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In Reply to: How to measure tonearm mounting distance? posted by David Lawrence on April 27, 2007 at 21:36:14:
You might want to consider the type of alignment you wish to employ before deciding on the mounting distance. The geometry used by Grace has an alignment that looks like this.This alignment has low distortion in the middle and inner groove area at the expensive of rather high distortion over the outermost one-third of the LP. This is shown by the red line, which incidentally is weighted such that a given level of distortion on an inner groove is exactly the same as on an outer groove.
If you would like an alignment that minimizes and equalizes the distortion across the entire LP, you might want to mount your tonearm slightly closer than 222-mm. Here is what Baerwald's alignment looks like for a 237-mm effective length tonearm, which requires a mounting distance of 219.5-mm for optimal results with your Grace 707.
A measure of overall distortion across the entire LP playing surface is given by the number in the turquoise square in the upper left corner of the graph. This is only one indicator to consider. You also need to assess the red curve, which shows distortion at specific positions on the LP.
As you already probably know, I prefer Baerwald's alignment because it does not favor one portion of the LP over another.
Follow Ups:
Sorry, John, can't resist. I'm playing with a borrowed RS-A1 tonearm, can't believe how great it sounds and ... can't understand how it works at all. Everything wiggles or wobbles, nothing is attached firmly to anything (including the base, which just sits there) and, the instructions say, "Small difference in the arm base position does not make any big difference in the sound quality." A straight flat arm, no offset, no cueing lever, no anti-skate, no fixed counterweight, no grounding possible. In other words, take that, you anal retentives :-)And it sticks to the grooves -- inner, outer, everwhere -- like there's no tomorrow. Without even a hint of distlortion (audible, anyway).
I wouldn't have this arm on a bet -- my eye-hand coordination isn't up to getting the stylus into the lead-in grooves and out of the lead-out grooves with any degree of safety or consistency. But it's the best-sounding arm I've ever heard, and I've heard a lot of them.
I remember reading a thread about this tonearm.....Sounds very interesting indeed! Can you send us some pictures?
You may be referring to the thread I started on this arm a while back. I'll see about a picture. Didn't intend to hi-jack the thread.
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