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Technics EPA-250 Cartridge Matching Concerns

Hi, I am awaiting delivery of a Technics SP10 mkII with EPA-250 arm (i.e. EPA500 armbase & EPA-A250 Wand). Documentation states that Effective arm mass: 14g (without cartridge). Separately, I've read that the Technics headshell weighs 7.5g (with option to add 2g or 4g weights when needed). As I study up on this arm and try to narrow my sights for a cartridge purchase a couple of headscratchers are bogging me down. Any insights are appreciated.  

1) For use of resonance calculators does the 14g effective mass include or exclude the 7.5g headshell?  

2) The EPA-250 owners manual includes a little chart showing "Suitable Cartridge Weight & Compliance Relationships". It suggests adding headshell weights w/carts from 3g-6g; No headshell weights with carts 6-8g; and adding the auxilary counterweight for carts weighing 10.5-12.5g. No mention is made of the range 8g-10.5g! Of course, this range fits a number of my cartridge candidates. So what's the best way to adjust for that? Specs show "Cartridge weight range 3,0g – 12,5g".

3) In general, I've read that moderate mass tonearms are good companions for moderate to low compliance cartridges. One of the carts I'm considering is AT ART9, which is rated  18 x 10-6 cm / dyne (@100 Hz),  35 static. Formulas I've read suggest that to convert to 10hz calculations to multiply the 18 by 1.5-2.0. So that would avg. a compliance of 31.5.  The other method suggests halving the static figure, which would lead to compliance of 17.5. Using the first method concludes that with a resonance ~7hz my tonearm is not a good match. The second method yields more favorable results.  What's the real world result more likely to show? I've read all the raves on the ART-9 already, but want to focus on whether or not its compliance is too high to mate with this arm? Would a lighter than the 7.5g headshell help and are their any particular ones that you'd suggest. Most of the headshells I see are heavier.

4) Any EPA-250 users care to share their preferred cartridges on this arm? 

Cheers,
Spencer


  
128x128sbank
sbank's avatar
sbank OP
3,379 posts
 
@lewm It's amazing all that there is to learn! Just today I went through a panic when the seller told me basically that there is no room on the EPA-250 for an "additional weight" and that the arm I'm buying only has one weight. I sent him pdf of the owner's manual showing him figure #17 which shows the "additional weight" which screws into threads on the back of the main weight. Meanwhile while waiting for a reply I found weights for sale but most were described as for SL1200 and costing $10 or less. The lone vendor with an EPA250 weight wanted $40 and weeks of shipping from Japan. 
Lo and behold, the seller saw the pics, confirmed that a) He does have the weight to send me and B) Yes 100% interchangeable with the SL1200 weights. Lesson learned. Cheers,
Spencer
jpjones3318's avatar
jpjones3318
149 posts
 
Yes, the aux weight that came with the EPA-A250 is identical to the aux weight for the SL-1200MK2, et al. 


lewm
13,243 posts
 
Sbank, If JP says the two are identical, you can "bank" on it.  However, if there is a problem, any good machinist can make you what you want if you give him the specs.  One guy is Colby Lamb out in Oregon.  He is an audiophile/machinist par excellence.

After 40+ years, I think I know everything there is to know about what equipment was made by whom and when, but every once in a while I have an epiphany like this that reminds me I really don't.  Now I just need to find a B250 arm wand for MY B500 base.
lewm
13,243 posts
 
Sorry, that's "A250" arm wand.  There I go again.

sbank's avatar
sbank OP
3,379 posts
 
Thanks, guys. 
@lewm If I run into anyone selling one of those A250 wands, I will point them in your direction. Cheers,
Spencer
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