Sme arm "Bridge Removal"


Hello,

Just a query, hopefuly someone can shed some light.
I have seen a few references of the bridge being removed fom the sme 1v and v arms, apparently bringing about greater resolution..?

Anyone experimented with this?
Cheers
sme10
I have had an SME V in my system for numerous years now. I have modified it in the following ways:
1. changed external wiring first to Cardus and then to Siltech Avondale;
2. changed internal wiring first to Van den Hul MCS 150, and then to Kondo;
3. removed the ‘bridge’;
4. applied very small amounts of damping material (in fact a sort of adhesive putty very similar to ‘Blutack’) externally to the armtube at certain key points (near the bearings, near the headshell).

When the arm was sent to SME for the second rewiring it was already without the bridge. SME did the job without demur and returned the arm without replacing the bridge. On the phone they said that they had seen a number of arms modified in this way (they simply warned me to take care - should I one day decide to replace the bridge - not to tighten the screws too firmly : apparently this could damage the bearings).
The following well-known modification I decided to forego:
5. bypassing the headshell clips and running a single length of internal wiring from the cartridge clips to the five pin connector in the base.
I abandoned this idea on advice from SME and others (Definitive Audio, UK): the more delicate the internal wiring, the greater the likelihood of breaking one of the strands while changing cartridges.
The application of the damping material was done on the basis of advice received in this forum (Dertonarm, who I thank). There are also posts on Vinyl Asylum that recommend this. I experimented quite a bit, varying the amount of the material and the position. I ended up rolling it out in order to reduce the thickness and obtain the best extension for a given weight of material (I doubt if the total amount I used was greater than a small pea). Once applied it can easily be coloured with a black felt-tip pen, thus reducing (but not completely masking) the undesirable aesthetic impact. Of course, downforce has to be adjusted after application.
The more recent of the above modifications - the change to Kondo internal wiring, the removal of the bridge and the application of external damping - have all (in my opinion) contributed to increase the neutrality of the arm. The playback I am getting now is more relaxed, more airy and richer in tone colours and in spatial definition than it was before (cartridge: Benz Ruby II, retipped and modified by Roberto Torlai. Turntable: SME 30/2).
Best wishes.
Could someone explain to me what "loading" the bearing means? And how having the bridge in place, or not, affects that "loading"?

Yesterday, I removed the bridge on my SME V, and to me, it looks simply bolted to the main tonearm yoke casting. The attachment bolts themselves do not appear to do anything more than simply hold the bridge in place (they do not hold the bearing in place!) -- and tightening them wouldn't do anything more than hold the bridge tighter and tighter until you snap the bolts! There does not appear any way that tightening (or loosening) these bolts affects the the tonearm's vertical bearing, which is already press-fit into the main yoke casting and would not be affected by the presence or absence of the bridge.

Having the bridge in place completes the gimbel design look of the mechanism, and IN THEORY would keep the top of the main casting from spreading apart, perhaps with slight variations in temperature; but such microscopic changes are, it seems to me of little consequence, and in any case, do not affect the built-in "tightness" of the bearing (if that's what is meant by loading?)
Dear Neil,
I suppose that 'loading the bearings' is the same thing that Dertonarm refers to as 'pre-tension of the bearings' in the following (which,incidentally, is the explanation that convinced me to go ahead with the application of damping):
"While all done and designed in the best intention [= the SME V design],the shape of the magnesium armpipe with the widest diameter at the bearing does somehow amplify and ill-control armwand inherent resonance. The heavy pre-tension of the bearings doesn't ease things in this manner at all."
[http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1266367593&openflup&142&4#142]
I suppose that what he is referring to is the degree of tightness of the bearings in their sockets.
Exactly what the role of the bridge is in all this, I am not so sure. As you say, it is simply bolted to the yoke. When I decided to remove it (a long time before applying the external damping), I did so on the simple (and perhaps simple-minded) basis that it was just a cosmetic element (and in fact the arm does look better with it in place) which could resonate and degrade the sound to some small degree (after all there those who remove the fluidd damping trough for the same reason). Its cosmetic nature appeared to be confirmed by SME, who assured me that it played no structural role in the design and could be removed without untoward consequences.
Best regards,
Peter
Sme10 - I did not hear any of the changes you and others have reported. Frankly, if I did, I would would be more alarmed than pleased. But I'm still very anxious to understand what this "loading" terminology refers to, and hope someone will explain it.

Thanks.

Neil
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