Need help trouble shooting 3D arm

Need help trouble shooting 3D arm

Postby Bill Stevenson » Sun Dec 16, 2018 5:44 pm

I have a Prime with two arms, one 3D and one metal both fitted with dual pivots. The 3D arm is fitted with a Counter Intuitive. The 3D has a 2M Black and the metal has a 2M Mono SE (i.e. the 2M Black modded for mono). The metal arm works fine. The 3D has distortion starting at about mid play and getting worse toward the spindle. VTF has been checked and re-checked. I have checked visually and cannot see any interference. The arm is sitting properly on the unipivot, the arm is parallel to the record surface or nearly so. Everything looks OK. I removed the arm and inspected for damage and everything looks OK. I inspected the stylus under my Wild Heerbrugg microscope and everything looks OK. I've tried several records with the same result. I've played some with the periphery ring and some without, and it does not seem to affect this problem. Although I don't normally use the anti-skating device, I tried it and found that it makes the problem worse. I am out of ideas. Any suggestions short of throwing the Prime over the transom would be appreciated.
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Re: Need help trouble shooting 3D arm

Postby jonathanb » Sun Dec 16, 2018 5:48 pm

Have you realigned the cartridge yet?
Prime Signature #0009
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10" 3DR/Transfiguration Phoenix S
10" 3D/VAS Nova Mono
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Re: Need help trouble shooting 3D arm

Postby teenage diplomat » Mon Dec 17, 2018 12:23 am

There could be several issues at play, including most importantly IMHO, tracking force and the amount of antiskating actually being created by the 3d’s wire loop. On the former, make sure that you are measuring tracking force at the level of the record, not by putting a conventional gauge on the platter. HW long ago did tests that showed doing it with the gauge on the platter overstates actual tracking force - you actually are tracking at a lower force than what the gauge says by about .2 g. The only exception would be a digital stylus force gauge that uses an outboard platform at record level on which you place the stylus. On the question of antiskate, it has been my experience that as it comes from VPI, the degree of twist in the wire is too tight; it exerts too much antiskating force, and sibilance in the right channel occurs. Try an experiment: blutac a small weight to your counterweight, one with just enough mass to allow the arm to float just above record level. Move the arm in towards the center. Let it float. If it moves away from the spindle quickly, you have too much AS force. Untwist the wire a full turn of the lemo and retest. Continue untwisting until you have only slow outward drift on the floating arm. Take the blu tac’ed weight off and listen. If AS was the cause, and the distortion was mostly in the right channel, it should be better. Oh, you also might want to take the bit of tonearm wire an inch or so above where it exits the arm and bend it towards the lemo, forming a (more or less) right angle turn. Hope these ideas help.
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Re: Need help trouble shooting 3D arm

Postby Brf » Mon Dec 17, 2018 11:20 am

Switch the cartridges between the two arms. If the problem follows the switch, you will know that it is a cartridge problems and not a arm/cartridge issue.
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Re: Need help trouble shooting 3D arm

Postby teenage diplomat » Mon Dec 17, 2018 4:20 pm

Just a small correction to my previous post: excessive sibilance occurred in the left channel, and disappeared after I untwisted the wire, lowering the amount of antiskate.
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Re: Need help trouble shooting 3D arm

Postby Stringreen » Tue Dec 18, 2018 6:56 pm

If the left channel is mistracking you need to increase the antiskate and/or increase vtf. Your assessment sounds odd.
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Re: Need help trouble shooting 3D arm

Postby teenage diplomat » Tue Dec 18, 2018 10:51 pm

Stringreen, I know that is the textbook answer. All I can tell you is that with my arm, there was so much antiskating force being applied that sibilant portions of LPs spread hot “s” sounds from the center to the left of the soundstage. Reducing the antiskate force in the manner I described resolved the issue. Theory: misstracking left channel due to too much antiskate. Simple to test my theory if that is what the OP is hearing. That may not be his problem.
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Re: Need help trouble shooting 3D arm

Postby Golear » Wed Dec 19, 2018 4:01 pm

Perhaps once a cartridge misbehaves too much, all bets are off.

I also suppose there's nothing wrong with setting the anti-skate via twisting the wire. The big question is: how much force does the twist generate? If there was a way to measure this and adjust it, then it should work as well as any other method. There are many kinds of wire, and they're no doubt mounted in the arm in different ways, so there'd be a lot of variations. The Soundsimith's method of setting the anti-skate may still be relevant for arms where the anti-skate is set by twisted wires.
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Re: Need help trouble shooting 3D arm

Postby Mr_Putty » Wed Dec 19, 2018 10:25 pm

Golear,
What you mention about the wire is what I confirmed today. I removed more twist in my Prime arm wire as there was too much antiskate. It is now much better and I do not need the weighted-mechanical arm for skate, so far. I use a second pivot and it’s required downward force is also more consistent across the record path. To be clear about the antiskate, after the wire was relaxed, there is no apparent force on the arm at the beginning of a record (or very little).
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Re: Need help trouble shooting 3D arm

Postby audiom3 » Thu Dec 20, 2018 2:03 pm

Not intending to hi-jack your thread, OP but maybe my issue can help you solve yours. I'm also having an issue with transient distortion in the right channel as the stylus gets closer to the spindle. Sibilants aren't really an issue at all, however. Which is what most describe IGD as. I'm talking about old Led Zep LPs where Plant sings dynamically and it breaks up only in the right channel. I tried a test on the song 'Out on the Tiles'. Original US press vs. the 2014 re-issue. Although the re-issue has less transient distortion, it is still there. I attribute this to how much more subdued the master is. 'Cripple Creek Ferry' by Neil Young is another guilty track. I have a very clean original but this song breaks up during the chorus in the right channel. But these are just a few examples. I have a lot of 70s and 80s records and the majority have this issue. I've taken most of the year off from vinyl because it's been so discouraging. I have aligned things as best I can with a Mint Arc Protractor. VTA from way too high at the rear to as low as it'll go in the tower. I've taken test tone rips while tweaking azimuth each way and then trying some LPs to check the results in the real world. I use a few test records. Hi-Fi and AP. I can pass the first two bias tracks on Hi-Fi but get right channel distortion on the 3rd. And I get distortion around 5 seconds from the end of the bias track on the AP record (I'm assuming all TTs fail this part though as the distortion is equally in both channels). I am using MAX bias (3 donuts). I am pretty certain this has to do with bias but I cannot fix it. The left channel is always clean except for a few nasty sibilant records (PG's original US press of So; the re-issue of Zappa's Apostrophe; MJ's Thriller but especially Billie Jean). I'm going to install my Benz Wood SL this weekend on my spare 3D arm to see how it sounds but I'm at a loss on the Kiseki Blue NS. It has less than 150 hours on it too (probably closer to 100).

Oh, the arm wire has never sat in a nice arc like all my other wands. It leans back away from the arm because the little rubber grommets aren't snug against the Lemo or the 3D arm. Not sure that would make a difference.
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Classic w/ 3D arm & VTA Tower; Kiseki Blue N.S.; Benz Micro Wood SL; Sutherland 20/20 Phono Preamp
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