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|24th May 2010, 08:17 PM||#1|
Join Date: Dec 2009
After the Terminator copy now the Schick alike
I had been using a rather nice Acos (Pioneer PL-71) 9" arm.
When I bought the deck (SP10 slate plinth) I tested a SME V12 - that was a tad expensive as nearly new and I though it sounded a bit to laid back and was probably not quite right for the Ortofon SPU Royal N I use.
Having looked at the Schick 12" I thought, could I build something like that to better what I have?
1st stop bearings - did some research, thanks to posters on bearing thread and I got me some Abec9 3,5 6mm spindle dia bearings to play with.
Let the project commence.
pics of the 3mm Abec9 bearings running in.
Bodged together rig to spin them and first suitable motor I could find...
Not bad photo's from a Nokia N97mini!
A quick test before running in (as they will work in the pivot) showed no discernible play - good start. Lets see if still ok after 50hrs+ of spinning.
The wand cut, bent supplied by redbeardanalogue - really nice guy - he included some silver arm wire too:^
I got a proper SME replacement arm / headshell socket / collar to fit the tube.
To get something 'long' up and running I intend to use a SME3009 armbase I have and mod the pivot to take my 3mm vertical bearings.
Then my own design on a brass base and pivot assembly could start. True to his word the wand has arrived from Jeremy and looks very good.
Here's some pics of the parts I assembled for the project.
idea of how it will sit.
Sort of insitu - Camera to hold up headshell end for photo
SME socket is nice fit.
One idea Jeremy had was to use heatshrink as damping for the arm - easy to take off again. I don't think I need to hide the SS arm as it looks pretty enough.
If it makes a difference then I might think about foam filling but let's see.
Off to the lathe.
"If anyone needs me I will be in my workshop - I am not be disturbed"
Spinning the nuts that clamp the centres of the bearings.
Twisted signal and earth - easy to push through. The twisting was Jeremy's recommendation.
Didn't have a grommet small enough so some duct tape in small strips is used to cushion the hole edge.
Coloured felt pen for red/green, white(no colour)/blue.
Important to heat shield the tags or you melt the plastic inside and the spring contact effect is gone! - Pal of mine has done that on his arm...
Tested and ready to go in
Socket in - nice tight fit and true
Action shots of hole cutting the base - 20mm
Based turned up
Then tapped the base for grub screw to lock the SME arm pivot tube and two holes in the base for screwing down.
Plus turned up a suitable (230gram) counterweight and tapped it for grubscrew to secure it to arm tube.
The weight was based on two ordinary weights hung on the back with the SPU / Sumiko on.
Placed on deck to see how it looks / check alignment
Close up of pivot - bearings epoxied on to SME pivot - incredibly strong - perhaps epoxy is not for the purist though!
Bit dusty too.
The business end
Can re-use the previous arm rest lash up for Acos arm, but in other armboard hole.
Still had the arm lift to sort out.
So at this point left to do:
-Remove armboard and drill mounting holes / thread & mount armbase.
-Solder up wires to phone sockets.
-Sort out a lift holder - preferably off top of SME arm pivot ala SME so that it moves up and down with VTA adjustment.
I did a quick check of VTA and it will be fine.
Also checked headshell level (azimuth) and that's ok.
Tried a common protractor I use and that aligned nicely. Of course it ran out way past the 240mm marks on pulling back towards rest;-) Well it would as the length pivot to base is 296.5m.
Figured out a cueing device from a Rega one I had 'in stock' so to speak. Bit of a lash up but it works and looks ok'ish.
More of a faff than building the arm tbh! These things always are.
Anyway. Mounted the arm did the last soldering - arm leads straight to phono sockets and then checked all measurements and alignments. All good.
Balanced her up at my SPU usual of 3g.
On with the amp - and cue up a record. Ah, no left channel.
Turned out it was the phono plug not quite home - bit fiddly with the plus under the deck you see.
That sorted - proper music.
Interesting - similar result to Pete's SME V12 I tried, which is saying something. Calmer, less what I can only describe on the 9" arm as colouration / distortion.
Quite a lot of bass and lovely cymbal character and shimmer I've not appreciated as much before. That was on
the ol' favourite - Armstrong and Ellington - Together album.
Ok on to some testing stuff - Tori Amos.
Lovely and expressive and again calmer - can listen at a volume that would have had a hint of setting my teeth on edge before I think. It's not quite as visceral as the 9" though.
Listening to other stuff I think the Sumiko heavyweight headshell is probable overkill or I could loose some mass off the back and slide the weight further out - decided to try that first...
Will also canvass for 'what headshell for my 12" arm' I think.
Wish I had the Techi one still to try as that was a bit lighter. I have the Pioneer PL-71 one but don't think the SPU will fit under it quite...
Anyway fun and games.
It definitely works well enough to be a keeper and refine.
Expect the Acos PL-71 arm to be back on the Pioneer PL-71 and on Ebay soon!
Now to get those big abec 9's bearings for the horizontal SME pivot, run them in and try them.
This has been a great project. Every bit as enjoyable as the Tannoy 15" Rect birch plywood cabs project and nice to do some metalwork after all the woodwork I've been doing.
Then I tried dropping the counter weight down as many top end arms have
Now with lower CofG counterweight - so many pro arms seem to use this idea.
Got around to doing a proper arm lift holder out of flat brass.
Similar clamp on arrangement as SME's with a height adjustable holder for the Rega armlift I have. Work very nicely and feels very secure.
Next stop the lash up arm rest - next weekend.
Photo taken with Nokia N82
I still felt the 12" lacked some of the emotion of the 9" arm.
Was I never to have the best of both worlds?...
UPDATE! Cracked it!
Had a long think about the negatives & positive of the 12" arm. Back to basics - the bearings.
Ran them in for another 48hrs at least and then flushed the grease out with solvent and high pressure airline (tip from wigwammer).
Result - I could not tell in my hand but on plumbing in and trying the SPU Silver Meister I now have the thing is transformed!
The bass is very good (was before), cymbals were good too - both better than the 9" arm.
Hum free which is more than can be said of the Acos arm - that will be the twisted sig and ground - will do same on Acos arm.
The new improvement is midrange punch and life / emotion is there. So now I have the best bits of the 12" sound and none of the negatives (a bit over calm / unemotional) I had before.
The 12" still has a calm authority about it that the 9" can't match when the going gets complex but it is not intruding on the music any more - far from it, it helps.
Perhaps it is that the Silver Meister suits the 12" config better than the Royal N, however I am preferring what the Silver Meister does on the 12" better than the 9" now and that is the main thing.
Couple of pics.
This is SPU'tastic now!
I am confident the changes have brought about a really good arm.
If anyone wants a DIY 9" or 12" one let me know and we can discuss. The 12" is done to SME standard of 296.5mm pivot to spindle.
10" depends on jig development so not for the time being.
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