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Supatrac: the world's best tonearm?

Tried to post the same question over on SteveHoffman but was unsuccessful, probably for the same reason. That post is now suspended waiting for admin approval and I can't delete it so will eventually appear as a duplicate.
 
Struts001 said:
I remember reading somewhere (can't find it now) about a formative experience from engineering school where you had to make a bridge from an under dimensioned sheet of metal. You made (iiic) a sort of telescopic Y-section which proved to be very strong.
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Yes - that was Roy Gregory's interview here:
https://gy8.eu/blog/work-in-progress/

Struts001 said:
Made me wonder, why isn't the Blackbird (or any other tonearm for that matter) made with a Y-section. Or indeed an equilateral triangle*? I assume pultrusion doesn't allow tapering but maybe even an untapered triangle would be stiffer than two boxes?
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It's a good idea - I would certainly be interested in a Toblerone cf pultrusion, but I'm not aware of any such product. I'm not yet ordering enough to have custom pultrusions made.
 
sonddek said:
It's a good idea - I would certainly be interested in a Toblerone cf pultrusion, but I'm not aware of any such product. I'm not yet ordering enough to have custom pultrusions made.
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Understood. Looks like I can post the link now, here. To save folks clicking through here are the salient points:

The problem of determining that shape of column which has the largest critical buckling load is solved, assuming that the length and volume are given and that each cross section is convex. The strongest column has an equilateral triangle as cross section, and it is tapered along its length, being thickest in the middle and thinnest at its ends. Its buckling load is 61.2% larger than that of a circular cylinder. For columns all of whose cross sections are similar and of prescribed shape-not necessarily convex—the best tapering is found to increase the buckling load by one third over that of a uniform column. This result, which was independently obtained by H. F. Weinberger, is originally due to Clausen (1851). For a uniform column, triangularizing is shown to increase the buckling load by 20.9% over that of a circular cylinder. The results lead to isoperimetric inequalities for the buckling loads of arbitrary columns.
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I understand that the increase in stiffness for the same weight of a Toblerone over your bonded boxes may be marginal, and of course must be set against the additional cost and complexity of sourcing. Tapering seems beneficial but of course is not compatible with pultrusion. Presumably this would mean moving to something like casting or 3D printing for wand construction (or just Dremelling away layers of material at one end a la SAT..)

Thanks for reposting the Greogry link. I really enjoyed reading that interview and will enjoy rereading it!
 
Thank you! I've just ordered 100m of the square stuff, so this minimum order is fine - I had not realised that this was available and that minimum orders for custom shapes could be so low. Brilliant. If this ever ends up in a new model and you're interested, touch me for a discount!

There are still a couple of uncertainties. The bonded spine down the middle of the Blackbird arm tube serves a useful purpose over and above the stabilisation of the flat platforms which bolt onto the thrust box and the cartridge.

There's also the issue of top-heaviness, an aspect of the design where a Toblerone could be superior since it has a low centre of gravity.

As I've said elsewhere, as long as you construct a sensible arm tube, results are very good. It's my opinion that the real magic happens in the bearing, yet everybody is obsessed with arm tubes which make a relatively marginal difference.

Great discussion.
 
Alex S said:
I want to hear how the Supatrak sounds on the Rega Naia - they look a good match.
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When are you next in London? I probably can't match your stunning system, but I still have the Naia and hope to give it a listen before selling...
 
sonddek said:
Thank you! I've just ordered 100m of the square stuff, so this minimum order is fine - I had not realised that this was available and that minimum orders for custom shapes could be so low. Brilliant. If this ever ends up in a new model and you're interested, touch me for a discount!

There are still a couple of uncertainties. The bonded spine down the middle of the Blackbird arm tube serves a useful purpose over and above the stabilisation of the flat platforms which bolt onto the thrust box and the cartridge.

There's also the issue of top-heaviness, an aspect of the design where a Toblerone could be superior since it has a low centre of gravity.

As I've said elsewhere, as long as you construct a sensible arm tube, results are very good. It's my opinion that the real magic happens in the bearing, yet everybody is obsessed with arm tubes which make a relatively marginal difference.

Great discussion.
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So if the Chinese Toblerone works out, you could presumably halve the price and reduce the lead time to 2 weeks?;)
 
vesuvian said:
So if the Chinese Toblerone works out, you could presumably halve the price and reduce the lead time to 2 weeks?;)
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A huge amount of the work goes into constructing the arm wand itself, but also the many other parts. I do not rule out a more expensive arm nor a cheaper, but it is going to take a considerable effort to prototype and develop for production. With the order book growing and the need to scale up production I have many problems to solve before I get the time to think about future models. It will happen, but don't hold your breath.

Meanwhile, I think the current Bkackbird is one of the most future-proof arms ever made. I will be uploading videos on how to make and replace pivot bolts, and how to replace the hoists, so that end users can see easily how the arms I make will continue to deliver top notch performance, potentially for hundreds of years. I hasten to add that I have never had to replace a pivot bolt or hoist in four years, so I am thinking a long way ahead.
 
Finally (as The Rock used to say), I got to hear the clips through my system. First impressions when I listened on the laptop with headphones is that C is louder and brighter. I put the clips into Audacity and matched the results by YesMan. C really is louder, by 1.33dB in the left channel on 0.45dB in the right channel (so Mr Fremer didn't get the channel balance the same in both set-ups!). Also, C has some digital clipping at the end of the track that D doesn't. The peak-to-rms ratios are the same for C and D so one does not measure more dynamic than the other.
I adjusted the rms levels for D to match C and made a new copy for comparisons. C does have a bit more life but I suspect that is from the frequency balance difference, with a bit more treble that adds to the percussion and the piano attack. I compared the spectra of the two level matched clips in Audacity and C does get a little louder above 6kHz with more than a 1dB difference at 10kHz. PFM won't let me paste in the picture :(

I could happily live with either. Perhaps, I'll invest some money and wait for compound interest to give me enough for the SAT and see whether that happens before my Supatrac order is fulfilled.
 
13th Duke of Wymbourne said:
C really is louder, by 1.33dB in the left channel on 0.45dB in the right channel (so Mr Fremer didn't get the channel balance the same in both set-ups!). Also, C has some digital clipping at the end of the track that D doesn't. The peak-to-rms ratios are the same for C and D so one does not measure more dynamic than the other.
I adjusted the rms levels for D to match C and made a new copy for comparisons. C does have a bit more life but I suspect that is from the frequency balance difference, with a bit more treble that adds to the percussion and the piano attack. I compared the spectra of the two level matched clips in Audacity and C does get a little louder above 6kHz with more than a 1dB difference at 10kHz.
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Sounds like the kind of difference that 0.1g of excess downforce might introduce.
 
The SUPATRAC Blackbird will be exhibited in at least four rooms at Munich this year. We are a partner in the Moonriver/OePhi/Sonner/Panchanko room (H2 F11) and there will be a Blackbird on the Döhmann Helix One in the Cessaro room (H4 F001), on a Grand Prix Parabolica in the Vienna Acoustics room (A 4.1, E101), and on a Techdas in the Marten room (A 4.1, F119).
 
sonddek said:
The SUPATRAC Blackbird will be exhibited in at least four rooms at Munich this year. We are a partner in the Moonriver/OePhi/Sonner/Panchanko room (H2 F11) and there will be a Blackbird on the Döhmann Helix One in the Cessaro room (H4 F001), on a Grand Prix Parabolica in the Vienna Acoustics room (A 4.1, E101), and on a Techdas in the Marten room (A 4.1, F119).
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Well done Sir - your tone arms must be doing something right. 👍
 
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