A unipivot made from scrap

[cressy]

Wiring arrived the other day, so today rather than dodging intermittent rain showers outside trying to cut out layers in the plinth for the docs 99, i thought id get the loom made for this and wait for the weather to brighten.



Firstly the cart pins. This wire is transfi litz from vic and has a silk insulation which is nigh on impossible to strip, so I followed his instructions and tinned the ends without trying to get the silk off. It burns off the silk where it is tinned and fuses the silk so that it doesnt start to unravel. Much easier. Then fitted the pins and colour coded heatshrink.

I twisted the wiring up into a bundle to get it down the tube and cut it off to the length I wanted then tinned the other end.

The earth wire for the arm tube was soldered to a piece of solid core wire which is bent into a v shape then shoved into the housing end of the tube. and contacts the inner walls as a resistance fit.

The plug was a six pin not five as o was supposed to get, so I pulled the centre pin out to avoid it shorting on anything inside the body. The twisted up wiring then had several layers of heatshrink applied to make it thick enough for tue plug body to be tightened around it. Once wired, that was the wand loom done

The loop of wiring hanging out the back provides bias when twisted, which is why the socket will be on the right hand side, it tries to shove the back of the arm anti clockwise

[cressy]

And with the shure m97xe installed

[cressy]

Crap pic, couldnt get the angle right and it was wobbling as I took it but it lines up perfectly on both null points



Good job I had a trend digital bevel to mark the headshell up for cutting and drilling it.

The headshell is fixed and has fixed holes rather than slots. Borrowed that idea from the naim aro. In order to alter the alignment, the idea is borrowed from both sme and slatedeck. Sme insofar as the pivot to spindle distance can be altered, and slatedeck, as the way to do this is to rotate the arm board in the cutout. The hole is offset from the centre to allow a degree of adjustment

Should allow around 15mm of adjustment, so plenty there.

Assuming that the 10mm measurement between the mounting hole centres in the m97 body and the stylus tip is pretty common which I think is a fair assumption, it cant really be much more or less given the size of a cart,
The arm should should take pretty much anything I could put on it. In terms of dimensions anyway

Next job is to figure out how to get a din socket on the underside of the baseplate for the arm cable, and mount the 5 pin connector on the top.

Not bad for a lash up so far.

Of course, it could still sound shit though.......

[cressy]

Looks seem to match the deck well too, perhaps better with a silver arm tube. Might paint it if it sounds alright and I do the finishing work on it



Could still sound shit though

[cressy]

Haha! It works!

[cressy]

A very positive first listen to it, the bass end is absolutely stunning fantastic awesome. I am not kidding. It makes The modded rega look like absolute rubbish. I havent had, bought or made an arm that comes even close.
Mid seems very good, top end, errrrrr, not so good. S'all there, but abit dull, abit veiled.
I have several ideas as to why.

[Cressy Snr]

Yes, I heard it this afternoon and the bass is absolutely stunning. I truly have never heard bass like it; tight, fast tuneful, excellent tone, texture and positively subterranean in its depth capability. The image from the 4ft Mets is cinematic, but there are problems with the top end, which we discussed and think we know how to fix.
Hopefully, the fix won't destroy that bottom end or the Planetarium soundstaging. We'll see.

[IslandPink]

Great effort ! Hopefully the HF will come good - I tend to think in an arm like this there are fewer places for it to go wrong than in a metal arm. If the bass/timing and mids are good you've got the geometry and C of G more I less correct, I would think.

[cressy]

Nice thing is that i can bugger about with the pivot height. Which means I can effectively move the centre of gravity up and down.

I think the arse end of the arm is basically there, i concentrated the mass around the pivot and that seems to have worked as intended. The first port of call is the headshell. Its actually pretty lightweight at 6g, but there seems to be just abit too much weight too high up. Its the concentrated mass of the walnut block that I think is a part of the problem, its making the front end top heavy, meaning that as it osscilates, it doesnt settle down as quickly as it should. Like the pendulum on a metronome, which maybe partially why the top end isnt as good as it could be.

[cressy]

I quite like the copper arm tube too, it doesnt seem to ring like aluminium does. The rega casting rings like a bell, but there seems to be bugger all ringing with this wand.
It probably does ring, but not in the same way as the ally casting does.
I also wonder wether the wire arm rest is causing an odd harmonic as it vibrates in use

[IslandPink]

part of the problem, its making the front end top heavy, meaning that as it osscilates, it doesnt settle down as quickly as it should. Like the pendulum on a metronome, which maybe partially why the top end isnt as good as it could be.

I doubt this is going to oscillate at 5kHz or 10kHz.

[cressy]

No, but while it is flopping about the azimuth is changing so the stylus is not tracing properly

[IslandPink]

So is it flopping about ?
Surprising that the bass and timing would be OK in that case.

[cressy]

Not exactly flopping around, it takes longer than I would like to settle down when cued.
The 6g mass that is the walnut block is about 15mm above the stylus which is quite a distance in terms of an arm. So for a small stylus movement with respect to azimuth, that block is moving quite a bit. Cos its top heavy, it rights itsself slower than I would like.

Its a cx500 arm

Infact, i shall call it the cx

Plan is to make another arm tube, and rather than having the block, having the acrylic plate glued directly to the tube.
This will take the cart up by around 3mm which can be taken up by moving the bearing pin and cup upwards, and will remove the mass above the cart.

The wiring loom is made to be removable, as is the wand. Pull the bearing pin out and it releases the wand.

I expected to have to change things, I wasnt expecting much out of it tbh which is why Im pleased that initially there arent a million issues, and that the majority is positive

[cressy]

Been playing with the damping in the bearing cup, started with it full of lithium grease, took out most of it to get to where it was the other day. Took the rest out now so its just got what was still on the needle and a teeny bit in the bottom that a cotton bud didnt get.

Better. Need to sperryment with different stuff. I have some light machine oil to try, just the stuff used around the house. Nothing special