Thorens TD160 turntable

My Thorens TD160 Mk II with SME 3009 Mk II fixed head shell has gone through a number of tweaks over the years. I now have a turntable that sounds significantly different to its original specification due to a platter arrangement that includes an additional top plate and fixed coupling of the centre hub to the outer platter. A chamois leather mat. Platter damping via a conductive rubber foam pinched between the platter sections. A slightly shorter belt. A few tweaks to the suspension. Adding much thicker main bearing grease including silicone and mixed with a small quantity of anti seize copper compound. A substantially more robust plinth weighing in at 14kg constructed from several different materials including 40 X 120mm Utile sides (see below), two mid section in fills of kitchen work top screwed together and glued with rubber solution and a top plate made from 30mm solid beech block work top (available from Ikea!). Turntable top plate damping is provided by large foam blocks cut to fit so as not to impede the sprung under chassis and compressed to half the cut height by the fixing of the turntable chassis to the plinth. Large diameter rubber feet 60mm pending the development of the air suspension alternative. Alternative connection has been provided by making a rear connector panel with gold plated phono sockets and using high quality OFC cabling to the SME arm. The ground connection is also provided here in a banana plug socket. Cartridge is the same as in the original i.e. an Ortofon VMS20e.

The engineering of the platter upgrade was the most mechanical. A piece of 10 gauge aluminium was acquired marked with a quarter inch centre hole and cut to 12 inches diameter. This forms the bond between the two parts of the old platter system. A series of slightly random holes are drilled into the new top plate and counter sunk to take M5 3.5mm brass or stainless steel countersunk machine screws. Don't use ordinary steel screws. You will hear them interacting with the cartridge magnets as they pass underneath. I found brass was the best even if there is a potential chemical reaction between the two metals it would seem to need some sort of catalyst to start any deterioration and since the holes are dry it should be okay. Holes should be arranged so as not to locate directly over the motor pulley or the speed change mechanism whilst at the same time ensuring maximum rigidity. I'm afraid I discovered by accident that there is very little clearance over the top of the main motor pulley so my screws are located just to the outer edge of it and needed fine tuning of the suspension and delicate filing of the screw length before it was right. The plate is split into six equal angles with holes placed inside the hub area and with a 20 degree offset on the outer rim part of the platter. 18 screws are required to make a really good "solid" construction if you intend to go both inside and outside the motor pulley area although I have got away with only 12 which is probably the number to aim for. After offering up the top plate to the platter the holes are then marked through onto the two platter parts with the addition of datum marks to ensure future alignment. Holes are drilled and tapped for M5 threads. The platter cast aluminium is quite thin and needs care during this operation. I used a first taper tap and didn't go right through the metal. This gives something of a pinch during the last half a turn on the assembly stage and ensures that there will always be some meat to bite into for subsequent work. A 6x305x305mm high density conductive foam damping pad (purchased from Maplin for Integrated Circuit storage FA82D) can then be cut to fit. This sits between the new top plate and the existing platter parts. This has a number of advantages. It is conductive so the earth bonding between the parts is maintained even if we don't screw the parts together and the rubberised feel of the foam can be compressed damping out all the old platter assemblies ringing. When the parts are screwed together the foam compresses to around 2mm. I have also continued the through holes associated with the belt and it’s fitting over the motor pulley. This isn't the easiest part of the assembly but it can be done! The belt should be fitted over the hub unit then have it drop carefully into the bearing whilst holding the belt extended out to meet the pulley unit via one of the access holes.

The addition of this weight causes the turntable to sit much lower and the start up to be slightly slower too. A new belt will help the latter whilst the suspension springs can be adjusted to raise the turntable slightly. You should be careful to monitor this as you do it as too high will result in the belt coming off when you change to 33.3rpm.
The chamois leather mat was an after thought. The top plate allows only a small amount of the locating spigot at the centre of the turntable to stick through. There would be no chance of using the various weighted disk damping devices here. There is just too little for any of these devices to grip onto. It was necessary to provide the disks with a clean and safe mounting whilst moving away from the original raised rubber mat. A good piece of Chamois was acquired from my local motor factor shop. Be aware that some chamois is sewn together so have a look at it before you buy. You want a smooth, stretch free, flat piece. This is not easy to come by but well worth the effort. I cut mine to fit the top plate and then used some Prit glue to just hold it on to the aluminium. Otherwise it will try to lift off every time you remove a disk as it rather likes the vinyl surface. I have found subsequently that it is not easy to keep the chamois in shape. It tends to want to stretch in all directions. I have now cut another one and have washed and stretched it over the old rubber mat and cut it again to size. This of course is an on going experiment. I am not too keen on the resulting finish once the chamois is washed. It seems to loose that almost oily feel that makes it so good in the first place. I may return to the original that I had to "slot" to keep it flat! The only way of stopping it stretching even more seems to be to glue it to the platter which then means it might not come off easily. This wasn't really what I intended but it does at least make it look reasonably neat.
You will now note that the platter is to all intents and purposes dead! It doesn't ring in any significant manner unlike the original that rang like a bell. Try an original without its mat. Sounds lovely but is really not at all what we want for hi-fi. This one now gives just a dead "thunk" no matter how hard you hit it or what with!

The plinth was going to be even more solid. I found that it was just too much of a pain to cut out a fancy shape that allowed only the suspended sub chassis, speed switch, and motor power pack to protrude into the plinth and opted instead for a square hole with diagonal mounting corners. This shape is followed through the top beech block wood panel and the top chipboard worktop panel. This gives approximately 70mm of space for the sub chassis to "hang in". The bottom worktop panel is solid having no holes or cut outs at all. When the core block was complete and thoroughly dry I built a three sided mitred surround which was extensively glued and screwed onto the core from the inside out. This wood was so hard I had to use a very tough saw to cut it accurately enough. Utile originates from Ghana, it has a very fine grain, no obvious source of splinters and cuts almost like a metal. This is a wood that is likely to disappear very soon as it is near extinction. I only used it as I had a length of it at home and I didn't want to waste such a beautiful material. I would advise you to try to find something from a sustainable supply if you plan to make something yourself.
The mechanism sits on top of the beech block panel and is "ring fenced" by some 20 x 8mm window quadrant hardwood such that most of the beech is invisible. There are three locations where large blocks of expanded high density foam can be located under the mechanism and be made to pinch down as the deck is screwed into place. The first is between the power unit at the rear of the chassis where 45 x 30 x 120mm of foam is fitted. The second is immediately under the arm at the cartridge end where a large block 120h x 45w x 100d mm can be fitted. This is compressed substantially during assembly from 120mm down to 75 or so. The third block is 120h x 80w x 45d mm that has to be shaped slightly and sits under the front middle edge of the mechanism. The decks original 1.25inch PK screws have been reused to fix the mechanism to the plinth. The original Perspex lid is to be refitted. This now sits inside the edge of the now much larger plinth and actually sits on the angled hardwood that is the mechanism ring fence. The original hinge system has been retained by drilling into the new timber at the rear plinth edge and mounting the hinge brackets in slots.

Refitting the lid was achieved by using all the old fittings. A pair of small oblong holes were created in the rear edge of the quadrant timber right through to the beech. A small cut out was made in the back edge of the beech wood and the hinges were mounted here in much the same way as the originals. Epoxy resin was used to fix the hinges in place.
So how does it sound? Well we now have serious firm bass. If you have an original configuration you will know there are all sorts of suggestions that say "the cartridge needs some additional capacitance" or try different phono leads etc. None of these are really effective. I have recently returned to my original, supplied SME leads but intend to try something in gold again later. I have found that the most effective improvements have been by modifying the platter, increasing its mass and damping it so that it doesn't ring. Then adding the Chamois leather to "glue" the disk to the platter is really a revelation. The original tracking capability of the Ortofon is undiminished. Sure it isn't exactly up to the current crop of mega cartridges but then it is in some cases only 100th of the cost! The effect is to make the LP sound much more dynamic and perhaps more CD like. There is of course advantage in using the good old vinyl, the smoothness and especially the high end detail is so much better. I'll let you know more about this as I audition more of my black plastic.

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