[S Clark]

Yeah, I have that info.  I guess I can get out my dividers and fab a template.  As long as I know the overhang I can just use a generic Baerwald template from VE to align the cartridge?

When are we going to see pics of your set up?

I don't even have a picture yet in my mind.  I think I'm going to go to a local woodworker and have him rebuild a plinth for my SP-10.  In the meantime, a buddy has loaned me a Vyger; I think I'll cut a section of mesquite out of the firewood, give it to the wood guy and have him plane the ends and drill it for a tonearm pod


img]

[ACHiPo]

I don't even have a picture yet in my mind.  I think I'm going to go to a local woodworker and have him rebuild a plinth for my SP-10.  In the meantime, a buddy has loaned me a Vyger; I think I'll cut a section of mesquite out of the firewood, give it to the wood guy and have him plane the ends and drill it for a tonearm pod


img]

Like that orange Vyger!  The SP-10 and Panasonic arm should be a match made in vintage heaven!

[neobop]

Man oh man, that's a killer looking arm.  Bet he sounds as good as he looks.   

For those getting the PA70.  You might have to adjust the pivot to mounting hole distance slightly, to achieve your favorite alignment.  Most older Japanese arms were designed with Stevenson like nulls.  One of the Loefgren alignments is usually preferred.

From the factory info on page 1:  Eff length = 282mm  overhang = 12.5mm   That gives a mounting distance = 269.5mm
If you mount the arm at 267mm, I'm reasonably sure you'll be able to use whatever alignment you like.  If someone wants to use an SPU type cart (nonadjustable), we can figure it out.

note: An arc protractor is based on a set mounting distance. 
neo

Yeah, I have that info.  I guess I can get out my dividers and fab a template.  As long as I know the overhang I can just use a generic Baerwald template from VE to align the cartridge?

You wouldn't happen to have a Dennesen, Geodisk, or Feikert protractor, by any chance?   One of those three would make things a bit easier, but it will just take a few minutes longer without one. 
If you're making a pod to sit on the counter, there can be no relative movement between it, and the platter.  Does the motor sit on the counter or part of the plinth?  If it's on the counter, vibrations between motor and arm should be considered.

Height - Do you know the height of the cart?   Set the arm height adjuster to the middle of its travel.  With your headshell attached and a typical record on the platter, measure the cart height distance from the record to the mounting plate of a level headshell.  That gives armboard height.

Mounting distance - Easiest way to get Baerwald mounting distance depends on pod or bolted to a shelf.  Either way I think you can't lose subtracting 3mm from the factory mounting distance.  That should also give you flexibility if you want to change carts or try Loefgren alignment. 
It's difficult to use a protractor to determine mounting distance unless the arm is bolted down and secure.  This might sound like catch 22, but it's doable with a pod which can be moved.   What's your situation?
neo

[ACHiPo]

Neo,
I'm finally back at this project.  I found a phono cable and it's on its way, so I need to get busy with armboard construction.

I have a 3" x 3" x 10" block of cocobolo that I'm planning to mill out for the arm.  My plan is to rip the cocobolo to 1.5", drill a 2.5" hole for the tonearm mount, then laminate the pieces back together with Herbies' isolation material between layers to provide similar vibration isolation to the WTT.  The whole assembly should weigh around 8 lbs when I'm done, so with a little Herbies' pads on the base it should be pretty stable.  I can always add another maple platform to the armboard to more securely locate the arm with respect to the table.

It seems the easiest would be to know the right overhang for the arm, which could get me close enough to adjust the cartridges with the alignment slots.  The only things I have for alignment are a printed Baerwald template from Vinyl Engine, and a generic mirrored template.

Any suggestions on how to proceed would be apprecated.

AC

[neobop]

This is going on a pod next to the plinth?   Have you figured out the height and is there room for the arm cable to exit?  How are you going to bolt the arm to the armboard?  Normally an armboard sits atop a larger hole.

The wood isn't stable enough by itself, are you clamping it to the shelf or support?  You envision this as a 3" x 10" block sitting behind the table?
Well, you don't need a 10" block, but if it fits you could use the underside or part of it to add weight to the pod.  Got any lead?  You could make a hollow space and fill with sand. 

You should lay it out first and figure out what's possible.  You could use a round or kidney shaped pod and weigh it down. 
Cut a piece of cardboard the size of a ruler and make a hole in one end to put over the spindle.  Draw 2 straight lines that intersect the hole, like a target.  From the center of the hole measure and mark off 267mm and 269.5mm and cut off the end of the cardboard.  Now you can see where the hole center has to go.

I think you might need some construction ideas, techniques.   Normally an armboard is 1/4 - 1/2" thick and made out of aluminum or hardwood.  It usually bolts onto the pod so you can tighten the nut or change cable.   Don't be afraid of aluminum.  It's soft and pretty easy to work.  You can embed 3 or 4 threaded receptacles into the wood beneath.  That way you don't have to thread the armboard.
neo

[ACHiPo]

Neo,
Thanks.  I realized I failed to attach pictures that I took last night that might make it a bit clearer.


Here are a couple photos of the arm at approximately the right height and position.  The plan is to have the top flange of the tonearm mount sit on the cocobolo block.  There is a pin in the top flange that registers the tonearm relative to the armboard.  It seems critical the relationship to the spindle is pretty precise, as is the effective distance between the pivot and spindle.







The reason 1.5" thickness for the armboard seems a good choice is the Pioneer SA-70 arm has a ~2.5" diameter body that is threaded to just less than 1.5", and there is a nut that screws onto the body and clamps the arm to the armboard.



Here's a photo of the cocobolo block (this one is not quite 3" x 3"--I have another one around I think that is a full 3x3).  The idea is to cut a 1.5" thick by 3" wide slab from the cocobolo to act as the armboard.  The remaining piece of cocobolo will be cut down to 7" long and act as a base for the armboard, which will cantilever out the back, allowing room for the right-angled phono cable to exit.  The mounting and registration holes in the armboard will be machined, and the armboard will mount to the base with Herbies' elastomeric stuff between the two pieces for vibration isolation.  I'm also planning to cut "dots" to put between the cocobolo and maple shelf for vibration and friction.  Obviously I'll need to adjust the height such that the top of the armboard is coplanar with the turntable plinth.



I just weighed the cocobolo block and tonearm.  The block is 2.5 lbs and the tonearm is 4.5 lbs, so it's got pretty good mass.  I like the idea of adding lead, but I'll need to pick some up today.  I can hollow a cavity in the base and add another few pounds to the base.  Cocobolo is very dense, so while lead is denser, it's not quite as big of an increase compared to say aluminum.

[neobop]

Pioneer P-3A table - arm eff length 282mm.  Pivot to spindle - 269.5mm.  Overhang 12.5mm.  Factory alignment nulls - 58.7mm, 117.5mm.
Want Baerwald or Loefgren?  Move it up to 267mm. 

I'm not entirely sure what you mean by the armboard cantilever out the back, but I don't like the smell.  If you mean what I think you mean, having the armboard hanging over the end far enough to allow cable exit, it's a terrible idea IMO.  Either you're being lazy or I misunderstood.  There's also no reason to make the armboard 1.5" thick.  It might be less convenient to make, but what's needed is a more conventional approach with a heavier pod.  Your arm weighs twice as much as the pod?   

Lose the Herbie's stuff.  It's a recipe for overdamped mushy sound.  What you need is weight, mass coupled to the platform and a rigid mount.  There should be no compliance, no possibility of movement, or detail is lost.

A cubic ft. of cocobolo weighs approx. 69 lbs.  A cubic ft. of lead weighs 707.96 lbs.   I guess you could make your design work, but as long as you're doing it, you might as well do it right.  If you replace the bottom piece of wood with something heavy, and with holes to accommodate a 1/2" thick armboard and a cable exit, all you need is short spikes on the bottom.   The armboard should be rigidly bolted on the supporting structure.
neo

 

[sunnydaze]

I'm with Neo,  you're waaaaay over thinking and over complicating things.

My advise?

Forget the audio snake oil tweaks.   Not necessary.  Solid,  rigid,  and massive is what you need.   Securely attach your solid outboard pod to your massive solid rack.   Simple and basic.   

Check my earlier posts and pics,  this is exactly what I did.  It works superbly.  All carts tracks like a dream.   Passes the Fremer CLUNK test, and even more violent disturbances, with flying colors.

Proof is in the pudding.   I have 4 arms.   I rotate them all between my DIY pod and the table's normal plinth mounting scheme.   The DIY mount sounds at least as good,  maybe better.

[ACHiPo]

Neo, Sunny,

Thanks again for your advice and guidance.  I'm obviously doing a lousy job communicating what's in my head, because it's not that complicated (to me, anyway), and makes sense with the design constraints I have (e.g. not wanting to attach the armboard to the top shelf and the design of the PA-70 arm).  You guys know a lot more about this stuff than me.  I do, however, know my way around a shop and have a decent understanding of engineering principles.

1. Armboard thickness.  Most tonearms bolt/screw into the armboard.  The PA-70 arm does not.  It is made to clamp onto the plinth armboard, and there needs to be about 1.5" of meat for it to clamp, because that's where the threads end.  As a result a 1.5" thick armboard makes sense.

2. Cantilever.  This is a pretty common design, especially for multi-arm turntables.  The difference in my case is that my armboard is basically a pod. 

Here are a few I found that gave me confidence my design approach is viable.








3)  "Tweaks".  I'm not really trying to get too fancy here, just trying to isolate the arm from the motor the same way the turntable does.  The WTT Reference plinth is made of 2 slabs of massive Corian-like stuff with elastomeric pads between them, and rubber feet.  The motor sits in a cut-out in the plinth and sits on its own rubber feet.  My thinking is that I want to approximate the isolation of the WTT between the motor and the arm since the motor sits on the shelf.

4)  Mass.  The cocobolo piece was too small, so I ended up using it for veneer and made a box from rock maple.  I couldn't find lead shot here (I live in CA, the only thing I could find was lead sinkers, which could work, but they were pretty expensive for what I needed).  I found copper BBs--not as dense as lead, but gets the mass of the pod up well over 10 lbs once I filled the cavity.  I can always mount the turntable and pod to a common board if movement becomes an issue.

The assembly is glued and clamped.  I'll post pics once it's done.

Thanks again!
Evan

[sunnydaze]

Hi Evan.....

The cantilever approach is a common and excellent one.  It allows for easy cable clearance / routing from the arm bottom.   Also,  since arm mount plate usually attaches via a single bolt to a heavy base,  it can be pivotted to swing relative to platter to easily achieve correct mount distance.   I think i mentioned earlier I like this approach,  but problem with outboard pod is that  one needs to devise a very heavy base to prevent toppling and to keep arm pod properly located.   (not an issue for cantilever mount plates anchored securely to plinth,  some examples  shown above).  Outboard pods typically done by machining something.   I have neither the shop access nor know how,  so I proceeded as I did w basic woodworking  and firm attachment to my BB top shelf.

But I surely do undetstand you not wanting to deface your nice rack w bolts or glue.    Me neither,  which is why I went with clamping.   Very rigid / solid / immovable,  no scars.

Sounds like you have the basics sorted:  pod / arm plate height relative to platter,  arm board thickness,  arm cable clearance / routing,   enough pod weight / mass for stability and prevent cantilever effect toppling, etc.   I think this last one is the most difficult in your situation.

I'm sure you are well on your way to an excellent outcome.   I look forward to seeing the final result!   

~John

[neobop]

The cantilever approach really isn't that common and I never liked it.  You're not a company like Micro Seiki or VPI that can do vibrational analysis and play around with it.  It will probably work.  Good luck with that.

One thing to consider - there should be no relative difference of motion between platter and arm.   A Micro Seiki or Avenger has the armboard (pod) attached to a chassis so movement, vibrations are common to each.   This is not the case with a separate pod.  Both table and pod should be planted on the platform.   
"I'm not really trying to get too fancy here, just trying to isolate the arm from the motor the same way the turntable does.  The WTT Reference plinth is made of 2 slabs of massive Corian-like stuff with elastomeric pads between them, and rubber feet.  The motor sits in a cut-out in the plinth and sits on its own rubber feet.  My thinking is that I want to approximate the isolation of the WTT between the motor and the arm since the motor sits on the shelf."

Your WT arm is attached to the plinth and will move with the platter.   The rubber feet on the table will vibrate differently than the pod.  I don't think motor vibration is the problem.  You might want to try spikes on both table and pod.
neo

[ACHiPo]

The cantilever approach really isn't that common and I never liked it.  You're not a company like Micro Seiki or VPI that can do vibrational analysis and play around with it.  It will probably work.  Good luck with that.

One thing to consider - there should be no relative difference of motion between platter and arm.   A Micro Seiki or Avenger has the armboard (pod) attached to a chassis so movement, vibrations are common to each.   This is not the case with a separate pod.  Both table and pod should be planted on the platform.   

Your WT arm is attached to the plinth and will move with the platter.   The rubber feet on the table will vibrate differently than the pod.  I don't think motor vibration is the problem.  You might want to try spikes on both table and pod.
neo

Good points.  I'm experimenting here.  I think I've got a reasonable approach, but realize it may not work well enough to be acceptable.  That being said, I'm not crazy about the amount of differences I measure for VTF on the WTT arm, which tells me that the damping trough is affecting a lot more than desired.  The precision of the Piineer should bring something to the party, even if vibration management is in the wrong direction.

I like the spikes idea--I'd need to figure something out for the motor as well, though just to keep it coplanar.

[neobop]

On Halcro's DD thread on Agon, most were arguing that the armboard should be rigidly coupled by some kind of chassis which prevents independent motion.   This is the norm, and if you deviate, abandon hope all ye who enter here.  This makes sense for a suspended table.  The arm must move with the platter, but for non-suspended, I think you will be okay if you consider it as a turntable system.

I don't know how the rubber feet are attached to the WT plinth, but it might be easy to replace with spikes.  Many older Japanese tables have a threaded 6mm receptacle on the bottom.  Could be similar? 

If you change the height of the table you could modify or change the feet on the motor.  This is the logical place for damping. 

To evaluate your set-up you might want to try the arm with a stereo cart of appropriate compliance.  You have a Dynavector or Lyra I think. 

If you have time, a blow by blow account would be appreciated. 
neo

 

[sunnydaze]

The cantilever approach really isn't that common and I never liked it.  You're not a company like Micro Seiki or VPI that can do vibrational analysis and play around with it.  It will probably work.  Good luck with that.

I see many many tables that employ cantilever armplate.    A high fraction of the total?  I have no idea.  Also, I have no idea if it's good, bad or indifferent.  But I do see it on pricey high- end tables, so some respected analog designers (and experienced DIY oriented vinyl-philes) have embraced it.

Neo, I get the sense you mainly operate in the vintage realm.  I don't see it on that stuff, mainly modern tables.  Is this why you dislike it?  Is your opinion based on theory, or actual experience?

Me?   I don't spend much time canoodling theory.  Lean more towards practical / hands on.  I try it.  It either sounds good or it doesn't.  If it doesn't, I try different materials / tweaks.    Listen again.  Repeat.  Vibrational analysis?!   Seriously?!   

IMO.......overthinking, paralysis by analysis.   Just try it!    Listen.  Keep adjusting till you get a good result.  I'm convinced you'll be happy with solid build and rigid attachment.  My ears tell me this, can't support it with science, nor do I care to.

[neobop]

I see many many tables that employ cantilever armplate.    A high fraction of the total?  I have no idea.  Also, I have no idea if it's good, bad or indifferent.  But I do see it on pricey high end tables, so some respected analog designers have no problem with it.

Neo, I get the sense you mainly operate in the vintage realm.  I don't see it on that stuff, mainly modern tables.  Why don't you like the approach?  Theoretical?  Actual experience?

Me?   I don't spend much time canoodling theory.  Lean more towards practical / hands on.  I try it.  It either sounds good or it doesn't.  If it doesn't, I try different materials / tweaks.    Listen again.  Repeat.  Vibrational analysis?!   Seriously?!   

IMO.......overthinking, paralysis by analysis.   Just try it!    Listen.  Keep adjusting till you get a good result.  I'm convinced you'll be happy with solid build and rigid attachment.  My ears tell me this, can't support it with science, nor do I care to.

You see many tables with a cantilevered armboard because you're looking for it and you see custom tables.   How many production tables employ this approach?  Only a few I think, and that's out of hundreds of current production tables. Tables like Delphi, Gyrodec have a steel or aluminum attachment to the chassis and a 3 or 4 bolt armboard.  I don't consider this the same. 

You make fun of vibration analysis, but what does a weight on the end of a cantilever do?   I never said it wouldn't work, in fact I said it would work.
Mount a weight on the end of a board attached only at the other end, and you have a diving board on a swimming pool, only more rigid. 

I don't know about you, but I must have read about a million times someone saying, I thought it sounded good until I did such and such, but I had no idea.  There's always something better and my thing is to get the most out of things, to get them sounding like real music.
neo

[ACHiPo]

If you have time, a blow by blow account would be appreciated. 
neo

I will post progress (or lack thereof) as time permits.

I finished the assembly last night.  Key findings:  1) the cantilever design is a bit more tippy than I'd like (the lever + mass of the tonearm is too close to the lever + mass of the pod even with BBs--while it doesn't tip, if I press down with ~1 lb of force on the back of the arm board the front of the pod tips up), so I will modify it to use legs behind the tonearm rather than in front as they are now, and 2) the Herbies dots work great to keep the pod fixed to the shelf, so once I add the legs I should be good to go.

The feet on the WTT screw into the plinth, and are likely 1/4-20 or 6 mm, so could be replaced with spikes, and I can replace the feet on the pod with spikes as well.  The problem is the feet on the motor, which I don't think are adjustable.  I'll have to check it out tonight, and if they can be replaced, then I just need to find spikes with the right thread.

I'll try to post some pics tonight so it's a bit clearer.

[sunnydaze]

You see many tables with a cantilevered armboard because you're looking for it and you see custom tables.

Not specifically looking for it.  I look at turntables period.  All types.

You make fun of vibration analysis, but what does a weight on the end of a cantilever do?   I never said it wouldn't work, in fact I said it would work.  Mount a weight on the end of a board attached only at the other end, and you have a diving board on a swimming pool, only more rigid.

Wasn't making fun of it.  Simply saying IMO an elaborate scientific study is not required to try something.  It doesn't hurt one iota to just proceed without a seismometer.  Play around with things.  You'd be surprised at how good it can be without getting all audio geeky and shit.  Besides, who has the tools / equipment for sophisticated analysis?  Tools you need are on the side of your head.  You're entitled to feel differently -- have at it.

I did say that executing a stand-alone cantilever mount that it is sufficiently rigid and stable and not tippy is quite problematic.  This is just intuitive.  For the average guy with simple tools and no machining know-how, it's impossible.   It's why my DIY mounts are traditional -- arm centered on a balanced and solid wooden platform. 

With very stiff materials and proper build, I suspect a cantilever platform can give excellent SQ results.  Just intuition based on the very high level of setups / gear I see using it.  But I don't know for sure, nor can I prove it.  And I suspect you can't either, regarding your claim that excessive spring / vibration are inherent in the design.

I don't know about you, but I must have read about a million times someone saying, I thought it sounded good until I did such and such, but I had no idea. 

Agree, and good point.  But I've already said (several times) that my simple / crude but rock solid DIY mounts (both of them) sound at least as good as the factory mounting systems on both my tables. 

Three conclusions:  (1) either they are just as good;  (2) my tables' stock mounts are crap; or (3) I have tin ears.   I seriously doubt (2), but I'm fine with admitting (3).    

But my local audio buds (all very experienced w/ hi-end systems) that hear my rig will disagree.     

Carry on!     

[neobop]

Sunnydazed,
I stand by what I say.  If you can find more than a few current production tables with cantilevered armboards, what are they?  Maybe I'm wrong.

You don't need a seismometer to check for vibrations and I wasn't suggesting a scientific study. 

Yes, I've read about turntable design.   I suggest Pierre Lurne' - has 4 or 5 interviews on the net and they're quite enlightening.   There are some general principles you can apply while flying by the seat of your pants, but you would need to read the interviews.  Energy dissipation vs. damping, is enlightening.

"But I've already said (several times) that my simple / crude but rock solid DIY mounts (both of them) sound at least as good as the factory mounting systems on both my tables."

What does this have to do with cantilevered armboards?   Just an opportunity to brag about your table?   Have you considered option #3 (tin ears), and your buds don't want to hurt your feelings?   

Just kidding, I'm sure it sounds great.
Stay cool,
neo

[ACHiPo]

Here's a pic of the motor feet.  Sure enough they are screw in (guessing M6?  Smaller than 1/4-20 I think), so cones are an option, but they'll need to be on the small side.  I'll also want some pads on which the cones can sit so I don't ding the shelf.



Of course the threaded inserts I used in the pod are 1/4-20, so I'll need to find cones that come in either size.

[neobop]

Evan,
It might be easier to consider the feet - height of the motor, plinth, and pod, at the same time.  The motor might be better with rubber or sorbothane underneath, and the plinth and pod with spikes.
neo