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Old 3rd March 2010, 04:45 PM   #1
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Default need to bounce some tonearm ideas around...

Hello everyone.

Once again I am back to annoy!

I have been thinking a bit (sorry for the excess ozone output) and was wondering what the down side would be to a longer than 12" tonearm.

My thought process is if a 12" is better than a 10", maybe a 14" (or more for that matter- 24" tonearm?) is better still based on the arc radius and the ability to get closer to a 'linear' path for the stylus across the record. I understand it will never be truly linear (even with a 24 FOOT arm), but if the radius of arm travel is flatter, shouldn't the performance be better?

Open to any and all comments. I figure if I'm making it myself, why not optimize it as far as I can!

I had another idea as well- may go with a golf driver shaft for my tube. Tapered carbon fiber! Yummy!
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Old 3rd March 2010, 04:57 PM   #2
kevinkr is offline kevinkr  United States
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There were some transcription arms from outfits like Fairchild that were much longer than 12." One of the big problems with arms much longer than 12" is that the effective mass of the arm becomes high enough that finding cartridges with low compliances to match becomes problematic. Tracking due to all of that mass may also be an issue. The longest I've seen are under 14" probably for this reason.

You can completely eliminate tracking angle errors with a linear tracking tone arm. Take a look at some of the Souther arms for examples of excellently engineered examples of this approach. These are completely passive types using low mass arm wands and low friction bearings.

Rabco made a good actively controlled linear tracking tone arm into the late 1970s.

A number of Japanese companies (Technics for one) made very inexpensive linear tracking tone arm equipped tables in the 1980s. These are mostly junk but might provide some usable parts and controls for a diy effort.

If you are seriously interested in diying a tone arm you should probably check out www.vinylengine.com which specializes in turntable related subjects and has an extensive forum and library entirely devoted to turntables, cartridges, and arms.
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Old 3rd March 2010, 06:01 PM   #3
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Thanks Kevin.

I just signed up and posted over there with the same question.

I guess 20-odd years ago when things like Carbon fiber and other exotic materials were science-fiction (or NASA secrets) tone arms could get pretty massive pretty quick.

No, I think the weight could be controlled much better in the 21st century with lithium alloys and carbon...

Are these mass issues due to bearing drag, or just to keep the arm from building too much inertia and skating out of the room?

Not arguing, just trying to understand...
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Old 3rd March 2010, 06:08 PM   #4
amt is offline amt  United States
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You might grab the lastest copy of Stereophile. It has a very interesting article on the general history and implementation of various tonearm geometries and how they perform. Pretty good read and technical enough to offer insight but not be numerically baffling.

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Old 3rd March 2010, 07:31 PM   #5
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if you want a low mass arm and zero tracking error build a linear tracking arm as was suggested. You can also take a look at the Opus 3 Cantus linear tracking arm which is a mechanical design at Rauna of Sweden and use your Google translate to turn the Swedish into English. Bo (the owner of Opus 3) has demonstrated playback of his master acetate disks compared directly to the master tapes the disks were cut from and there is virtually no difference between the two. Your disks are cut with a linear machine so why would you want to build anything else. I don't mean to dis those who build radial arms as there are some beautiful and well designed arms out there but it all just amounts to polishing a turd to me. The arguments against linears tend to revolve around the moving mass, tell me what do you think the mass of a twelve inch arm of any kind of material is? A lot more than that of a Souther or Cantus arm and with a linear you do get zero tracking error. There are some inexpensive air bearing linears out on the market but I have been told by those who know more tha I do about this that they do not perform as well as mechanical designs. I have listened to the Souther design back in the 80's and it is still the most impressive arm that I have ever heard to date.
For a get you up and running arm I can think of no better project than Nanook's $2.96 unipovit arm (on this forum). I have watched Stew build one of these things from scratch in less than three hours and they work better than a lot of multi thousand dollar arms out there. Simple fast and inexpensive and sounds fantastic. Just my two cents worth.
Like I said I am not putting down the great work people do on radial arms as I am constantly impressed to see the often incredible work done by members here I simply do not believe in the design itself.
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Old 4th March 2010, 04:16 AM   #6
fftulip is offline fftulip  United States
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A couple of ideas for making a very long pivoted arm with fairly light mass.

1. Thin flat arm of lightweight material, like the infamous NAD "floppy" arm principle. Not very stiff in the vertical direction but it will be simple to build.

2. Much more complicated to build - long arm with pivoted "vestigial" micro arm at the end to reduce effective mass. See various examples like Transcriptors, etc.
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Old 4th March 2010, 01:00 PM   #7
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Thanks for the replies guys!

I have received a lot of excellent advice over at Vinyl Engine as well. AND I learned (from them) that Clearaudio offers an 'off the shelf' 14" tonearm too!

At about $1800.00, it is about $1,799.00 more than I have right now!

So, I know the linear tracking arms are a better, more accurate design. However with my (lack of) budget, I am trying to make the best I can with the least monetary outlay. The $3.00 arm sounds intriguing, and I think I have read through that thread already doing my research up to now, but will check it again.

Turntable Forum :: View topic - Hello! and a technical question...

This is the thread over there that I started....

PS will look into that Stereophile issue as well. Do you know which month it is? IS it still in the bookstores? (a cover photo would help immensely for me to find it quickly!)
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Old 4th March 2010, 04:48 PM   #8
amt is offline amt  United States
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Jim,
Its the March issue which I think, is still the latest. An interesting point in the article is that the difference between the 9 and 12 inch arms in lateral tracking error distortion is lost without very careful setup and maintenance. The added mass etc, may not really justify the longer arm. The conclusion most tonearm makers must have come to as well.

The author also has some cool freeware on his website, including a program to add LTE distortion to 10 sec. of a .wav file. I havent done it yet but will this weekend.



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Old 4th March 2010, 05:02 PM   #9
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Quote:
Originally Posted by amt View Post
Jim,
Its the March issue which I think, is still the latest.
cool thanks!

Quote:
Originally Posted by amt View Post
An interesting point in the article is that the difference between the 9 and 12 inch arms in lateral tracking error distortion is lost without very careful setup and maintenance. The added mass etc, may not really justify the longer arm. The conclusion most tonearm makers must have come to as well.
Well, as the saying goes: "If it was easy, everyone would be doing it" probably applies here more so than other places... You likely hit the nail on the head. However, I think "careful set up and maintenance" is the true key. The best gear set up incorrectly (or in the wrong size room) can sound like total crap.

Quote:
Originally Posted by amt View Post
The author also has some cool freeware on his website, including a program to add LTE distortion to 10 sec. of a .wav file. I havent done it yet but will this weekend.
I looked and saw that... Pretty cool! Make your CD's sound MORE like vinyl with the careful addition of analogue reproduction distortion!
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Old 4th March 2010, 07:52 PM   #10
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Here is a link to a thread on the Opus 3 Cantus parallel tracking arm. I am told (and I believe it) that this arm is superior to the Souther design. It is simple and elegant, it can be purchased for a very reasonable sum. If you wanted to build one I suppose you could experiment with that too. I am told that Bo (the designer/owner of Opus3) has demonstrated his master acetate disks played with the Cantus and compared to the master tapes the disks were made from and there is little to no difference. Job done.

Opus 3 Cantus parallel tracking arm
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