Mint LP a no go – now what?

Talk with Steve at 'The Analog Dept.'

http://www.theanalogdept.com/

He made me a very nice arc protractor for my 12.5 after I, too, failed to get one from Mint (though at some point I hope Mint can do one for me). Not made to the same standards as the Mint, but still very good, and let's just say that the price was right. My review of it can be seen at the Oswald's Mill site.

The sound is night and day different than with the VPI jig, and by that I mean night and day better. Sorry Audifeil, I think the VPI jig *is* deficient, and HW should reconsider his setup parameters. Perhaps the jig is designed for ease of use, as Srwooten says, but if so, I'll take accuracy and sonics any day as a trade off for putting in the labor necessary to make it right.

Steve's work well too!! wasn't sure if he was making them a public offering yet but I would check him out too. Ken's are really nice in that they have 4 different geometries on them.

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

Thom-

No, the JMW arms are not easily adjusted at their mounting position on the plinth. Thankfully, it's easy-at least, as easy as any arm-to measure spindle to pivot. Pulling the arm reveals the pivot point, and believe me, it's a 'point'-the greatest threat isn't an inaccurate measurement, it's the potential to draw blood on that thing.

An extensive study on the JMW arm geometry was done on VinylEngine

http://www.vinylengine.com/vpi-tonearm-geometry.shtml

which showed relatively conclusively that VPI uses a proprietary cart adjustment geometry. Not necessarily a bad one, depending on what you're seeking sonically, but definitely not a Baerwald or Loefgren. Incidentally, this all came about because J. Elison could not get HW to cough up the math that he used to generate the VPI mounting jigs. Not the lengths or distances, mind you (those are available on the VPI website, for all arms other than, oddly, the 12" arms) but the math.

For the record, the VPI alignment does, as it seems to be intended, deliver a bit less distortion on the inner grooves, but since switching to Baerwald I'm much (much) happier with the sound over the entire record.

BTW, I agree that this info should be easily available, for *all* the JMW arms-why it's not is mystifying. Frank Schroeder sure wouldn't pull this crap. Can you imagine HW helping diy-ers mimic his arms, the way that F.Schroeder so generously does? Guess it's a personality thing.

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