|
|
Post by julesd68 on Mar 12, 2021 10:41:16 GMT
I remember auditioning an A&R A60 back in the day against most of the main contenders in that price range.
I found it too smooth, reserved and dynamically flat if memory serves me right. An amp that wouldn't offend like some but wouldn't excite either.
That's around 35 years ago though! I think they are still quite popular so if you bought one at a good price you should be able to move it on.
|
|
|
|
Post by ant on Mar 12, 2021 13:14:50 GMT
Yep ive never been keen on the a60, but the delta 60 looks a different prospect
|
|
|
|
Post by julesd68 on Mar 12, 2021 16:06:52 GMT
Sorry I misread your previous post, I missed that you're not a fan of the A60!
|
|
|
|
Post by Slinger on Mar 12, 2021 20:05:14 GMT
The main complaint I've heard about Arcam seems to equate to " a bit too civilised," from what I remember. I must admit though, I've enjoyed mine. I started with an Alpha 2, which I had for years, and since then I've had an A75, an Alpha 8 + 8p combo, and an Alpha 9. Perhaps I'm just a bit too civilised?  Funnily enough though, I've also heard the comments " a bit too laid back," and " polite," made about the Primare i21 I'm using now. |
|
|
|
Post by karatestu on Mar 13, 2021 6:43:24 GMT
The main complaint I've heard about Arcam seems to equate to " a bit too civilised," from what I remember. I must admit though, I've enjoyed mine. I started with an Alpha 2, which I had for years, and since then I've had an A75, an Alpha 8 + 8p combo, and an Alpha 9. Perhaps I'm just a bit too civilised? Funnily enough though, I've also heard the comments " a bit too laid back," and " polite," made about the Primare i21 I'm using now. Whatever floats yer boat Paul. I went into a hifi shop in 1997 and listened to Arcam, Audiolab, Naim, Linn, Meridian and a few others. I remember Arcam being to snoozey for my liking. |
|
|
|
Post by ant on Mar 13, 2021 17:47:59 GMT
Been busy.  Cx unipivot mk 4? by anthony cresswell, on Flickr All the parts for the wand itself are done, as is the bearing and arm pillar  Cx unipivot mk 4? by anthony cresswell, on Flickr The pillar was machined from a piece of 25mm black bar, big bit is 18mm, thin bit is 12mm. The bearing cup is machined in the thin end. The big bit has a 7mm hole up through it so that i can put silicone in it to damp the part. I can take a reliable pass of about 0.2mm in steel with carbide inserts with my md65 lathe, any more than that and it gets abit laboured so it took a while to machine it down to what i wanted. I like to try to get the longest spirals i can when cutting, got some good ones doing this  Spirals of steel by anthony cresswell, on Flickr The outrigger which will hold the arm rest will sit on the shoulder and have a small setscrew through it to secure it to the post. These are the bits so far  Cx unipivot mk 4? by anthony cresswell, on Flickr The wand is carbon fibre, the bearing housing, counterweight stub and cartridge mount are made of Delrin. I decided to try Delrin as I like the fact that it is not very resonant. Im going to damp the arm wand internally with rubber baffles when i come to assemble it. wiring will run inside the tube and exit out of the side rather than through the front, it will then come out of the top in a loop and plug into a connection box. To make the cart attachment i turned the delrin down to the size I wanted, then used the little proxxon dividing head to hold it and mill it flat on the top and bottom, then mill out the slot. to drill out all the required holes in the bearing housing i did the same, as the compound table allowed me to find the centre of the cylinder and drill the pilot holes at the required angles. I then had to bodge the compound table onto the drill press table so i could use the drill press to make the correct sized holes. the biggest bit i can get in the milling machine is a 4mm. next bits are a counterweight, an outrigger and a collar for the arm. delrin does not like being sanded though so finishing will be thought provoking but not today onwards! |
|
|
|
Post by MartinT on Mar 13, 2021 18:17:29 GMT
Nice work! Where did you take the geometry measurements from?
|
|
|
|
Post by ant on Mar 14, 2021 12:17:53 GMT
Its just standard rega geometry
|
|
|
|
Post by ant on Mar 17, 2021 14:25:00 GMT
Bit more progress on this, I've got some more parts made  Cx unipivot by anthony cresswell, on Flickr I've done the counterweight (turned from some black bar), the height adjustable mounting collar and the nut, part of the arm rest, and the cartridge mount. Theres an old vms3 on it to check it worked as intended. The delrin ring with the smaller hole is part of the arm rest. This goes over the arm pillar and slides down to the shoulder where it will be epoxied in place. There are going to be 2 5mm x 50mm aluminium rods coming out of it, one for the arm rest and the other at an angle to carry the bias weight guide. The bias guide rod will be trimmed when I've checked how long it needs to be. The collar was the first time I'd done any threading on this lathe, a bit of a pig to set up because of the 4 change gears for the power feed, and the fact that the dog clutch was not playing ball and had to be taken apart to get it to work. The internal thread on the nut was simple enough once the clutch was fixed Need some more m3 setscrews for the height adjust, but the normal machine screws will do for now.  Cx unipivot by anthony cresswell, on Flickr the drill bit stuck out of the from of the arm rest collar shows where the arm rest bar will go.  Cx unipivot by anthony cresswell, on Flickr The cart mount was simple enough to do, 4mm thick so that there is plenty of thread for the mounting bolt, and the cart sits in line with the bottom of the arm tube which is where the pivot is at the moment. Although it looks a little messy because I forgot to reset one of the dials on the mill to 0 so the cutouts for the mounting nuts aren't exactly right. I can't be bothered to redo the part at the moment, it's a prototype anyway. I didn't have the right length m3 bolt to fix it on, hence the pair of nuts to space it up so it doesn't hit the top of the cart. Another thing to add to the list of bits to buy for it.  Cx unipivot by anthony cresswell, on Flickr And it dry assembled. to the left of the dummy drill bit you can see the hole where the bias guide arm will come out. Next jobs are to mill some flats into the mounting collar nut, make a pair of lateral balance weights that are heavier than the thumbscrews Iv'e used to test it, make the rest of the arm rest when the rods turn up, and drill and tap the counterweight for a locking screw. onwards! |
|
|
|
Post by ant on Mar 18, 2021 15:03:31 GMT
I had a think about the lateral balance weights, and rather than making a new pair I decided to install a ring weight into the bottom of the bearing housing instead.  Cx mk5 bearing housing by anthony cresswell, on Flickr Can't see it too well on the picture but the ring was made from some 40mm steel bar, so I had to turn it to the correct diameter then drill and bore the internal diameter. Then part it off. This lathe doesn't do parting off of steel very well, aluminium, brass, and the delrin are no problem, but it has trouble with steel. It just isn't rigid enough. I got about a third of the way through and bottled it, took it outside and sawed it off instead. Then just faced it off on the milling machine. Much less taxing. The ring is 3.5mm thick and weighs 12g which is just over what I wanted (10g) and is enough to lower the centre of gravity. It's now abit lower than it was and has stopped the tendency to want to fall over when the pivot it in line with the centre of the counterweight stub. I machined a recess into the underside of the housing for it to fit in, and while I was at it gave the housing a very light skim pass to refinish it. Delrin really needs to be machine finished, it doesn't respond well to sanding as I discovered. So it looks better now. Having bought a 4 jaw chuck, I now think it's definitely worth having in spite of the faff to set it up with a dti every time, I wouldn't have been able to put the part back in the 3 jaw and it be concentric. |
|
|
|
Post by ant on Mar 20, 2021 16:09:49 GMT
Nearly there  Cx mk 5 unipivot by anthony cresswell, on Flickr The parts for the arm rest and the bias guide are now done, and the correct setscrews and button head machine screws have arrived so have been installed Also installed are the arm finger lift, and a 3mm grommet I found in the spares box for where the wiring will come out of the arm tube. Still need to drill a hole in the top of the bearing housing for the wiring to exit.  Cx mk 5 unipivot by anthony cresswell, on Flickr The two outriggers for the arm rest and bias guide are aluminium, the bias guide itsself, the upright for the arm rest and the finger lift are 2mm stainless. The outriggers have height adjustment for the rest and guide via button head machine screws in the ends of the rods  Cx mk 5 unipivot by anthony cresswell, on Flickr The rest is just made from a bit of delrin rod, it needs some fettling yet, but I cant be arsed today. Just need some wiring, and the silicone tubing to arrive that will be inside the arm tube to damp it. I worked out the effective mass of it as is, and it came out at 7.3g. With the silicone tubing inside the arm tube it comes out at about 10g based on an estimate of the difference in weight the tubing will make. This was based on a cart, mounting plate, and fixings figure of 12g. I took a sample of quoted weights of 20 different carts to get an average, which was 8.3 and change. 10g should be fine. I'll redo it once I know the actual weight figure I could start gluing it all up, but I want to do some drawings of all the parts before I do. Like usual, I started off with a drawing of the idea, but then the rest fell out of my head so I haven't planned all of the bits. If I want to reproduce it I'd better have all the details to hand........ |
|
|
|
Post by ant on Mar 22, 2021 17:01:47 GMT
Closer  Cx mk5 unipivot bte designs type 3b lenco by anthony cresswell, on Flickr Got the dry built arm on a deck, not much use on its own..... It required a new arm board to be made. I just drilled the middle out of the original one, skimmed the face of it down in the lathe to reduce the height to take the perspex into account, then put a perspex face on it and turned it to match the diameter of the original. Then used my dr feickert setup jig to scribe it at the right s/p distance and drilled it for the arm. Simple  Cx mk5 unipivot bte designs type 3b lenco by anthony cresswell, on Flickr Looks quite nice on this type 3b Lenco I chose this one to put it on rather than my other type 3(a) because A: the other one is on the top of the wardrobe and its really rather heavy so I couldn't be arsed to try and get it down, and B: this one is almost identical to the one that mi dad has so it can be compared with the SME 3009 on his without faffing about. Need a pair of the same carts though and I don't know what it is on his. But thats getting ahead of myself, I've still got to install the damping for the arm tube, wire it, and make a bias weight. I suppose I could buy a bias weight, but why bother, I've made everything else.. Waiting for bits is a pain Onwards! |
|
|
|
Post by MartinT on Mar 22, 2021 18:02:05 GMT
Seems like a good effective mass. Do you yet know what compliance cartridge you intend using, to work out the resonant frequency?
Really nice bit of engineering, by the way.
|
|
|
|
Post by ant on Mar 22, 2021 18:38:03 GMT
Probably my spare dv20x2, cant remember what its compliance is off the top of my head, its higher than quoted though because its quoted at 100hz not 10.
Should be in the range though, i need to recalculate it anyway once ive got the internal damping in there
|
|
|
|
Post by MartinT on Mar 22, 2021 20:01:40 GMT
Nice cartridge that, used to have one. Has some grunt and welly to it.
|
|
|
|
Post by ant on Mar 25, 2021 14:42:28 GMT
Got it up and running  Cx mk5 unipivot by anthony cresswell, on Flickr Bias guide outrigger could have done with being longer, there's not much clearance between the guide and the left hand lateral balance when the arm is in the clip. The clip needs redesigning to have a bit more to rest the arm on when its not clipped in The wiring needs some sort of little clip on the top of the bearing pin to route it through, as it is it, the hole for it to come out of the wand is about 10m forward of the pivot so it tries to push the arm over as it rotates which alters the azimuth. if its held above the bearing pin it stops it from doing it. Setup of the cart was simple, vta was simple, these are pretty standard methods of adjustment, setting the azimuth was an arse until I realised it was the wiring that was changing it as it moved. Bias is via a 2.5g nut with some string through, I couldn't be bothered to make a weight today, and I figured the weight would want some adjustment so best to use something to get it where I wanted it and then make that weight to the eventual figure. A pretty small list of fixes |
|
|
|
Post by ant on Mar 25, 2021 17:16:27 GMT
 Cx unipivot bodge by anthony cresswell, on Flickr 2 issues fixed simple fix for the bias guide problem, just a longer string and reorientation of the guide so its further out. second issue with the azimuth changing, fixed using a piece of airline tubing with a little slit in it to grip the wiring and hold it smack above the centre. no more issues with wonky azimuth. I shall have to come up with a permanent part on the same principle |
|
|
|
Post by ant on Mar 26, 2021 17:29:57 GMT
Ok, so with the bodges in place I have a few observations of it.
This is running into a project phono box se which im not entirely familiar with, but is necessary because of where it has to be set up. Cart is the spare dynavector dv20x2h
It's is very even up and down, it doesn't seem to be emphasising the top end, midrange or the bottom end, although I can hear a little bit of colouration in the mid. But this is compared with the air bearing arm which has none. At all. So wether someone else picks it up will be interesting.
It seems very clean and ordered, especially when things get complicated it seems to tease things apart. Not necessarily clinical, but heading in that direction.
Bass has some really good texture, and voices seem to be nuanced.
It seems to be tight and fast and clean.
Strangely, it seems to make the dv really quiet in the groove, pops clicks and scratches seem quieter that they do when its on the air bearing arm. Not sure why.
Handling wise, I took the lessons from the earlier iterations wrt where and how the bias guide is located to make it very stable. How it's set up means that for it to rock in either direction it has to pull the bias weight up, so when you cue it, it immediately centres itself once you let go of the fingerlift and doesnt rock at all. It doesn't do that little shimmy that other unipivots I've used do when they have a little wobble before settling down when the are cued.
So pretty natural sounding, a little bit of 'character' in the mid if im being charitable, and very stable.
|
|
|
|
Post by petea on Mar 26, 2021 18:50:20 GMT
This is proving to be a very interesting project, Ant.
|
|
Funnily enough though, I've also heard the comments "a bit too laid back," and "polite," made about the Primare i21 I'm using now.
