A unipivot made from scrap

Love it or hate it, it just won't stop
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#196 Re: A unipivot made from scrap

Post by Ant »

Because im not overly impressed to be honest, although im not sure why.

its doing pretty much what i was hoping for, perhaps its that bit of colouration and the fact that im listening critically to it. Or that i am a great big pedant. Or it isnt doing the same disappearing act as the air bearing arm does.

I dont like talking about the sound of things ive built because i have no idea as to wether my thoughts about it will tally with those of other people, someone else might completely disagree. Which is why i usually just say things sound fine, good, ect.

I appear to have achieved the design goals i set myself but im trying to pick holes in it
I could do with feedback on it from someone else
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#197 Re: A unipivot made from scrap

Post by Cressy Snr »

Drop the TT up here. The MoFi stage as you know will accommodate moving coil carts and I’ll have a listen to it.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#198 Re: A unipivot made from scrap

Post by Ant »

Its a homc so it works with the mm settings
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#199 Re: A unipivot made from scrap

Post by simon »

Perhaps just needs a bit of time with it? Second opinions can be really informative.
User avatar
Paul Barker
Social Sevices have been notified
Posts: 8863
Joined: Mon May 21, 2007 9:42 pm

#200 Re: A unipivot made from scrap

Post by Paul Barker »

If you want to sell it, try it on my 301?
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#201 Re: A unipivot made from scrap

Post by Cressy Snr »

Well, the turntable is at my house now and all levelled and set up, so I’ll have a listen this evening.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#202 Re: A unipivot made from scrap

Post by Cressy Snr »

Ant wrote: Fri Mar 26, 2021 6:41 pm
... perhaps its that bit of colouration...
I know what you mean, but I’ve solved that particular problem to my satisfaction. I’ll talk about that later.
Let’s just think Naim Aro for the time being. :wink:
Sgt. Baker started talkin’ with a Bullhorn in his hand.
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#203 Re: A unipivot made from scrap

Post by Cressy Snr »

So let’s start with that colouration Ant’ was hearing. It was a sort of weird fog that hung over the upper mids. You knew there was something in there trying to get out but it was being gagged. A bit of lateral thinking on my part about the the kind of environment that the Naim Aro on the LP12 and the Roksan Nima on my long departed Radius V turntable worked in, and I quickly produced a 6mm Rega felt mat from the cupboard. I removed the ribbed rubber mat from the Lenco, replacing it with the felt mat and Bam! the fog lifted, the sound liquefied and the groove was released. All further listening was done with the felt mat. So here we go. Short but sweet. I’m not a professional reviewer, so I’ll try my best.
80C9E587-D0AC-481C-9BDD-95D05A698B11.jpeg
80C9E587-D0AC-481C-9BDD-95D05A698B11.jpeg (106.37 KiB) Viewed 3859 times
I'm a voice freak. Any piece of audio equipment that doesn't sing well drives me up the bleed’n wall. I’m particularly particular about black female soul voices and this arm’s handling of such voices is excellent. It’s the best I've heard female black voices sound on my system. On the latest Brand New Heavies LP ‘TBNH’ the track ‘Beautiful’ has Beverly Knight on guest vocals and she was reproduced without a hint of screech, which was frankly incredible to be honest. Also the the track poled along superbly, the insistent groove absolutely precise and flowing like liquid. It was impossible to keep still. It’s a great arm to dance to, with high octane boogie factor. I was encouraged to get out my Motown vinyl. :D

A few of my torture records, showed off the arm’s composure. No matter how much was going on in the groove, the thing remained unflustered. I get the impression of improved tracking and solid stability. This translates into peace of mind for the listener. There’s no subliminal cringing when something difficult comes along. For example, ‘In The Gallery’ from Dire Straits debut album, had a fine coal miner for the NCB, on it rather than the ‘en SSTHEE, bee’ and on side one, there was a six blade knife not a ‘SSSTHix’ bladed one. Nothing I played led to any hairy moments and I really did try to provoke it. Over the all important midrange, the arm was quite free from compressed dynamics. When the going got loud, the timbres stayed intact and the instruments remained separate and easy to follow.

At the frequency extremes, the highest highs did sound a mite shut-in, leading to a very slight lack of air on some recordings. But that might be a product of my single driver speakers or the fact that my hearing stops at 10KHz. The bass end was even tempered, with a total lack of bloat. The synthesised bass on ‘Don’t Go’ from Yazoo’s “Upstairs at Eric’s” went deep and fast. Similarly Paul’s bassline on “Come Together” from Abbey road, stayed boom free and under total control. The very nth bit of extension was missing, but again, that might have been my speakers. These minor foibles, if they were actually there, given the limits of my system, couldn't detract from the arm’s overall excellence though. It sounded completely unmechanical, and just let the music do what it wanted to do.

Points to ponder:

I don’t like the position of the fingerlift. It makes the arm more difficult to cue than it needs to be. The fingerlift might be better placed so it sticks out of the circular base of the headshell, so you are handling the arm right where the cartridge is.

The wire loop over the rear needs to go. The leads would be better off inside the arm and going down through the pillar to a conventional five pin DIN socket, or failing that, emerging from under the bell housing at the rear and looping around the front to a socket in the armboard, as did the Naim Aro.

If the fingerlift position and the cabling arrangements are given further work, this arm will be a great bit of kit.
When those things are sorted, I want one.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
JohnG
Old Hand
Posts: 418
Joined: Sat Mar 25, 2017 10:59 am

#204 Re: A unipivot made from scrap

Post by JohnG »

Hi Cressy, Ant
A good write up on the impressions made with Ant's Tonearm.
Cressy's review, makes the Tonearm sound like there is a lot on offer from the design,
resulting in leaving a very good impression.
It would be good to hear this at a future event.

When I am assessing any New Devices on a TT, even down to a exchange of a Sub Plinth Material.
I will assess the effect of the changes with Platter Mat Material exchanges as well.
My experiences have shown on many occasions that certain materials work extremely well together and others even though respected and in use, do not deliver their best when used in a certain type of environment that is created.

Your use of a Felt Mat in place of a Rubber Mat and the results that are being reported back, is a experience that I have been familiar with.
Some times it is more like a slight change of a Flavour, at other times the perceived change can be quite noticeable and wanted.
When at a Friends a I brought along a few different Platter Mats made with different Materials.
A Foam Mat which was used to replace a long term used Felt Mat on the TT, produced a very noticeable improvement to the presentation.
The Felt had been selected over a few other materials from a previous investigation that had taken place many years before my visit.

I am not suggesting that the Felt Mat used by yourself can be improved upon.
I am sharing my support for your experience to be willing to experiment with different materials used as a Platter Mat.
User avatar
Ray P
No idea why I do this anymore
Posts: 6294
Joined: Thu Nov 22, 2007 5:18 pm
Location: Somerset

#205 Re: A unipivot made from scrap

Post by Ray P »

That's a nice write-up Steve, it sounds as though Ant's downbeat perspective was a bit premature.
Sorry, I couldn't resist!
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#206 Re: A unipivot made from scrap

Post by Cressy Snr »

Ray P wrote: Sun Mar 28, 2021 12:22 pm That's a nice write-up Steve, it sounds as though Ant's downbeat perspective was a bit premature.
Yes, the arm is very good. I can understand his downbeat verdict with the rubber mat on the TT. I think theres a bit more to it, possibly a bit too much structural damping inside the arm tube and I’ve relayed that to him. However it’s a superb piece of work without doubt. Given the use of a felt mat, it easily competes with the Roksan Nima and the classic Naim Aro as it stands right now.
JohnG wrote: Sun Mar 28, 2021 11:00 am ...Your use of a Felt Mat in place of a Rubber Mat and the results that are being reported back, is a experience that I have been familiar with.
Some times it is more like a slight change of a Flavour, at other times the perceived change can be quite noticeable and wanted.
When at a Friends a I brought along a few different Platter Mats made with different Materials.
A Foam Mat which was used to replace a long term used Felt Mat on the TT, produced a very noticeable improvement to the presentation....
Yes, the felt mat is interesting, My Grado/SME combination on my own Lenco sounds great with a cork/rubber composite mat and so-so with felt, so one does, as you say, have to consider every interface involved when testing a pickup arm.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
JamesD
Old Hand
Posts: 997
Joined: Tue Oct 09, 2007 4:26 pm
Location: North Yorkshire

#207 Re: A unipivot made from scrap

Post by JamesD »

Really good to read about this and the end result :-) A great piece of diy!

Quick observation on the CF arm tube - the dampening of the arm tube is critical to its performance -Morsiani always said that less is more and over dampening it kills the life and air in the performance - he very lightly dampened the tube using a little sheep's wool - he liken the over dampening to using a wood wand without lacquering the wood first...

Korf Audio blog has some measured comparisons of different arm tubes including attempted CSD tubes - and these are horrible illustrating the arm wand dampening is something to be very cautious about.

ciao

James
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#208 Re: A unipivot made from scrap

Post by Ant »

I knew it was overdamped as soon as i put the rubber in. Dropping the tube on the bench made a strange ring, the resonance alot lower than it was without it. Pulled it too low.
But i pressed on because i wanted the extra effective mass.
Bits arrived yesterday to make another one, apart from a din socket.
Need to work out how to get the wiring down the inside of the pillar without it being cut by the edge of the hole it has to go through, and some sort of transport lock so the wand doesnt get pulled away from the pillar and snap the wiring
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
JamesD
Old Hand
Posts: 997
Joined: Tue Oct 09, 2007 4:26 pm
Location: North Yorkshire

#209 Re: A unipivot made from scrap

Post by JamesD »

Interesting test method that drop test :D but it does seem effective...

I've bought some 300mm 10mm diameter solid graphite rods to test in my Mission arm but I haven't got around to it yet - I'm hoping they will be stiff enough and well damped enough to beat my carbon rod (old fishing rod) and the original Mission arm - if it equals the lacquered mahogany I will be pleased...

Really impressed with how you made this and addressed the balance and stability problems of the unipivot - its made me re-look at my designs...

ciao

James
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#210 Re: A unipivot made from scrap

Post by Ant »

Well the teeth knashing issues with unipivots ive used have all been pretty much the same. (Mayware, nima, decca international)

Counterweights with offset holes are a pain in the arse as the azimuth and tracking force adjustments are altered by each other. The mayware counterweight will also eventually creep downwards and cock the azimuth up, even with a replacement bush. Decoupling the counterweight in this way seems to muddy the bass response to me too.

Using the counterweight to lower the centre of gravity is not the best way to do this imo, because it moves.
Separating these two adjustments was the first thing i looked at.

Using mass in the right place was also something that came out of the different ones ive built, and using the least mass i could to achieve stability, i think is important as it all contributes to resonance in the wand.

Thinking carefully about the way bias is implemented is something i consider important as it will always affect the azimuth to a greater or lesser degree. Getting it to pull in line with the pivot will stop it interfering with this, but doing so isnt as simple as it sounds, because it has to be able to pull all the way across the record and not catch in the guide. There is only a finite amount of space to do this.

Having the pivot high up and using the weight if the wand to gain stability (eg mayware, all the weight is below the pivot point, the stylus is at least the cart height below the pivot) is also a compromise because the higher it is, the worse warp wow will be. Ideally the pivot in an arm should be in line with the stylus, but again this is easier said than done. There is only a finite amount of space, and its a balancing act between stability, effective mass, how much height adjustment you can actually achieve and clearances so that it actually works and doesnt bottom out on itself.

The more weight above the pivot, (wand ect) the more weight has to go below it to make it stable and the less space there is for this.

I tried with this one to get sufficient adjustment to allow it to fit on a deck with a 25mm record height which is fairly low. It was not so easy to do. It just scrapes in with a normal height cart which is about 17mm. Anything less will need a shim at the cart to make it possible to get the arm set up so it is parallel with the record.
Theres a little bit of wriggle room in the design but not much.

The amount of things to consider isnt trivial.
I did also consider using a cursor weight on the arm tube to allow the effective mass to be altered, im still considering it if i can get away with a small weight, because it will alter the weight distribution and stability.

Further buggering about is required for that, maybe a small piece of stainless tube with a 12mm id and some felt inside to make it stay in place.
Hmmm
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
Post Reply