Bushman's "TD 166 Ambiance"
Above photo ) Not even close to standard issue, this Thorens takes extreme measures to tame resonance inside the box. The unit is based on a TD 166 MKII. Note absence of traditional TD 16X controls. Replaced by a switch, the standard issue Thorens speed-changer-on/off-switch mechanisms and linkages are removed. For a view of the standard speed changers view this link. The switch is all you need when you play a steady diet of 33-1/3 rpm LP's. If you really must play a 45 some day, speed can be changed to 45 rpm by moving the belt by hand to the upper register of the belt pulley.
Also removed is the Thorens cue control knob, underneath mechanisms and cable. The standard tone arm is replaced with a modified Rega RB-250 tone arm.
Bushman's comments on knob and selector removal: "I am still a bit amused by the change I experienced since removing the selectors completely. The reason is I can not believe this mod should result in such a change. The bass is much better defined and also deeper."
The cork platter mat is more than it seems. Layered over a sheet of carton material, this material is chosen after trying felt, various Thorens mats and the rubber "Oracle" mat. According to Bushman, "it is the most neutral and has the best ability to extract detail."
"Not shown in the pictures is how I damped the outside platter. The damping material is balsam wood."
Above photo ) Looking at the RB250 tone-arm. The brass counterweight and end stub is non standard. The eccentric mounting bore allows the center of counterweight mass to ride at stylus level.
Bushman's comments on the RB250: "You will see that I have extensively modified my RB250 arm. For example, I have added a rubber ring between the end stub and arm in order to reduce mid bass resonance while also maintaining a good mechanical connection between the arm and the end stub. The end stub and counter weight is also made from brass which seems to have better sound characteristics than other metals."
Further changes include an Incognito VTA adjuster. An Incognito wiring kit was also used. More about the wire in bottom photo. The arm board is cut from the same laminated material as the base.
Above photo ) Top plate with outer platter off. Note absence of the speed change lever . (Square hole to left and below belt pulley) Standard issue inner platter for the TD166 is plastic. Bushman has exchanged his plastic one for a Die-cast Zinc inner-platter from a Thorens TD 150. This particular platter is unique in that it makes use of a single ball bearing fitted to its bottom spindle tip. Thorens tuners take note.
Seen through the cast-in holes of the platter, cork damping to the top of the suspended sub-chassis is visible.
Bushman's notes on damping: "You will see from the pictures how I damped my Thorens. For example if you look close you will see that I have damped both sides of the sub chassis with cork. The height of the sub chassis cork is not higher than the spring rubber extension on the top side of the sub chassis. Adjusting the suspension is not more difficult but the added damping does wonders."
Above photo) Under the RDC bottom plate, extensive damping with cork material to the underside of the Thorens top plate, Thorens sub-chassis and also to the outside of the spindle bearing housing. From this view, it becomes apparent that the higher quality Incognito tonearm wires are one continuous lead from head shell clips to the RCA plugs. Note the 16 volt terminal to the Thorens motor is custom. Clean workmanship is obvious throughout.
Even more non-standard is the custom built laminated wood base. These are Bushman's comments about the base: "A few comments on the cabinet; It is made from laminated wood. The corners are strengthened using biscuit joining techniques. Sheets of mica are glued to the inside walls of the cabinet. The reason for all this is to better control resonance. For example, on advice from Ken Lyon, I used the mica sheets, reason is they up the natural resonant frequency of the structure. You do not want the structure to naturally resonate at say 400Hz, or any other audible frequency. Also the principle of a light but rigid structure has been followed."
Not shown in the photo but fitted under the base is the *RDC bottom plate. Bushman's comments about the RDC bottom plate: " The RDC bottom plate is also a key factor in the performance of my Thorens".
"Future mods to include: Damping of the inner platter with cork. A different arrangement at the corners of the cabinet to allow a more direct coupling of the top plate to the RDC bottom plate."
For a view of the standard TD160 MK I underside link here. (see the difference)
* RDC: "Resonant Damping Control" mfg. by Clearlight-audio in Germany. A resin-based compound containing grains of lead, rubber and other materials. The concoction is claimed to be incapable of sustaining resonance and is able to transmit energy in a linear fashion.
Photos by Bushman
Text is by user510 with edits by Bushman