[rcag_ils]

Some of the explanation is too overwhelming, so basically, find the spindle to pivot distance of a particular tonearm, measure that distance, then drill the hole.

Is that it?

[neobop]

That should do it for starters. Are you drilling an armboard or directly on a plinth? If directly on a plinth, then you might want to take some of this into consideration. An armboard can be replaced.

If you look up the arm in the database, it will list the specs including null points, if the info is available. Most arms can not achieve all alignments due to cartridge variations and headshell limitations. If you see what a particular arm is designed for, then you might decide to alter the mounting distance somewhat, depending on your preference.

If you just use the inner null spec as a guide, it's easy to tell which alignment it uses or is close to. The inner null of the standard alignments are:
Stevenson - 60.325mm
Baerwald - 66mm
Lofgren - 70.29mm

Baerwald is the most popular alignment. Most of the commercially produced protractors (Dennesen, Geodisc, DB Systems) are Baerwald. Stevenson is the least popular.

If you want specific information on how to mount for a different alignment, I'll be glad to help you. There are other things to take into consideration. Sometimes a long cartridge body won't fit into a headshell with a particular alignment. Cartridge mounting hole distance to the stylus is not standardized. Some arms won't work right with an altered mounting distance. Things like that can mess you up.
neo

[neobop]

One more thing. It was suggested previously that you take your deck to a machinist and have the hole drilled perfectly, at a known distance, and have the hole drilled so that there is no slop between the arm and the mounting board or plinth. It's nice to have a good looking hole  , but the part about no slop is not a good idea.

Arms are designed to have at least a small space between the arm pillar and the armboard. It's actually the mounting of the arm's base plate that will determine the spindle to mounting hole distance. You also don't want vibrations from the deck or cartridge to be transmitted directly, back and forth. Arms are designed for the arm base plate to be rigidly mounted, not the pillar.  Arm manufacturers give a range of hole sizes that will work, in the arm mounting instructions. If your mounting hole is too tight, it will interfere with height adjustments on height adjustable arms. But the part about vibrations could seriously degrade performance. If you second guess mounting instructions and get less than stellar performance, don't blame it on the equipment. The same goes for changing effective length or mounting hole distance. There are some things you might be able to change slightly and actually improve performance, but a mounting hole tight against an arm pillar is not one of them.

Besides the tonearm database, Vinyl Engine has a library with many tonearm manuals and mounting instructions, and templates. You might want to look at some. They will usually tell you if something is important. However, most also assume that the set-up is being done by someone qualified. You don't need a doctorate of science degree, but a little experience and common sense, can help.
 
neo - former turntable set-up specialist

[Wayner]

If you do not control tolerances of arm mounting, you will not be able to determine what the actual arm spacing is, so your comments about arm mounting are certainly not how I would do it. The Rega RB300 requires one singular hole to mount it. I'm not talking about an interference fit but a fit that has virtually no sideways movement. It is important that the arm be totally sunk to the plinth or mounting board. If the mounting hole is slightly large, wrap some electrical tape around the threads to take up the gap. If you have an AudioQuest style arm, then the 3 or 4 screw mounting points for the collar must be in tight tolerances, as well. In this case the clearance hole for the VTA adjustable arm, it can be sloppy, so as not to interfere with the arm adjustments, vertically.

As far as recommending who's null point's to use, Dr. Frieckert uses Lofgren's B position and so do many others. Here is why:

 

In the above graph, you can see that the distortion(s) in the center of the record are relatively high (counters what was stated previously) but has lower distortion at the beginning and the end of the record. It's average distortion is .431. This is Baerwald's Perfect arm graph.



In the next graph, you will notice higher distortion values in the beginning and end of the record, but much lower distortion thru most of the side. Average distortion is .388. This is Lofgren B curve with a 210mm spindle to pivot arm.

Wayner. Designer of turntables and alignment tools.

 

[steveblezy]

Just to add a little confusement to the issue, I have been using the Dr. Frieckert alignment tool for quite some time. It is a very nice tool and I like the procedure, measure your spindle-pivot distance and set your overhang first. Then align your cart. Double check your overhang. but here is the part that I do not understand, while speaking to the folks at Frieckert, when it comes to a Rega arm, they suggest a spindle-pivot of 218mm-219mm when using 'their' protractor. Traditionally, a Rega is mounted at 222.23mm using their protractor (Stevenson I think).

Seeing that the Dr. Frieckert tool is so damned easy to use, I decided to give it a shot as my custom Rega based arm allows me to adjust the spindle-pivot distance. The end result sounds quite good.

Wayner, any idea why Frieckert would suggest 218mm-219 vs the norm of 222.23mm?

Steve

[Wayner]

Steve, I do have a good idea why they recommended that spacing. Some longer cartridges (from mounting hole to stylus) may not reach the required overhang. The Rega is not your typical 9" arm, it's longer, like about a 1/4" so much care must be taken. Again, the more posts added to this thread confirms that there is no universal spacing, that I think we all can agree on.

My ARMod arm is mounted at 220.675 cause the machinist guy wanted a measurement in inches, and I liked 8.688 (8 11/16). That gives me a 17.848 overhang to achieve my desired Lofgren B null points. I have about 3 to 4 mm to go with slot room, so If I change to a longer cartridge, I hopefully will have room to set the stylus correctly.

Wayner 

[rcag_ils]

I'll be drilling the arm board, one for a Grace 707. one for a Linn basik +. I've found the spindle to pivot distance.

Isn't it if the S to P distance is correct, then the null points have to be correct? The arc doesn't change with where the tonearm's mounted on the board, does it?

[Wayner]

No, that is only part of the equation. After you get the correct S to P distance, then the proper overhang will determine that, along with which null points you favor.

To understand this better, I copied this from another post:

As someone who has studied this geometry for  some  time, it is very interesting to find the relationships between  spindle to  tonearm center, overhang and offset angel. I have included a  list of 5 tonearms  that have a spindle to tonearm pivot distance from  200mm to 220mm. It's  interesting to find (and as it should be) as the  arm gets longer, the overhang  decreases as does the offset angle, if  one is to maintain null point positions.  For my illustration, I used  the null positions favored by Loefgren B curve that  has the inner null  radii at 70.285 and the outer null radii at  116.604.
   
SPINDLE TO TONE ARM PIVOT    OVERHANG     STYLUS TO  TONEARM PIVOT    OFFSET ANGLE

200                                                  19.535                         219.535                                 25.192                           

205                                                   19.099                         224.099                                 24.644

210                                                   18.682                        228.682                                  24.118

215                                                   18.282                        233.282                                  23.613

220                                                   17.898                        237.898                                  23.128   

Of course, if  we continue to make the arm longer,  the overhang and offset angle will  start to approach zero, but then, the tonearm  pivot would have to  located over at the neighbors, ha.   I also included some CAD drawn graphics to better  illustrate  this.
    
200mm
 
205mm
 
210mm
 
215mm
 
220mm

Wayner

[rcag_ils]

S to P distance does not change, overhang and offset angles can be adjusted by adjusting the cartridge. My goal is to drill the hole on the right spot on the armboard that would allow me to adjust the cartridge for the correct null points. Am I correct.

Let say if the correct S tp P distance for a Grace 707 is 226mm, then it should be 226mm, right?

[neobop]

I'll be drilling the arm board, one for a Grace 707. one for a Linn basik +. I've found the spindle to pivot distance.

Isn't it if the S to P distance is correct, then the null points have to be correct? The arc doesn't change with where the tonearm's mounted on the board, does it?

If you drill at the specified distance, you should have no problem getting the manufacturers specified null points. No, the arc won't change unless you drill at a different distance. If you want to use Loefgren A, the Linn is set up for that. The 707 is ia little odd in this respect. Manufacturers nulls are 66.8 and 103, as opposed to 66 and 120.89 for Loefgren A (Baerwald). Maybe that is a typo, but owners often use Baerwald. That arm is very good with high compliance cartridges. Often the cartridge dictates what alignment you can use, once the arm is mounted. Even then, you can alter your alignment,  as I previously posted.

If you want to learn a little more about alignments, there is a very brief, easy to understand guide here:
http://www.vinylengine.com/protractor-user-guide.shtml

As far as hole size - go with the manufacturers recommendations. Positioning of the mounting bolts in most arms determines mounting distance. With the Linn, you'll need 3 bolts on a 6 bolt pattern. The template is available in the VE library. Look under Linn - Ittock.

A lot of confusing and some wrong information on this thread. If you're off by a mm or 2, it won't matter with these arms. That is not the case with all arms. I'm not trying to sell you anything. Use any alignment you like. Whatever you do, you're not going to change the distance between the pivot(s) and the end of the headshell slots. There is a protractor called Chpratz you can also download for free. It is a calibrated straight line with a grid all the way down. With it, you can experiment with alignments other than those mentioned. Maybe you'll come up with an alignment you like so much you'll call it the Rcag_ils alignment.
neo

[neobop]

No problem, certainly all valid points; as you say (and as I alluded to with respect to Conrad's software) an arc protractor to be effective requires that the arm be mounted precisely at the manufacturer's recommended P to S distance.

I do think that Wayne's comment/point regarding the relationship between overhang and offset is a valid one though, at least when using an arc protractor and using an alignment different from that specified by the tonearm manufacturer (and there have been many reports from users who have done so and felt they heard improvements).

Change the alignment protocol (ie. from Stevenson to Baerwald) and hence the overhang (while still achieving an effective alignment) and the offset will change as well which is why the cartridge will not sit square in the headshell and be twisted or skewed. There seems to be an abundance of confusion on this particular aspect of alignment among many vinyl users. You can have a virtually perfect alignment without the cartridge being square in the headshell and that's because the offset changes to achieve alignment (along with all the other parameters-overhang, effective length etc.) at the different null points.

If the overhang changes, the offset has to change as well.

Blakep,
Do you really think an arc protractor is appropriate for the OP on the original thread? He asked a question about mounting his arms, and look what he got. "The most critical aspect of alignment is the cartridges offset angle (in relation to it's overhang), but mere decimal points of a degree will cause a rapid increase in tracking distortion." That statement is particularly helpful 

I definitely think it is a mistake to approach this from an arc protractor point of view, for someone who is inexperienced, and might miss the mark by a couple of mm. It turns out that the arms (so far) he will be mounting will be OK with a conventional protractor. In which case you don't have to approach this as overhang vs offset angle. Overhang is useless unless you're mounted perfectly at manufacturers spec. If you get 2 acceptable null points, you've got a good alignment. Throw your overhang gauge away if you want a different alignment, because it will change. Most arms don't have them anyway.

neo

[rcag_ils]

As far as hole size - go with the manufacturers recommendations. Positioning of the mounting bolts in most arms determines mounting distance. With the Linn, you'll need 3 bolts on a 6 bolt pattern. The template is available in the VE library. Look under Linn - Ittock.

Thanks for the inputs.

I probably will be using the arm base as a template to get the correct hole size. The Linn template at vinylengine.com, I can never print it out in 100% actual size, also the guy who came up with that combined everything into one template, and it's quite confusing.

PS, Yes, It will be fun, I may have enough MDF left over to built some shelves for my Lead Balloon turntable stand. The later models of the Lead Balloon had optional shelves, they were cool looking, I saw one with 4 lead bars, (mine has two) and the optional shelves at Audiogon. Cool stand.

[neobop]

I had the same problem downloading from VE. The trick is to go into your printer settings and turn off the auto sizing function. You might have to set it on landscape. I didn't, but some say that works. All those free protractors are nice too. If you use regular paper, you might want to mount them on thin cardboard like a cereal box or tissue box. Just don't use too much glue. It can shrink up and curl the cardboard.

I had a Linn Basic yrs ago, on an LP 12. It was the straight one. Not a bad little arm. I also had a Zeta and still have an Alphason 100S. They all have the Linn geometry and mounting pattern. I think some use the other 3 holes.

I'll bet you'll feel great when you have it up and running. BTW, that 707 is really nice too.
Enjoy,
neo

[Wayner]

Overhang is useless unless you're mounted perfectly at manufacturers spec.  neo

  What planet are you from? I just got done proving that your statement is totally false and you still keep on. Do you not understand geometry?

If rcag_ils gives me his spindle to tonearm distance that he wants to drill, I can give him the exact overhang to achieve any Baerward or Lofgren's null point locations. The 5 drawings I submitted above have 5 different spindle to arm  spacings, yet all achieved the same null points.

[neobop]

  What planet are you from? I just got done proving that your statement is totally false and you still keep on. Do you not understand geometry?

You've proven nothing. What statement is false?

It's obvious from your posts that you're the one who can only copy the approach of others and have little grasp of the concepts. An arc protractor will work ONLY if the arm is mounted EXACTLY at the specified distance.
neo

[steveblezy]

Here is something that I have used in the past to mount an arm to a table that allows me to adjust my spindle to pivot distance depending on the arm style.

If you have access to a machine shop it might be of use. I did a quick check to see what the manufactures distances were and had an armboard cut but instead of drilling a hole the size of the pillar mount, I had a larger circle cut. I then had a disc cut to that hole size, with a shallow lip on the top and it was threaded to the bottom so I could lock it to the armboard with a large nut. On that disc, I then had a hole drilled for the armtube pillar, but it was 4mm off center. Now the assemble and set-up.

The larger disc is mounted to the armboard. before tightening it all up, I loosely mount the armboard to the table. By rotating the 'outer disc', the distance from the center of the pillar hole to pivot can be adjusted within a range of 8mm. Remember, the inner hole, the armtube pillar hole is off-center to the larger outer disc. Once I am happy with my distance, I tighten it all up and drop in the arm and tighten it to (now locked) disc. Next, I remeasure the pillar to spindle distance. Set up my cart and I am good to go.

If I want to expirement with a different S-P distance and cart alignment method, I simply loosen the armtube pillar and the outer disc, rotate, measure, set the arm straight forward again and tighten it all up.

This setup has been extremely useful when I want to try a new setup.

Steve 

[steveblezy]

Regarding the conversation a few post above pertaining to calculating the overhang, I would say regardless of how exact your S-P distance is, it is imperative to have a way to calculate the overhang, preferable as the first step. I have run arm a few mm off of the manufactures S-P distance and have been able to hit the null points. Am I tracing a perfect curve, I do not know nor can I prove, but I can hit both of the null points. To do so, and to save myself a boatload of time, I measure the S-P distance, calculate my overhang, set that distance and align my cart to the chosen protractors inner null, and if I have not changed the overhang in the process, the outer null point has always drop in. If it were not for knowing the overhang in the first step I would be going from the inner null point, to the outer null point and back and forth slowly achieving the same overhang distance and eating up a lot more time to get to the same place. If Wayner can provide the overhang via CAD and a little math, take him up on the offer and save yourself an hour of finite adjustments. If you know the overhang, one can set up that aspect in less than 15 min.

Steve

[rcag_ils]

Correct me if I am wrong, from what I understand, the overhang adjustment is accomplished by adjusting the cartridge on the headshell to get the correct null points.

If the S to P distance is correct, that means if the hole is drilled correctly, then there should be enough room in the headshell to adjust the cartridge to get the correct null points.

SME has the slotted hole for the tonearm pivot, because the SME headshell doesn't have the slotted hole for overhang adjustment. I think it's very clever on SME's part to have a adjustable S to P distance, that make things a lot easier to get the correct null points.

[steveblezy]

Correct. (Correct me if I am wrong, from what I understand, the overhang adjustment is accomplished by adjusting the cartridge on the headshell to get the correct null points.)

By working with the parallelism of the two null point, you can achieve the correct overhang. It is a process of setting one of the nulls to have the cart parallel then checking the alignment with the other null. Depending on the second null, you move the cart forward/back and restart the process. You then narrow it down so both null points are parallel. It can take some time, or,...

If you know your required overhang, set it first, go to the null point (I use the inner) and get that parallel without changing the overhang. If you managed to do that, you will find that the second null is perfect. Use the second null as a double check. It is simply a faster way to do the job. Always check the second null point for the cart alignment. I simply prefer starting with my overhang as it is way way faster. I can align a cart in less than 15 min this way.

As per your second point, if all measurements are correct, typically there is enough room for the needed adjustments. But in an imperfect world, some carts have long bodies and other have shorted bodies so there are some cases where a particular cart/arm combination leaves very little room for adjustment. It is not too common but sometimes it does happen.

If your SME allows you to adjust the S to P distance then you are sorted. That is a very handy feature to have.

I use a set up disc that has an arm to measure the S to P distance. I then read out the numbers and without turning the platter, I drop the stylus on the required spot on the setup disc. This sets my overhang adjustment. Next I rotate the disc and align the cart to a null point. If I did not change the overhang in the previous step when I check the second null point, it is spot on the money. If it is not, I start the finite adjustments or, I return to the overhang step again and repeat. The overhang, and the 2 null point are tied together in a unique way. If any two are correct, the third is also correct.

So, in a nutshell one can use the two null point to achieve the overhang by going back and forth (long process) or set your overhang and set the first null point and use the second as a verification (the fast way).

Both methods will get you to the exact same place. Then you crack a beer and enjoy the music

Steve

[rcag_ils]

If you have access to a machine shop it might be of use. I did a quick check to see what the manufactures distances were and had an armboard cut but instead of drilling a hole the size of the pillar mount, I had a larger circle cut. I then had a disc cut to that hole size, with a shallow lip on the top and it was threaded to the bottom so I could lock it to the armboard with a large nut. On that disc, I then had a hole drilled for the armtube pillar, but it was 4mm off center. Now the assemble and set-up.

I did the same, but no machine shop. The hole I drilled for my Rega R200 was off, I expanded the hole then used a big washer to cover the gap, sort of an ugly version of the SME set up.