DIY 47 Labs RS-A1 tonearm? or "Clonearm"

Hi Folks,

So, it seems everyone's building gainclones. Why not flatter 47 Labs some more and build a clone of the RS-A1 tonearm with the pivoting headshell?

I just wonder if it really has to have such a high main pivot (it wouldn't fit under my turntable's dust cover at that 16º angle). I read somewhere that their cartridge is designed for a high pivot point to "match the cutter head". I, of course, will be using one of my existing cartridges. I'm guessing a high compliance cart would mate well with the low inertia of a pivoting headshell. Conventional wisdom would have the pivot as close to record height as possible to avoid changes in stylus pressure while warp riding. True, this arm is not exactly about conventional wisdom, but...

If you have no idea what I'm talking about, check here:

http://www.sakurasystems.com/articles/rs-a1.html

Any thoughts before I source materials and fire up the milling machine?

-Max
 
interesting principle of design

i think the hieght of the arm will be a prob if u have a lid....and the extra mass in the arm tube may lose any advances in the tracking angle stuff

its at this point i think back to my old decca gold garrot micro scanner...it had the cantiler coming straight down ...like the cutting head that cut the grove

thanks for shareing that link

here is a pic of my own new arm...any comments will help thanks

best wishes
j7
 

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Brian Clark said:
... if you scroll down to "Yamamura Churchill" here :
http://audiotools.com/oldlp_z.html
you will see what is believed to be the prototype of the RS-1.
Fabricated out of perforated metal channel by a specialist motor racing outfit in the South of England! :)

Yes, I saw this one too. Looks like the same thing, 47 Labs just went with less flashy constuction. If you look at the 47 Labs HS-3(?) pivoting headshell, you will see they are not into fine finishing work. How many of these Yam-Churches were actually made?

AudioOrigami said:
its at this point i think back to my old decca gold garrot micro scanner...it had the cantiler coming straight down ...like the cutting head that cut the grove

Vertical cantilever? I cant imagine that to track warps very well. Do you have any pictures?

here is a pic of my own new arm...any comments will help thanks

Nice workmanship. Is that brass, anodized aluminum or just my monitor making it that colour? Looks like a gimball pivot, yes? If so, the pivot is not paralell with the cartridge. (I assume those nubs on the sides and top are where the bearings are.) This will cause a slight azimuth change when riding warps. Looks like you have no provision for adjusting overhang for different cartridges. Does one just move the base of the arm to achieve this?

I see on your site that you are familiar with the Cardass 33gauge wire. Is this supple enough to let a pivoting headshell move freely? I ask because it's available in Canada from Take five and I would like to know before ordering a bunch.

All this talk of warp riding makes it sound like my LP collection has been left in the sun. I just want the tonearm to be able to handle the rare old wobbly ones when needed.

Max
 
hi
the old decca was a great cartridge
bear in mind Big warps are not really what the arms are carts are made for ...esp if u want perfection...most peeps would want flat vinyl

thansk for the coments on my arm ...yes its brass...and gold plate is my next area to look at
and yes its a gimbal bearing ...has a lot of design from syrinx and heloius and alpha...so u may see some simularities in it

the arm tube rotates and pulls in and out

the cardas internal wire is very good...and its very thin so it dont restrict the arm movement very much

...so i can recomend it

best wishes for now
j7
 

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AudioOrigami said:
hi
the old decca was a great cartridge

Looks like the Decca has a normal pivoting cantilever with some sort of plunging magnet. Is this a mono cart, designed for vertically cut grooves? I suppose it would be very linear, so to speak, acting pistonically, like a speaker driver.


thansk for the coments on my arm ...yes its brass...and gold plate is my next area to look at
and yes its a gimbal bearing ...has a lot of design from syrinx and heloius and alpha...so u may see some simularities in it

Does the brass have any problems with ringing or resonance? What, if anything, have you used to damp it internally? Gold plate ought to keep the buffing work to maintain that polish to a minimum.


the arm tube rotates and pulls in and out

Good you won't be stuck with just one cartridge that fits.

Max
 
hi
no the decca has nothing similar to normal cantilever
the white string holding the vertical cantilever is what u see
the cantilevr comes straight thro the middel of the coils
its not the clearest picture....the decca resembles the cutting head arangement

the decca has much writing about it...maybe try vinyl engine for more info on it

my brass arm uses dampening material in the tube---- and around it ...as well as a silicon oil bath....more details will follow soon on its design....
....it should be on show @ the hifi show in heathrow next month