Are you absolutely positive all your adjustments are as good as you can get them?....are you sure, the arm is has free motion....not hitting/rubbing on anything?
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Audible IGD is not necessarily "part of the deal" with vinyl. (Tracking angle error is typically greatest at the innermost grooves but this is not necessarily linearly related to audio signal distortion.) Can you describe what you hear and when you hear it? As in, where is the stylus in relation to the innermost grooves of a typical LP when the distortion sets in? Is it related to actual tracking or to the distance between the stylus and the spindle? If the latter, look for something that is obstructing the travel of the tonearm, like a wire that is getting fouled or a problem with anti-skate or with your tonearm bearing.
I hear it mostly in horns and vocals. It's a fuzzy halo around the sound of the instrument. Also in loud passages of orchestral works that occur in the inner grooves. I start to hear it about 3/4 of the way from the edge of the record to the end of the grooves and it gets worse as it gets closer to the center. It's worse on some records than others and sometimes, I think it's the record that's the culprit but it seems that the turntable and cartridge are playing a role as well. I checked for anything obstructing the travel of the tonearm but I didn't find anything. I tried adjusting the anti-skate. Some fine-tuning helped a little (maybe, not sure I trust my ears sometimes) but it was still there
Both channels? Or one channel more than the other?
cleeds, I think your thought about alignment is reasonable, but as was noted elsewhere, misalignment is not usually that obvious in my own experience and that of others.
Also, where is the motor located on the Rega P3? Is it under the platter or outboard and perpendicular to a line drawn from the pivot to spindle?
cleeds, I used an alignment protractor and my eyeballs :) I used a tracking force gauge to calibrate my tracking force. The anti-skate on the P3 is pretty primitive so that part is imprecise,
lewm, both channels and the motor is located under the platter in the center and on the rear side of the plinth
I used an alignment protractor and my eyeballs ...Not all cartridge alignment contractors are equally precise. Many align the cartridge itself, which isn't ideal. The best alignment gauges, imo, align the cantilever. They're much trickier to use, but I think worth the effort.
It sounds like you’re using one of the freebie alignment printouts?
Some of those are okay for alignment only after having set overhang.
How did you set overhang?
Overhang must be set accurately first. Otherwise if overhang is off it will cause your cartridge to be rotated too much one way or the other, which you may not notice until the inner grooves where it becomes more obvious.
My favorite for being fast, easy and accurate, is the MoFi Geo-Disc https://www.mofi.com/product-p/mfslgd.htm which you will notice has a ridge line running A to B which must be aimed directly at the tone arm spindle vertical axis. Then you tape the platter so it doesn’t move while you’re tweaking alignment.
Even though you are not using the Geo-Disc nothing changes. The Stevenson you’re using must still be placed accurately in relation to the tone arm spindle, and both the gauge and the platter must be held stationary.
Try again with these tips and overhang set first and see how it goes.
https://www.analogplanet.com/content/uni-din-versus-l%C3%B6fgren-b-just-clarify according to Mikey's findings, Stevenson alignment has the most distortion most of the time. Unless you're playing very long records you will experience the most distortion near the end of any album side.
Greg, the saving grace of Stevenson alignment is low distortion at inner grooves, compared to the two popular alternatives. One could argue about alignment all day but I strongly doubt that misalignment or Stevenson alignment can account for this problem. I’m now wondering whether motor is interacting with the cartridge as the two get closer to each other. To test this, with the platter spinning, pick up the tonearm and holding it above the platter but close as possible to it bring it over toward the spindle with volume control fully advanced.
One could argue about alignment all day but I strongly doubt that misalignment or Stevenson alignment can account for this problem.It's much easier to get phono cartridge alignment wrong than it is to get it right. If LPs exhibit inner groove distortion, alignment is the first place to look if you want to be methodical. You're likely to be just chasing your tail if you don't first confirm that the alignment is correct.
A distortion analyzer can easily show the results of a misaligned phono cartridge.
Cleeds, I don’t think we are listening to each other. I am saying that I do not think that the particular symptom reported by the OP is due to misalignment. I did not say that misalignment could not cause distortion, although I have my private doubts about the audibility of such distortion. You say that misalignment can be detected on a distortion analyzer. Do you know of any published data to that effect? I would be interested to read any article about that, but I have been unable to find such an article after doing a computer search. By the way, all three of the popular alignment algorithms result in some degree of tracking angle error at the inner grooves, as you probably know. Of the three, the innermost null point for the Stevenson alignment is closest to the spindle. For that reason inner groove distortion with the Stevenson alignment is probably not worse or significantly worse than that of any of the others.But this is a minor point. I agree with you that most of us have made a tiny error here and there in aligning our cartridges. That means nearly none of us is listening to a perfectly aligned cartridge.
I think that the OP might be experiencing an effect of the Rega motor on his cartridge due to EMI. The fact that it gets worse as the cartridge approaches the spindle is consistent with that, just as it is consistent with inner groove distortion. Furthermore, it seems to me that I recall that Rega motors are known to interfere with some cartridges, in particular Grado cartridges, as I recall. But I could be wrong. Checking out the role of the motor in this phenomenon is actually easier than checking tonearm alignment.