Fastening The 301 To The Plinth
At this point in my investigations, I'm against putting fasteners into the mix... Certainly Metal Fasteners of any mass or bulk. It's not strength that is the overall objective here; in point of fact you could do a few 'dots' of glue per layer and the plinth would be strong enough, and so would the armboard mount.
What I'm after is to keep motor rumble travelling --- conduct it, punch it's ticket, make sure it doesn't leave any baggage behind at the station--- and send it on it's way.
If it manages the whole trip and exits at the spikes, cones, or the Aurios I'm now using, great. Sayonara, keep moving. If it falls asleep on the trip and kind of just zones out and deteriorates to nothing on it's way thru the plinth..... Fine, as long as it doesn't wake up again.
What I'm not after is having the motor rumble bouncing back off a weird boundary layer or pinging off steel fasteners and coming back in a time & phase shifted way to the armboard. In my previous plinth I ended up using hardwood pegs to attach the armboard for a similar reason. Steel (I tried it) conducted some aspect of audio-band motor rumble directly to the armboard it was fastening.
What I'm also not after is any detour or translation taking place with the motor signature, hence no 'contrast' layers for me in the plinth -- whether similar to the birch ply or dissimilar, like lead. The glue I'm using, which luthiers use for difficult bonding chores like violin bodies, does more to integrate adjacent layers, and fuse them physically and sonically ...than it does to form any intermediary layer.
The 'purist' (take w/ grain of salt, everybody's a purist, and nobody agrees) approach I'm taking on my current project is : Baltic Birch only, hardrock maple armboard, hide glue only, roller bearings for footers. Wide and deep (20x24"), but not too (3.75") thick, keeping that heavy motor very low to the ground, and very seriously rigid.
Every plinth maker seems to want the 'Only Way To Do It' crown for his way, which is ridiculous. I will, however, mention the following :
Nine out of ten articles about 301/401 practices properly mention that the Japanese are roundly regarded as the sponsors of the Garrard 301 Rennaisance that took place somewhere around the mid-eighties, just as we here in the enlightened West were discovering Compact Disc to our extended delight.
If you take a long trip thru the Japanese sites that show a 301/401 being used in Japan, most are in plinths of stacked ply & glue. Coincidence ? Possibly. Can it be done other ways ? Very definitely could be, but isn't. Conclusion ? Your call.
One last thing to wonder about
is why Shindo-San doesn't do birchply plinths, when in fact he knows quite a
lot about the issue. I think the answer there has to do with the fact that
he's in the business of selling $20K super-luxe iterations of the 301, and can
afford, in those budget confines, to be more luxurious with every phase of
design and materials.
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Spin It Up Long Before You Play Records
The Garrard 301 doesn't just sound better, it needs warmup to settle into equilibrium. Lots of heavy metal there, more than a couple moving bearings, and a tall column of grease that need warmup. It's not a big ordeal to warm it up for about thirty minutes before playing Lps, and it improves performance.
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Removing A Vibration Loop
Something I've come across that I thought I'd post is a little vibration-exchange point that I think goes overlooked in some 301 setups.
It should be mentioned that the 301 game is largely one of tracking and re-routing vibration pathways, and the motor-leads are one of the primary venues for motor vibration. Which wants to be either A) handled by the six motor suspension-springmounts or B) safely routed down and away, into plinth, rack or beyond.
So here goes ................. The little bakelite 'junction box' for the AC feeds and voltage-strapping is attached to a section of fiberboard by a threaded machine bolt which has several nuts (to attach to the fiberboard, to attach the 'strap' section, and then to attach the bakelite cover.)
Adjacent to that machine bolt--
kind of 'behind' the box-- is the lower-motor-cover fixing bolt (that on some
models has the ground tag).
So if the bolts in question TOUCH they are creating (by de-isolating) a vibration-loop that would be unintended and deleterious to the noise levels. If these two bolts are transferring energy, it's raw unsuspended motor pulse, and they're nulling a kind of iso-mount.
It's pretty logical to me that since one of the common things that get changed on a 301 during it's lifespan is the mains cable, and that the junction-box fixing bolt may get backed up into the motor unnoticeably. It needs only to be backed away incrementally so it no longer touches, then tightened again.
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Keeping motor and linkage clean during the plinthing procedure.
Cover the motor, suspension and adjacent linkage levers in a taut wrap of 'saran' or other kitchen clear-plastic wrap. This keeps the lubricated parts shielded from stray dust or debris while still allowing the multiple fittings and try-outs necessary for a contour-cut plinth. Simple but worthwhile precaution.
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Two Specific Modifications
There are a couple of interesting modifications of the 301 which have surfaced in various places on the internet, which I'll be looking into.
First is the Thrust Plate Cover modification to the spindle assembly, which replaces Garrard part no. 9, a thin sheet-metal plate that captures the spindle bearing's Thrust Pad, with an 8mm thick bronze plate. Noticeable improvements are reported.
The Second is the H-Bracket modification, which takes a stiff steel bracket and imposes it as a bridge across the interior of the platter well, traversing the spindle-bearing mount, and adding some 'spine' to the structurally-challenged motor-plate area.
Both of these have gotten good marks from reliable users, and I'll be looking into installing both at some time in the near future. Additionally I'll try to nail down and offer credit as to their origin ........
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