Twelve incher.

[Chops54]

I thought I'd better start a new thread. I've always fancied a twelve incher and after listening to Johnnie's PU7 at Paul's a while ago I decided I'd have one. However work has been patchy since the beginning of the year and attempts to save up have come to nought so I decided to have a go and make my own. I had an old Project arm, the one with the soft ally tube flattened at one end for the headshell and as both Johnnie and Paul condemned it I decided to use that as the basis for my arm. Essentially I've used the gimbal bearings, the pillar and the mounting flange having remade everything else. I also made a brass plug a la Incognito into which I glued the phono leads. I'll have the arm on my deck in a day or two and I'm hoping it'll be worth the effort.

http://i83.servimg.com/u/f83/11/73/38/69/12_inc14.jpg (http://www.servimg.com/image_preview.php?i=562&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc15.jpg (http://www.servimg.com/image_preview.php?i=563&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc16.jpg (http://www.servimg.com/image_preview.php?i=564&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc17.jpg (http://www.servimg.com/image_preview.php?i=565&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc18.jpg (http://www.servimg.com/image_preview.php?i=566&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc19.jpg (http://www.servimg.com/image_preview.php?i=567&u=11733869)

This last pic is the extended armboard needed to fit the arm to my deck. It bolts into the hole left by the original nine inch arm using the two ally bushes and I can the swing it to adjust the mounting distance of the new arm.

[TIU]

Great work Si, although I haven't a clue what you're on about but admirable work nonetheless. Would be even better if you used a flange. (Again, no idea what that is, just wanted to post with that word in it.) :D

[Roksoff]

What a disappointment....Claire thought she was gonna see a massive cock.:D

Only joking Chops. Looks good man.
I like your style, see something you want....go make one.
:^

ps...That thread titles gonna be popular with google. Can you imagine all those lonely housewives disappointment when they come here and see a tone arm....LOL:)

[Roksoff]

Great work Si, although I haven't a clue what you're on about but admirable work nonetheless. Would be even better if you used a flange. (Again, no idea what that is, just wanted to post with that word in it.) :D

Flange and twelve incher in the same thread...:eek:
Mods are gonna be busy with the guests:D

[TIU]

Let's not disappoint them eh. (I put 'cock' into Google Images with the safe filter off so you can imagine what it brought up. Unnatural they are I tell thee.:eek:

http://gamesmuseum.uwaterloo.ca/Archives/Culin/Hawaii1899/graphics/cock3.jpg

[j7]

hehe

nice 1 si

[cartridgemangler]

Nice one.
I wonder if a similar arrangement would work on a Gyro or Orbe. According to Michell the critical part for the suspension is the mass of the arm+armboard: arm+armboard = 1kg. I had the idea of a 12" arm on my Gyro for a while now.

[TIU]

More than nine inches is just showing off, surely. :p

[Ems]

Is 12 inches the max length for a tonearm? What about 13 or 14 inches could someone explain it using words if few letters as im not up to speed on this subject.:dunno:

Cheers BP

[Chops54]

Is 12 inches the max length for a tonearm? What about 13 or 14 inches could someone explain it using words if few letters as im not up to speed on this subject.:dunno:

Cheers BP

I have seen a couple of longer arms out there. As the arm gets longer, distortion reduces but on the downside, it's mass increases and it's torsional strength reduces accordingly. The 12 " tonearm was originally made for those 16" diameter broadcast turntables I think.

[Chops54]

Nice one.
I wonder if a similar arrangement would work on a Gyro or Orbe. According to Michell the critical part for the suspension is the mass of the arm+armboard: arm+armboard = 1kg. I had the idea of a 12" arm on my Gyro for a while now.

One kilo is a fair old weight Kenny, 2.2 lbs. but that would be measured at the arm mounting point on the original armboard so if you fit a longer armboard you have the leverage to contend with. I still think you be ok though and you could always put some extra weight at the other spring positions. On the new tt I'm currently building I can move the spring at the arm position in and out to compensate :)

[The Professor]

One kilo is a fair old weight Kenny, 2.2 lbs. but that would be measured at the arm mounting point on the original armboard so if you fit a longer armboard you have the leverage to contend with. I still think you be ok though and you could always put some extra weight at the other spring positions. On the new tt I'm currently building I can move the spring at the arm position in and out to compensate :)

Kenny and i discussed this before, i wondered about the extra mass been swung out far would cause more issues, my guess is it would need to be a lot less than 1 kilo, i also reckon using acrylic on the gyro would change it's sound quite a bit, and ally that was stiff enough might be too heavy, what do you think?

Nice arm BTW. Respect!!!

BP you can have a longer arm, i believe up to 16" have been used in transcription libraries, but the longer you make it, the bigger the effective mass, 12" seems to be a happy compromise.

[WullieD20]

Kenny and i discussed this before, i wondered about the extra mass been swung out far would cause more issues, my guess is it would need to be a lot less than 1 kilo, i also reckon using acrylic on the gyro would change it's sound quite a bit, and ally that was stiff enough might be too heavy, what do you think?

Nice arm BTW. Respect!!!

BP you can have a longer arm, i believe up to 16" have been used in transcription libraries, but the longer you make it, the bigger the effective mass, 12" seems to be a happy compromise.

Some of you guys must have seen this, but 12" looks inadequate compared to this jobby..... The violin Bow tonearm.

http://www.hifiwigwam.com/view_topic.php?id=38574&forum_id=8&page=2

[cartridgemangler]

certainly with the Gyro, the mass being swung out shouldn't be too much of an issue. I would expect that an adjustment of the springs should correct any problems.
for those that don't know the Gyro/orbe intimately, the "mickey mouse" sub-chassis has a mass affixed underneath at the motor "ear" to balance the mass of the Arm+armboard combination. Additionally, the Orbe (and any Gyro/Orbe conversions) have some mastick type "DensoDamp" material inside the sub-chassis to dampen its ringing.

[The Professor]

that just looks silly. :D

[The Professor]

certainly with the Gyro, the mass being swung out shouldn't be too much of an issue. I would expect that an adjustment of the springs should correct any problems.
for those that don't know the Gyro/orbe intimately, the "mickey mouse" sub-chassis has a mass affixed underneath at the motor "ear" to balance the mass of the Arm+armboard combination. Additionally, the Orbe (and any Gyro/Orbe conversions) have some mastick type "DensoDamp" material inside the sub-chassis to dampen its ringing.

The gyros that i have tried i would have said their srings are too short to allow that much adjustment, to me the motor housing doesn't have enough space round about it, an offset 12" could cause problems, be better to dsipese with Gyro mickey mouse shit and do as chops has done and make a whole new subchassis and use bearing platter springs etc, or stick to a 9 inch, you'll have no end of problems matey.

[cartridgemangler]

Some of you guys must have seen this, but 12" looks inadequate compared to this jobby..... The violin Bow tonearm.

http://www.hifiwigwam.com/view_topic.php?id=38574&forum_id=8&page=2


I like how the turntable base is shaped like a grand piano.:)

With regard to violin bows, its not uncommon for a *really* good bow to cost more than Silver Deco 20s

For a top flight bow, add on the cost of Ongakus.

[cartridgemangler]

The gyros that i have tried i would have said their srings are too short to allow that much adjustment, to me the motor housing doesn't have enough space round about it, an offset 12" could cause problems, be better to dsipese with Gyro mickey mouse shit and do as chops has done and make a whole new subchassis and use bearing platter springs etc, or stick to a 9 inch, you'll have no end of problems matey.


I know what you're saying, but its also in my mind that the bulk of the 1kg mass is the actual armboard itself - for a rega mount its around 700g (some Origin Live arms are quite heavy so need the armboard hollowed out to remove some of the mass). by substituting for a lighter material, such as acrylic it might help. also with an SE Gyro you're not limited to having the motor in the left-hand 'ear' - a number of 2-armed Gyros use the left hand ear for the second arm. (I presume that the extra mass underneath has been removed in order to get the suspension right)

this is all ponderings anyway. thinking out loud :)

[Chops54]

In reply to Paul's and Kenny's comments I'm going to put the arm on my original acrylic tt first as I haven't got very far with the new one yet. I'm also using Orbe springs and pillars as well don't forget but I've positioned my springs differently to the Orbe. The extension armboard will only need to go out three inches and the extension piece I made weighs bugger all. If you want to have a go Kenny I'll happily make you an armboard out of aluminium and I'm sure it can be lightened sufficiently without compromising it's strength.

[cartridgemangler]

Thanks for the offer Si. I'm a bit of a ways away from being ready to experiment with a 12" arm just yet. I'll probably revisit it at some point in the future when my fortunes have changed. :)

[Chops54]

Thanks for the offer Si. I'm a bit of a ways away from being ready to experiment with a 12" arm just yet. I'll probably revisit it at some point in the future when my fortunes have changed. :)

You never know mate, one of your good friends might just loan you a 12" PU7 for a while :)

[Chops54]

After a lot of buggering about I finally managed to fit the arm to my turntable. Look at that spring! I'm not bothered as the arm will be going on a new tt soon but if I was going to leave it I'd put some ballast on the other side of the subchassis.I had to remove the cueing device as it got in the way but I'll make a new platform to cure that. Initial listening impressions are quite good with very low surface noise. Bass is very good indeed with all the instruments seperate and easily identified. Not bad considering I didn't pay any attention to effective mass or any of the other things that I don't understand :D

http://i83.servimg.com/u/f83/11/73/38/69/12_inc21.jpg (http://www.servimg.com/image_preview.php?i=569&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc20.jpg (http://www.servimg.com/image_preview.php?i=568&u=11733869)

[j7]

looking good m8 :)

[Chops54]

Thanks John,

By the way I didn't copy your geometry for this arm, I couldn't be that cheeky mate ;).I used the figures given for the SME 312 which gives a slightly longer arm tube. Out of interest what angle is the headshell offset on your 12" arm?

[j7]

hehheh the angle is ****

[Roksoff]

^^^^^^^^^^^^^^^^^^^^^

:rotfl:

[Chops54]

Hey, no worries John, I understand.

[Andy831]

Si very kindly "taught" me how to solder last night. As part of that deal we had to have a few songs played using the 12"er, and very good it sounds to.

Seperation is good, instruments can clearly be identified and located and it was mucical to boot. An excellent effort Si and like all the stuff you make, it does not look at all "do it yourself" its appearance is very professional.

Great effort mate you are to be congratulated

[Chops54]

Thanks for that Andy. If you'd told me it was crap I'd have accepted that as you have a good ear and you're brutally honest LOL. You should try one of JR's counterweights on your Rega mate. I'm sure John would be pleased to accomodate you especially as you have an innate fondness for the Rega.

Next step is to reset what I think may be a slightly tight bearing, increase the bias and then remake that awful counterweight:eek:

[Si74]

Looks very nice to me!
Would I be right in thinking your sub chassis actually hangs from the springs?
I have a plan to use all the bits from my Funked Linn with a redesigned sub chassis
and toplate.
I want the sub chassis hanging on rather than sat on springs. A spare set of springs for the Oracle look likely candidates but given their compliance or lack of it, it would need a heavier sub chassis , more along the lines of the Sole than the Funk one, to get the frequency of the bounce? (real scientific stuff here:-( ).
Oops, sorry getting a bit of thread!

Simon

[Chops54]

No problem Si, yes it hangs off the springs. They're Orbe springs and towers, the early ones before they put a ball bearing in or summat. I fitted acrylic feet rather than screw the towers into the plinth. They just sit there and it works well though I really need some extra weight on the other side now. That arm hanging out there is giving that spring a hard time.

[Chops54]

After using to the arm for a fortnight I decided that the counterweight had to go. I put a cross piece under the main counterweight because it wasn't heavy enough and because I didn't have a bigger piece of brass :( I decided that rather than make another counterweight it might be better to trim some weight off the arm first so I bought some electronic scales and did some measuring. I weighed the arm at the headshell with no counterweight fitted and no cart. It weighed in at 31.2 grams. A 9 inch arm I measured came in at 14.2 grams so I decided I had to do something. Now I expected my arm to weigh more as it's longer and I wanted a bit more mass anyway so I set my target at 20 grams. Bear in mind that I have absolutely no idea what I'm doing, I'm just going off my gut instinct. Anyway last night I spent a few hours cutting, drilling and polishing the headshell and I managed to get 7.5 grams off it. I feel I spoiled the shape of it though by rounding the front corners but I had to get the weight off somehow. The headshell was nearly 5 mm thick, now it's a touch over 4.

So today I started on the armtube. I decided to drill it but I agonised over doing a spiral and in the end opted to drill a row of 4mm holes in the underside of the tube. I cut 8mm of the end of the tube as I didn't really need it and I removed some of the foam filling. It was packed in tightly, now it's a bit looser. Finally I shortened the leads as they were far to long anyway. All back together and it weighs 21.24 grams. I'll put it back on the deck tomorrow evening and all will be revealed.....I hope :)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc24.jpg (http://www.servimg.com/image_preview.php?i=587&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc27.jpg (http://www.servimg.com/image_preview.php?i=590&u=11733869)

[TIU]

Hi Si, very neat work, you must have a lot of patience. Have you looked at the tonearm database on vinyl engine? I had a quick look at a few comparisons and it quickly becomes very complicated and requires a lot of maths to work out. Search by effective mass and there are a few arms by Thorens and Fidelity Research that are less than 12 inches and have a higher mass than yours was, i.e. the Thorens TD126 mkIII has a mass of 34g (244 mm eff length) and the Thorens TP97 is as much as 36.5g. The Fidelity Research FR64 arm is 245 mm eff length and 35g mass. Nothing is registered higher than that though as I doubt many carts would be compliant. Also arms of this high mass are in the minority considering the high number of arms in the database.

Longer arms such as on the SME 3012 series I and II have an eff length of 305 mm but a far lower mass of 14g (must be a very light alloy?) and the Project 12C arm has the same length but is even lower mass at just 11.5g.

I think for cart compliance matters (without understanding all the geometry aspects) you have done the right thing.

[Chops54]

Hi Gary,

I took my measurements from the SME 312. Eff length 308.12mm and mounting distance 295.6mm. There's no mention of mass but it has a removeable headshell with a bolt in it so it won't be as light as earlier 12" SMEs. I'm happy with mine at around 21 grams and I think it will partner a Denon 103 nicely. Incidentally the gimbal bearings I've used are from an old Project arm but I'm already on the way to making my own for the next incarnation.
Yes, I do have a lot of patience but I get so much enjoyment messing around like this. I remember as a youngster my dad building a radio in the shed from old bits and pieces. Clever bloke my dad, AMImechE, AMIelecE. Worked all over for Decca, Cossor, AB, Blackburn Aircraft etc etc. Even my dad with a big family had to make some of his own gear. It either wasn't available or it was too expensive and I guess it's filtered down. Y'know, if you don't know or understand something, by the time you've built it you know a damn site more I reckon and that's why I post on here. Maybe it'll encourage someone else to have a go at something and you can listen to nice choonz while your at it :) Better than cabbaging in front of the telly :eek:
Anyway I'm going to put the arm on my deck now and try it out. Back later.

[TIU]

:^

[Chops54]

I've had an hour with it this afternoon and at first I thought I'd firked it. It sounded bloody awful. Vocals were thin and drums especially sounded so grey and woolly. In my rush to get it up and running I'd left the headshell securing screw loose :o and I mean loose. Tightening this up sorted everything out. I couldn't believe how this destroyed the sound as the headshell is a fair fit on the tube to start with. Anyway, I'm happy that the slimming exercise is a step in the right direction. It definitely sounds better, with quicker bass and transients have more slam. Voices have their own space and left right separation is pretty damn good. Incidentally, when I made the new acrylic extension piece I decided to ditch the arm base and put the pillar directly into it. I think Notts do this and I wonder why others don't do it. Michell use a thick aluminium arm board so it would be no sweat to put the arm pillar straight into it would it?
So what do I do next? I'm going to make a slightly heavier counterweight so I can get it nearer the pivot point and then I think I'll leave the arm as it is and just enjoy listening to it :)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc33.jpg (http://www.servimg.com/image_preview.php?i=596&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc30.jpg (http://www.servimg.com/image_preview.php?i=593&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc30.jpg (http://www.servimg.com/image_preview.php?i=593&u=11733869)

http://i83.servimg.com/u/f83/11/73/38/69/12_inc28.jpg (http://www.servimg.com/image_preview.php?i=591&u=11733869)

[TIU]

By chopping some off the arm (was it 8 mm?) has this affected the overhang or is that adjusted at the arm base end? I think the Denon 103 will be a good choice.

[Chops54]

There was a bit to much tube poking into the headshell after I reduced the width of the clamp so I lopped a bit off. Even though the effective length is ok I maybe should have left it on as I've now lost any options that I previously had. However as this is just a prototype, sort of a learning curve I'm not too bothered.

I like the 103 and I used a nude one on an Ittok for a while and then on the Audiomods Rega. It does like a massy arm so yes, I think it will work well.

http://i83.servimg.com/u/f83/11/73/38/69/denon_12.jpg (http://www.servimg.com/image_preview.php?i=597&u=11733869)

[Dougie]

By the looks of your counterweight Chops, it seems as if it's about to fall off, I agree with you a heavier one is needed. I never noticed that when I was down, but then again you've lightened the tube!

[Chops54]

I've significantly lightened the counterweight Dougie. I've removed the cross piece in an effort to tidy the looks up a bit. I'll make a slightly heavier one next week. I have another battery supply to finish first.