@Pete_the_painter
I started off using dome nuts, these devices were designed as an improvement on them (and exceeded my expectations that way - I though they’d only be a marginal improvement, but the improvement turned out to be quite substantial).
@TOBYJUG
The ‘black bit’ ensures that the ball can’t be pushed out of the recess in the brass.
The depression in the brass is only 3mm diameter, so yes the ‘black bit’ is necessary.
Yes the acoustic interface to the underside of the brass will make a difference if it changes the coupling (such as using a visco-elastic substance or an adhesive. Putting it in a shallow recess would make no difference acoustically, but would ensure a consistent location.
@Yeti
Yes…
Why make life more complicated for yourself if you can buy an almost ideally shaped component in the right material!
@ChrisSU
Not currently (current glass is only 8mm as it was speced for the lighter XS series components) but I’m about to do so.
The tungsten carbide balls are an optional upgrade to the lower priced option, and as standard on the better ranges are Grade 10 (10ppm deviation from sphericity).
The silicon nitride balls I used are Grade 5 (twice as good as the standard grade 10 balls). I also notice that on the top series, the ball is in direct contact with the underside of the platform as I am doing with the glass.
Interesting. Functionally my design is quite similar to the Symposium Rollerblock 2.
My design is however a little less expensive (£6 for 3, vs $199 for 3).
I wanted also to point that it’s the first time a company says which ceramic balls they use, instead of the other brands cited above.
I have no idea of which type of ceramic can sound best. Perhaps the components associated with it may vary the results.
The cost is perhaps due to the machined steel or aluminum, the cups, which are nicely machined and finished?
The type of ceramic that sounds best will vary dependant on the other materials and also on the equipment being supported; but the fact that they specify tungsten carbide is interesting. Also interesting is that Nordost actually do specify silicon nitride in their Sort (the word translates as black) range of isolation devices (at least in all except their most basic range).
I also have a grade 10 depression in the brass lower plate (it takes me about 10 seconds to make each one, but I could do it in less than 5 seconds in a production environment).
Not so sure about aluminium / steel / aluminium, both from the sound perspective and from the perspective of corrosion, and sticking visco-elastic pads on them defeats the very principle of the design.
Brass / silicon nitride / glass is a better combination
You are very probably right. It just that it looks as the Symposium above , but for 1/18 of the price. Just replace inside the balls and you are with a similar product, not,
So you feel, or calculated, that nitride balls in direct contact with the glass isolate better than brass cup above the balls, brass cup in contact with the glass?
So the glass shelf rolls freely on top of the ball, right?
No sure I could manage something similar. My glass shelves are about 20-25 Kg. The amp is 25 Kg, which makes about ~45-50 Kg on those little balls. It could crack the glass shelf.
Because of the ‘cup’ in the brass the ball settles into the bottom of the well rather than really ‘rolling’ around. More than about 30 kg would be getting too much for cartridge brass, you’d need a different material.
I think you’d be surprised how much pressure toughened glass can handle - in my design it’s actually limited by the brass!
The other option is to use larger ceramic balls: 9mm diameter will give twice the weight bearing capacity.
The ‘well’ in the brass is a small concave spherical depression. The brass is locally hardened in this area.
To prevent ‘micro rattles’, you should use 3 contact points to the glass rather than 4, and with 6mm balls I’d limit the load to no more than 10kgf each; with 9mm balls I think 20kgf per support is viable. It’s also important to ensure that the balls and the underside of the glass are clean when mounting or remounting the glass.
