A unipivot made from scrap

Love it or hate it, it just won't stop
User avatar
izzy wizzy
Old Hand
Posts: 1496
Joined: Fri Nov 02, 2007 7:02 pm
Location: Auckland NZ
Contact:

#271 Re: A unipivot made from scrap

Post by izzy wizzy »

Or could there be a phono EQ difference down low?
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#272 Re: A unipivot made from scrap

Post by Ant »

I dont think its that the schroeder is bass light, your digital side should be flat so if you have set your levels using a combination of the 401 and the digital side they should be pretty flat
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

#273 Re: A unipivot made from scrap

Post by simon »

izzy wizzy wrote: Sat Jul 10, 2021 11:39 pm Or could there be a phono EQ difference down low?
I used the same PHONO II with a 39k load resistor, so should be close enough with Ant's MM cart?
simon
Thermionic Monk Status
Posts: 5600
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

#274 Re: A unipivot made from scrap

Post by simon »

Ant wrote: Sat Jul 10, 2021 11:57 pm I dont think its that the schroeder is bass light, your digital side should be flat so if you have set your levels using a combination of the 401 and the digital side they should be pretty flat
This is the uncertainty in my mind. Since I built these speakers I've been listening to vinyl exclusively, apart from maybe when they were first built. So what I perceive as "normal" might not be.

It's not easy to switch between vinyl and digital but I need to find the same album on both and see how they compare.
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#275 Re: A unipivot made from scrap

Post by Ant »

The 39k in your phono 2 is not far off the 47k in my benedict audio, i cant see there being a great deal of difference with the loads

Its at the old mans house at the moment, so we shall see what he reckons compared to the mk 5 and mk 6 versions

The one thing i didnt address is the handling which he didnt like with the mk5, in fact i made it worse with the little fingerlift :roll:

I could really do with some other carts to try on it, or to be tried on it, the dynavector isnt that typical a cartridge
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
User avatar
izzy wizzy
Old Hand
Posts: 1496
Joined: Fri Nov 02, 2007 7:02 pm
Location: Auckland NZ
Contact:

#276 Re: A unipivot made from scrap

Post by izzy wizzy »

Ant wrote: Sun Jul 11, 2021 6:06 pm The one thing i didnt address is the handling which he didnt like with the mk5, in fact i made it worse with the little fingerlift :roll:
Stiff string? ;)
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#277 Re: A unipivot made from scrap

Post by Cressy Snr »

Been listening to the new arm:
It sounds very good, more evenly balanced through the frequency range. Treble is detailed but remains smooth with the Dynavector MC cartridge. There is a slight hint of mid-forwardness coming through that wasn’t there on the earlier iteration. This combined with the tuneful, articulate bottom end makes it sound even more like a Naim Aro. This characteristic gives a sense of no nonsense power and solidity to the presentation. No thinness or lack of dynamics. It’s bloody good in my opinion.

Still don’t like the position of the fingerlift. It might be worth incorporating it into the side of the circular cartridge mounting platform; that way it will stick out at right angles to the cartridge itself rather than at right angles to the arm tube. This should make handling a lot easier.
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

#278 Re: A unipivot made from scrap

Post by Ant »

Interesting... just been looking at dl103's while looking for carts. As we know, they have have a compliance of 5, and i suddenly remembered that that figure was arrived at measured at 100hz. So its not 5, its somewhere around 9 ish at 10hz. Hence looki g at them at all.
I then found an article that martin colloms did and he reckoned it came in at 12x10-6 at 10hz. Presumably this was calculated using a test record
That, coupled with this arms effective mass of 12.6g with an 8g cart, gives a resonance of 9hz, smack in the middle of the green zone on the vinyl engine resonance evaluator

So a 103 will work fine in this arm. Shame they have a spherical stylus......
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#279 Re: A unipivot made from scrap

Post by IslandPink »

Hmm, 9Hz is still adding a bass roll-off though. Anyone who's used one for a while knows that extra mass helps a lot. I think James went as far as a 50p piece blu-tacked to the headshell on his Kenwood.
It's interesting to hear the compliance numbers for 10Hz and 100Hz though, thanks.
"Once you find out ... the Circumstances ; then you can go out"
User avatar
pre65
Amstrad Tower of Power
Posts: 21373
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#280 Re: A unipivot made from scrap

Post by pre65 »

IslandPink wrote: Thu Jul 15, 2021 1:08 pm Hmm, 9Hz is still adding a bass roll-off though. Anyone who's used one for a while knows that extra mass helps a lot. I think James went as far as a 50p piece blu-tacked to the headshell on his Kenwood.
It's interesting to hear the compliance numbers for 10Hz and 100Hz though, thanks.
I used a 20p piece.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#281 Re: A unipivot made from scrap

Post by Ant »

On this arm the brass mounting plate is what adds the weight
Because it is directly over the top of the cart, and moves with the cart when it is aligned, i have to calculate the plate in with the cart weight rather than as a headshell. It does interesting things to the calculation if you add it in as a headshell, the calculation assumes that a headshell is in a fixed position and adds it to the bare arm mass. This is to compensate for headshells of different weights.

So working it out for this arm i have to treat it as a fixed headshell arm with additional weight added to the cart itself.

If the resonance of the arm is at 9hz (or whatever figure it might be), i wouldnt see that as a rolloff, id see it as an LF spike at that point as the arm adds its contribution, like the fr of a speaker cone when you see a hump in the plots at the fr point,or am i wrong in thinking this?

Need to work out some way of measuring without an accelerometer available
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#282 Re: A unipivot made from scrap

Post by IslandPink »

Maybe I'm wrong in describing it as a roll-off yes, it's a resonance peak.
So, the resonance peak has an increasing phase shift associated with it, as you go down from upper bass into the low bass - which will affect the perceived timing and quality of the bass.
"Once you find out ... the Circumstances ; then you can go out"
User avatar
Nick
Site Admin
Posts: 15707
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#283 Re: A unipivot made from scrap

Post by Nick »

Maybe I'm wrong in describing it as a roll-off yes, it's a resonance peak.
The only difference between the two is the Q of the system. Below the peak it will be a roll off. The Q governs how abrupt the phase change is.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#284 Re: A unipivot made from scrap

Post by Ant »

Did a little more work on the arm, made a heavier counterweight. I did try adding some lead to the existing one but it altered the mass distribution of the counterweight and did strange things to the lateral balance so i sacked that and did it properly with some more steel.

If anyone wants some stick on lead strip let me know, my father in law gave me 2 huge great rolls of it from when he was doing leaded windows. Theres about 5 kilos of it.....

The new one is 150g as opposed to 115g, and took an inordinate amount of time to make with the amount of times i took it out of the lathe chuck and weighed it, faced some more off it, and buggered about boring the centre hole to fit the stub.

Thats because id not used 10mm polished bar stock and had turned down what i had in to make the stub..

It will drop the effective mass a little to 11.5 g with the dv in it.

I have some more brass coming to make a smaller one of the same weight, id prefer it was more compact.

Havent listened to it yet, i dont think it will make a great deal of difference though, but it looks better not hanging off the end of the stub

Onwards!
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
Ant
Shed dweller
Posts: 2332
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

#285 Re: A unipivot made from scrap

Post by Ant »

Decided to try an aluminium bearing housing instead of the acetal one.

ImageCx unipivot version 7/a by anthony cresswell, on Flickr

The carbon fibre tube and aluminium stub and headshell is off the one that our Simon assessed, I'll make a new pillar as I have another v jewel. I'll also make a new outrigger set instead of using the one off that version as I reckon there's some odd resonances coming from it. The wiring and mdin socket will also be reused from the version 6 arm

The reason I've decided to look at a metal housing is that I think that the acetal is blocking the path for some resonances to get out of the tube and down the arm pillar, and having some aluminium to play with, it seemed a reasonable thing to try.

The housing is exactly the same as the acetal one, and has a brass weight insert in it instead of a steel one to compensate for the heavier weight of the metal.

ImageCx unipivot version 7/a by anthony cresswell, on Flickr

I'll also need to make another mounting boss and cartridge carrier, should have enough aluminium left for those

I've also been kindly loaned an Ortofon 2m blue to try on this arm and the brass version so I'll be able to see how they behave with something other than the Dynavector in them which should give me more of a overview of what traits the arm is adding to the whole.

This version will go on the big Lenco so I can kind of A/B then on practically the same deck.

I'll also need another cable, I've been looking for something that has a reasonable cost, found one by a firm called the vinyl adventure, one called 'the rebel'. £40 is at least reasonable

Onwards!
Also starring Rex Hamilton as Abraham Lincoln

www.bte-designs.weebly.com
Post Reply