garrard 401 plinth suspension or not!

[hifinutter]

i have made an oak plinth for my garrard 401 but wondering about some kind of sound deadening between the plinth and the deck any thoughts [maybe some kind of sorbathane washer or gasket?]

 

[hifinutter]

i have made an oak plinth for my garrard 401 but wondering about some kind of sound deadening between the plinth and the deck any thoughts [maybe some kind of sorbathane washer or gasket?]

a pic to ogle at- - - Updated - - -

a pic to ogle at

this is before i danish oiled it

/monthly_2013_10/SAM_1313.jpg.e5cad53716c6334e14aaea4974edba9e.jpg

 

[hifinutter]

i am still going to build the stack ply plinth as a comparison

 

[Non-Smoking Man]

Loricraft advocate washers/grommets, others advocate direct clamping to the plinth. So opinion seems divided.

Its often the ubiquitous squash ball thats drafted in and I have used tennis balls in the past (in a different arrangement).

Whats the depth of the wood on that one? It doesnt look thick enough to be brutally honest with you - you might thimk about doubling it from what ive read.

If you google away there's quite a lot of info out there. Also take a look at the SP10 sites - one of them lists the damping factor of various materials used in plinth construction. (The SP10 when in 1000 mode has an obsidian plinth and alternatives to this are discussed.)

The 3rd issue (after 1. decoupling with grommets; 2, choice of plinth material) is whether to decouple the arm pillar from the motor board to avoid unwanted vibration.

Hope this helps.

Jack

Your layered alternative could well be better than the one you've pictured. Some designers use layers of different material eg., a thin aluminium sheet, to break up the vibration.

 

[Vinyl Art]

If you are fixing your arm and Garrard to the same top plate then introducing any compliant material between them effectively removes a fixed pivot to spindle distance. I stand ready to be corrected, but I don't know of any turntable manufacturer who does this???

Oak has a relatively low damping factor, you may well be able to introduce a degree of damping by surface mounting a sheet of damping material to the underside of your plinth or even intoducing a constrained damping layer to the underside (would be my preference given the starting point). You can mass load the plinth, but this will not remove any energy from the system and will only have a limited effect at certain frequencies and amplitudes and will certainly effect any damping solution you do apply. Pop over to the Audio Qualia web site, lots of info over there and Mr Cat Squirrel knows his stuff.

Do ensure that the Garrard is well fettled, new rubber drive wheel, bearings, bearings oiled etc and this will give you the best start. No amount of plinth damping or mass addition will ever cure a badly fettled Garrard.

To protect from external vibrations then wall mount it or invest in some very low frequency isolators.

 

[i_should_coco]

If you are fixing your arm and Garrard to the same top plate then introducing any compliant material between them effectively removes a fixed pivot to spindle distance. I stand ready to be corrected, but I don't know of any turntable manufacturer who does this???

No material will be rigid at all audio frequencies so the whole concept of rigid coupling between bearing and arm is flawed IMO.

 

[Vinyl Art]

Agreed, the question then remains that at what point does a lack of rigidity have an audiable effect? I would still suggest that trying to introduce compliance between the motor unit and the arm to damp vibrations from a relatively low frequency input from the Garrard rumble machine would potentially result in an audiably worse solution.

It is relatively cheap to do, so pop some sorbathane or similar in there and have a listen, see what you make of it, all part of the fun.

 

[bandit pilot]

This one had felt mat isolation between the arm and motor.

 

[i_should_coco]

Agreed, the question then remains that at what point does a lack of rigidity have an audiable effect? I would still suggest that trying to introduce compliance between the motor unit and the arm to damp vibrations from a relatively low frequency input from the Garrard rumble machine would potentially result in an audiably worse solution.

Why?

 

[hifinutter]

This one had felt mat isolation between the arm and motor. do you just mean the mat on the turntable ? :dunno: or do you mean under the arm !

please elaborate cheers

 

[bandit pilot]

I mean that if you look at the deck, it is 3 separate boxes. The 2 outer boxes are decoupled with some very dense felt. You can just about see it.

 

[Vinyl Art]

Why?

Differential movement between the arm and motor unit. If I have fallen into a Pooh trap be gentle, I'm suffering this evening as it is. Mind you, never a bad idea to have accepted wisdom questioned.

It will go back to why you think it is flawed to have a rigid coupling, what would be the advantage of a compliant coupling, how compliant, in what axis?

If fully floating then surely the cart would just show pitch instability as it was first dragged up and then released back down the groove. I would assume that to be not desirable, so apply some damping and take toward the rigid end of the equation, at what point does it become desirable? Is it more than just a compromise between isolation of the arm base from motor unit or are you suggesting there is something inherently advantageous with a compliant coupling in it's own right?

I seem to remember something from Origin Live that recommended not torquing the hell out of the fixing bolt on its tonearms as the more rigid coupling wasn't desirable, but it really didn't say much more than that. Cartridgeman has a compliant mount between cart and tonearm and Well Tempered are fairly unique in their approach.

 

[i_should_coco]

Differential movement between the arm and motor unit. If I have fallen into a Pooh trap be gentle, I'm suffering this evening as it is. Mind you, never a bad idea to have accepted wisdom questioned.

My view is that it's (differential movement) gonna happen anyway. Ultimately the cartridge is held in place via it's mass and cantilever compliance combination. vibration fed up the arm (perhaps by some nominally rigid coupling) from the motor unit is going to affect the cartridge anyway.

It will go back to why you think it is flawed to have a rigid coupling, what would be the advantage of a compliant coupling, how compliant, in what axis?

It's not that it's not desirable, it's that I believe it's simply not possible. if you look at how what appear to be solid materials behave under dynamic conditions, I think you'd be surprised. I guess you can illustrate it by tapping a piece of metal (or whatever). If it makes a noise (any sort of noise) it's not rigid.

If fully floating then surely the cart would just show pitch instability as it was first dragged up and then released back down the groove. I would assume that to be not desirable, so apply some damping and take toward the rigid end of the equation, at what point does it become desirable? Is it more than just a compromise between isolation of the arm base from motor unit or are you suggesting there is something inherently advantageous with a compliant coupling in it's own right?

I'm not suggesting so much compliance that speed stability is audibly compromised. In fact I'm not suggesting introducing any compliance, just pointing that the 'rigid' coupling (e.g. a steel or ally plank) isn't actually rigid at the frequencies of interest! Having said that, in the Garrard, isolating the arm mount from motor vibration would be a good thing, I'd have thought.

I seem to remember something from Origin Live that recommended not torquing the hell out of the fixing bolt on its tonearms as the more rigid coupling wasn't desirable, but it really didn't say much more than that. Cartridgeman has a compliant mount between cart and tonearm and Well Tempered are fairly unique in their approach.

Just my 2p FWIW (probably not much). I'm happy to be corrected.

 

[hifinutter]

So would using a gasket between the turntable and the plinth say something like rubber or sorbathane be a good idea or am i better to use something under the whole plinth instead and just bolt the plinth straight to the turntable ! ps good stuff so far cheers

 

[paulf-2007]

There was a thread on here involving a 401 sat on a gasket of some kind set into the plinth so the chassis was flush with the plinth but not touching around the edge. Cannot remember who posted it but was making it for a customer, didn't get to know the outcome of how it worked. Will do a bit of searching

 

[f1eng]

I agree with coco here 100%

I think we were all blighted by the "tighten all bolts until they nearly break" and much quoting of "rigid" back in the flat-earth days which I thought we had grown out of.

Firstly, tightening up bolts reduces damping so, whilst it is likely to make a speaker or turntable sound different, and the effect may be liked, it is certainly less accurate than the normal engineering way.

As Coco writes, no material/structure is rigid over the audible frequency range.

SME used to supply the 3009 mkII with soft grommets through the fixing holes and recommend that the fixing screws were tightened just sufficiently to not compress the grommet. This is IMHO a better way to isolate any plinth vibration from the cartridge body than trying to isolate the TT chassis a bit.

Time for a vibration engineering rant!

Amazing how many ignoramuses using static arguments for dynamic systems have been in this business, and how long they survived.

A cartridge is a seismic vibration transducer. The objective of the arm is to gently guide the body such that the VTA SRA and alignment remain correct. In a properly balanced system -no- vibration above 20Hz will make it into the cartridge body/arm from the stylus. The cartridge body, by that frequency, will be (hopefully) stationary relative to the stylus and all stylus movement will be converted to an accurate output signal.

I write "hopefully" since any vibration where the arm mounts on the plinth will be transmitted to the cartridge body via the pillar and arm. The amount of this will depend on how lively a bit of the plinth the arm is fixed to and the modal behaviour of the plinth. It also depends on the vibration characteristics of the arm itself. A stiff arm, designed to be as stiff as possible (and it will still be as floppy as hell above ~1kHz even then) will transmit -more- of this vibration to the cartridge body, over a wider frequency range and be peaky, compared to a conventional arm.

So in terms of minimising that which is added to the cartridge signal any vibration of the LP itself whether due to disc vibration, motor noise, belt scuff noise airborne and structure borne vibration from the speakers must be eliminated since it will move the stylus. All plinth vibration passing up the arm and vibrating the cartridge body also is added to the cartridge output since it vibrates the "static" element.

In terms of minimising the latter an arm machined out of solid will likely add more to the output than one of the conventionally engineered arms which are thankfully returning to popularity.

OTOH in my own listening tests I have not always preferred the more accurate solutions I am afraid... Moving the record player out of the listening room, for example, which removes structure and airborne additions, sounded a bit flat and less real - leading me to believe that the extra bit of reverb I was getting that way was missed.

In fact, IME the only thing which always sounds worse is poor speed stability. The other additions -can- sound nicer, and there is a huge potential for experimenting and tuning to taste...

 

[turning japanese]

it was PAC1 I think - cable manufacturer from Glos area - not seen much of him recently but he seemed convinced about the garrard plinth design

 

[It Cost How Much!?!]

You mean Pac67, who is now banned I think.

 

[Cambs12]

Don't think he was banned Bob,I think it was his own choice to leave.

You mean Pac67, who is now banned I think.