My Lenco L75 Master Turntable Build

[reubensm]

After talking about how I acquired a near mint black Lenco L75 and a brand new Jelco SA370H tonearm, its time to now get some action going on this project. Starting a new thread for documenting my journey through my very first build of this nature. This will hopefully set me off on the right path before I can look at entering the big league with the Thorens, Garrards or EMTs.

Took the deck out of storage today, set about removing the stock tonearm from the chassis. It turned out to be a very easy task:

Deck with stock tonearm:

Deck with stock tonearm, lift mechanism and tonearm stand removed:

The Lenco L75 stock tonearm, bits and pieces:

Its time to pack up the stock tonearm and all associated bits and pieces:

Now to check out on some possibilities with tonearm positioning, got a spare Technics headshell with cart, on and first took a look at classic tonearm positioning on the turntable chassis:

But honestly, this is how I'd like to have my tonearm and turntable chassis positioned on a multi-layered plinth (used the lift mechanism of the stock tonearm just to hold the Jelco in place )

Now, I'd like to sit down and look at it for some more time and take a final decision on the positioning. I usually take my own sweet time to do this as I need to consider all options. Also I have to give some thought to sending the chassis in to fabrication and have all the stock tonearm mount holes covered up. Then would like to have the chassis power coated or painted with automobile paint. For now, I'm just going to sit down a keep looking at it, while the mind brainstorms.

On another note, this thread is going feature very slow progress as my priority is my work and career. My hobby get into whatever time I have after spending the remaining of my time with family and the kids.

 

[sachu888]

I am building my plinth same way(turning the top plate by 90 degree) to accommodate various length of arms,using different arm boards.

Regards,
Sachin

 

[anilva]

I am not trying to discourage anyone, but L75 is not in the same league of a Thorens or a Garrard high end idlers. It is a good point solution with all the right mods and upgrades done. It is not a typical motor board and an arm board combination.

Therefore, please finalize a nice tonearm and build a system of L75 around that tonearm and enjoy music. My recommendation is not to get into various arm board and tonearm combinations. The build quality of a L75 is not outstanding compared to some of the illustrious ones. \

I hope my suggestion is taken in the right spirit and not as someone who is criticizing a Lenco. I have a few of them and like them very much as well.

Cheers.

 

[shafic]

I am not trying to discourage anyone, but L75 is not in the same league of a Thorens or a Garrard high end idlers. It is a good point solution with all the right mods and upgrades done. It is not a typical motor board and an arm board combination.

Therefore, please finalize a nice tonearm and build a system of L75 around that tonearm and enjoy music. My recommendation is not to get into various arm board and tonearm combinations. The build quality of a L75 is not outstanding compared to some of the illustrious ones. \

I hope my suggestion is taken in the right spirit and not as someone who is criticizing a Lenco. I have a few of them and like them very much as well.

Cheers.

As always a straight shooter!! Your opinions are always very fair and frank. Should be taken in the right spirit the same as they are given.
regards,
shafic

 

[shafic]

Carry on Reuben!!

 

[cat's squirrel]

I believe that turning the Lenco 75/8 through 90 and having a separate (and better arm) is the way to go. However, a way of supporting the pan where the bearing is, is essential. I have done this with a Goldring 99 with u-shaped brackets to very good effect and I am about to use 8mm threaded rods on a Lenco 75. In the latter case, I am using a modded Rega250 arm and Denon DL110, with lovely music being produced.

 

[jls001]

The L75 has two weaknesses - one, the top plate which is 2 mm steel sheet is not rigid like the cast top plate of a (say) Garrard 301 or a Thorens TD 124; and second, it doesn't have a good tonearm. I personally would consider the second point a non-issue, because a G301 (or 401) came as motor unit, and one has to buy one's choice of arm. I am not sure if a 124 came with a Thorens arm, but I rarely see one paired with a Thorens arm.

The first issue is solved easily enough. Use a carefully cut multi-layered plinth so that the pan of the top plate below the platter rests firmly on the plinth below.

Having played extensively with my TD 124 Mark I and my L75, and having tweaked the hell out of the Lenco (yes, it needs lots of tweaks to come up to the level of the legendary idler drives), I would say they are equals. The Lenco has the more authoritative presentation and carries more bass weight. The 124 is the more polite of the two, but only relatively speaking, as it also has the slam of a good idler drive. But the L75 is by far the more fun turntable as one can go about tweaking and learning so much about turntables in general. In contrast, the 124 presents very less opportunity to tweak.

 

[reubensm]

I am not trying to discourage anyone, but L75 is not in the same league of a Thorens or a Garrard high end idlers. It is a good point solution with all the right mods and upgrades done. It is not a typical motor board and an arm board combination.

Therefore, please finalize a nice tonearm and build a system of L75 around that tonearm and enjoy music. My recommendation is not to get into various arm board and tonearm combinations. The build quality of a L75 is not outstanding compared to some of the illustrious ones. \

I hope my suggestion is taken in the right spirit and not as someone who is criticizing a Lenco. I have a few of them and like them very much as well.

Cheers.

I think this is a key point and the same thought process flashed passed me when I looked at the deck. Yes, that's why I've dropped the 2 tonearm approach and will use only the Jelco with the L75. Don't want to speculate at this point but the experience garnered out of this project will be leveraged for the bigger project to come. For me this one is a learning experience, more than anything else

 

[reubensm]

The L75 has two weaknesses - one, the top plate which is 2 mm steel sheet is not rigid like the cast top plate of a (say) Garrard 301 or a Thorens TD 124; and second, it doesn't have a good tonearm. I personally would consider the second point a non-issue, because a G301 (or 401) came as motor unit, and one has to buy one's choice of arm. I am not sure if a 124 came with a Thorens arm, but I rarely see one paired with a Thorens arm.

The first issue is solved easily enough. Use a carefully cut multi-layered plinth so that the pan of the top plate below the platter rests firmly on the plinth below.

Having played extensively with my TD 124 Mark I and my L75, and having tweaked the hell out of the Lenco (yes, it needs lots of tweaks to come up to the level of the legendary idler drives), I would say they are equals. The Lenco has the more authoritative presentation and carries more bass weight. The 124 is the more polite of the two, but only relatively speaking, as it also has the slam of a good idler drive. But the L75 is by far the more fun turntable as one can go about tweaking and learning so much about turntables in general. In contrast, the 124 presents very less opportunity to tweak.

Yes, that's why I'm spending valuable time on the L75 and haven't gone straight for the Garrards. The idea is to gain the experience required before I can venture out. Interestingly no one's mentioning the Technics SP10 (another league all together).

 

[Gerry_the_Merry]

The Lenco motor is an absolute monster at 19 watts. Even the Garrard 301 is only 16 watts. Th 401 is a anaemic 12 watts. The TD 124 just a piffling 10 watts. But the L75s stock tonearm and its low price gives it a down market image. but ultimately, the motor and the quality of the motor are in the same league. The motor board of the 301 etc are not anyway used standalone, at least in CLD plinth, and there is substantial damping / mass enabled by the plinth. So I feel that will narrow down the delta caused by motor board quite a bit.

But congrats Reuben on starting the journey...

 

[cat's squirrel]

.............snip.......The motor board of the 301 etc are not anyway used standalone, at least in CLD plinth, and there is substantial damping / mass enabled by the plinth. So I feel that will narrow down the delta caused by motor board quite a bit.

But congrats Reuben on starting the journey...

the term cld is a misnomer if you mean the multilayered ply variety. It is not cld, but a glulam (a contraction of 'glued laminate'). Contrary to most people's belief, a thick ply plinth has a lot of mass but very little damping, and as the thickness means a low critical frequency, the mass of the plinth has virtually no effect whatsoever.

So, if the plywood glulam plinth is changing the sound for the better, it's not down to damping or mass!

 

[Gerry_the_Merry]

Cat's squirrel ... Thanks for this... I have no experience of making CLD plinths, but I merely meant that the motor board of the lenco being lightweight may not have much bearing on which TT has great potential when put in a good plinth. Plus I think the Lenco has a slightly heavier platter.

 

[kuruvilajacob]

I have read posts which proves that a Lenco L 75 can be modified to stand against the best TTs in the world. I believe it has the potential to reach greater heights with the right plinth, tonearm etc. In India, good marine plywood is the best material we can get to make a decent plinth.Moreover, it is easier to work on and not too expensive. The improvement using other material may improve sound quality marginally IMO.

 

[jls001]

the term cld is a misnomer if you mean the multilayered ply variety. It is not cld, but a glulam (a contraction of 'glued laminate'). Contrary to most people's belief, a thick ply plinth has a lot of mass but very little damping, and as the thickness means a low critical frequency, the mass of the plinth has virtually no effect whatsoever.

So, if the plywood glulam plinth is changing the sound for the better, it's not down to damping or mass!

The term "CLD" seems to be understood differently by different people. Anyway, that is not really what I want to ask.

Can you please explain a bit more on why the large mass of "glulam" doesn't damp much? What would be the ideal damping material? Or perhaps the most ideal combination of materials?

And what is meant by critical frequency with respect to a plinth?

 

[cat's squirrel]

The term "CLD" seems to be understood differently by different people. Anyway, that is not really what I want to ask.

Can you please explain a bit more on why the large mass of "glulam" doesn't damp much? What would be the ideal damping material? Or perhaps the most ideal combination of materials?

And what is meant by critical frequency with respect to a plinth?

yep, certainly. Another misunderstanding is that mass damps. It doesn't. Although there are many different kinds of damping mechanisms, the one which we should be concerned with is that involved in turning vibrational energy into heat energy by friction. This mechanism depends on the intrinsic damping (factor) of the material/s in question, and not the mass of them. Materials with a damping factor above 0.1 are of interest, those above 0.4 are highly desirable. Needless to say that materials which have a damping factor above 0.4 are scarce, and most are not natural. There are two woods that I have found that qualify, ironwood (S. Africa and S. America) and ironbark (Australia). Other materials include resinated woods, such as Panzerholz and Permali, and bamboo, together with composites like bentonite loaded resin.

Choosing the best (or better) materials is the first decision to make when attempting to design a plinth. Look here for ideas:
http://http://audioqualia.prophpbb.com/topic29.html

I'm pretty sure you won't find the term constrained layer damping (cld) applied to multilayers of ply (or other materials) in any field other than hifi. True cld comprises three (or five layers in double sided cld) layers, the first layer is the panel to be damped, the second layer is a viscoelastic layer, and the third layer is the constraining layer, often made of the same material as the panel to be damped. The damping occurs because of shearing in the viscoelastic layer. It is only useful for panels, and so could be applied to the Lenco top plate. It has been used on loudspeaker enclosure walls.

Hope that helps.

 

[cat's squirrel]

The term "CLD" seems to be understood differently by different people. Anyway, that is not really what I want to ask.

Can you please explain a bit more on why the large mass of "glulam" doesn't damp much? What would be the ideal damping material? Or perhaps the most ideal combination of materials?

And what is meant by critical frequency with respect to a plinth?

cld (constrained layer damping) is a term that is misapplied to plinths in hifi. Please Google cld to understand the proper definition of this term.

Mass does not damp. Damping in this context means the exponential reduction in amplitude of vibrations (or oscillations) in a periodic system, over time. The damping of a material is described by its intrinsic damping factor, the higher the number, the better. see here for values: http://audioqualia.prophpbb.com/topic29.html

The critical frequency is that which divides the frequency region controlled by mass and that controlled by damping, although damping controls the amplitudes of all vibrations, especially resonances.

The critical frequency is dependent on the thickness of the panel (plinth), the thicker the panel, the lower the critical frequency. With plywood, for example, a 1mm thick panel has a critical frequency around 16 kHz, but a 100mm thick panel would be near to 160 Hz, and if the resonance frequency was anywhere near this, the region controlled by mass would be very small indeed. Also, above the critical frequency the panel starts to radiate vibrations. So in our example, a 100mm thick plywood glulam (typical of plinths) would not only have very little damping (damping factor for Russian/Baltic ply is 0.04), but it would be heard radiating sound above about 160 Hz!

Please believe me, plinth making is not about thinking up a design because it seems a good idea, or looks good, but involves understanding. With the Lenco 75/6/8 and GL88 and G99 type of turntables, because of the thin top plate, the bearing and motor posts must be supported, so that they do not vibrate. If the tone arm is mounted on the top plate, steps must be taken to ensure vibrations do not journey up the arm base, and into the pickup cartridge.

Hope that helps.

 

[Gerry_the_Merry]

Cat's Squirrel - a few questions -

1) Since you mention that the damping happens through the ability of the material to damp the oscillation amplitude exponentially, where is the shearing of the middle layer coming in?

2) Would not the shearing depending on the glue also, and not only the material? Art Dudley seems to make a fuss around Hide Glue.

3) I have almost entirely forgotten engineering physics, but I vaguely remember 0.5mv2 (v squared) as the formula for kinetic energy, so the v for a given kinetic energy must depend on mass also. Since the time period of movement is fixed, and higher m must result in lower v, it must also result in lower absolute distance moved.

Would love to know where i am going wrong.

 

[cat's squirrel]

Cat's Squirrel - a few questions -

1) Since you mention that the damping happens through the ability of the material to damp the oscillation amplitude exponentially, where is the shearing of the middle layer coming in?

firstly, I was trying to define damping in context, as exponential loss of amplitude of vibrations, over time. Many think of mass as having damping ability, whereas in fact it attenuates, rather than damps, ie, it does not decay.

2) Would not the shearing depending on the glue also, and not only the material? Art Dudley seems to make a fuss around Hide Glue.

The layer to which you are referring has to be viscoelastic in nature, think jelly/jello, although in reality, a viscoelastic glue is used, which never sets hard. If hide glue sets hard, then a plinth made of layers of wood and hide glue cannot be cld, but a glulam.

With regard to kinetic energy, yes, you are correct, but all that says is that, regardless of mass, the energy remains the same in the system. The same result is obtained with Newton's second law of motion, Force=mass x acceleration. The force in our case is the vibration input, the acceleration the vibration amplitudes. Double the mass and the acceleration (and therefore displacement) is halved, but the energy remains the same. And can only be dispersed by damping!

Hope that helps

3) I have almost entirely forgotten engineering physics, but I vaguely remember 0.5mv2 (v squared) as the formula for kinetic energy, so the v for a given kinetic energy must depend on mass also. Since the time period of movement is fixed, and higher m must result in lower v, it must also result in lower absolute distance moved.

Would love to know where i am going wrong.

mass will attenuate vibrations at 6dB/octave with increasing frequency, but only between the fundamental resonance frequency and the critical frequency. As the usual way of increasing mass is to make the plinth thicker, and as thickness is increased, critical frequency is decreased and fundamental frequency is increased, the region where mass would be of benefit is made very small indeed. Call it catch 22 if you like! Some people add lead as added mass, and this is OK, but fall into the trap of stating that lead is good at damping, which it isn't, although probably the best of common metals.

 

[reubensm]

After RP's and Shafic's knighthood, I can't hold back the excitement and have both some good news and bad news for you all.

First to the bad news: My Lenco Master turntable build is put on hold indefinitely. Not sure when I will resume work on it, maybe after a couple of months or a bit longer.

Now to the exciting news: YES!!! YES!!! YES!!! (as Daniel Brian would say), I too have been knighted. Sir Garrard 401 is also making his way to my home. The deck is sitting happily at my friend's place in London and will be hand-carried down, next month. It is from an audiophile, who had it for many many years (from new). Here are all the pictures that my friend sent me after receiving the deck (wanted to hold back disclosure till the deck arrived, however, its raining Garrard 401s on our forum, so why not get a bit wet in the rain). Here are the pics:

A very special THANK YOU, to Sir RP for his honest and intricate guidance, without which, this adventure and achievement would not have been possible.

 

[Record Player]

After RP's and Shafic's knighthood, I can't hold back the excitement and have both some good news and bad news for you all.

First to the bad news: My Lenco Master turntable build is put on hold indefinitely. Not sure when I will resume work on it, maybe after a couple of months or a bit longer.

Now to the exciting news: YES!!! YES!!! YES!!! (as Daniel Brian would say), I too have been knighted. Sir Garrard 401 is also making his way to my home. The deck is sitting happily at my friend's place in London and will be hand-carried down, next month. It is from an audiophile, who had it for many many years (from new). Here are all the pictures that my friend sent me after receiving the deck (wanted to hold back disclosure till the deck arrived, however, its raining Garrard 401s on our forum, so why not get a bit wet in the rain). Here are the pics:

A very special THANK YOU, to Sir RP for his honest and intricate guidance, without which, this adventure and achievement would not have been possible.

It was about time!

My hearty congratulations to you Sir Reuben. A very fine acquisition indeed. Motor looks in top notch condition and I am sure we will all love this British legend. This also makes the build up project so collaborative now.

Wait, I see something unique. Not sure if you noticed this, but this piece is an early 401 which has the Flat Strobe which is said to be quite rare.

I am delighted that I could be of some help to you. Your help to me from the very beginning has been invaluable.

Cheers to you from all us. We both have our builds to come so let's get to it...