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-   -   Alignment protractor? (http://www.diyaudio.com/forums/analogue-source/197354-alignment-protractor.html)

robgilmo 26th September 2011 06:41 PM

Alignment protractor?
 
My arm, an ADC ALT1 has an effective length of 237mm with 19mm overhang.
I have set it up however ADC state that it should be aligned to null points 69mm and 129mm. Fair enough except my protractor has grid boxes at 66mm and 121mm.
Could I just mark ADC's alignment points on my protractor and use them with the same grids? The cartridge will sit a few millimetres to the right of the null points set out on the protractor but will still be within the box grids.

You can see what I mean here, I have marked the new null points in pen.

http://i84.photobucket.com/albums/k9...e/SAM_4792.jpg

http://i84.photobucket.com/albums/k9...e/SAM_4791.jpg

kevinkr 26th September 2011 08:18 PM

You might want to post this question over at www.vinylengine.com.. My feeling is that you should probably be using the baerwald alignment which is common and probably the basis for your protractor, unless you cannot set the standard null points in which case you could use the ADC recommendations.

YMMV, and noting that I am not an expert in such matters, although I play a lot of vinyl on a variety of gear.

robgilmo 26th September 2011 08:27 PM

Thanks Kevin, vinylengine is off line so I cannot use any of their calculators.

I set the overhang at 19mm then tried the null points given to me by ADC in the arms manual and they are well off.
Is it safe to assume that if I use the null points , over hang and spindle to pivot distance provided by ADC that when set up correctly the cartridge should sit square in the head shell?

kevinkr 26th September 2011 09:37 PM

Quote:

Originally Posted by robgilmo (Post 2725155)
Thanks Kevin, vinylengine is off line so I cannot use any of their calculators.

I set the overhang at 19mm then tried the null points given to me by ADC in the arms manual and they are well off.
Is it safe to assume that if I use the null points , over hang and spindle to pivot distance provided by ADC that when set up correctly the cartridge should sit square in the head shell?


Just checked Vinyl Engine | The Home of the Turntable and it is up.. Might have been a short outage..

I don't want to lead you astray as I 'm not familiar with this arm and therefore not sure I know the answer to that question, but it would seem though that the cartridge should sit square in the shell unless it is a straight arm in which case the cartridge will be angled.. Normally you would set the overhang by using the protractor to position the cartridge in the head shell such that the criteria of the two null points are as closely met as possible. Not being familiar with this arm I don't know whether or not it has a detachable head shell - if it does check to make sure you have the right one for this arm.

robgilmo 26th September 2011 10:53 PM

Thanks Kevin , vinylengine is back up so I ahave posted there also.
Even if I change the alignment to bearwald by shortening the spindle to pivot distance as well as the overhang the cartridge still sits askew to align it in the grids.
I would have thought ADC's alignment figures would have had the cartridge sitting square in the headshell.

kevinkr 27th September 2011 02:21 PM

Quote:

Originally Posted by robgilmo (Post 2725317)
Thanks Kevin , vinylengine is back up so I ahave posted there also.
Even if I change the alignment to bearwald by shortening the spindle to pivot distance as well as the overhang the cartridge still sits askew to align it in the grids.
I would have thought ADC's alignment figures would have had the cartridge sitting square in the headshell.

Does this arm use a fixed or detachable head shell? And if detachable are you sure you have the right one?

robgilmo 27th September 2011 08:15 PM

Its the right headshell, I figured out in the end that the effective length of 237 could not be achieved because the headshell would not allow me to pull the cartridge (goldring 1012gx) back far enough, the least I could get was 238ish.
So , using an effective length of 239 which allowed me room to faf around I had to put the pivot to spindle distance from 219.5 to 221.5 and use 66 and 121 as my null points.
Vinylengine's calculators are a god send.
Anyhow the cartridge visually sits square in the headshell and hopefully everything should be OK.

I wonder how many ADC ALT1's are out there with their effective length more than the specified 237 due to cartridge missmatch.

sreten 27th September 2011 09:14 PM

Quote:

Originally Posted by robgilmo (Post 2725317)
Thanks Kevin , vinylengine is back up so I ahave posted there also.
Even if I change the alignment to bearwald by shortening the spindle to pivot distance as well as the overhang the cartridge still sits askew to align it in the grids.
I would have thought ADC's alignment figures would have had the cartridge sitting square in the headshell.

hi,

If its sits askew so be it, all mine do to some degree, get a good inner
point by twisting, see how that affects the outer zero point as you
vary the effective length, ignore the cartridge being parallel.

rgds, sreten.

Only if the arm mounting point is exactly right will you get what you want.

kevinkr 27th September 2011 09:32 PM

:up:

robgilmo 27th September 2011 10:08 PM

Thanks guys, sreten I cant get the arm mounting point right, well not according to ADC's specification anyway, I cant believe ADC would make an arm that has an unachievable specified effective length, perhaps their own cartridges are a better fit?
Either way it's now running fine and sounding nice so happy days..

Although I am now looking at fixing the loose shaft bearings and perhaps a re-wire and while I am at it that weight on the back could be exchanged for something with a lower centre of gravity and a more solid way of fixing it to the stub, a carbon fibre wand might also do it some justice lol.........


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