What considerations apply to material selection for cartridge mounting bolts?


I have found myself needing some longer bolts to relocate a Shure V15 Type 3 cartridge to a Holbo air-bearing system.

The Holbo tone-arm is a tangential tracker with a rigid rectangular 'launch pad' for the cartridge.  The pad is 3-mm thick which is much more than the fixed SME head-shell my dad bolted the Shure to some 45 years ago.  If it was supplied with longer bolts, they disappeared decades ago!

I will most likely have a similar issue with my Audio Technica VM540ML cartridge which is probably a better fit for the Holbo.  It was supplied with a head-shell 4-mm thick, but the bolts slots are recessed by over 2-mm.

A quick internet search turned up bolts made of stainless steel, titanium, aluminium, brass, plastic and nylon.  Some brass bolts are gold-plated (for corrosion resistance presumably).  As a one-time metallurgist, I know that stainless steels can be non-magnetic, or magnetic.

Plastic and nylon are lightweight insulators and immune to electro-magnetic effects like induced eddy currents.

The lower the material density, the lower effective mass of the cartridge.  Here brass is clearly the worst, being denser than steel and weaker than the other metals.

I presume that the main engineering requirement is to firmly couple the cartridge to the tone-arm but I have no idea how firmly.

The Funk Firm has an opposite view with its Houdini coupler which in effect splits the bolts in half, with an elastic suspension between the cartridge body and the tone-arm.  It seems to allow the cartridge body to swing easily to the left or right side.  Does anybody here use these?

richardbrand

Cartridge mounting screw material affecting sound.

Next year's resolution- don't goof on audiophool claims.

Years not done yet.

I bet if that company did a more colorful hype write up, they could charge DOUBLE, and people would be hitting the buy now button.

I guess if you can afford a fully loaded Dohmann or Tech Das Zero, you buy them.

 

 

 

I guess if you can afford a fully loaded Dohmann or Tech Das Zero, you buy them.

Hahahaha - good luck with that.

Tech Das are M2.6 ( Japanese standard )

Acoustical Solutions M2.5 ( euro standard )

Good luck rooting your pricy cartridge with the wrong size.

Always pays to check the screws provided with the cartridge.

The 2 sizes are not interchangeable.

 

 

Confession - my embarrassing failure when setting up my new Holbo system.

The system needs to be quite level and there is a further adjustment on the rod which is the track for the tangential tone arm.  To make this adjustment, the tracking force has to be set to 0.1 grams at which point the arm just glides on air like a blob of mercury on a glass plate.

I have a Chinese digital scale with Chinglish instructions to measure tracking force, but I found 0.1 extremely hard to set.  Further the arm was prone to fall over backwards.

Once that was done, the real tracking force needs setting so as a test I went for 0.7 - again it was extremely hard to set exactly.  Next came my Acoustic Research Demonstration Record which starts with a Bach organ piece.  The Holbo simply could not track it.  I thought I had made a very expensive mistake, so had a cup of tea, a Bex and a good lie down, as the Aussie ad says.  Bex = headache powder.

Then it dawned on me - the scales had to be wrong and I had not bothered to use the 20-g weight to calibrate them.  Then I discovered they were set to measure in gn which I misread as gm for grams,  Now a grain is about 0.065 grams so I was attempting to track at about the weight of a bee's dick - a traditional Australian measurement.

@dover 

Tech Das are M2.6 ( Japanese standard )

Acoustical Solutions M2.5 ( euro standard )

That's the great thing about Standards.  There are so many to choose from.

Both my current cartridges need external nuts, probably because they have plastic bodies.

I think there are good sonic reasons to couple the cartridge as tightly as possible to the tone arm in order to channel vibrations away from the business end.  The fact that Rega makes a torque tool (AUS-369 mind you) supports the concept as do Wilson Benesch research papers.

At the same time, keeping the inertial mass of the business end low also makes sense.  Combine the two requirements and titanium wins of the metals.  Nobody here seems keen on nylon.  Nylon has the advantage that it is immune to eddy currents and to magnetic effects

 I was attempting to track at about the weight of a bee's dick - a traditional Australian measurement.
 

LMAO

I have a digital scale that I thought was accurate. It was off by a full gram!!!

so instead of 2gr my vtf was set to 0.9 and distortion like I’ve never heard before. 
Got a riverstone audio stylus force gauge and all is well now.