the TT with the new arm, I noticed that the S-P distance was about 5 MM short, say 217 MM. I own a protractor and checked alignment. As I suspected, the cartridge overhang was about 3-4 MM over the sweet spot indicated on the protractor. BTW, I was able to move the cartridge back in the arm shell towards the pivot point, but even with the maximum adjustment, as stated, I was still off 3-4 MM.
My question is how much distortion will this error introduce in the playback? Ordinarily, I would ship the TT right back to the tech for adjustment, but I am reluctant to do so because of the possibility of damage from shipment. Further, I suspect that the fix will entail cutting out a part of the undercarriage in order to accomodate the larger arm and I suspect the tech will argue. The old arm had a S-P distance of 215 MM. If the error is signifant, I will have to reconsider what may next steps will be.
Thanks for your advice.
A tech recently installed a new tone arm on my old turntable base. The new arm has a spindle to pivot (S-P) distance of 222 MM. Upon return of the TT with the new arm, I noticed that the S-P distance was about 5 MM short, say 217 MM. I own a protractor and checked alignment. As I suspected, the cartridge overhang was about 3-4 MM over the sweet spot indicated on the protractor. BTW, I was able to move the cartridge back in the arm shell towards the pivot point, but even with the maximum adjustment, as stated, I was still off 3-4 MM.
My question is how much distortion will this error introduce in the playback? Ordinarily, I would ship the TT right back to the tech for adjustment, but I am reluctant to do so because of the possibility of damage from shipment. Further, I suspect that the fix will entail cutting out a part of the undercarriage in order to accomodate the larger arm and I suspect the tech will argue. The old arm had a S-P distance of 215 MM. If the error is signifant, I will have to reconsider what may next steps will be.
Thanks for your advice.
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- 16 posts total
Rodman, Yes but he can plug in the deviation and check the change in distortion. He can even print a new protractor to compensate. A lot can be done. Remember effective length is a design element with a nominal figure. Take a look at an SME where there is no nominal length but an exact length but yet pivot to spindle distance can be changed and that is all. The headshell if fixed for all parameters for the most part. If you are lucky a poor setting can end up being the correct setting. Just like some arms can be setup w. Lofgren A or B. |
You can approximate unknown or non-standard parameters by using a separate alignment calculator to come up with the unknown parameters. For example, if we assume that the design geometry of the original tonearm was for Lofgren A/Baerwald then the parameters are as follows... Effective length: 232.8mm Overhang: 17.8mm Pivot-to-spindle: 215.0mm Offset angle: 23.7 degrees And the design geometry of the new tonearm is as follows... Effective length: 239.3mm Overhang: 17.3mm Pivot-to-spindle: 222.0mm Offset angle: 23.0 degrees Then the current setup (based on Bifwynne's estimate of pivot-to-spindle distance) should have a geometry as follows... Effective length: 234.7mm Overhange: 17.7mm Pivot-to-spindle: 217.0mm Offset angle: 23.5 degrees However, Bifwynne states that the overhang is about 3-5mm too long so, using the lower value, the overhang is now 20.7mm and effective length becomes 237.7mm. (What's missing is which alignment protractor geometry is being used to estimate incorrect overhang.) Compared to the "correct" alignment parameters the current setup doesn't look very promising, as shown in the chart and graph from VinylEngine VinylEngine Tonearm Alignment Comparator Regards, Tom |
- 16 posts total