Beechwoods' Goldring Lenco GL-75

[John]

Looks in good condiction. Hope you have fun with it.
Are you going to keep the arm or go for something better amd what are your thoughts so far around plinth design

[Beechwoods]

Hi John I think an arm swap is more than likely, but as it stands I've no real thoughts on what to swap it with. I am going to give the stock arm a go, at least to get me up and running, but I know I can do better. There is loads of choice, particularly if I go with one mounted away from the base of the original Lenco arm... obviously allows for playing with alternative arm geometry.

The plinth is the bit I'm really looking forward to. I'm thinking of building up a wooden deck with quite thin slices, alternating woods, possibly an acrylic layer as a counterpoint to the wood, and possibly some ballast for weight. I have some victorian 8" sq clay paving slabs that might make an appearance! Working with thinner wood should be easier, and the thinness should help avoid resonances building up, but I'm conscious that more thin slices means more glue and that may affect it's sound properties adversely. I'm still reading about plinth design and have yet to reach any firm conclusions, mind...

[Cotlake]

IMO, Slate is the way to go for your plinth but it is relatively expensive. Thereafter a CLD (constrained layer damping) multi layer as you describe is very good. The amount and the variety on layers is the key rather than the glue unless you intend to use something really viscous like silicon rubber glue. With PVA you'll be fine mixing and matching and from what I can tell, the more layers and the denser it is the better. Remember not to fix the TT right through the layers or introduce any fixing through them other than glue. That destroys the benefits of the CLD approach.

Many have had good results with this type of plinth however I'll add that those who have later moved onto Slate would never go back, myself and Nick (Lurcher) being just two of many.

[Beechwoods]

My ideal plinth would be a Slatedeck. They are beautiful and as an inert mass they have an obvious edge over wood, but cost-wise it's prohibitive. Wood is also something I can work with myself, so it fulfills the 'must be fun' component of this project Thanks for your comments re. glue. It sounds like my instincts are right and it means I'll be able to build things up slowly and see what works.

I haven't thought yet about how to attach the TT to the plinth, but from your notes I guess it should just attach to the top layer, to avoid transmitting vibrations through the layers destroying the damping affects of the 'laminated' approach...?

[Cotlake]

Yep, you've got that right. Good luck!

[Retro Audio]

Hi, with the GL-75 I think you have the basis of an interesting and worthwhile project. I’ve had two of these, the first bought new from Comet way back in the seventies, this one was returned after the first weekend, the table was OK but the arm was really quite poor, the rubber bits were saggy as new and the head shell was poorly aligned, the supplied G800 cartridge was not up to much either!

My second GL-75 reintroduced me to vinyl after a longish break, the previous table being an LP-12 with SME 2 which I never got on with. This 75 I found in the back of a cupboard at work, I junked the plinth, suspension and arm. A wee bit of hacksaw work and a block of aluminum produced an arm mount for a Rega RB-250. The plinth was an off cut of low density chip board which sat on spur shelving via some hard rubber feet.

I installed a cheep Grado cartridge, I had no pre-amp at the time so made up some rough circuit boards for a couple of Hitachi SIL RIAA amp chips with a couple of Farnell double ended PSU’s and fed that lot into a Beard P100 driving Quad 57’s, stacked 57’s and later Magnepan MG2’s. It all sounded great and was fun to do!

The only real problem will be sorting the arm mount out, I used half inch aluminum and I had to get the large hole for the Rega done for me, cutting the clearance on the 75 was also a faf but not too big a deal and well worth the effort.

Speed will not be a problem, the 75 has a low torque synchronous motor and the grid still supplies a reasonably stable frequency so don’t worry about it.

Have fun,

Nigel.

[John]

I have a friend who got a slate plinth cut from a stone masons and also heard someone going to a sink stone specialist I think WElsh blue looks great bt there are other materials worth considering that be cheaper you mainly need to ensure its has a high density also check to see how it asborbs sound if you ever consider going down this route Think my friend plinth cost him £250 and it sounds great.
I think what is really good with this is have all that fun cutiing glueing etc and as and if funds become more available take it onto another level.
I should get my super scout master chassis and rim drive in 2 weeks so will update as and when that comes together. Managed to sell my parts to VPI HW19 I no longer need. so no turntable until this I get the new parts

[Retro Audio]

Seriously I would not get too hung up on this mass thing! There is a misunderstanding that chucking mass at a problem will solve the problem, this is so untrue! Mass and energy are one and the same thing, E=MC2 remember? OK in an amplifier it’s normally good to increase the “mass” with big reservoir capacitors, a bit like the flywheel component in a “normal” car! That’s because you want to use this extra stored energy to fill in for what is not actually available form the engine on an instantaneous basis.
However with loudspeakers and turntables (excluding the platter, perhaps?) the situation is somewhat different! We are looking to get rid of unwanted energy as fast as possible and adding mass only increases energy in the system, in effect the exact opposite of what we think we are going to achieve!
There are effectively only two ways of getting rid of unwanted energy, stopping it dead! Or dissipating it as quickly as possible. The fist solution requires that we hit the problem with mass, lot’s of mass, the amount of mass required to consummate this act is? Infinite! This is unachievable other than in states of non-ordinary reality! The second way is achievable by selecting materials that are light and stiff, in this case less really is more!
All this may seem counter intuitive but it’s not really, the proof of this pudding is quite evident after a couple of mouthfuls!
The parallels with other areas of performance are quite revealing, like you would not put heavy wheels on a car to make it “stick” to the road? No you use the lightest possible wheels and tires, if you race you might even inflate those tires with nitrogen to keep the “unsprung” mass/energy as low as possible so it’s easy for the suspension to handle i.e. keep the unwanted energy as low as possible!! In this case the energy fed back from the road or track!
So I’m strongly inclined to avoid high mass solutions period! Ok slate plinths do look very cool, but they are expensive and are almost certainly not the rout to audio nirvana!

Regards,

Nigel.

[lurcher]

So I’m strongly inclined to avoid high mass solutions period! Ok slate plinths do look very cool, but they are expensive and are almost certainly not the rout to audio nirvana!

Well, each to his own, but I suspect from what you have written, that your views are almost certainly not based on direct experence?

[Beechwoods]

This is certainly an interesting line of discussion. Since I am a novice in the area of plinth design I'm keen to understand the different schools of thought here. I'd have thought that density were important, rigidity and strength. Resistance to vibration, and resistance to resonance (hence laminate construction). Slate is laminar also so I'd say that that contributes to it's benefits in plinth construction, along with it's density, as much as mass.

I guess there are two paths you can go down in terms of turntable plinths. The one, sprung, relies upon the dissipation of energy to avoid colouration of the sound, but at the expense of that lost energy which otherwise might have been focussed upon sound reproduction.

The second path is to present an immovable and non-resonant mass to the turntable, allowing as much energy as possible to focus upon moving the coils in the cartridge. My gut says that getting the latter approach right is more tricky than achieving non-resonant isolation through damping.

I'd never considered the base physics outlined by Nigel though. I need to give it more thought.