ADC LMF-2 tonearm mounting info - diyAudio
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Old 1st October 2005, 05:21 AM   #1
Herb1 is offline Herb1  Australia
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Question ADC LMF-2 tonearm mounting info

Hello. I am putting together a record player. I have an ADC LMF-2, that I have had in it's box since I was a kid. I now have a BJD GST1 deck. I have no knoweledge at all in the setup of how to mount the tonearm. What distance and angle should the head be in relation to the record. Any help would be great. Thanks.
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Old 1st October 2005, 08:30 AM   #2
Nanook is offline Nanook  Canada
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from the vinyl engine:

ADC LMF 2
237mm effective length
15mm overhang
21.6 degrees offset
222mm mounting distance
null points:60.3mm / 114.2mm
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Old 2nd October 2005, 09:11 PM   #3
Herb1 is offline Herb1  Australia
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Thanks for the technical info. Does anyone know how to translate these figures into working out the mounting position? Thanks.
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Old 2nd October 2005, 11:10 PM   #4
Nanook is offline Nanook  Canada
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Default mounting position...

See "mounting distance" , 222 mm or 22.2 cm or 8.74 inches from the record spindle.

The math can easily be done to calculate all of this based on the effective length and the mounting position.

The keys here are the length, the mounting distance and the offset. (the "bend" in the headshell).

The null points explain where on an alignment gauge you should be able to align the cartridge to. You must rotate the alignment protractor to do this for the two points.

There may be alignment protractor available here or on other sites (thevinylengine.com or enjoythemusic.com).
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Old 3rd October 2005, 03:27 AM   #5
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Default arm position

Hi Herb1

Here's one way,

Get an 18" piece of 2"x1", drill an 8mm hole close to one end. Measure 222mm from the centre of the 8mm hole - accurate as you can and drill another hole that will be a close fit for a pencil.

Now fit the 8mm hole on the tt spindle and with the pencil in the other end, draw an arc over the top right corner of the deck. Get the ADC arm and try it along the arc till the front and back are inside the plinth edges, mark the spot on the arc. Drill a hole big enough to give 2-3mm of adjusting slack for the arm collar.

I don't know the deck you have, is the arm mounted on metal or wood. If metal, I prefer to use a thin (4/5mm) mdf or ply 'washer' between the collar and the metalwork.

Hth

Colin
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Old 3rd October 2005, 11:10 AM   #6
Herb1 is offline Herb1  Australia
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G'Day Guys. Thanks very much for the info. I now have my lovely arc ready to go. Just making sure that it doesn't matter where on the arc I fit the arm (before I drill the hole!). It is going to fit better if the resting position isn't at right angles to the deck. Will this matter? (the arm is longer than the original and when it is straight it is very close to the On'Off knob).I assume all other adjustments (null points) pertain to the cartridge (that I have'nt got yet). Cheers for your time, Herb.
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Old 3rd October 2005, 05:12 PM   #7
Nanook is offline Nanook  Canada
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Default Got a pix of the turntable?

I don't know what it is:-) and am interested to see it, as brands from around the world do not often make it here to Canada.

The monuting location does need to be on the arc. As long as the arm does not use an SME type "sled" then location can be anywhere on the arc. SMEs follow a location that provides the correct distance but also a radial path so that their arms can be aligned (there are no slots in an SME arm, just two holes for the mounting screws). The alignment needs to wait until you have a cartridge, but they are dependant on the arm length and overhang. And they are not "set in stone", as there are a number of alignments available, but I was working from manufacturer's data as far as I know.

Good luck, and enjoy the table:-)
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Old 4th October 2005, 11:10 AM   #8
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Hi, I'm not sure if those figures are the original ADC ones, but quite a number of arm manufacturers seemed to publish measurements that just didn't work out.
That outer null radius surely isn't the standard Baerwald/RIAA spe for an LP (?) - that works out to 146.05mm and the other measurements look kinda wrong, the offset angle in partiular.

Working backwards from a 237mm effective arm length, I get:
overhang 17.44mm
offset 23.22 degrees (which looks much nearer to normal)
mounting then rounds to 219.5mm

If you look at these measurements against the well-known Rega figures, a couple of mm longer, they seem to agree nicely.
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Old 4th October 2005, 04:23 PM   #9
Nanook is offline Nanook  Canada
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Default the tonearm spec are from ...

thevinylengine.com as posted. I am only working with the numbers that were provided there. I did draw it out though and it appears to be correct.


A link on how to align a cartridge can be found at:

http://www.theanalogdept.com/2_pt_align.htm
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Old 5th October 2005, 07:28 AM   #10
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Thanks guys. Now I have 2 sets of figures. Confusion is setting in!! A little knoweledge is dangerous for an amateur! Is a couple of mm going to make much difference? My CD player is starting to look good again. Cheers for the help.
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