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AT6 center to pivot distance - anyone have that info?

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AT6 center to pivot distance - anyone have that info?

Postby RKnack » 13 Feb 2018 11:02

Wanting to generate a protractor for my AT6 mk. II to accurately align my Pickering V15 cartridge, so I can use elliptical styli (I THOUGHT I had it, but I am getting a lot of sibilance as opposed to using a conical, now). I have tried measuring it myself but can't seem to get an accurate arc on the protractor generator. Can someone Help me out here, please?
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Re: AT6 center to pivot distance - anyone have that info?

Postby A70BBen » 14 Feb 2018 09:51

This won't be much Help but the AT6 tonearm (and ANY tonearm among the Autoslim chassis) is not the best at lateral tracking error. That's because it is shorter than optimum, for compactness; and because when a cartridge is set up straight in the headshell, the greatest tracking error is at the INNER grooves where accurate tracing by the stylus is most critical. This wasn't so important in the AT6's era when styli were almost exclusively spherical.

If you are having problems with sibilance at the inner grooves, check your tracking weight first, make sure it is sufficient. The AT6 will not operate at extremely low tracking force anyway, and as such it is not suited for small tracking radius ellipticals such as 0.2 x 0.7 mil. A 0.4 x 0.7 mil is probably optimum. Then I would try to align the cartridge by eyeball for minimum tracking error at typical end of records. This will make the tracking error higher on the outer grooves but it is less critical there.
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Re: AT6 center to pivot distance - anyone have that info?

Postby RKnack » 14 Feb 2018 13:12

A70BBen wrote:This won't be much Help but the AT6 tonearm (and ANY tonearm among the Autoslim chassis) is not the best at lateral tracking error. That's because it is shorter than optimum, for compactness; and because when a cartridge is set up straight in the headshell, the greatest tracking error is at the INNER grooves where accurate tracing by the stylus is most critical. This wasn't so important in the AT6's era when styli were almost exclusively spherical.

If you are having problems with sibilance at the inner grooves, check your tracking weight first, make sure it is sufficient. The AT6 will not operate at extremely low tracking force anyway, and as such it is not suited for small tracking radius ellipticals such as 0.2 x 0.7 mil. A 0.4 x 0.7 mil is probably optimum. Then I would try to align the cartridge by eyeball for minimum tracking error at typical end of records. This will make the tracking error higher on the outer grooves but it is less critical there.

The stylus I have is a Pfanstiehl 4604-DEC, which is a 0.3 x 0.7 mil elliptical. The sibilance I am getting seems to be at the outer AND inner grooves. Tracking weight is set at a hair over 3g (using a digital scale), which is what the recommended tracking weight is on the stylus package.

So, I should use a "standard" mirrored protractor like the one I have, and just align to the innermost bullseye grid, and not worry too much about the outer one?
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Re: AT6 center to pivot distance - anyone have that info?

Postby RKnack » 14 Feb 2018 15:59

Might the Mobile Fidelity Geo Disc be a good one to try?
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Re: AT6 center to pivot distance - anyone have that info?

Postby DSJR » 14 Feb 2018 23:13

The inner null point for ANY older Autoslim deck is around 70mm from disc centre I think. My 60mk2 is definitely set this way and you can't finely adjust it either. The Pickering V15 (and corresponding Stanton 500A and E) work just fine as-is so please don't worry about it. I think the elliptical styli as you're using track at 2g or so but may need a smidge more depending on the deck sample and its service condition. I even get just a little sibilant mistracking with an Ortofon OM Pro at 4g in my 60mk2 but it could be the conical tip hitting a bad bit of the groove...

One other thing to check is the cartridge VTA. These Garrards have a down-tilt to the arm which will upset the VTA for an elliptical stylus. Garrard used to supply a wedge to correct this for the SP25 III and I believe all C2 carriers came with it. the M7 shells may not have done although the half-inch cartridge mounting plates were available with different spacer heights cast in (I have several). The Pickering mounting bracket can be tweaked to tilt the cartridge in an attempt to correct this but it's not really reversible and I accept no responsibility for the consequences...
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Re: AT6 center to pivot distance - anyone have that info?

Postby RKnack » 14 Feb 2018 23:20

DSJR wrote:The inner null point for ANY older Autoslim deck is around 70mm from disc centre I think. My 60mk2 is definitely set this way and you can't finely adjust it either. The Pickering V15 (and corresponding Stanton 500A and E) work just fine as-is so please don't worry about it. I think the elliptical styli as you're using track at 2g or so but may need a smidge more depending on the deck sample and its service condition. I even get just a little sibilant mistracking with an Ortofon OM Pro at 4g in my 60mk2 but it could be the conical tip hitting a bad bit of the groove...

One other thing to check is the cartridge VTA. These Garrards have a down-tilt to the arm which will upset the VTA for an elliptical stylus. Garrard used to supply a wedge to correct this for the SP25 III and I believe all C2 carriers came with it. the M7 shells may not have done although the half-inch cartridge mounting plates were available with different spacer heights cast in (I have several). The Pickering mounting bracket can be tweaked to tilt the cartridge in an attempt to correct this but it's not really reversible and I accept no responsibility for the consequences...
I have both the "tall" and "short" 1/2" spacers. Currently using the short, just because it looks odd with the cartridge hanging so far below the headshell (I am using the newer style shallow headshell).
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Re: AT6 center to pivot distance - anyone have that info?

Postby DSJR » 14 Feb 2018 23:27

Then can you make a card spacer of some sort and fit behind the screws to tilt the cartridge slightly?

P.S. if you want to stack singles as I believe you are referring to in your other thread, I'd stick to conical styli and the Stanton 500A/500v3 and whatever the Pickering equivalent was (same body) and track at 3g or so...
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Re: AT6 center to pivot distance - anyone have that info?

Postby RKnack » 14 Feb 2018 23:31

I stack singles AND LP's. Would I probably be better off sticking to the conical styli, then?

Only thing I don't stack is 78's (different stylus anyway) - the older ones can be brittle. Thankfully, I have both the stacking and single play spindles.

Which way to tilt the cartridge, using spacers? Back higher, or lower, than the front?
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Re: AT6 center to pivot distance - anyone have that info?

Postby A70BBen » 15 Feb 2018 03:02

For playing single records, back lower than front, level on one record. For stacking records, level at midpoint in the stack. AT6 is supposed to be able to stack six LPs, eight 45s, I think.
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Re: AT6 center to pivot distance - anyone have that info?

Postby smee4 » 15 Feb 2018 06:30

I think you will find a conical stylus is best for your needs for 45s and LPs. Maybe an AT3600L that tracks up to 3.5 g and has a 0.6 mil stylus might Help the general sound.
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Re: AT6 center to pivot distance - anyone have that info?

Postby DSJR » 15 Feb 2018 14:09

Oh, I think a serviced AT6 can take better than an AT3600. The 91 looks similar but has a better performance and a nicely polished conical tip. It should manage tracking at 2g as long as the arm and linkages aren't binding and my early issue AT6 (pictured in my gallery) is happy at 3g tracking a Stanton 500a on singles - the OP has a Pickering version I believe which is mechanically similar.
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Re: AT6 center to pivot distance - anyone have that info?

Postby smee4 » 15 Feb 2018 23:43

DSJR wrote:Oh, I think a serviced AT6 can take better than an AT3600. The 91 looks similar but has a better performance and a nicely polished conical tip. It should manage tracking at 2g as long as the arm and linkages aren't binding and my early issue AT6 (pictured in my gallery) is happy at 3g tracking a Stanton 500a on singles - the OP has a Pickering version I believe which is mechanically similar.


The 91 and 3600 are essentially the same cart, just different tracking force capability. Both have the 0.6 conical, and that is the main reason I suggested it. They punch well above their weight in quality. I run a 91 in my main system for testing secondhand records and it does a VERY good job.
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Re: AT6 center to pivot distance - anyone have that info?

Postby DSJR » 16 Feb 2018 15:02

A 'posher-badge' version of the AT91 is the Rega Carbon - review here if you don't mind using a translator

-https://www.lowbeats.de/test-rega-carbon-mm-tonabnehmer-fuer-einsteiger/

My old experiences of the 3600 was that it was dull as ditchwater and bland with it. Since some have found the same with the Carbon, but were tracking at nearly 3g rather than just under 2g as mine happily does, maybe 'we/they' were playing the 3600 too heavily as VTA will be affected by a gramme difference in tracking weight. Sorry to get anal about this... If you've tried the 3600 and found very little difference, then that's great 'cos it's about the cheapest half-decent mm type around these days...
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