Lenco arrived. Next steps?

[jls001]

We should not use the term "CLD" lightly

(unless we're planning on including a genuine elastomer damping layer)

 

[jls001]

Lest I'm misunderstood, I just want to clarify that I'm not discouraging or disparaging against CLD. It's talked about a lot on forums but it's very rare to see an actual implementation. So it would be nice to see someone actually build one and report back on its sonic benefits.

 

[arj]

Lest I'm misunderstood, I just want to clarify that I'm not discouraging or disparaging against CLD. It's talked about a lot on forums but it's very rare to see an actual implementation. So it would be nice to see someone actually build one and report back on its sonic benefits.

Could not agree with you more. concept of a CLD is to have multiple layers of different materials to provide for a higher range of frequency absorption. Other than Jean nantias have not seen or heard of anything of a breakthru nature for lenco. Shindo was the master in getting this right

Arj, I assume you mean that the Birch ply plinth was not CLD. So a Birch ply CLD should be ideal.

Is the CLD plinth heavy enough by itself or are you guys loading it with something?

from my experience prefer keeping mdf out as much as i can and preferred the Birch ply only. the heavier you make it the better it seems to be eg you can load a layer with lead shots or iron filings as well or add an acrylic or aluminium layer at the bottom as needed.

 

[Hiten]

cat's squirrel has done comprehensive study and measurement about plinth. Details are here - Turntable Plinths-AUdio Qualia
He is also a member here in HFV. Also on diyAudio and Vinyl Engine forums.
Regards.

 

[atharva]

Finally got to cleaning the Lenco and playing my first record.

Oh my god! This sounds awesome. I put my spare AT95 cart on the stock arm and played it via Schiit Mani. It is much more punchier and has a better soundstage than the DL103R/AudioMods/HQMCPS/Thorens 160 combo. The Thorens combo sounds "sweeter" (could be DL103?). Hmmmm. Everything on the Thorens is much superior to the Lenco and I haven't even replaced the v-blocks and the arm rocks a bit. Am I biased or is the Lenco really doing its magic?

BTW, did the following service.

1. Cleaned main bearing. Don't have circlip pliers so removed the spindle from the top and oiled it with Singer machine oil.
2. Applied a little lithium grease to the speed selector connector and now that is smooth.
3. Replaced the stock tonearm wire with one I made from Belden cable.

Is there a local paint colour that matches closely to the original to touch up some marks on the chassis? The other way seems to be to build a different plinth where the top plate is cut off retaining only the on-off switch and speed selector.

Planning to to do the motor servicing once I buy circlip pliers.

 

[atharva]

Joshua, I did some reading on CLD and you are right! It needs a visco elastic sandwich layer.

However, this has confused me. I can see that there two main vibrations we are trying to dampen. One is from the motor and the other from base (e.g with footfalls in homes with wooden floors). Now, I can see how the damping layer can absorb and prevent the vibrations from the floor going up to the arm. But, if the motor and arm are directly coupled either via the plinth or through the motor-idler-platter in case of idlers, then how does the damping layer help?

 

[atharva]

What I meant to say is could it be that in our "tiled" houses/flats that a simple layered plinth would work just as well?

 

[jls001]

However, this has confused me. I can see that there two main vibrations we are trying to dampen. One is from the motor and the other from base (e.g with footfalls in homes with wooden floors). Now, I can see how the damping layer can absorb and prevent the vibrations from the floor going up to the arm. But, if the motor and arm are directly coupled either via the plinth or through the motor-idler-platter in case of idlers, then how does the damping layer help?

Typically a metallic cone footer placed below a TT (or speakers or amp) will drain away the vibration from the plinth to the shelf of the rack, then to the floor through the structure of the rack. The travel of the vibration is one way - from the large flat surface area of the cone which acts as a large coupling receptacle for the vibration from the much larger surface area of the bottom of the plinth, to the point of the cone which is very, very tiny compared to the flat surface. The reverse direction will effectively be like an open circuit, much like a mechanical valve or electronic diode, because the point of the cone is too small to couple any significant amount of vibration from the rack/floor back to the plinth.

Many TTs also use soft footers (think SL 1200) which acts as a damping layer, but the difference is it works to isolate vibrations from TT to rack, and vice versa.

The idea of CLD (as far as my limited knowledge of the science) is to restrain/damp the vibration on one layer A with another layer made of a different material B, making the composite material A+B formed from two materials a better dampener than A alone.

The plinth will absorb the vibrations from the motor. The absorbed energy will be wasted as heat.

Isolating the motor as in PTP from the rest of the top plate will reduce the amount of vibrations that travels to the motor platter cartridge tonearm reflected from the pivot of tonearm cartridge, which leads to smearing of the desired sound signal.

Another not so popular method of motor isolation is to mount the motor on a separate structure placed directly on the shelf (and not on the plinth) such that it is correctly aligned in height as well as laterally. It's complicated. However, the shelf of the rack is still common to plinth and motor mount, but whatever vibration that travels from the motor to the plinth will obviously be much diminished.

Yet another method of isolation is to create a tonearm base separate from the plinth. Disadvantage is the arm base needs to be carefully placed after each move of the TT. And perhaps periodic checks would be required for correct pivot-spindle distance. This base also will need its own cones like the main plinth. Again, the shelf is common, etc in this case.

But having said that, don't over think. Just build a regular multi layered plywood plinth (use the best plywood you can get hold of - ideally void free) and you'll find that it sounds pretty damned good. Just make sure that you get a competent carpenter to glue and finish the veneer to heritage furniture grade (don't accept anything less). Higher mass in this case is really better as repeated often by arj, because the motor is so torquey and can put out lots of energy.

PS: I really like the idea of throwing away the useless parts of the top plate - it gives you total flexibility in choosing an arm (or arms) and also eliminates the biggest weakness of the Lenco - it's thin top plate. Do retain the on-off switch, though.

Hope I've not confused you further

 

[arj]

i would like to talk a little bit more on a couple of points made by jls001 above

1. for the footer use 3 steel spikes if possible. 2 on 2 adjacent corners and one on the opposite side middle forming an isosceles triangle

2. as mentioned by joshua, IF you can it makes sense to have the top late cut around the circle of the platters depression but such that you retain both the speed changing knob and the on off one. this will also give you more options around the tonearm as the standard armhole will also go away

3. from my experience, i do not recommend a separate tonearm base ( unless you are able to achieve near perfect vibration isolation). i tried that and then moved back to a single plinth setup and found it to be less noisy ( maybe because the platter and tonearm have the same vibration pattern - my guess)

4. service the bearing once and oil it.

5. listen to it when your power is really clean.being an AC motor the frequency of the mains controls the speed and the voltage the torque. since minor variations in torque are insignificant but frequency varies. in bangalore during day time the frequency can drop to 48hz and hence instead of 33.33 it runs at 32Hz and than makes music very boring ! so this can have the maximum impact on sound !

 

[Beginner_N]

Hi All,

Just finished with CAD model of Lenco L75.?

Attached is 3D PDF.

Regards,
Nishant

Sent from my MotoG3-TE using Tapatalk

 

[atharva]

Joshua, I understand what you are saying. I think we are agreeing in that we should worry (super optimise) about a true CLD plinth ONLY if we've isolated the motor as in PTP and the rest of our chain is equally optimised.

arj, I am hoping to make slot in the plinth which can accommodate arms like this https://i0.wp.com/www.bartola.co.uk/valves/wp-content/uploads/2013/06/20130609-174115.jpg Hopefully whoever makes the plinth for me can handle this . Am keeping my fingers crossed that I can cut the top plate.

Nishant, Thanks so much.

 

[jls001]

arj, I am hoping to make slot in the plinth which can accommodate arms like this https://i0.wp.com/www.bartola.co.uk/valves/wp-content/uploads/2013/06/20130609-174115.jpg Hopefully whoever makes the plinth for me can handle this . Am keeping my fingers crossed that I can cut the top plate.

Are you planning on throwing away the top plate? If yes, I'm totally with you :thumbsup: Cutting off redundant part of top plate ought to be possible with pro metal working shops. I've been planning in this direction for ages, but it needs complete stripping and I've not been able to pay much attention to it. Also, I'm still not completely clear on how to cut out the second layer of the plinth to accommodate the on/off levers (as I want to retain on/off switch). I guess a complete strip down and creating a dummy cutout for layer 2 will be the only solution as people who've done something similar have not bothered to make formal cutout drawings (I've asked a couple of people on LH). Or one could make non-final cutout and slowly creep up to the final dimension as done by many woodworkers. It's do-able.

 

[arj]

arj, I am hoping to make slot in the plinth which can accommodate arms like this https://i0.wp.com/www.bartola.co.uk/valves/wp-content/uploads/2013/06/20130609-174115.jpg Hopefully whoever makes the plinth for me can handle this . Am keeping my fingers crossed that I can cut the top plate.

.

looks awesome !!!

Are you planning on throwing away the top plate? If yes, I'm totally with you :thumbsup: Cutting off redundant part of top plate ought to be possible with pro metal working shops. I've been planning in this direction for ages, but it needs complete stripping and I've not been able to pay much attention to it. Also, I'm still not completely clear on how to cut out the second layer of the plinth to accommodate the on/off levers (as I want to retain on/off switch). I guess a complete strip down and creating a dummy cutout for layer 2 will be the only solution as people who've done something similar have not bothered to make formal cutout drawings (I've asked a couple of people on LH). Or one could make non-final cutout and slowly creep up to the final dimension as done by many woodworkers. It's do-able.

i had considered of this for a long time and had finally thought of keeping just the portion of the top plate with the lever as is and then pasting a wood veneer over it with a cork sheet or any other damping material just below so there is no gap where the top plate is not present

 

[cat's squirrel]

if you stick many layers of ply together, it is a glulam, NOT a cld, which is a way of damping. Ply has very little damping, so be prepared for your Lenco plinth to provide lots of enhanced sound. Cork is not good at damping, believe it or not!

 

[arj]

if you stick many layers of ply together, it is a glulam, NOT a cld, which is a way of damping. Ply has very little damping, so be prepared for your Lenco plinth to provide lots of enhanced sound. Cork is not good at damping, believe it or not!

Its really great to see you here !

Whats you view on Birch ply layers stuck together ? is it good enough to damp the lower frequencies or is there any way of making it better ?

 

[cat's squirrel]

any plywood, on its own, is going to be poor. Glueing a number of layers of ply together really makes the situation worse, not better.

If you really want to use ply, then use it as a ply/aluminium/ply laminate. It does not need to be thick, 12mm, 18mm or 24mm ply will need 3mm, 2mm and 1mm aluminium plate respectively. It's all to do with bending stiffness. Stiffness is needed, but not too much.

Damping is improved enough to be used as is, without further damping, although not as good as some other materials.

HTH

 

[Naturelover]

If you really want to use ply

What are the alternatives to ply? What would you use or suggest?

 

[arj]

any plywood, on its own, is going to be poor. Glueing a number of layers of ply together really makes the situation worse, not better.

If you really want to use ply, then use it as a ply/aluminium/ply laminate. It does not need to be thick, 12mm, 18mm or 24mm ply will need 3mm, 2mm and 1mm aluminium plate respectively. It's all to do with bending stiffness. Stiffness is needed, but not too much.

Damping is improved enough to be used as is, without further damping, although not as good as some other materials.

HTH

Thanks ! i need to figure out how to unglue my plinth
In your opinion would making a sandwich..2 mm Al on top and bottom make this better in anyway or is it better to think of a new plinth ?

Maybe i should think of some form of a Hardwood single layer thick plinth..

 

[reubensm]

I have seen some plinths with rubber sheets sandwiched between the layers of ply. Any comments on these?

 

[cat's squirrel]

the important parameter in this case is bending stiffness. If you use aluminium panels each side of ply (or mdf) then 25mm ply with 1mm aluminium has about the same stiffness as 18mm ply with 2mm Al, and with 12mm ply, 3.5mm thick Al, although the 12mm ply or mdf with 3.5mm Al works best of those three. Thicker is not better. 10mm ply also works quite well with 4mm ply/mdf. But no cigars!

If you want to use hardwood, make sure it has damping qualities, not many do! And plinths containing layers of rubber are best just put to one side. Are they stiff?

To choose a suitable material, it must have some stiffness, some mass and a lot of damping. Its a fine balancing act getting all three to work together, but not impossible.