been a while since i updated this blog , since the last 12" arm i have made another , this one is based on a thorens tp16 , it had a damaged armtube , i was going to put it on ebay as spares or repair , then i thought i would disassemble it and check the bearings , the bearings were all fine and of a far higher quality than i was aware of , i should have known as thorens didnt really make anything we could call 'poor quality' ,
  i set about giving it a bit of thought and decided on a stainless steel armtube with dropped weight and direct clamped headshell , the effective length is 324mm , all the other numbers were taken straight from the arm calculator on the vinyl engine , and use lofgren A alignment
eff length               324mm
mounting distance 311.4mm
over hang                12.5mm
offset                       16.7 degrees ,
the only deliberate damping that i have built into the arm is from the carbon fibre dropper plate and the expansion wedge used to mount it , see the other post in this blog to see what i mean by 'expansion wedge ' , i have also used a small amount of high density foamed rubber at the headshell end of the armtube , around 5mm long , also the delrin (acetal) as an arm board as i have found it can have a very positive effect with arm structures that are very efficient at transmitting vibrational energy , arms that have compliant mounting within the arm structure are less receptive to it though so experimentation is recommended.
 the end result is somewhat disarming (no pun intended ) , the alloy arm based on the audiomods bearing assemble was really nice , but this is in a whole other league , Melody Gardot is rendered in a stark realism that i simply didnt think a home made arm that cost about £25 and 3 hours to make could ever achieve , bass? , all the way down without any unevenness , the sound is remarkably open and uncoloured for what it is , even the at95e sounds quite stunning ,
 i have still to fabricate an arm lift and nice looking rest for it and will post up more info when its all sorted but for now ,here is a quick pic of it on the 401 test plinth . :-)

mounted in an SME 2000/12 plinth , i know the plinth has a bad reputation which in my opinion is deserved , however it has some traits i like , the mid band is nicely animated and easy going , as soon as you crank the volume it soon makes its presence known , resting a hand on it demonstrates it is highly susceptible  to vibrating strongly at certain frequencies . Rather than give up on i took the springs off and replaced them with hard rubber doorstops , improvement was quite immediate but still wasn't quite usable , then i sat and thought about it a bit and considered what else is made from  1/2" ply wood in the world of hi fi , the bbc speakers and harbeth speakers sprang to mind , then i used a stethoscope to determine where it was resonating the most , i found a line running from the corner of the garrard closest to the arm base that runs to the front right corner was the worst point  , makes sense as the garrard clamps and damps the main part of the top plate , the arm board likewise , i used a ash stave 5/8 thick and 3/4 wide  that was secured by the 401 mounting stud then ran it along the pink line shown below , it is screwed to the top plate at two other points along its length , just this simple bit of wood and two screws have transformed its abilities ,

 prior to this the sme brought terribly uneven bass , after adding this bit of ash the bass is now as even handed as I have heard , i will try stiffening the carcase too as bad as its reputation is , with a little careful modding i think it may be a go'er , its main advantage is low mass which seems to bring out the best of the 401 , the mid range is more akin to a Thorens td124 , still with the Garrard grip but with a delicate velvet glove on .
 i will add more on this after some investigation and trying a few simple tweaks to sort the carcase .
more soon ;-)