advertisement


Sideways Uni-Pivot Arm, SUPATRAC Blackbird, formerly "Ekos Killer (Price?)"

That string finger lift would definitely 100% stop me from considering that arm. No matter how strong a case is made for how well it works it looks terrible and I doubt it'd get better looking over time. I'm also entirely happy with how the traditional finger lifts work on every other arm I've used (and they work absolutely fine) so changing that is a solution without a problem IMHO.
 
Your post is still incorrect, third party references notwithstanding.

I’ve given you the relevant equation, it’s easy enough to apply. As an illustrative example, consider a tone arm made from a tube having mass, say, m = 15 g. The overall length, cross section shape and area are not relevant. Now the effective mass of this arm tube by itself will be m/3 = 15/3 = 5g. This is hardly ‘vanishingly small’.

Lastly, damping does not require an infinitely rigid connection to the paddle and has no effect on inertia.




Vinny said:
Unfortuantely what I said is CORRECT - I would refer to to a very neatly and accurately worked example over on Vinyl Engine. I am merely quoting from it.

Pick holes in the maths there, no-one else could or did for the few years that it has existed, barring minor nit-picking - posted originally April 2015.

The very great majority of inertia in a conventional arm is due to the headshell and the CB weight. Fact.

As for damping troughs - if the paddles were locked solid to the tonearm.......... but they aren't.
Click to expand...
 
@al2002 - take your disagreement up with the person working the maths of the example on VE, not me.

I worked through his maths and reasoning, you have provided no example whatsoever, worked or otherwise.

I'll go with the worked, real, eaxample.

All totally irrelevant anyway. Let us wait for what Sonndek comes up with.
 
yuckyamson said:
Well that's not combative.

It would seem in terms of opinions on the queueing mechanism you have 5 FOR put in a finger lift, and 0 against. Well, 1, when you count yours.
Click to expand...

I've said a more traditional finger lift will be included. They are also available from third parties at a cost of £1.32. I don't think this needs to be a bone of contention. Let's keep audio fun ;-)
 
al2002 said:
sondek, your post 189 above was very helpful. Can you also comment on damping? Will a damping trough assembly be available?
Click to expand...

I have no plans to add damping. I don't see how it allows an arm to cope well with warps and eccentricity which are often present to some degree, even if small. In fact this arm design is partly my response to what I suspect may be overdamping in certain other arm designs.
 
Vinny said:
@al2002 - take your disagreement up with the person working the maths of the example on VE, not me.
Click to expand...

I am only responding to your post in order to correct some serious misconceptions. I prefer to keep it technical. Not interested in arguing with anyone.

Where is this article you refer to?


Vinny said:
@al2002 I worked through his maths and reasoning, you have provided no example whatsoever, worked or otherwise.

I'll go with the worked, real, eaxample.
Click to expand...

Go back and read my earlier posts. Is not:

I =(m* l^2)/3, therefore (m effective) = m/3 = 15/3 = 5 g,

a clearly worked out example on how to calculate effective mass for a hypothetical arm tube of mass 15g ? It can’t be any simpler.


Vinny said:
@al2002 All totally irrelevant anyway. Let us wait for what Sonndek comes up with.
Click to expand...

Not irrelevant at all. Even if only for the record, erroneous information needs to be corrected.

Yes, looking forward to further developments from sonddeck.
 
An analogy I’ve posted elsewhere might help. Visualise a car wheel and its suspension. Ask yourself what effect does the damper (or shock absorber) have in controlling the motion of the wheels over bumps?

Of course, it is your design and the final decision is yours, but I see no harm in offering a paddle/damping trough assembly for those who want it. This might require minor redesign of the arm post in order to accommodate a trough.

sonddek said:
I have no plans to add damping. I don't see how it allows an arm to cope well with warps and eccentricity which are often present to some degree, even if small. In fact this arm design is partly my response to what I suspect may be overdamping in certain other arm designs.
Click to expand...
 
al2002 said:
An analogy I’ve posted elsewhere might help. Visualise a car wheel and its suspension. Ask yourself what effect does the damper (or shock absorber) have in controlling the motion of the wheels over bumps?

Of course, it is your design and the final decision is yours, but I see no harm in offering a paddle/damping trough assembly for those who want it. This might require minor redesign of the arm post in order to accommodate a trough.
Click to expand...

Interesting analogy, although I'm not sure how apposite. You could argue that the car shock absorber will make many of the smaller bumps in the road inaudible. Is it your intention to reveal the bumps in a record or hide them?

In the light of the detail retrieval and dynamic performance of a certain other suspended and damped arm, I decided that I want all the energy of all bumps (aka signal) converted to millivolts, not absorbed by some energy sink other than the cartridge, and I am pleased to say that to my ear the result is what I hoped for: very energetic/dynamic and detailed playback.

But it's an interesting question and clearly there are different ways of thinking about it.
 
Sonddeck, not quite. Let me attempt to clarify.

The damper allows the *tone arm* to better follow record warps, particularly around the LF resonance. This damping does not directly affect the stylus’s tracking of the groove.
 
Car shock absorbers dampen the oscillations of the springs, without them the car would bounce on the springs almost for ever while being driven.
 
I understand you can have under-damping, over-damping, or critical damping. The arm's mass can provide adequate inertia against which the stylus works. Over-damping will stretch out the time it takes the arm to react to changes like warps and rapid changes in signal strength. I suspect that avoiding over-damping will prolong record and stylus life, by ensuring the cantilever spends less time outside its more comfortable deflection range.

I do not know where the critical damping threshold lies, but my guess is informed by the difference in performance between an Ekos II and a Well Tempered arm. That's why I decided to build a light rigid undamped arm. I am open-minded, so if someone installs a damping trough on one of my arms I shall be delighted to come and listen to it, but it's not high on my list of priorities for the reasons above.
 
I think its brilliant.
Melding the Well Tempered Turntable bearing well side bearing with the WT hanging tonearm ideas.
You should call the tonearm WTF (Well Tempered Firebaugh) as an homage.
 
Last edited:
cromodora said:
I think its brilliant.
Melding the Well Tempered Turntable bearing well side bearing and the WT hanging tonearm ideas.
You should call the tonearm WTF (Well Tempered Firebaugh) as an homage.
Click to expand...


Thank you - yes, it is unlikely that the innovation in this bearing would have occurred to me without the inspiration of the brilliant Mr Firebaugh. I would love to talk to him one day. Supatrac is somewhat a response to what I see as limitations in the Well Tempered arm design. I'm actually planning to make a 10 inch one for my Amadeus.
 
Serial number 1 is sold. It is a 12.5 inch version, and I'm sure you can guess which turntable it will be serving:

sn.one.jpg


http://supasound.com/sn.one.jpg
 
al2002 said:
Ask yourself what effect does the damper (or shock absorber) have in controlling the motion of the wheels over bumps?
Click to expand...

It doesn't, as such, it damps oscillation of the spring, hence the name. It prevent booooiiiiiinnnnngggg (or however it is spelt).
 
It would not be hard to replace "the wick" with something fancier-looking. I really like the way you tonearm looks. Reminds me of one of these Sorane/Abis tonearms but your tonearm has a more sculptural look in the way you have designed the counter-weight:
soraneza12transcription-37.jpg
 
You must log in or register to reply here.


advertisement


Back
Top