Recently as a result of this thread on DIY audio I became inspired to try my hand at some serious cart modding, most of the info regarding my progress and how this transpired are on this thread, which was started by another member.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100408The sonic results of all this have turned out to be terrific and I thought some of the information might be of help to others looking for a few tweaks.
Here is the list of mods, there are some pics of the cart in progress on the above forum and I will be posting pics of the finshed cart on my webpage in the near future.
http://homepage.mac.com/braddles/Menu2.html, should be in the next 3 days or so.
1) Metal casing was completely removed
2) Plastic mounting tabs cut off
3) Plastic chassis filed down
4) Wires from coil to metal pins rerouted so they did not twist around each other so much
5) Plastic stylus holder filed down and shaped so it had no hard angles
6) Balsa wood body made into which the cart chassis could fit, with no hard edges/corners
7) Aluminium inner shield made and earthed to minus pin
Coils embedded in epoxy
9) Stylus holder epoxied into chassis after the internal holding pins were pushed inwards to tighten the grip they have on the shank of the holder, the shank which is plastic was also thinned down prior to gluing in.
10) The balsa body had a integral cross bar to hold outrigger weights
11) The body was lacquered 6 times to harden the outer shell and give a nice finish
12) Once the body and chassis were mated all of the joints were epoxied to give a totally homogenous structure
13) 3 Cavities in the top of the glued up body were filled with very fine sand
14) The top of the body was capped with a small sheet of aluminium shim
15) Double side foam tape was added to the top of the cart.
16) An alloy plate with integral bolts was attached to the top of the foam so as to allow easy mounting and adjustment
17) The perimeter of the cart where it mounts onto the foam tape was given a bead of bluetac to make a better bond and strenghten the edge of the foam
18 The magnet was glued firmly to the cantilever, this seemed to be a weak point
19) The cantilever was notched just behind the elastomer and a very fine copper wire ring glued in place to prevent the cantilver pulling through the elastomer under pressure on lare modulations
20) The stylus tip was filed down considerably around the mounting area for the diamond to remove all excess metal
21) The shank ahead of the elastomer was filed down to taper towards the stylus
22) The shank was smoothed off with very fine sandpaper
23) A single loop of very fine cotton thread was placed around the shank, half way between the stylus and elastomer this was super glued in place.
24) The cantilever was mounted into the holder and the finest dabs of super glue touched to the surface just above the elastomer so it ran down to the lip of the elastomer and locked it in place preventing forward motion of the elastomer (this was quite nerve wracking as any glue on the elastomer would have hardened it and ruined it.
25) Metal weights were attached to each end of the cross bar (integrated longhorn mod)
Having now found the time to listen carfully to the results, which I am sure will be better once 20hrs or so have playing time are logged I can make some comments on what has changed an why I think it did, which might be of help to a few others.
Resolution right across the range is improved, and this is especially the case with the highs above 8khz, spatial information is also better, but there are some other improvements that were unexpected. Surface noise is considerably lower and the cart tends to track better right across the disc and this despite the fact I have not yet done any final adjustments. One unusual thing I noted was that when I run the cleaning brush across the stylus to lift the dust off the noise made is quite different to the previous modded cart and very very different to the unmodded cart. The best way I can describe this is that as you drag the brush over the tip you hear a smooth swishing noise, the unmodded and even midly modded versions I have make a rough noise.
I have a number of LPs I use for system testing, one of these is Brothers in Arms, playing Money for Nothing reveals several characteristics. First the attack on the drums at the begining is far tighter, it is easy to make out the individual impacts of stick against skin, secondly there is a far reduced if not eliminated tendancy for confusion on complex componenets where volume is high. The third charactersitic is that of the abilty to reproduce subtle differences, basically this track makes great use of guitar distorion effects, but now you can hear the distortion much more clearly, in other words it doesn't itself get lost in the distortion of the system itself, which seems to add an extra dimension.
I feel the main gain is due to better location of the cantilever and lightening of the stylus end of the cantilever, this I feel improves tracking under pressure and and means the cantilever does not oscillate for and aft on heavy modulations, the loss of the metal case seems to have opened up the sound somewhat, though the cart is more prone to hum (somethig I will fix at turntable level). Better mounting of the magnet to the cantilever I think makes a difference at the high end and the overall total integrity of the body etc means that there are much less vibrations being re-inserted into the sound which I feel gives greater overall clarity.
I am sure many of the mods could be applied to almost any cart, but of course the potential for damage is great so it would need some practice on old wrecked ones first.
You can probably gather I am very happy with the result, of course that won't stop me tweaking, but it is nice to be able to say it is an unqualified success on this occasion.
