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Old 3rd March 2015, 05:13 PM   #1
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Default Some DIY arms

Having made the Nanook uni-pivot, I have sort of been enthused to start a small production line. I only have five TTs and will need a few arms for when I get numbers 6 and 7.

The one problem I had with the Nanook was feedback. Above a certain volume it just went out of control. Not sure why or if anyone else has had this problem.

Anyway, I was taking some old hard disks apart and the motors looked perfect for using as the horizontal bearing in a tonearm. There is absolutely no play and they are very free running.

I converted the uni-pivot into a 10" and have built a 12" as well.

Details to complete but given the sound with the 10" just resting on an old Garrard SP25, there is definitely some performance in these arms. I will make a suitable support for my Origin Live based TT and see what they are really capable of. There is only a Shure M75ED in the 10" so more to come in that direction too.

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Old 7th March 2015, 08:24 AM   #2
2wice is offline 2wice  South Africa
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Isn't there an indent in those HD motors, got some here that have it.
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Old 7th March 2015, 11:00 AM   #3
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Originally Posted by 2wice View Post
Isn't there an indent in those HD motors, got some here that have it.
I'm not quite sure what you mean by that. Could you elucidate please?
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Old 9th March 2015, 06:19 PM   #4
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What a setup. You gotta say whoa.

<< The one problem I had with the Nanook was feedback. Above a certain volume it just went out of control. Not sure why... >>

It's an off chance, but it might not be feedback, it might be mechanical resonance. You might try changing the mass of something, or the length of something, or...something.

Or another off chance, it might be feedback from the speakers to the tone arm. The sound waves from the speakers being strong enough to vibrate the tone arm.

Last edited by bentsnake; 9th March 2015 at 06:25 PM.
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Old 9th March 2015, 06:36 PM   #5
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Originally Posted by bentsnake View Post
What a setup. You gotta say whoa.

<< The one problem I had with the Nanook was feedback. Above a certain volume it just went out of control. Not sure why... >>

It's an off chance, but it might not be feedback, it might be mechanical resonance. You might try changing the mass of something, or the length of something, or...something.

Or another off chance, it might be feedback from the speakers to the tone arm. The sound waves from the speakers being strong enough to vibrate the tone arm.
Thanks for the help. You are quite right. It is an arm resonance problem. I wrapped the arm tubes in plastic tape and the feedback has 'almost' disappeared. The volume has to be at insane levels to set it off however.

Now I've done that, the 10" arm sounds better than the 12" whereas before, it was the other way round. All strange stuff this. Having absolutely no technical knowledge and just bunging stuff together to see what works makes for a lot of fun
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Old 22nd March 2015, 08:45 PM   #6
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Default Still playing

The 12" arm is now a permanent fixture on my OL based deck. I prefer it to the OL Rega250 now. I tried the technics in it but it didn't match at all well but sounds terrific with a cheap Audio Technica cartridge.

Also trying an arm with the pivot to one side and a straight headshell. This one sounds very interesting and will have further development. It is highly critical of the balance weight position. The weight of the arm including the counterweight has to be offset quite precisely or the bearing loads up and it hesitates whilst tracking. Get it spot on and it tracks anything with terrific bass and rock solid image. It has a Goldring Elan in which seems to suit it very well but I'll put something better in once it's sorted 100%.

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Old 23rd March 2015, 12:19 AM   #7
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Quote:
Originally Posted by gus 3049 View Post
Also trying an arm with the pivot to one side and a straight headshell. This one sounds very interesting and will have further development. It is highly critical of the balance weight position. The weight of the arm including the counterweight has to be offset quite precisely or the bearing loads up and it hesitates whilst tracking. Get it spot on and it tracks anything with terrific bass and rock solid image. It has a Goldring Elan in which seems to suit it very well but I'll put something better in once it's sorted 100%.

Click the image to open in full size.
Fascinating creation, Gus! Please contribute more information, if possible, to the other thread in this forum that discusses this particular genre of tonearms. We can all learn along the way. Thanks for posting!

Your arm has a striking resemblance to the creation by Doug Tuthill in this post. But yours doesn't appear to have a guiding mechanism to conform to the quasi "Birch" geometry.

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Old 23rd March 2015, 07:25 AM   #8
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Quote:
Originally Posted by directdriver View Post
Fascinating creation, Gus! Please contribute more information, if possible, to the other thread in this forum that discusses this particular genre of tonearms. We can all learn along the way. Thanks for posting!

Your arm has a striking resemblance to the creation by Doug Tuthill in this post. But yours doesn't appear to have a guiding mechanism to conform to the quasi "Birch" geometry.

Click the image to open in full size.
Ha! So much for originality!!

I wouldn't know what a quasi Birch geometry was if it bit me on the bum!! I just bung stuff together and see if it works. If you throw enough ideas into the pond, eventually, one of them might float.

I'm not sure what I can contribute to the other threads, there is no science or reasoning behind what i do. I'm a guitar maker who just dabbles in hi-fi as it is so closely connected to my main passion.

When my brother in law has made my suggested adjustments to the parallel tracker we are developing, then I may have something relevant to say. He actually knows what he is doing as he is (was before he retired - now just a genius) a design engineer.
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Old 12th April 2015, 08:53 AM   #9
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Default A new one

Right then...here is the latest try. Parallel tracker using the principle of a Sarrus Linkage - Sarrus linkage - Wikipedia, the free encyclopedia

To say that it was difficult to adjust would be a slight understatement. Incredibly sensitive to level and balance. However, when it works, I have never heard anything to approach it for sheer musical information.

We have to work a few things out and make it prettier but the principle seems a good one. The main problem is finding a way to incorporate a lift.

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Old 12th April 2015, 09:57 AM   #10
Dyolf is offline Dyolf  Norway
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Wow Gus.
Where do you find the time?? You have got to be the incarnation of the people this forum was meant for
I cant even try to figure out the way this tracker moves across the surface. If it was a steam-driven locomotive yes, but how the h... can you move this contraption with a diamond attached to a cantilever Are there any way you can post a video of "the thing" in action? Thumbs up!
Steen
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