One way could be to ream out the centre holes and make a
set of press fit inserts with various eccentric offsets built in.
You can also buy a device for cutting out the centre of records to
allow use in jukebox's. This would allow a 45 adaptor to be used.
It won't get you to 1 or 2 groove widths though.
sreten.
set of press fit inserts with various eccentric offsets built in.
You can also buy a device for cutting out the centre of records to
allow use in jukebox's. This would allow a 45 adaptor to be used.
It won't get you to 1 or 2 groove widths though.
sreten.All,
it is not necessary to repunch the record.
The excentricity topic has been discussed here: http://diyaudio.com/forums/showthread.php?postid=54784#post54784. and following
My initial idea was based on having a vacuum platter. Now i had some more ideas.
Let's assume our vacuum platter keeps the record strictly on its position once the vacuum is applied. The vacuum system does not need a puck or clamp sitting on top of the record as it has two sealing lips, one at the outer perimeter and one at about the radius of the inner groove. We apply the vacuum by a cylindric nozzle thru the center hole. The center pin has 3mm dia, allowing 2.1mm of excentricity. The nozzle has two ends, one flat and one with a shoulder centering the center hole (7.2mm dia) to the center pin. The vacuum hose is radially attached to the nozzle and the nozzle's center hole is drilled thru.
Let's assume we have a jig for measuring and marking record side excentricity. The jig has a platter and a beam carrying a groove microscope and a center puck having the same outer dia as the vacuum nozzle. The beam is radiallay oriented and has a hinge at its end and locates the µscope just over the lead-in groove; the center puck rests on the records surface at approx. the position of the center. The platter is mounted on a linear guide and can be adjusted to a certain amount of excentricity in respect to the center puck.
***
Remember, if you do not want to go vacuum but want to have centering, then any clamping device smaller than a record label which does avoid to rotate the disc while clamping will do instead.
Just make sure that the jig's center puck and the record's clamp outer dia are the same.
***
If we want to mark excentrcity of a record side, we put the disc on the platter and rest the beam with center puck on the record. we rotate the platter while looking thru the µscope and check whether the groove pattern is excentric. If yes, we search the excentricity maximum and adjust the platter away from the center until excentricity seems to have disappeared. We decide the record is excentric and needs correcting and and has to get a pencil mark around its center hole. We lock the jig so that no accidental misalignment is possible and draw a circle around the center puck, using the puck's cylindrical perimeter as drawing template. We know: the pencil circle is concentric to the groove pattern. Hence we don't have to pay attention to how much the record side is excentric or how the excentricity is oriented.
Now playing records:
Scenario 1: the record is centric.
We look for a circle and dont find any => record is centric => we need the shouldered side of the vacuum nozzle to center the record. We apply vacuum. Done.
Scenario 2: the record is off-center.
We look for a circle and find one => we need the flat side of the vacuum nozzle and center the pencil circle to the nozzle (the human eye is super-sensitive to concentricity; i'd expect less than 50µm centering error). We apply vacuum. Done.
It should be evident that we undergo the marking procedure only for records we like and/or find sonically rewarding.
All who find my procedure described below too complex and effort-loaded, please consider that you may need a similar jig and a similar procedure to locate the proper punching location. I prefer my method as i do not have to make permanent (and mistake-prone) changes to the records; i can erase and replace my pencil marking anytime.
Now you ask me how to get a ****ing groove µscope?
1st, illuminate the groove from almost level in radial direction using an ultra-bright green LED so that you see the grooves.
2 options:
1) use a 20x magnifier with big lens2focus distance instead, and have a pointer cut from paper slide on the record surface. Does a fine job ... all you need if you are careful
2) build yourself a µscope from optical components obtainable from companies like Edmund Scientific or from what you find at your local thrift store. Get a crosshair (preferably illuminated, too) in the intermediate image plane between objective lens and ocular lens. Now you have your pointer, the crosshair optically on the record surface but mechanically in safe distance.
Moreover, your head (don't forget your nose tip) is in safe distance from the record surface... after all you don't want to impregnate your record surface with the skin grease from your nose.
For the ocular You should get a lens system meant to be used as an ocular. For the objective any lens system with positve focus length is usable; you do not need hightech stuff with huge aperture and ultra-plane image plane. If you can project an image of an object on a screen, the lens system will do. Happy experimenting !
it is not necessary to repunch the record.
The excentricity topic has been discussed here: http://diyaudio.com/forums/showthread.php?postid=54784#post54784. and following
My initial idea was based on having a vacuum platter. Now i had some more ideas.
Let's assume our vacuum platter keeps the record strictly on its position once the vacuum is applied. The vacuum system does not need a puck or clamp sitting on top of the record as it has two sealing lips, one at the outer perimeter and one at about the radius of the inner groove. We apply the vacuum by a cylindric nozzle thru the center hole. The center pin has 3mm dia, allowing 2.1mm of excentricity. The nozzle has two ends, one flat and one with a shoulder centering the center hole (7.2mm dia) to the center pin. The vacuum hose is radially attached to the nozzle and the nozzle's center hole is drilled thru.
Let's assume we have a jig for measuring and marking record side excentricity. The jig has a platter and a beam carrying a groove microscope and a center puck having the same outer dia as the vacuum nozzle. The beam is radiallay oriented and has a hinge at its end and locates the µscope just over the lead-in groove; the center puck rests on the records surface at approx. the position of the center. The platter is mounted on a linear guide and can be adjusted to a certain amount of excentricity in respect to the center puck.
***
Remember, if you do not want to go vacuum but want to have centering, then any clamping device smaller than a record label which does avoid to rotate the disc while clamping will do instead.
Just make sure that the jig's center puck and the record's clamp outer dia are the same.
***
If we want to mark excentrcity of a record side, we put the disc on the platter and rest the beam with center puck on the record. we rotate the platter while looking thru the µscope and check whether the groove pattern is excentric. If yes, we search the excentricity maximum and adjust the platter away from the center until excentricity seems to have disappeared. We decide the record is excentric and needs correcting and and has to get a pencil mark around its center hole. We lock the jig so that no accidental misalignment is possible and draw a circle around the center puck, using the puck's cylindrical perimeter as drawing template. We know: the pencil circle is concentric to the groove pattern. Hence we don't have to pay attention to how much the record side is excentric or how the excentricity is oriented.
Now playing records:
Scenario 1: the record is centric.
We look for a circle and dont find any => record is centric => we need the shouldered side of the vacuum nozzle to center the record. We apply vacuum. Done.
Scenario 2: the record is off-center.
We look for a circle and find one => we need the flat side of the vacuum nozzle and center the pencil circle to the nozzle (the human eye is super-sensitive to concentricity; i'd expect less than 50µm centering error). We apply vacuum. Done.
It should be evident that we undergo the marking procedure only for records we like and/or find sonically rewarding.
All who find my procedure described below too complex and effort-loaded, please consider that you may need a similar jig and a similar procedure to locate the proper punching location. I prefer my method as i do not have to make permanent (and mistake-prone) changes to the records; i can erase and replace my pencil marking anytime.
Now you ask me how to get a ****ing groove µscope?
1st, illuminate the groove from almost level in radial direction using an ultra-bright green LED so that you see the grooves.
2 options:
1) use a 20x magnifier with big lens2focus distance instead, and have a pointer cut from paper slide on the record surface. Does a fine job ... all you need if you are careful
2) build yourself a µscope from optical components obtainable from companies like Edmund Scientific or from what you find at your local thrift store. Get a crosshair (preferably illuminated, too) in the intermediate image plane between objective lens and ocular lens. Now you have your pointer, the crosshair optically on the record surface but mechanically in safe distance.
Moreover, your head (don't forget your nose tip) is in safe distance from the record surface... after all you don't want to impregnate your record surface with the skin grease from your nose.
For the ocular You should get a lens system meant to be used as an ocular. For the objective any lens system with positve focus length is usable; you do not need hightech stuff with huge aperture and ultra-plane image plane. If you can project an image of an object on a screen, the lens system will do. Happy experimenting !
MP-50 -
I just found a direct drive SONY tt outfitted with a MP-50 today.
The Cart and styli is in perfect shape. I just looked at the Sty under
the microscope and it comes up very beautiful.
My Fav. cart so far is a Audio technica AT150 series.
The MP-50 Nagaoka is very similar to the 150mlx. It's got
a line contact shape similar, and even the specs say it's Boron
like the MLX. It's a very fine thing.
I don't care about specs on paper, I always do my own tests and of course
listening tests. I despise Carts that colour the sound. I want as naked as
possible and then add EQ here at home. Since I transcribe records
I want them to sound like the artist wanted them, not to add tubby bass
or more midrange.
I will do listening tests and also digital metering in the near future
and compare it to the 150mlx. I'm sure it's a fine contender and it's
not a crappy needle, like some have said. They claim overpriced for
OLD thing? How can you determine because it's old, it's crappy?
hmph.
Now music enjoyment to be had. Great thread.
I just found a direct drive SONY tt outfitted with a MP-50 today.
The Cart and styli is in perfect shape. I just looked at the Sty under
the microscope and it comes up very beautiful.
My Fav. cart so far is a Audio technica AT150 series.
The MP-50 Nagaoka is very similar to the 150mlx. It's got
a line contact shape similar, and even the specs say it's Boron
like the MLX. It's a very fine thing.
I don't care about specs on paper, I always do my own tests and of course
listening tests. I despise Carts that colour the sound. I want as naked as
possible and then add EQ here at home. Since I transcribe records
I want them to sound like the artist wanted them, not to add tubby bass
or more midrange.
I will do listening tests and also digital metering in the near future
and compare it to the 150mlx. I'm sure it's a fine contender and it's
not a crappy needle, like some have said. They claim overpriced for
OLD thing? How can you determine because it's old, it's crappy?
hmph.
Now music enjoyment to be had. Great thread.
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