Tonearm mount to the plinth vs arm board vs rotating arm board vs isolated tower


Hello,

I am rebuilding a Garrard 301 and looking for a plinth. I am planning to buy 3-4 tonearms to try. I would like to know which is the best way moving forward.

Is there a difference between mounting a tonearm directly on a solid plinth vs arm board (same vs different materials) vs rotating arm board vs isolated tower. 

Thanks
Nanda
kanchi647
Of course there is a difference. For what you are doing though the most important considerations are flexibility and ease comparing several different arms. The best way to do this is with an arm board you can rotate to easily accommodate any length arm. Also if you need different hole sizes this is the easiest way as you can make several boards identical in every way except for the hole. 

This can all be done fast and cheap because its really only for comparing. It will be more than good enough to compare. Then when you know which arm you want it can be mounted in the plinth, or on a better more finished looking arm board. 

Another thing you can do along the way is make some arm boards out of different materials. Set up right, like with a notch in the boards, you could change them out so fast and easy it will be no problem to compare several. MDF, acrylic, different wood species, you can try easily and see. They each have their own characteristic signature sound and this will enable you to tune for the best result with your final arm choice. This is a far better approach than what most guys do trusting someone else and then paying them a lot for something they have no idea what it is.

This will also teach you enough to know whether you want the arm on a board like this or in the plinth, or inlay mounted in the plinth. In other words router out an area of plinth and inlay your arm in that. Either this or the rotating arm board are great ways to have a good looking table that can easily accommodate a range of arms going forward.
The best for me is armboard on the rails to change Pivot to Spindle distance quickly for various tonearms when needed. This design invented by Micro Seiki for Luxman PD-444, PD-555, PD-441 series back in the 70’s.

If you will look here such metal armboards mounted on the rails and can be moved left or right, they are fixed with lock. Clever design! The "plinth" of those turntables are metal (damped inside).

In modern design i see something similar on Dr.Feickert's turntables.  
Yes there is a difference that said is your plinth with these options 
going to be your final build/purchase or a test bed.

I built a plinth that accepts various arm lengths with multiple 
armboards. I decided the pivoting option was not for me and went with boards mounted directly to the plinth. Also various materials 
of construction for comparison.

One difference is the boards do not touch the exterior surface
and are attached to next layer below via threaded fasteners.

All sorts of opinions out there and some are easier to execute 
than others.

https://forum.audiogon.com/users/totem395





For practical reason this type of Steve Dobbins plinth for Garrard 301 is universal for different tonearms if you're going to use many. 
Same construction in Stereophile article 

Aesthetically Artisan Fidelity 301 is the best (imo), but you need many armboard to swap tonearms. 

Dear @kanchi647 : 1+  with millercarbon advise.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.
For practical reason this type of Steve Dobbins plinth for Garrard 301 is universal for different tonearms if you're going to use many.
Same construction in Stereophile article

Aesthetically Artisan Fidelity 301 is the best (imo), but you need many armboard to swap tonearms.
Well, I know Steve Dobbins. I have met him face to face and have had extended conversations with him about optimization of the venerable Garrard 301. Steve will tell you that the swiveling arm board is a compromise and is not optimum. It is a useful convenience feature. A very useful and very convenient feature but still a compromise. For optimum performance, he advocates mounting the tonearm directly to the plinth. No replaceable cut-outs, no extensions, fixed or rotating. Why should this be surprising when extensions resemble diving boards?
Everything needs to be kept in perspective. The Garrard 301 is not the ultimate in terms of being quiet or in terms of speed accuracy. Instead, it has it's own sound, a very good one. In light of that, one should not sweat bullets about having or eschewing a rotating arm board. They are clever and indispensable for those that want to use lots of different arms. The compromise in overall SQ is likely negligible. I would argue that it is only when using the very finest MC cartridges with the 301/401 that one should avoid any otherwise avoidable compromises. 
Steve will tell you that the swiveling arm board is a compromise and is not optimum. It is a useful convenience feature. A very useful and very convenient feature but still a compromise. For optimum performance, he advocates mounting the tonearm directly to the plinth. No replaceable cut-outs, no extensions, fixed or rotating

For Garrard or for Direct Drive too ? 
Such plinth is easy to made if we already have one tonearm to mount. 

We were discussing the Garrard 301 at the Axpona 2019 room featuring his turntable, a 301 on a Dobbins plinth with a Reed arm and a top of the line VdH cartridge and Magico speakers. I don't recall the electronics in that room. The room sponsor was Van den Hul's former distributor who has since then been replaced with VPI. 
My opinion though, fwiw, would not change with any type of drive system. 
I see, the goal of Reed is that a mounting hole is not needed under this tonearm, it can be screwed to the flat surface with 3 mounting screws from the top.
Here is the engineering principle that must be observed when designing a plinth for a turntable:

The plinth must be as rigid and as acoustically dead (damped) as possible. The mounting of the platter bearing in the plinth will be thus coupled as rigidly as possible to the mounting of the tonearm. If it is not, any vibration at all can be interpreted by the pickup (arm and cartridge) as a coloration.

IOW, if the arm and surface of the platter are able to vibrate at all, if they are always in the same plane of vibration, the pickup will not be able to pickup noise or coloration on that account. So a separate arm tower is a violation of this principle and induces coloration;  the same is true of a separate arm board. If the arm board employs damping and the plinth does not you'll get a coloration. It all simply has to be as rigid as possible and damped.
For the reason atmasphere just stated, I elected to have an armboard for my VPI HW-19 made from the same material at the top plate of the floating subchassis: acrylic. Delrin is harder and better damped than acrylic, but an armboard made of it will vibrate differently that does the acrylic plate, setting up another division between arm and main bearing/platter, and therefore between cartridge and LP (where the road meets the rubber ;-). Both the acrylic armboard and subchassis top plate are very firmly secure to the stainless steel bottom plate, minimizing relative movement between the two.  
When I was building slate plinths for various of my turntables, I adopted the practice of not creating any tonearm mounting boards or accommodating for them.  I therefore had to limit myself to surface mount tonearms, like Chakster says. These included the Triplanar, Reed, Dynavector DV505 and maybe a few more that I don't own.  I bolt the tonearm directly to the plinth.  Nothing moves.  I am not saying this is the best way to go; it certainly is not the most convenient nor the most flexible, but I think it adheres best to the principle of coupling the tonearm pivot to the platter and bearing.  For highest flexibility to use any arm any time, an outboard platform would seem best, if you're being pragmatic above all else.  A very heavy outboard arm pod that sits on the same support structure as the plinth itself is probably an acceptable compromise as far as coupling.
I think that it was Einstein that said  “Does the Station stop at this Train”

Now I know that I’m stretching the point a little but as Atmasphere said, to paraphrase..Relative movement between the arm mount and the platter is a bad thing.  We can have them both move in sync, within reason. 
If you agree with this principle, the arm mounting design options are narrowed considerably.

Thanks for all the information.
 I am considering a direct mount tonearm.
is there a sonic difference between Reed 3p and 2a
The mounting of the platter bearing in the plinth will be thus coupled as rigidly as possible to the mounting of the tonearm. If it is not, any vibration at all can be interpreted by the pickup (arm and cartridge) as a coloration.
That's the advice you get from 'amateurs'....🤪
HERE is the 'reality' from Mark Doehmann, responsible for the designs of the Continuum Caliburn and Criterion turntables as well as his own Doehmann Helix 1 and Helix 2 turntables.....all of which are carefully designed with the tonearm mounting bases ISOLATED from the bearing and plinth 👍
I've heard the Doehmann Helix in a system with which I am very familiar.  It indeed seems to be a fabulous turntable, perhaps the best belt-drive I have ever heard.  My friend has since sold it because he needs to downsize and decided to go all digital.  I could have bought it for a "nice" price, but even the nice price was a bit much for my blood.  As to the independent mounting of the tonearm, I don't recall that it was evident.  How did he make it look integrated with the turntable and yet isolate it?  By the way, smart guys (Atma-sphere, Richard, and Mark) can differ in opinion, which does not make the persons on the other side of the argument "amateurs".  If you wanted to make a list of competent designers who line up on one side or the other of this particular proposition, I daresay the "couplers" might have a larger contingent.  But you and I have been over this before, and I have no beef with your preference, nor do I wish to argue about it all over again.  Peace.
That’s the advice you get from ’amateurs’....🤪
HERE is the ’reality’ from Mark Doehmann, responsible for the designs of the Continuum Caliburn and Criterion turntables as well as his own Doehmann Helix 1 and Helix 2 turntables.....all of which are carefully designed with the tonearm mounting bases ISOLATED from the bearing and plinth 👍
Sorry Halcro, you fail to understand that both can be true.

Here is the brief from Dohmann...
The new ’table retains a somewhat simplified version of the unique "floating" armboard technology originally found in Mark Döhmann’s earlier designs, which physically isolates the board while maintaining (it is claimed) positional stability.
So Dohmann claims to provide BOTH isolation AND postitional stability.
I have not personally deconstructed the Dohmann but I understand that it uses a series of interlocking plates and composite materials to provide both isolation and maintain positional stability of the arm relative to the platter.

We are after all trying to measure a micro groove with the stylus - the stylus mounted on the armboard, the groove is mounted on the platter.
Any lack of rigidity between the platter and armboard will result in inaccurate measurment of the record groove. Its that simple.

If you want to perform an experiment - try measuring the height of your house whilst bouncing on a trampoline - you could post a video on you tube with and without the trampoline and we can then give you some feedback.


Sorry Halcro, you fail to understand that both can be true.
Duuuh.....🤪
You surely don't imagine for a second @dover that I could be advocating for an armboard to be 'moving' in relation to the platter....?
As you rightly surmise....
Dohmann claims to provide BOTH isolation AND positional stability.
But what he emphasises is the importance of 'isolating' the tonearm from the both the BEARING and MOTOR.
As @lewm states above...
A very heavy outboard arm pod that sits on the same support structure as the plinth itself is probably an acceptable compromise as far as coupling.
What irks me mostly is the declaration of FAKE facts....
Here is the engineering principle that MUST be observed when designing a plinth for a turntable:
The plinth must be as rigid and as acoustically dead (damped) as possible. The mounting of the platter bearing in the plinth will be thus coupled as rigidly as possible to the mounting of the tonearm.
Such dogma is anathema to our intriguing and not fully-understood hobby....🤗
There is an interesting conundrum at play here.
I quoted Einstein quite deliberately.
”Does the Station stop at this Train?

Looking at this another way, if the Station and Train are rigidly coupled together AND moving. A passenger in the train looking at the station will observe no movement.  
The challenge for the TT designer is to keep the relative positions of the platter and arm board constant under dynamic conditions. Does it matter if they are moving about provided they are rigidly coupled.? Obviously yes if this movement is large or violent because the acceleration will impact the arm and cartridge. But what happens if the movement is small and benign? 
Keeping the two parts still relative to each other isn’t easy. There is a YouTube video posted by Peter of Soundsmith where he quotes an Ortofon engineer who states that movement of 0.005 micron can be traced by a cartridge.
This tiny amount is almost beyond comprehension.






By the way, smart guys (Atma-sphere, Richard, and Mark) can differ in opinion, which does not make the persons on the other side of the argument "amateurs".
Please don't ask me to explain the difference between 'Professional' and 'Amateur' in relation to turntables @lewm ......🧐
Keeping the two parts still relative to each other isn’t easy.
Perhaps not.......
But certainly not impossible 🤗
Amateur?    Hmm. 
I would point you to this post.....

 OMA (Oswalds Mill Audio) Debuts K3 Direct Drive Turntable—An AnalogPlanet Exclusive Michael Fremer  |  Feb 28, 2020
The OP in this thread, is asking about an idler.

@kanchi647
The idlers are one of the crudest, oldest form of turntable, and with them comes.....(based on my personal direct experiences)

The most vibrations, least isolation, the most noise.

That's what you are dealing with.

For these reasons I would recommend you try a design that works to eliminate those three (at least) design symptoms.

When done well they (idlers) can be quite good. I own a Jean Nantais Lenco that contains reference level (Parts) see my virtual system. His design was called the best turntable by blogger A. Salvatore at one time.

His armboard design specific to your thread question, has gone to great extent to reduce the symptoms mentioned above.

To give you and others reading an idea of how far he goes; here is a picture of mine showing the extent he goes to....to reduce vibrations, noise and provide for isolation. 

https://photos.app.goo.gl/MdYZd7sBGJ1cCHyC8

Similar cavities exist under the motor. Even with these huge cavities, it still weighs 100 lbs.

Those who intend to build an new plinth for their TT's are in different
position from those who want to keep their TT as is. My Kuzm Stabi
Reference accept only 9'' tonearms. Triplanar can be mounted
because the arm(wand) is on the side of the VTA tower allowing
for longer lengt. I wanted an second arm and was forced to use
an armpod + 12'' arm. I ordered both by Reed. My Kuzma and
armpod rest on aan sand filled base resting on 3 spikes 
in an professional rack ( German ''Copulare'') . I have no idea
what ''optimal solution'' means but am satisfy with the situatiom
''as is''. 
Halcro, if your arguments are good, it’s really not necessary to be insulting.
The OP in this thread, is asking about an idler.

@kanchi647
The idlers are one of the crudest, oldest form of turntable, and with them comes.....(based on my personal direct experiences)

The most vibrations, least isolation, the most noise.

That's what you are dealing with.

For these reasons I would recommend you try a design that works to eliminate those three (at least) design symptoms.
If you look above, I said pretty much the same thing. 
But "crude" does not equal "inferior". 
Take the first ten vehicles featured here  https://www.townandcountrymag.com/leisure/sporting/news/g2165/best-vintage-cars/
Each and every one is "crude" by today's standards and yet they are-imho-more desirable and more "worthy" than anything available today at any price. You can argue all you want that a top Tesla is far more "precise" (think "accurate") but where will your Tesla be in ten years. Likely in a scrap heap. 
As crude as they may be, idlers are built to last and capable of giving incredible amounts of joy and pleasurable reproduction of music in the home. They possess a color, more-so than top direct drives, but I would rather have the slight color they provide. 
I agree with @halcro , it is essential to isolate the tonearm from the platter bearing and the motor.

I also agree with @atmasphere , it is essential to have the tonearm rigidly connected to the platter bearing.

I also agree with @lewm , bolt the tonearm to the plinth if possible, but compromise as necessary.

There is a material which is highly rigid, on the same order as aluminum plate, which is also very highly damped. That material is panzerholz. I built my platter board out of panzerholz and glued a layer of carbon composite to the top for further rigidity and constrained layer damping. Then I bolted my tonearm to the platter board.

Bearing is all air - high pressure amorphous carbon bearings in three dimensions. Bearing is grounded by offset steel columns connected through panzerholz blocks from (slate) tabletop to platter board. Platter bearing noise is nil.

Outboard belt drive with a flywheel allows excellent isolation of the motor. I say, "Let's have it all !"
Actually, a huge "THANK YOU" to all three of the above, who guided me to the above design. Also to the late Tom Fletcher. I certainly could not have done it without you.
Fantastic input from all the members. Challenging each other but I am learning a lot at the same time. I am still thinking of how to handle this..
Outboard belt drive with a flywheel allows excellent isolation of the motor. I say, "Let’s have it all !"
Actually, a huge "THANK YOU" to all three of the above, who guided me to the above design. Also to the late Tom Fletcher. I certainly could not have done it without you
I don’t mean to pick a fight, but your post is self-congratulatory, don’t you think?
There are those who would argue-correctly imho-that there is no such thing as perfect vinyl playback and not one option provides "it all", particularly any design that is belt drive.
As between idler, dd, and belt, belt is the worst in terms of speed stability and musical propulsiveness/dynamics. This explains why VPI plays around with using not just one, but two, and even three belts. This explains why some belt drive designers incorporate dental floss or non-stretch thread to drive the platter rather than a rubber belt. The very same material that decouples the motor through elasticity and vibration absorption-rubber-introduces other sins that are arguably worse.

I agree with @halcro , it is essential to isolate the tonearm from the platter bearing and the motor.


Among TD124 cognoscenti, this is a subject of debate. According to Greg Metz of STS who studied the TD124 in Switzerland under an original engineer involved in the design of that iconic table, coupling to and not isolating the tonearm from the bearing/motor is essential to the design. This is why the TD124 chassis encircles the armboard mount and the armboard is to be tightly screwed down to the cast iron chassis-the same chassis upon which the platter bearing and motor are mounted. The idea if I understood Greg correctly is that everything vibrating is concert is better than vibrating out of synch. The same school of TD124 experts state that a minimal mass plinth-really nothing more than a frame-similar to the stock base is best for the very same reason-a heavy solid plinth decouples the motor from the tonearm and would be the reverse what was contemplated by the engineers for best possible sound. So I am only saying that there are no absolutes. It all depends upon the design.
And yes, many people rave about the sound of their TD124’s mounted in slate and other high mass plinths. But how do we know that they have done valid comparisons? How do we know they are not judging based upon their eyeballs rather than being unbiased? The stock hollow framed base for the TD124 sure does not appear nearly as impressive as a huge hunk of slate, granite, or solid birch ply. IMHO, even the sorely missed Art Dudley got things wrong on his TD124 in this regard. He made an assumption and not an empirical decision as to what is best for the TD124. I say all of this because I used to have a heavy birch ply plinth for my hot-rodded restored TD124 and now have a hollow framed base not too dissimilar from what came stock back in 1959 (see pic in my profile of my present TD124 set-up). 
I agree with @halcro , it is essential to isolate the tonearm from the platter bearing and the motor.
This opens the turntable to colorations. Apparently Thorens has this sorted out:
The idea if I understood Greg correctly is that everything vibrating is concert is better than vibrating out of synch.
This is why the tonearm must be rigidly coupled to the platter bearing, and hopefully the surface of the platter as a result.
Nandric
Those who intend to build an new plinth for their TT's are in different
position from those who want to keep their TT as is.

@nandric 

Nikola
With these old idlers, (Garrard/Lenco's, etc...) like the OP of this thread is considering rebuilding ... everyone I know .......from the past, current, and I presume anyone on this AudioGon site, is not using this turntable type (idler)........ as is.

Buyers initially seek out the motor/platter system.

And....even then...... many folks, as in the case of the Jean Nantais Lenco version I ended up with; have replaced or significantly modified the platter, top plate, put in a new idler wheel, Spindle, thrust pad, bearing, etc.....

The finished tables people discuss on these audio sites bear very little resemblance to the originals.

@fsonicsmith , sorry to offend you. I was merely attempting to contribute to the discussion by suggesting that these desired characteristics could be obtained without (much) compromise, in part by finessing the problem, and partly by choice of materials. On re-reading my post, I realize that I was imprecise. I could cure this, but it might be tedious. Incidentally, baltic birch is a poor substitute for panzerholz. Ask me how I know.

@atmasphere , my imprecision obviously bothered you as well. I was trying to express the idea that an air bearing could be made silent, and so finesse the problem of transmitting platter bearing noise to the tonearm. I agree about a rigid coupling, which is incorporated into the design.
Dear ct, my first dispute in this forum was with Lew and regarding
Lenco platter. I was sceptical about possibilty to make a better one
in someone's garage or cellar. But my point was ''don't mess with
your TT''. His answer was : ''Nandric messing  with TT's is fun''. 
I was ''speechless'' . 
^^^^
It's very easy to mess with a used turntable that cost a couple hundred dollars to acquire.
@terry9; "offend" is not the appropriate word choice here. . 
I simply felt your post was a bit strong and worthy of comment. 
I will never challenge someone's love of their own table no matter how humble it might be. 
But when someone claims that their deck is perfect, my ears perk up. 
You took pains to claim that with the help of three people you had achieved perfection. 
Halcro by the way obviously has far more experience than I do and I have a feeling you quoted him out of context. 
I don't claim to have superior knowledge to anyone here. 
In fact, I know that I have less than many. 
But I do have some opinions that are only worth your 2 sense if you happen to agree with me and I don't mind those that disagree as long as the basis for the disagreement is rational. 
This is a topic that particularly interests me and I have some first-hand experience with it. 

@fsonicsmith , No. I did not say that my TT was perfect. Goodbye, Mr. Smith.
I came across Triangleart TT and was impressed by the design and looks.
has completely separate armpods..
it’s a belt drive

What do you all think about the Osiris tonearm? Suspended by a magnet. That great concept..
I echo Lewm's comments re the Helix TTs.
Mark Doehmann's design is innovative and unique. Way cool. I have heard them a number of times and they are exceptional. 
I have also met Mark twice. He is totally open to sharing his extensive knowledge about TTs and the industry in general.  A true gentleman. 
I echo Lewm's comments re the Helix TTs.
Mark Doehmann's design is innovative and unique. Way cool. I have heard them a number of times and they are exceptional.
I have also met Mark twice. He is totally open to sharing his extensive knowledge about TTs and the industry in general. A true gentleman.

THIS
👍
Yes, while Mark and I have taken significantly different paths in our designs, we both agree on the fundamentals. We just approached them from different perspectives.
Dear ct, with your ''cheap TT's argument'' you are actually strengthening my  which was ''don't mess with TT's''. This
than should be ''don't mess with cheap TT's''. 
@nandric 
Nikola.
I never used the words "cheap TT's". You did, and it changes the meaning.

To the idler fan (the subject of this thread is about an idler); there is "hidden" "intrinsic" value in what is acquired for this small sum of money .....if.

that person has the means to transport the "mechanical's", into another "body" (plinth).

Idlers bring unique challenges to Audiophile projects.

Dear ct, one can express the same thought with different words.
So persistence  on ''exactly  used words'' will not do ; meaning 
can't be nailed to specific words. Otherwise our memory would be
the same as by computers. 
Also the valuation of expression ''cheap'' may differ among
nations. The English saying is: ''I am not rich to bay cheap stuff''. 
My own is the usual understanding of this word. I as you deed
not emigrated from former Yugoslavia to the West for ''cheap
things''. On the contrary (grin). Check my carts collection!
For the record, Nikola, I have never replaced or modified the platter on my Lenco. Along with the motor and idler wheel, the platter is OEM. I am in fact skeptical of those who have doubled up on the platter, using two original platters, one on top of the other. And I am not even aware of anyone who makes a candidate aftermarket platter for a Lenco idler. And finally, I don’t approve of doing any of those things, because I think the drive system was designed and conceived to drive the platter as is. Altering the mass might not be a very good idea. So, perhaps at sometime in the past, which I don’t remember at all, we may have had a disagreement having something to do with a Lenco, but it could not have been regarding my desire to replace or alter the platter. Without consulting anyone here ever, I did do one thing: I had the platter professionally painted in a vibration reducing paint. And then I placed 4 large O-rings around the circumference to dampen the purported tendency of the platter to ring. I got that idea from Win Tinnon, the guy who makes the Saskia.
Dear Lew, You made me again speechless. Heavy paint? 
There are anti-vibration extensional compounds that are applied similar to paint.
Once you isolate the turntable all that damping stuff is passé. The isolation is a two way system. 🔛