Mint LP a no go – now what?

To put things into perspective, I've found the card-stock protractors that I print to scale on a laser printer to be far superior to any two point protractor I've used.

A wonderful tool like the Mint will get you the last 10%, but treat it like icing on the cake if you will.

It's been quite some time since I handled a JMW tonearm. Doesn't it provide for fine-tuning the pivot to spindle distance in the manner that the Schroeder Reference does?

My memory may have faded in this regard. Assuming that this is the problem (no easily adjustable pivot to spindle distance), you'll need a means of either accurately measuring p-s or alternatively getting this number from VPI.

Once you've established the pivot to spindle distance, you'll need to work backwards to establish the desired effective length.

Use the Ellison spreadsheet on the Enjoy the Music website (there's a link to it on my support page). Set the decimal precision to 3 decimal places (I'm nuts, so I set it to 4).

Iteratively plug in different effective lengths until you arrive at a pivot to spindle distance that VPI tells you they use (or the one you have measured).

I'll run into situations where someone has a fixed mount arm which is not easily changed, and this is how I solve the problem.

Once you arrive at the Baerwaald predicted effective length (that yields the VPI provided pivot to spindle distance), you can use the procedure I mention above to measure your effective length.

You want to see if it is close enough to Baerwaald to trust (remember, you have headshell slots to compensate).

If it is not in agreement, then VPI has either misdrilled your 'table or they are not using a Baerwaald. Even if they use a proprietary alignment, you at a minimum deserve a yes/no answer as to whether they use Baerwaald or Loefgren from VPI. These are not state secrets.

If you can't get the numbers to agree, then your only option is to move the arm mount, by using your measured effective length to derive the new pivot to spindle distance according to the Baerwaald equations.

Cheers,
Thom @ Galibier

WOW! Those are wild null points in the Vinyl Engine writeup. It's an interesting analysis, and raises an interesting question. Is this an alignment with great merit, but implemented with an inferior tool?

I suppose it's HW's call as to how his turntables are heard. He's obviously invested in his geometry, and thinks this is how we should hear his 'tables.

I think there's a better way to sell your prejudice than by merely refusing to divulge a fairly readily available number (p-s or eff. length, or both).

In fairness to Harry, he's a helpful sort, but I think he's not a numbers guy. I had to fabricate a custom armboard for a 12.5 a few years ago.

When I asked for the mounting pattern, Harry was good enough to send me an old acrylic mounting platform with the marked position of the 3 holes.

If asked the same question, I'd send someone a .PDF copy of the drawing. I think it's a matter of how Harry views these problems rather than any reticence on his part.

As an aside, there are quite a few alignments used by various Japanese manufacturers - alignments for which we Westerners have no name.

Plug for example the effective length of the Dyna DV-507 into Ellison's spreadsheet and you'll be surprised at how it varies from both Loefgren and Baerwaald.

Cheers,
Thom

Hi JohnBrown,

I have had great experiences with a well implemented Baerwaald alignment as well. The distortion profile of the JMW did however catch my attention.

A note to owners of DV-507's and other unconventional mounts when implemented on a fixed mount plinth. Even though you may have a fixed mount, you can likely still achieve a Baerwaald alignment.

Your protractor of choice will guide you. In the case of an arc protractor, it will take some messing with the Ellison spreadsheet, because you need to derive a new effective length that is consistent with your pivot to spindle distance.

First, verify your pivot to spindle distance. Then, iteratively work through the Ellison spreadsheet to find an effective length that yields your (non-moveable) pivot to spindle distance.

Finally, verify that you can achieve this effective length - that you don't run out of fore/aft adjustability in your headshell slots. Use the method I propose above to determine the effective length.

Note that a difference of .5mm pivot to spindle distance will drive you nuts. As long as you can verify your pivot to spindle distance (or there's a enough play in the mount to compensate), you'll be fine.

Fun with geometry ;-)

Cheers,
Thom @ Galibier

Greetings,

I go nuts when manufacturers won't divulge a simple spec. like effective length.

I've been trying to find this number for the Well Tempered arm for someone, and Well Tempered treats this number as if it were a military secret.

Don't these guys want their products to sound good? I consider an arc protractor to be an essential tool for vinyl playback and actually put up a dedicated page to Yip's product in my accessory section. I consider it to be be that important.

Rant off ...

How good are you at using a ruler? You can find a good enough working number for effective length for Yip to make you a protractor.

The easiest way to measure this is as follows:

1. Put a thin strip of masking tape on your headshell - between the two cartridge mounting slots and extending forward to the front of the headshell.

2. Move your cartridge midway (front to back) in the headshell slots.

3. Find the midpoint between the two cartridge screws and mark this point.

4. Measure forward of this point by 9.25mm (9 and "little bit").

This is the point where the "average" cartridge's stylus is located. This offset differs by manufacturer and is one reason for the slots in the headshell. The other reason is to allow for fine rotational adjustments to compensate for skewed cantilevers.

Now, measure the distance from the tonearm bearing pivot to this point where your virtual stylus is located.

This is your effective length, and all that Yip needs (other than your record spindle diameter).

Note, that a few of my customers have gotten confused by tonearms with offset mounts like your JMW, the Tri-Planar, and the Schroeder Reference. They mistakenly think of the center of the Tri-Planar's VTA tower knob as being the bearing pivot.

The with your JMW, this should be a bit more intuitive. If you remove the arm wand assembly and do this job on your desk, you won't inadvertently measure the distance to the VTA knob. It's too far away (grin).

As long as you're within 1 or 2mm, you'll be fine because you'll be able to compensate for various cartridge brands (having differing stylus offsets from the mounting holes) by moving the cartridge in the headshell slots.

Let's say you arrive at a 290mm effective length and later discover that the "real" number is 288. Don't lose any sleep. The difference is meaningless and don't let any "experts" tell you otherwise. As long as you align to a 290mm arc you'll be grinning ear to ear.

Cheers,
Thom @ Galibier