Thanks, everyone, for your thoughtful replies.
Twl, as usual, you are a fountain of useful information. Your explanation of cogging makes sense. I'll do some reasearch into DC motor-based tables. I'll also look into tables with heavy platters.
For those of you that commented on off-center holes, I see that occasionally, but not often enough to explain what I hear.
Violaguy, I am a former musician (trombone), though I haven't played in many years. I played in high school and college. I don't know if I have perfect absolute pitch or not but I'd say I have very good relative pitch, at least. I'm sure I could distinguish between A440 and 441. Thats about 1/8" on a trombone slide. A good trombone player is a lot more accurate than that - I'd say accurate to at least 1/32". I know what you mean about variations in dynamics and overtones. I love hearing the overtone beats of a piano chord, for example. That type of variation doesn't bother me at all. However, that's not what I'm hearing. I'm hearing real changes in pitch. I have heard variations in CDs but always assumed it was due to the master tape. Most CDs are fine. I've found the more overtones an instrument, or voice, produces the less likely it is to cause noticable flutter. It's the pure tones that get you.
From what you all are saying I think it's going to cost quite a bit to achieve the pitch stability I need. I'll keep my eye on the classifieds. (The SL1200 is going back to Crutchfield!)
Twl, as usual, you are a fountain of useful information. Your explanation of cogging makes sense. I'll do some reasearch into DC motor-based tables. I'll also look into tables with heavy platters.
For those of you that commented on off-center holes, I see that occasionally, but not often enough to explain what I hear.
Violaguy, I am a former musician (trombone), though I haven't played in many years. I played in high school and college. I don't know if I have perfect absolute pitch or not but I'd say I have very good relative pitch, at least. I'm sure I could distinguish between A440 and 441. Thats about 1/8" on a trombone slide. A good trombone player is a lot more accurate than that - I'd say accurate to at least 1/32". I know what you mean about variations in dynamics and overtones. I love hearing the overtone beats of a piano chord, for example. That type of variation doesn't bother me at all. However, that's not what I'm hearing. I'm hearing real changes in pitch. I have heard variations in CDs but always assumed it was due to the master tape. Most CDs are fine. I've found the more overtones an instrument, or voice, produces the less likely it is to cause noticable flutter. It's the pure tones that get you.
From what you all are saying I think it's going to cost quite a bit to achieve the pitch stability I need. I'll keep my eye on the classifieds. (The SL1200 is going back to Crutchfield!)