Plinth to armboard interface Garrard 301 plinth

The more closely you can make it to the plinth and arm board being like one piece the better. So if the arm board you have is perfectly flat then just screw it down because adding anything between will only detract from that. But if it is anything less than perfectly flat, if there are any voids or gaps, then using a very thin layer of Blu-tack will likely help. 

I've compared quite a few different materials- from exotic hardwoods to pine and oak, to MDF, acrylic, ABS, etc as well as combinations of some of these laminated together. 

Bottom line, all these common materials have so many tradeoffs (ie none is truly superior to any other) that it comes down to personal preference. That's the bad news- its a crap shoot. The good news is all these are cheap and easy to experiment with.

This by the way is why so many turntables are made with these same materials. Its not that they are particularly good or effective. Its that they are cheap and easy to experiment with. Look how many variations VPI and others have on what is really just MDF/acrylic/aluminum.

The only somewhat commonly available material that is clearly superior in terms of vibration control is carbon fiber. Even here its not the carbon fiber that's definitive, but the way its used. I know, having built my share. The composite that forms the bulk of the material is every bit as important as the carbon fiber fabric you see on the outside. Maybe even more so.

Not opinion. Experience.

What this means is you have three main options: One, select a hardwood you think looks really good. Two, use MDF. Won't look as good but there's a reason MDF is used so extensively: its sonic signature is benign.

Third, no nevermind you won't do it. Do one of the other ones.

I don't claim to have a lot of experience with different armboards for the Garrard 301 but I did recently buy a mint condition Garrard 301 and I am having a plinth built. Mine will be layers of solid cherry and birch ply. I intend to mount my Reed 3P directly to the plinth. IMHO, having a pocket under the armboard (as so many stock plinths do) is an immediate compromise. There are some fancy (read; expensive) Garrard plinths out there with multiple armboards that fold in and out from the plinth to support different length arms. Again, IMHO, this looks nifty but is a compromise. I believe that somewhere along the way, smart people figured out that with an idler, it is best to have one common resonance running through the entire plinth and tonearm mount. Otherwise, tonearm mounts would be completely isolated from the plinth. This approach-the completely isolated tonearm mount-is sometimes seen with exotic belt drive tables, but not idlers. You seem to be on that wavelength already so why do you need an armboard? The answer may be that you want to be able to swap out tonearms without a marred plinth (perfectly understandable) or that you need the extra height to achieve proper VTA, particularly if you have an after-market platter. So my own opinion-driven by reliance upon blind luck and intuition-is that different woods or materials screwed down to the plinth (why use adhesive and be, uh, stuck with it?) would have a small effect on sound.
Someone with far more experience than I (my plinth builder in the UK) says that layers of birch ply is the most neutral and that solid cherry is the most warm. I guess by layering the two, I hope to split the difference. I agree with Millercarbon that if the arm is to be mounted directly to the plinth, the plinth must be perfectly flat but it seems to me that adding an armboard screwed down to the solid plinth makes achieving a perfectly flat-relative to the platter-mounting surface even more difficult to achieve. 
I might mention (and will) that I also have a TD124 and at one time I experimented with 4 or 5 different armboards including one made of aircraft grade aluminum and yes, they all sounded different but that is an entirely different deck with the chassis supporting the armboard-unlike the Garrard. 

Thanks guys  for the feedback.

I had a plinth made by a local man who has made many plinths for both Garrard's and TD124's, good friend has two or three of his plinths all beautiful and effective. Mine is a multi layered Bamboo ply with some insets for decoration. my current arm board is made of Padauk (I love this wood simply beautiful) I cannot unfortunately get another piece to match so i'm going to get two made so I have options in materials. I have a stepped hole bored through for the tone arm cable other then that and the stepped larger hole for the table its solid. there is pictures in my system. I will be most likely boring another hole for the second arm. 

My plinth-table combo is close to a hundred pounds, it's true and flat but I do need a little height for the Jelco so my arm board is about 1.5" thick so when installed, it's recessed 1/2", it's about an inch above the plinth. 

I've been happy so far still not quite finished but 90% there just the second arm and some permanent footers I can live with. 

oh the second arm is most likely going to be an SME 3009 series 2 mk2 as I have one sitting on my floor next to the audio rack, a  friend wants to sell me. its got new knife edge bearings and Cardas rewire straight through cabling. 

Thanks again always good to learn form others cheers 

glen