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set up of 12" Jelco

337alant

337alant

Negatively Biased
Just bought a Jelco 750 12" tone arm for my Garrard 401 :) http://i259.photobucket.com/albums/hh290/337alant/jelco750-1.jpg
My question is regarding advice on the set up of the cart on this 12" arm?, I got the null points from the Vinyl engine site and the arm has an effective lenght of 305mm and a pivot to centre measurement of 290mm
I have set it up and note that the cart sits well back in the headshell to get the correct alignment, is that normal? :confused: http://i259.photobucket.com/albums/hh290/337alant/jelco750-2.jpg
I had to knock up a cheap ply plinth to house the 12" arm and even though its rough and unfinished it sound's excellent. http://i259.photobucket.com/albums/hh290/337alant/jelco750-3.jpg
The Jelco replaced a OL RB 250 and considerable improves on it IMO

Alan
 
I have one and use the Lofgren alignment from the Audio Origami (Seb's) protractor. I also find that cartridges sit quite far back in the headshells I've been using.

Here's a Technics EPS310MC in an ADC headshell
onJelco.jpg
 
Thanks Pure sound
it was the Lofgren B nul points I used 70.285 and 116.604mm that I used so its reassuring that you get a similar alignment.
I have a HFN test LP some where but its driving me nuts that I cant find it :mad:

Alan
 
If you want peace of mind that you have nailed the geometry, overhand etc then consider the Best Tractor. It's a bit pricey, but a worthwhile investment and comes with some useful tools that can be used elsewhere for stylus examination etc. I use one for my 10" Jelco.
 
I have just bought a 12" Jelco, which I am going to mount on an Iroko plinth where I had my 12" PU7.

The distance from spindle to arm cut out centre for the 12" PU7 is 291.4mm, but I doubt whether my cutting would have been 110% accurate.

If the 12" Jelco measurement is 290mm then I may be in luck, does the Jelco come with protractor as mine has now arrived yet.
 
Looking at Guy's pic and from what Alan has said and his pics, if you are both using Loefgren B then it suggests that 290mm may actually be a few mm short of ideal (I know it's what Jelco specify) - or put another way - the Jelco can happily use a few more MM spindle to pivot if you want it to.

For a given spindle to pivot length Loefgren B needs the longest overhang of the three common alignments - about 2mm longer than Stevenson and about 0.5mm longer than Baerwald. Looking at the pictures, if that's aligned with Loefgren B and the spindle to pivot is 290mm you could probably add 2 or 3 mm to the spindle to pivot and achieve alignment with any of the usual alignments. It's hard to see exactly from the images, but as it stands it looks as though Stevenson would be difficult to achieve should you choose to use it.

Flyfisher - I suspect you'll be fine.

At the end of the day it looks to me as if there's a good 6 mm spare slot in to the front of those headshells - you could move the arm back most of that and suffer no ill consequence ... unless you tried another cartridge with an especially long nose... certainly half of that with no worries at all I would imagine.
 
Thanks uncle ants I was wondering what would happen if I made the spindle to pivot distance 295mm.
I will have a go and revert as the hole under the arm board has a an enlarged hole undernith it so there is room for adjustment :).

Scoobs thanks thats an interesting tractor

Alan
 
337alant said:
Thanks uncle ants I was wondering what would happen if I made the spindle to pivot distance 295mm.
I will have a go and revert as the hole under the arm board has a an enlarged hole undernith it so there is room for adjustment :).
Click to expand...

Nothing bad. You'll get a slightly longer effective length (a good thing though it's a small enough difference I doubt you would notice) and the angle in the headshell might be minutely different. It'll give you the opportunity to try alternative alignments more easily should you wish.

If it's easy to adjust then I'd measure the space you have in the slots to the front of the cartridge as it is now and move the arm back by that amount minus a couple of mm to give a little wiggle rooom should you need it and then realign. It should finish with the cart around the middle, maybe slightly to the front of the headshell.
 
I had the same problem with the manufacturer spec last year. Using 290mm, my Denon sat really far back in the slot for Baerwald using my Feickert and I can't even use an Orsonic headshell/other cart with this MD and effective length due to lack of overhang adjustment. At that time i haven't bolted the Garrard down so I just shift it a little further away to increase the MD to get round the issue.

292-293mm mounting distance will allow more leeway with Baerwald and other alignment. This issue has been noted on vinyl asylum a few times among the 750D users too.
If you use the Jelco specified 15 overhang and actually measure the pivot to the stylus tip distance , i bet it will be a few mm more than specified 305mm which is odd.
 
scoobs said:
If you want peace of mind that you have nailed the geometry, overhand etc then consider the Best Tractor. It's a bit pricey, but a worthwhile investment and comes with some useful tools that can be used elsewhere for stylus examination etc. I use one for my 10" Jelco.
Click to expand...

You can't get Mint to make you one when the manufacturer's spec is screwy.
 
well I checked my measurements more accurately and found that i had set the pivot to spindle at 286mm :rolleyes: so just moving it to an accurate 290mm has improved it and the position of the cart in the head shell.
I found my HFN test LP as well which helped get my set up better.
I am also enjoying being able to swap carts quickly with having the detachable head shell so I have mounted a Ortofon MC25FL Ive had in the draw for a while and it sound much better in this arm.
I am getting a little sibilance on the right channel with all carts which I think is my Cambridge 640P:confused: so I could do with trying another phono stage just to check

Alan
 
I'll double check my mounting distance.

I like the ADC magnesium headshells and have accumulated quite a few now. I made up a new arm cable from a piece of Audio Note silver interconnect and redo the headshell wires with the same stuff.

I am enjoying the facility to change cartridges relatively quickly & have both sizes of c/weight. the arm does seem to offer very good value & a relaxed & spacious presentation.
 
Is it still possible to get the ADC headshells, I used to have 2 but my eldest son knicked them in his DJ days, I am using the Sumiko ones now which are excellent.
Q. Do other people use the rubber washers in between their Garrard 401 and the plinth?

Alan
 
I've been getting them from ebay for anywhere between 6 & 14 pounds. They are a bit lighter than the supplied Jelco/Sumiko item but seem very strong.
 
pure sound said:
I've been getting them from ebay for anywhere between 6 & 14 pounds. They are a bit lighter than the supplied Jelco/Sumiko item but seem very strong.
Click to expand...

Just out of lack of knowledge with headshells, with say the 12" Jelco is it best to match or balance the headshell with the cartridge.

I think I saw that a Denon 103 works best in an AT 18grm headshell which is quite heavy.

Is lighter but strong best solution?

If you look on US Ebay there are pages of headshells.
 
The 18g AT headshell on the 12" arm will be overkill for the 103 IMO. The stock shell is fine. I use an ADC shell for my 103r that has a 3g stabiliser fixed to it, which brings it back up to around 10g in total.
 
flyfisher said:
Just out of lack of knowledge with headshells, with say the 12" Jelco is it best to match or balance the headshell with the cartridge.

I think I saw that a Denon 103 works best in an AT 18grm headshell which is quite heavy.

Is lighter but strong best solution?

If you look on US Ebay there are pages of headshells.
Click to expand...


It's all about getting the effective mass right for the particular cartridge you wish to use. Bear in mind that the counterweight is also part the eff mass equation.
 
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