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Can anyone tell me the maximum mistracking on the inner/outer groves of a 500mm straight tone arm with straight headshell?
Is there a formula for this? I tried Vinyl Engine but they only have calculations for off-set arms.
Thx and much appreciated for any help,
Bob
"You have to leave something to your imagination"
Follow Ups:
I think you're talking about tracking error rather than mistracking because mistracking means the stylus is losing contact with one or both groove walls causing gross distortion. Here is a graph of how a 500-mm straight tonearm without an offset headshell should be aligned on an LP with innermost modulated groove radius of 60.325-mm and outermost groove radius of 146.05-mm. The blue curve is tracking error in degrees and the red curve is tracking distortion in percent. It requires an underhang of 6.183-mm to minimize distortion.
Thank you very much John for your help,
my arm at this set up sounds great. I can't hear any distortion - none that displeases me anyhow.
Bob
"You have to leave something to your imagination"
I own an RS Labs RS-A1 tonearm, although it is not in regular use. This is a 7 or 8 inch tonearm that is designed to be mounted with underhang. When I have used it, I am always impressed with its innate "smoothness" and musicality; when I have compared the sound of one or two cartridges mounted alternatively in the RS-A1 or in a conventional 9-inch tonearm with headshell offset and using overhang, I've had to admit to myself that in many ways I prefer the RS-A1. Recently, there is a newer product available, the Viv Rigid Float tonearm, that also is straight-line design meant for underhung mounting. It has received many favorable reviews outside the US, and I saw one in the flesh just recently in Tokyo. The designer contends that even though there is "more" tracking error on average with his designs (there are 7, 9, and 13-inch versions available), eliminating distortions produced by the additional skating force at the null points created by headshell offset, and eliminating the anti-skating mechanism per se, are keys to the pleasing sonics. I find his logic appealing. (The Viv also has a unique floating bearing which may in part contribute to its excellence, but the RS-A1 is just a simple unipivot.)
Thank you Lew,
I have also read about the RS Labs RS-A1 - looks 'out of this audiophile world'.
How would you describe there character of the sound? Why do you only 'sometimes' use it if you feel it does sound the best? Are you worried about tracking error?
I have three tonearms. Two are straight and one is conventional off-set. I am modifying my ebony 12 inch arm to accommodate an off-set headshell as I am worried about tracking error. . However, I have positioned my 500mm straight arm as to John Ellison's suggested null point of 78.872mm and it sounds fantastic. I am so happy.
Anyhow, I will still go ahead with the mod on the ebony 12 inch arm for experimentation.
Bob
"You have to leave something to your imagination"
All tonearm designs are compromised to one degree or another. Vinyl is also plagued with different types of distortion, but it still sounds good. In fact, it might sound good because of its distortion rather than in spite of it. Regarding the RS-A1 tonearm, I have never read anything bad about its sound quality even though it is a very unconventional design. On the contrary, all reviewers claim it to be the best sounding tonearm they've ever heard. On the other hand, you might be one of the few people who actually uses it because it is so difficult to use. In other words, sound quality is not at the top of the list of reasons people prefer their tonearms.
As for me, I prefer SME tonearms because I like virtually everything about their design. Furthermore, I prefer an offset tonearm because I prefer to minimize tracking error distortion.
To each his own!
Best regards,
John Elison
is simply mounting the cartridge without destroying it, because the unipivot is so unstable while one is trying to work at the headshell end. The whole apparatus is prone to tipping over if one is not careful. I know Dave Pogue had issues with cue-ing his at the beginning and end of each side, but that so far for me has not been a problem. Yes, the SME is bulletproof. I've got 3 other tonearms in active use, and all of those are conventional types. I was merely pointing out that these alternative designs may tell us something about which distortions are significant in our perception of reproduced music and which are not.
When I borrowed an RS-A1, love/hate ensued. Loved the sound, hated the ergonomics. Finally resorted to getting a gum massager at CVS whose angled head enabled me to pick up the arm from a record (and redeposit it) without destroying too many cantilevers and even getting the stylus in the right spot every once in a while.
Thx so much John.
If I were to try to reduce the tracking error to approx 4 degrees on thew outer and inner grooves, is just a matter of moving the null point more to the centre groove?What would be the distortion be?
Bob
"You have to leave something to your imagination"
If you move the null-point closer to the center by increasing underhang as shown in the graph above, inner groove distortion will increase.
The graph below shows the lowest possible distortion for a 500-mm tonearm with zero offset.
The only way to decrease distortion is to introduce an offset angle and move the base of the tonearm to the proper overhang. The graph below shows the optimal offset and overhang for a 500-mm tonearm. It requires an offset angle of 10.771-degrees with overhang of 8.043-mm.
If you want to play with the numbers yourself, you can download my spreadsheet at the following link:
Because with a straight tonearm (no headshell offset) you are far better off to use underhang. That way, the tonearm/cantilever can be made to be tangent to the groove at least at some point along the playing surface of the LP.
That's one heckuva long tonearm for sure.
If you go to chapter 17.4 in the ancient Radiotron Designers Handbook it covers the topic ...
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