, my only option is to build one myself , i have thought about unipivot type bearings to keep it simple but i have never heard a unipivot that has bass that can match that of a good multipivot arm , it occurred to me that i could use the audiomods arm kit to experiment with concept without any real risk and if it doesn't work i can simply re install the rega arm tube to the audiomods with no harm done .
I will be building two variants , one with stainless arm tube (high mass for low compliance carts) the other with aluminium arm tube(low/med mass for med / high compliance carts ) , the mass can also be adjusted via heavier or lighter headshells , we must note at this point that regardless of mass selection we must be able to balance the arm , i have several counterweights at my disposal so its not such an issue , if you plan to undertake building of an arm you could always give audiomods a shout and have a few made ,or if you plan to do an arm on the lowest budget possible then wait until the rest of the arm is made ,fit a cart or equivalent weight and then make a counterweight from anything at hand , once the arm is balanced you can weigh it then get one made to match .
The Arm Tube
more specifically , choosing and bending .
i went for some nice simple 10mm OD, 8mm ID 'seamless' 316 stainless steel , its easy to work with , cheap and plentiful , i got mine from eBay for a couple of the queens heads posted , the 8mm ID is slightly bigger than the bayonet insert as we must account for a very thin copper shim that goes between the insert and armtube which will also be the grounding point to which we will be soldering the ground wire .
i have already bent the tube to 17.3 degrees , for an effective arm length (stylus tip to arm pivot) 308.2 mm is close enough wit a mounting distance of 295.5mm , take your time , its easy to add a little more bend but its a pain in the posterior to bend it back , dont worry if you cant get the angle perfect , you can always turn the cart in the headshell to get the 'cantilever' aligned .
with further investigation i have found that the stainless tube with 1mm wall is just too heavy , effective arm mass with cart fitted came out at 49g , thats about 22g too much ,it would still work but i suspect the DL103 might complain a bit, fine if i was using an Ortofon SPU ,, so i am back on the hunt for thin walled stainless steel , i also have some titanium on the way as i prefer its sonic footprint to that of aluminium , i have tried carbon fibre too and it is not to my taste , if using carbon i have found that a bespoke tube is necessary with varied wall thickness and tube diameter , this is way out of my budget which for this project is set at £300 including a new diy kit at around £200, if its successful as i want to keep the rega tubed audiomods arm , its a bit special ,
this is where i am at , using the aluminium alloy tube ,
after a little head scratching i thought that i would try mounting the end stub as shown, its a simple expander wedge arrangement
first impressions ,
please bare in mind that the arm is a rough and ready prototype and will need some final tweaking ,
i have used the same arm wiring and cartridge from the rega arm tube to asses the 12" arm ,
so far i am getting better instrumental separation , a wider soundstage and most surprisingly better treble definition , than the rega arm tube ,bass is still a bit 'bloomy' but not in a bad way and i think it will be a bit tighter and dryer once the armboard is sorted out as its perched on the edge of test plinth with a single wood screw , i will of course have to try it with other carts and many records which entails sitting on my fat ass for many hours listening to music, (oh the hardship)
so far i am pleased with the initial result , its given me confidence to go ahead with the plinth arranged to take both the 12" and alphason arms .
i mentioned earlier that carbon fibre is not my favourite armtube material unless its 'engineered' for the task , i have found a caveat to that rule, inside the aluminium tube there is a carbon fibre tube , its a snug fit and needed to be gently tapped home , i then drilled through the bearing spindle bolt holes so the spindle bolt runs through both materials , the carbon extends all the way to the bend in the arm, this has brought a rather surprising leap in the arms ability to allow great expression of tonal colour and texture , the tonally grey and stark character of the rega tube has been replaced with subtly but easily discernible differences in John Williams and Julian Breams guitars on the 'together and together again' Lp's on the RCA red seal label , also now beautifully uncovered is the accompanying cello on a couple of the songs on together again , this was a bit lost with the rega arm tube ,
another Lp that i have played (remember i have only had the new arm in play for 5 hours so far) and been surprised with is book ends by Simon and Garfunkel , mrs Robinson has taken on a new perspective , vocals are pushed farther out to the left and right of the massive soundstage with the rhythm guitar locked centre stage , moving on to a bit of Wax Tailor with his stunning Lp called 'Dusty rainbows from the dark' , quite possibly the finest bit of production from what i think is thousands of samples carefully reconstructed into a beautiful ,and ,oh so relevant to every record collector , tale that has such depth and many many layers to the mix, i simply cant fathom how Monsieur Tailor can carry so much memory on records then put just the right bit in the right place in the soundstage to create such 'right' and cohesive musical picture , the new arm has certainly flung the windows open on dense mixes in a way that the rega variant cant .
i am not the first to try carbon fibre damping/reinforcement of alloy tubes in tonearms , the funk FXR springs to mind , although they chose to chop off part of the arm tube and use CF X-brace along the alloy tube , if i can find some X section carbon fibre that will be a good fit i will be giving that a try ,
so whats next ? more listening for starters , the bearing spindle is due some attention , the 3mm bolt is doing a sterling job but i am wondering what a 5mm diameter bolt will bring , also i am looking at doing away with the headshell arrangement and using an expanding wedge like in the counterweight but with a hollow bolt to allow the wire to pass through or even a clamp on type , investigation will continue . ;-)
the audiomods arm kit.
i love this kit , on a pound per sound basis it is worth every penny , Mr Spall did a superb job and i owe him many thanks , however, i had some minor issues with the split bearing journal , i couldn't get the bearings to stay in place, if i tightened the journal any more it would cause the bearings to stick , it was a very early sample and any such issues are no longer present on the retail kits , my solution to the issue my arm had was to do away with the brass journal and instead use a standard rega rb250 base . the vertical spindle on the audiomods is way longer than the standard rega which meant i coulnt fit the lower bearing, then , i realized that the spindle was long enough to allow a larger bearing to be fitted lower down in the rega arm base where the cable grommet usually resides in a standard 250 , so my arm has a rather huge bearing supporting the lower end of the pillar bearing spindle , i cant remember the exact size , 17x8x5 or something near,, without getting a new audiomods kit i cant tell what effect this new home brew arrangements is having , i do intend to get a new kit ordered up and when i have it i will be able to asses the differences the audiomods spilt journal will have .
more soon .
VTA , vertical tracking angle , its not that critical according to some folks , it was something i became aware of when i was about 14 , i had just bought an A&R p77 , it had a parabolic stylus , when i first fitted it to my garrard ap76 it had no bass , knowing the ap76 had previously had great bass with the sansui cart that was on it i started to wonder what was going on . i took a look at my dad's Sony TT and noticed that the arm was perfectly level , the arm on my AP was pointed down toward the headshell , so i went back to the AP and had a good look, there was a grub screw on the armbase , with some trepidation i undid the screw and the arm immediately dropped , i then set it to horizontal and tried playing a record , the doors , an american prayer , "WAKE UP,, IT CANT REMEMBER WHERE IT WAS , WONT THIS DREAM STOP" came belting from the speakers , i had forgot the amp was turned up ! , the bass was now there in buckets but my curiosity had been aroused and so i tried moving the arm up and down a tiny amount at a time and eventually found it sounded best with the arm at 1-2mm below horizontal , it was cleaner and easier to listen to at high volumes , no spit or overly pronounced sibilants but still a good sense of air and space . a lesson had been learned , i read up a bit on setting up record players and quickly discovered that stylus tips were sometimes a touch out of alignment and that even a little misalignment during manufacture could mean that the arm or cart needs to be set in a way that deviates from the ideal or logical set up ,
consider for a moment the tiny modulations we ask the stylus to trace and track , also how critical it is that we have the (often very expensive) stylus as square to the cut groove as possible , please note i said 'groove' not record , the closer we can get the stylus to the original cutting head used to cut the master disc the better.
, why people spend thousands on just a cartridge then claim VTA fine tuning is of no importance is to my mind ludicrous and in my experience a bit like owning a supercar then using it for the weekly shop! , get fastidious and as anal as you can when setting up , it will pay dividends .
a few small tweaks , i swapped out the aluminium arm rest and lift support plate for a carbon fibre item which on its own has brought a cleaner mid and top end , not a huge change but enough to uncover yet more detail that my other arms miss .
alignment
i started off using the dimensions and geometry from the sme 3012 during planning , most alignment systems use the best set of compromises , lofgren A or B , Stevenson , bearwald etc that have good numbers as far as tracing/tracking distortion goes but tend to move the distortion around , i am using the lofgren A arc protractor created with the arc protractor generator which is a free program kindly offered by http://conradhoffman.com/chsw.htm , the numbers say lofgren A has the lowest average and peak distortion numbers . i have also found another alignment which has left me scratching my head a bit as it is not a recognised method but every time i deviate from this odd alignment the sound loses some of its vividness and animation . I will be spending time investigating this as i cannot find anything anywhere that even hints at this . all the arms geometry is as close as i can get to the SME i mentioned yet this different alignment is clearly superior to the ear , however what i may be experiencing could possibly be distortion but, i would have thought that if it was then it would vary as the stylus traversed the record , this odd reduced overhang set up has me questioning the other alignment methods, but i will offer more on this at a later date .
i have found that the headshell mount needs a double pin type bayonet fitting on the headshell, one is on the way , i only discovered this when i did a resonance test and found the arm has 8hz lateral and 16hz vertical ! not good as i would expect the vertical to be within a couple of hz of the lateral , i changed carts 3 times to make sure is wasn't that and it was the same each time , then i noticed the headshell wasn't in tight contact with the bayonet flange . The single pin on the headshell /male part was being pulled tight, but,, at the bottom it isnt so this poor fitting is 'i think' whats effecting the vertical resonance , the real surprise is that it still sounds great and i look forward to trying the improved coupling . more soon.
the new headshell arrived , worth every penny , very fine quality including the wires !
back to the alignment issue , turns out the tip on my pickering cart is slightly askew hence it sounded better with the odd alignment , i have now fitted an SAS1 stylus to an A&R 77 body and used the lofgren A alignment , superb , i cant believe this arm is so capable , i will be trying a V2 at some point soon , i am thinking that a 12mm titanium tube that is die drawn down to 10mm then 8mm with the headshell clamped directly onto the Ti tube , this would of course mean loosing the detachable headhsell but would allow a continuous loom for the wiring
the stylus on a high amplitude bit of groove
No comments:
Post a Comment