Alphason Sonata Modifications

When the Wheaton Triplaner turned up, it wouldn't fit the Sonata. I decided to replace the flimsy mdf plinth with a welded steel tube construction filled with lead shot. The plinth design aim was to leave the Alphason plinth and subchassis intact so that if it wasn't successful, I would not have ruined a perfectly good deck. To date I have not wanted to put it back together. I have no idea if by changing the plinth, I've ruined a design goal of the original but it works for me.

Plinth

The steel box section has been butt welded into a "picture frame" shape leaving one end of each tube open. This was filled with small lead shot and sealed with foam and plastic end cap designed for this type of steel tube.

1/8" steel plates were welded on at each corner for the spring turrets. The turret tubes are of the same diameter as the originals and welded to these top plates - three in all. Two more plates were welded to the front and rear of the frame to take the motors.

Three 3/4" square steel blocks were welded inside the frame (diagram shows four) and tapped to take the adjustable feet made from bolts - washers welded to the two front feet and the rear sharpened to a point.

The cast iron sub-chassis had some spare holes in it and these were tapped for the right spring tower extension plate to clear the arm counter weight (the reason it wouldn't fit the original deck).

An 1/8" steel arm mounting plate was bolted to the arm mounting pad with tapped holes to take the Triplaner.

The motor regenerator PSU was moved to a new box given a decent power supply.

 

Note right spring extension plate visible under arm. Picture on right shows cheap and cheerfull air suspension and sand pit. Weight of TT alone 77lb/35kg

The change was dramatic! Gone was a whole bunch of stuff but until it went, I wouldn't have been able to identify that it was there. It's as though a whole layer of crud has been removed leaving the music bare. The more effort I've put into this part of the turntable, more of this crud disappears. I'm sure its the damping or removal of externally induced vibration and noise that allows the minute detail to be retrieved instead of being masked. Yet more is happening here because somehow groove rush is reduced as is surface noise. It is this that makes me believe some form of isolation for turntables is mandatory - mass alone can't do the trick.

Motor PSU

The Alphason comes with an AC regenerator type power supply. The original circuit looks to me to be a copy of the Linn Valhala power supply or The Rock power supply. No isolation from the mains is achieved as the unit has no transformer and very little regulation (don't know if Linn do this).

I used an old transformer to supply separate power supplies for the AC amplifier and sine wave generator. All this was transferred to its own case.

 

New power supply on left half. Right half is original unit transplanted from old plinth.

The Next Step

Further modifications would completely change the design basis for the Sonata so there are no plans for furthering the design. The next step will be a DIY design based on components from the Teres project.