A unipivot made from scrap

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jack
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Re: A unipivot made from scrap

Post by jack » Thu Apr 11, 2019 11:18 pm

This is deeply impressive!

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IslandPink
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Re: A unipivot made from scrap

Post by IslandPink » Fri Apr 12, 2019 12:22 pm

Ant wrote:
Thu Apr 11, 2019 9:21 pm
also made a new bias guide as I wasn't happy with the loop one. the new one presents a smoother travel for the string as it's a smooth curve rather than the tight bend in the first one, and it allows the string to run at the same height as the bias arm which is in line with the pivot point so the pull doesn't affect stability. Now it doesn't affect the azimuth by pulling it upward either.
This is a very important thing - good to you know you have looked at this. The groove needs to be very close in height to the pivot point, and also try & get the string pull horizontal over as much of the angular travel of the arm across the record. This is an area where unipivots can fail badly due to the azimuth being messed up as you travel from outer to inner tracks.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: A unipivot made from scrap

Post by Ant » Fri Apr 12, 2019 10:05 pm

Ok, got the wiring loom bodged on. It is a big fat bodge, I should've drilled out the wooden part of the arm tube, but it suffices for testing the arm..... It is sat in the mdf block as I was fed up of it falling over every time i looked at it funny...

ImageCx unipivot mk iv by anthony cresswell, on Flickr

The loom is also a little compromised as it's abit shorter than I would like, but it was pulled from one of the old wands, the mk 3 flat one that was not great.

ImageCx unipivot mk iv by anthony cresswell, on Flickr

Ive reused the small locking connector from that loom aswell as it was pretty good and really solid.

ImageCx unipivot mk iv by anthony cresswell, on Flickr

The loom would have followed the same pattern though, exiting the arm tube through the top at the same point the bodged loom bends up, through a grommet to insulate it from the tube. Probably with a silk sheath around it so it remains flexible.

The connector box is what I had in mind, turned from a block of walnut with a cover on the bottom turned to fit in it as a resistance fit like a box lid I will put an earth post on it if the arm needs one. Dunno if it will yet as the cart will be isolated from the rest of the assembly by the wooden bit of the wand. It might hum, it might not, will see. I didn't have any issue with hum with the flat wooden wand

ImageCx unipivot mk iv by anthony cresswell, on Flickr

So other than the wiring being taped to the arm rather than being inside it, this is pretty much how it will be.
Too late tonight to start dismantling a deck to put it on, a job for another day

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Mike H
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Re: A unipivot made from scrap

Post by Mike H » Fri Apr 12, 2019 10:32 pm

jack wrote:
Thu Apr 11, 2019 11:18 pm
This is deeply impressive!
Likewise!
 
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Re: A unipivot made from scrap

Post by Dave the bass » Sat Apr 13, 2019 8:50 am

Hyper-Shoddy +1 x that infinity thingum!
Dirt eating, low-voltage boy but "'Occasionally phenomenal'"

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Ali Tait
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Re: A unipivot made from scrap

Post by Ali Tait » Sat Apr 13, 2019 11:31 am

Very nice job Ant, very impressive.
Image[/img]

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Re: A unipivot made from scrap

Post by Ant » Sat Apr 13, 2019 12:52 pm

Dont forget, it might sound like shite when I get it fitted to something... :mrgreen:

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Re: A unipivot made from scrap

Post by Mike H » Sat Apr 13, 2019 4:27 pm

Dave the bass wrote:
Sat Apr 13, 2019 8:50 am
Hyper-Shoddy +1 x that infinity thingum!
X the number of all the atoms in the universe.

And the universe next door. :D
 
I never make the same mistake twice. Instead I prefer to fill my day with a variety of different mistakes

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Re: A unipivot made from scrap

Post by IslandPink » Sat Apr 13, 2019 6:26 pm

Ant wrote:
Sat Apr 13, 2019 12:52 pm
Dont forget, it might sound like shite when I get it fitted to something... :mrgreen:
Very probably not ! ... but to make some effort to pick holes in your approach :D , did you use Danish oil on the wooden bit of the wand ?
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Dave the bass
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Re: A unipivot made from scrap

Post by Dave the bass » Sat Apr 13, 2019 7:23 pm

Mike H wrote:
Sat Apr 13, 2019 4:27 pm
Dave the bass wrote:
Sat Apr 13, 2019 8:50 am
Hyper-Shoddy +1 x that infinity thingum!
X the number of all the atoms in the universe.

And the universe next door. :D
Yes.

Yes.

+1
Dirt eating, low-voltage boy but "'Occasionally phenomenal'"

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Re: A unipivot made from scrap

Post by Ant » Sat Apr 13, 2019 8:55 pm

Well I got it installed and had a cursory listen to it, and initial impressions are very promising.
I had to make a turret for it so it could be installed to run on the lenco. Which was a pain in the arse. I dug out an offcut from a plinth I did to make it

ImageCx unipivot mk testing by anthony cresswell, on Flickr

Cut a chunk out of this and turned a tower out of it which was an arse as neither ply, MDF or the particleboard core turns very well at all. It ate the chisels because of the heat build up, they had to be sharpened a couple of times while doing it.

ImageCx unipivot mk testing by anthony cresswell, on Flickr

Turned out ok though, but the install is not the greatest ever. It wants fitting to a deck properly. It was an absolute sod to get the cart adjusted so I had to settle for a close alignment as I simply couldn't see or get at the cart properly to do a proper job. But it suffices for testing.

I could also run both arms at the same time so I could do an A/B between them. So I did.

ImageCx unipivot mk testing by anthony cresswell, on Flickr

I then took the Goldring E3 cart off and fitted the AT150 sa to the CX so both arms had the same cart on.
Also had to bodge something fr the connector box to stand on and supported the long cables to it on the hook for the curtain tie-back....

ImageCx unipivot mk testing by anthony cresswell, on Flickr

So, impressions are that it has guts and that it is very stable for a unipivot, I think I got the weight distribution about right. It has a solid and dynamic sound to it, similar to the mk2 had but it seems to be more grippy than I remember that one being. I cant really say much about the treble as the cart alignment was out, but it seems ok so far. It also seems to image really rather well which was unexpected as the mk 2 one was ok but nothing special, and that its easy to place instruments in the image.

for want of a better word, it seems pretty musical, even if that is something of an amorphous term. One mans 'musical' is another mans 'coloured' or whatever other term someone cares to use.

But overall very promising. And not much hum even without an earth

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Re: A unipivot made from scrap

Post by Ant » Sun Apr 14, 2019 5:51 pm

I've put it on the lenco properly now rather than on the turret now, taken the at arm off.
So I'm now comparing it with the audiomods arm that's on Paul's 301.
Other than an odd static problem I'm rather pleased.
Onward!

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Re: A unipivot made from scrap

Post by Mike H » Sun Apr 14, 2019 8:23 pm

I like the use of the curtain hook :D
 
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Re: A unipivot made from scrap

Post by Ant » Mon Apr 15, 2019 3:04 pm

Proper install. Its on an arm board that was the original one from when the deck was built, set up for an rb250. I used the same geometry so it fits properly on this board

ImageCx unipivot testing by anthony cresswell, on Flickr

Interestingly the static problem seems to have resolved itsself, then come back for some reason, and the more odd thing is that it is related to the rotation of the platter and not the motor.... set the platter spinning and the static crackles appear. turn the motor off and they stay. stop the platter by hand and they go away.... odd.

I need to understand why so i can solve the conundrum.

ImageCx unipivot testing by anthony cresswell, on Flickr

some earthing may sort this

ImageCx unipivot testing by anthony cresswell, on Flickr

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Re: A unipivot made from scrap

Post by Ant » Sat Apr 20, 2019 10:09 pm

Figured out what was causing the static problem.
Proximity to the curtains......
They are nylon. And also drag on the carpet.
Who knew.
Put the deck back in its usual place and no issues
Hooking the wires over the tie back hook might have made it worse

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