Garrard 401 plinth plan looking for feedback

[ev9048]

Hi, I am new to the forum, name is Tim, I live in Seattle, WA, USA
I have read lots of the plinth/build/401 entries on this and other forums.
there is so much information and sometime conflicting opinions, that i want to make sure i have a good plan.
I just received a 401 from England with a 60hz pulley, and it has been serviced sometime recently by CTC.
I am planning/plotting/starting my plinth build and wanted to give my general plan and solicit this forums excellent brains.
I also have a piece of 21.5 inch x 18.5 inch x 3cm soapstone i plan on using for the top and some small soapstone leftovers.
my current idea is
401,
3cm soapstone cutout for 401
layer of either 2mm car damping sheet (tar with aluminum sheet) or 5mm bitumen/torch down roofing
3/4" baltic birch plywood
1" tall footer - i have black diamond racing cones that are 1.5" diameter that are composite
foot receptacle 3 inch x 3 inch x 3cm soapstone scrap
.
i have everything but the plywood.  Any ideas on how to best glue the dampening to the stone and plywood, silicone? liquid nails/construction adhesive?
is my sequence of layers appropriate?
i am hoping to try to do some heavy damping, some wood, and some open frame here.
the plan above gives me right around 4" for the motor clearance.  i haven't unclamped the motor yet to its springs to see how much clearance i really need, but could goto 1" or 1.5" of plywood as needed. 
thank you for your support.....
Tim

[wenig watt]

soapstone is not really desireble...
https://www.tapatalk.com/groups/audioqualia/damping-factor-values-t20.html
nor is plywood.
At least as far as vibration damping is concerned. The sound may still be good, but the clarity of the reproduction does not benefit.

Best regards

Arndt

[Tobbe]

As bonding compound you may want to look into MS polymer based glued/bonds like Tec7.

I used it between two of the layers on my plinth build. I made the bond 6mm thick using spacers, so it forms an extra layer in the plinth. It's strong yet flexible and has vibration damping properties.

Disclaimer: my build is not finished yet so I can not say anything about how it sounds. But that stuff is strong and sticks to any material I have tried.

[Adnick]

Your going to get lots of opinions, but there’s something peculiar to Garrard 301/401 idlers when it comes to plinth design, a divide between extremely heavily built and moderately built.

I’ve built many idler plinths, most idlers require well designed heavy plinths that are dampening, transferring, and directive and deadening to unwanted vibration, & frequencies (noise).

The Garrard 301 grease bearing in stock form is the quietest idler I’ve ever encountered in stock form, this caused me to research the differences in the two main schools of thought for 301/401 plinths.

Here’s part of a conversation between myself and another 301 owner who made a granite plinth for his:

“I‘m thinking it really doesn’t need an extremely heavy constrained layered design, at least not like I’ve built for ROKs & Russco’s. Realize that’s against common knowledge but the motor just doesn’t transfer noise in the same manner as other idler drives, at least that’s my observations, whatever that’s worth ”

“Others have come to that same conclusion. Look for information on "Vinylista" plinths by the late Martin Brenner -- they're similar to the Loricraft approach, a fairly simple board plinth suspended in a frame. I have friends who use these, and like them very much.

EDIT: The Vinylista site is gone but not gone gone, courtesy of the wayback machine.

Overall my favorite approach for idler plinths is a constrained layered approach, this can be accomplished with many different material types, plywood, glass, rubber, fiberglass, steel, aluminum and man made synthetics have all been incorporated, just to name a few (glass is highly reflective of noise).

There’s a wide range of acoustic caulks & glues, epoxy, Dynamat type material and sticky foam, on and on…….

Many thoughts and theories on plinth building are highly contested and argued about, so look at general approaches used by the majority.

Good luck with your project and build, please yourself and remember to post pictures.

Best Regards,

Andy

[ev9048]

Thank you all for the comments.  It looks like my plotting and planning for this build is far from over....Luckily I was assuming this would be a slow and methodical build.  I know I am going to use the soapstone, so I can continue with the plan to template the 401 cutout and verify the pattern and then make a bunch of noise and dust over Xmas holidays.  I will try and post some interesting photos.  Thanks Tim

[Andr039]

I will try and post some interesting photos. 

That's exactly what we like here. Thanks!

[ev9048]

soapstone for the plinth, and the template that will be used to mark the soapstone for drilling/cutting

[Lynnot]

Just an odd question: Where exactly in the process of drilling/ cutting the plinth are these valves involved?

Rgds, Tony

[ev9048]

Hi, no valves are involved, I am using the ikea boxes they are in as a temp tt support.  I need to test on some of the scrap stone, but I think the plan is to drill holes with small masonry bit along the periphery of the cutout (100+) and then connect them using my jigsaw.  I need to goto the cheap tool shop near me (harbor freight) and by a bunch of throw away blades, and bits.  One of my scraps is 4 inches x 20 inches x 1.3 inches, and I want to make feet from that, that are 4x3 inches, so will need to try cutting that with either an abrasive or diamond saw blade I have on a handheld skil saw.  That is going to be a mess, I need to do outside, and using my cheapest saw in case the dust kills the bearings or motor.

[Adnick]

Cover the soapstone with sticky clear acetate or even masking tape….

Andy

[ev9048]

thanks for the soapstone protection idea, good thought.
.
today i verified the power was set for 110-120volts and attached an IEC, and powered up the table to make sure that was good.  I lightly oiled the spindle shaft and then ran it for a minute.  No noises, grinding, etc, a slight whirring, which i assume is the idler wheel.  The strobe did not come on, so i am guessing that is the bulb, but it is a 50hz platter, so it doesn't really matter at the moment.  I am planning on ordering the 50/60hz conversion light housing from the UK, just haven't got there yet.
.
I did loosen the motor clams bolts and verified the motor hang was pretty much exactly 4", so my plan of 4.5" clearance is very good.  in the photo you can see the 4.5" ikea boxes holding the table up and the plywood underneath is .75 inch, so that makes sense.
.
Gotta go to work tomorrow, so may not get to this again until next weekend.
thanks for the suggestions
.

[ev9048]

Hi, I have made a little progress.  Not too much on the plinth.  Christmas season sure is busy. 
Lubed under the 401 Chassis, things do move better.  I also adjusted the pulley height to hit the correct speeds.  I do think I have a slow leak common to the bearing, not sure yet, if I need anew gasket or what.  Here is what the thrust plate, looked like.  I do plan getting the SPH bearing, but funds are not in place yet.

[ev9048]

I have also drilled some plinth test holes in the 3cm soapstone. The bits I got are pretty small and will take a couple hundred to do the periphery.  I am planning on using a 75mm hole saw in some of the radius to get going quicker.  Had a heck of a time getting the stone plug out of the hole saw.  Am wondering if one or two of those might be a nice spindle weight? Or turn into footers? Or possibly legs for the table. Not sure if they will be pretty enough.might try chucking one in my drill press to see how it sands...lots of ideas not a lot of time.

[ev9048]

Continuing on, not very clean or pretty, but is slowly working.  I am starting the holes with smallest bit, then drilling thru with 3/16", then enlarging some holes.  If I could get it waterjet cut for less than $100 I think that would be worthwhile (in hindsight).  I think I am then going to try and connect the small holes by drilling at an angle with the bits I have worn out, then use my jigsaw with metal cutting blades to finish connecting the dots.  Then I will clean up with a file and test fit the 401 and trim more as needed

[ev9048]

Got the stone cut, and an underlayer of maple cutting board, and oiled a piece of the soapstone