New Fatboy at Rancho De Luxe West
 

I recently converted my trusty old 12” JMW 12.5 unipivot to a new Fatboy gimbaled arm. Couldn’t be happier — my Dynavector XV1-S sounds better than I’ve ever heard it in all the years I’ve had it.

Not that the 12.5 was bad by any means, but the Fatboy — wow!

Now, some of this might be due to hitting the analog equivalent of the lottery with my alignment. In a hurry to get the arm in play I basically set up the cartridge by eye and ear, using the VPI 12” arm jig, double-checked cantilever angle with a WallyTractor, and set the arm tube to level with an inexpensive Hudson lucite block with parallel horizontal lines from Amazon, after first making sure the VTF was within the recommended range with an inexpensive but accurate digital scale.

When I went back and checked SRA with a USB scope and azimuth with an oscilloscope and test record, lo and behold, they were both spot on — 92 degrees SRA and crosstalk difference right at 0.5 dB. I should have bought a Powerball ticket when I did that set up!

I thought long and hard about giving up the easy interchangeability of the unipivot for the increased stability of the gimbal, but being honest I haven’t swapped to my mono Helikon more than a half dozen times in the last couple of years. If I really, really feel the need in the future to be able to swap quickly between cartridges, well, I can always fabricate another armboard and add another arm to my DIY Teres ‘table. My phono stage will accommodate three more arms. . .

Steve Z

How it’s done
 

So, for anyone contemplating swapping their older VPI arm for a new Fatboy gimbaled arm, the process couldn’t be easier.

The arm comes with a new arm rest to fit the larger diameter arm tube, a bushing to adapt the larger hole in the VPI arm base to the threaded post attached to the gimbal assembly, and a new stainless steel nut to snug the arm to the base.

After removing the the old armwand from the base, the existing round nut under the “boomerang” platform holding the unipivot needle is loosened and removed using a pin spanner (Park bicycle tools makes an inexpensive one).

The old arm rest is removed using a small allen wrench to loosen the set screw in the side of the “boomerang”. The new rest is set in the same hole as the old arm rest, and the set screw snugged up.

The new arm’s threaded post with the supplied bushing is placed in the pivot hole and the new nut is tightened up. If needed, readjust the height of the new arm rest and snug up its set screw again.

Place the new counterweight over the arm stub with the two holes (for adding an additional and not supplied weight plate for balancing heavier than normal cartridges) facing away from the gimbal bearing. The hole concentric to the counterweight that faces the gimbal bearing is larger than the central hole on the part that faces away from the bearing. This allows the counterweight to slide completely over the clever little carriage-and-lead-screw adjusting assembly on the arm stub.

Plug the new arm’s Lemo connector into the connection box.

Voila! You’re done with the swap. Mount your favorite cartridge, align, and add vinyl.

Note: the sharp-eyed will see that my counterweight is butted up against the shoulder of the VTF adjustment mechanism instead of being slid completely over it. This is because my Dynavector’s weight is just enough that I couldn’t get VTF within the recommended values without the additional counterweight weight plate. But, by reversing the counterweight it rides just far enough back on the arm stub to do the job until the additional weight arrives from VPI.

Best part of the whole conversion besides the sound? For a limited time participating authorized VPI dealers are offering a very generous trade allowance for your old arm wand on a new Fatboy.

A Fatboy unipivot is a very similar procedure, however my understanding is that the existing unipivot needle bearing on the base assembly needs to be swapped out for a new compatible needle assembly.

Steve Z

Congrats! I have the Fatboy on my Wish List. I have made a ton of changes to my system in the past 3 months, new listening room, TT, cartridge, power conditioner and cable loom. I have everything about 95% dialed in. I am really really trying to listen to this set up for at least a year before upgrading to the Fatboy. We’ll see how that goes.

Hi ,

Ive done the conversion as well in my HR-X . I replaced my metal 12.7 arm to the Unipivot w/ dual pivot Fatboy . Conversion was not a straight forward compared to the gimbal version of the Fatboy . I made adjustments to the pivot spike by increasing its height so that the dual pivot can be accomodated . I also removed the delrin spacer of the VTA base and mounted the VTA base directly to the HR-X plinth. The reason for removal of the spacer is because I ran out of downward adjustment of the VTA to achieve the 92 degree SRA . Azimuth adjustment was easy using the dual pivot .

Tdh888

Hi ,

Ive done the conversion as well in my HR-X . I replaced my metal 12.7 arm to the Unipivot w/ dual pivot Fatboy . Conversion was not a straight forward compared to the gimbal version of the Fatboy . I made adjustments to the pivot spike by increasing its height so that the dual pivot can be accomodated . I also removed the delrin spacer of the VTA base and mounted the VTA base directly to the HR-X plinth. The reason for removal of the spacer is because I ran out of downward adjustment of the VTA to achieve the 92 degree SRA . Azimuth adjustment was easy using the dual pivot .

Tdh888

Hi ,

sorry for duplicate post

Tdh888

Thought this new review from Positive Feedback would be of interest here.