|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
24.220.98.32
Hi,
This is a simple question, but I don't know the best answer. I want to mount a Grace 707 on my Rek-O-Kut B12H, and need to measure 222 mm from the spindle center. I don't have the template, but don't understand exactly how that would work anyway. The issue is that the platter bearing hole (or spindle itself if the platter were installed) and the plinth are at different levels. Should I just estimate it by sight with the ruler over the bearing hole, or make some kind of jig??? Thanks.
David Lawrence
Follow Ups:
NT
(credit for the image goes to Ian from Lenco Lovers )
I use a disposable version making a jig from card stock paper. Lay out the line, drill two clean holes of appropriate sizes, trim the paper to a usable shape, draw a radius just like the ruler-jig shown, and then throw it away!
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.
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.
First, pull out the platter. Now you have the main bearing at the same plane as the tonearm mounting hole. I like to use a sturdy wire and measure out 222 mm. Mark the point and you are ready to drill.Make sure these measurements are from the center of the main well to center of the 222 mm tonearm hole.
On My B12GH the 222 mm tonearm hole ended up occupying the very far corner of the turntable platten.
Make sure you get this level as well as properly distanced.I hope this helps.
There is enough slop in the system to generally accomodate the unkown pivot to spindle distance. I am not sure how the arm manfacturer decides on their publihed effective arm length. Most carts and headshells have several mm's of adjustment. Play with Ellison's alignment program.Jim N
- http://www.theanalogdept.com/images/spp6_pics/Alignment Spreadsheet/Baerwald-Lofgren B.xls (Open in New Window)
Since there's no such thing as "Rocket Science"; just Propulsion Engineering(Mechanical and Electrical), Structural Dynamics and loading - all based on fundamental physical laws such as Newton's third(simplest of all!), don't be so sure! Devil's in the details, as ALL Rocketeers, professional and otherwise have learned the hard way-naturally!!
...drill two holes in a ruler/piece of wood such that the centers are precisely 222mm apart. place one hole over the spindle and a pencil through the 2nd hole so that you can trace an arc @ 222mm from the spindle hole. you would then line up the center of your arm's mounting template at a point along that arc.estimating by sight would be sub-optimal.
there are more precise methods than the above, but it would do alot better than estimation.
This post is made possible by the generous support of people like you and our sponsors: