Lenco #2, plinth comparisons, plans etc.

[helma]

Btw. I did some recordings to see the effect of idler arm damping - I previously already had put a pass of electrical tape around the arm, so I added some bits of blu-tack and another round of electrical tape and rumble was further reduced from 1 to 3 dBs - the initial damping had a similar effect, so it does pay off to damp the idler arm (I've seen this one debated). If you have already replinthed and gone over the deck, I don't think damping the idler arm would make for a very obvious improvement since the noise floor should be sufficiently low already, but all the little noises do add up.

I've done some more listening and this skeletal thing seems to work OK, and the way it is now it's already better than the modified stock plinth (but I didn't bolt the deck through the bottom plate for that one). I think I'll move on though, mainly because I'm not sure how to tweak this plinth further without making it uglier (most thing I could do would be very visible) and since I'm not a big fan of the looks to begin with, I'll be happier with something that pleases the eye more.

[helma]

A photo for good measure, probably the last anyone is gonna see the deck in this configuration The placement is very temporary, but desktop speakers were used for listening so acoustic feedback (or feedback through the floor) was not an issue.

I have to say that while it's been interesting and some of my curiosity has been satisfied, I'm also starting to wonder if there really wasn't anything better for me to do today than fool around with this thing. Yet, there's still some hours of daylight left and I could work on the plinth... ugh

boltlenco2.jpg

[Wakefield Turntables]

Now the whole thing is stuck together with the 4 threaded rods, M4 rod is quite flexible so it's not a super rigid assembly, though adding tension upward tension from the large bolts helps with that.

Doing some low volume listening and a couple measurements while at it, fiddling with the pan support bolts. There's a definite if somewhat subtle (at least at these volumes I'm currently using) change with / without the bolts. Not sure which I prefer, with added pan support the sound seems to tighten up somewhat, but I also sense there might be a certain harshness somewhere in the midrange perhaps - definitely need more listening. Without the pan supports the sound loosens up some, overall the sound is a bit more relaxed, but not in a bad or imprecise way - more like there's just a better natural and flowing quality to it. But for now I'd be inclined to say the pan supports add "fake precision" ie. colorations in the mid-range (and upper bass perhaps) which initially might make it sound more "tight" but doesn't hold water in longer listening. But that's my initial impression... I need more listening, but am also feeling impatient and might move forward before I get a chance to do that

I tried the pan supports with and without rubber cushions between the bolt and top plate and there wasn't much difference to be honest. Measuring it seems without pan support is better (at least the way I'm doing it atm). This is interesting, because screwing / bolting down the pan seems to be the "standard" among tweakers, but so far my ears tell me to let the pan do it's thing without additional support. To be fair the way I'm doing it now is not exactly same as bolting it down. Though I recall talking in person to one Lenco enthusiast who has done many builds, and his opinion was supporting the pan kills the sound. We'll see.

I'm inclined to probably ditch this skeletal thing altogether, glue the two boards together and fill the insides with something viscoelastic, leaning towards the acrylic mass I have used in many other TTs for damping because I'm familiar with it and it seems to do a pretty good job. Unless extended listening convinces me otherwise, but this far nothing suggest this arrangement is better than the plinth of my #1 Lenco which is my reference for now. That arrangement would still make it possible to experiment between bolting/screwing down the pan and not.

Perhaps you dont need to bolt the pan down onto your plinth maybe a layer of dampening material or something like EVA (2-3mm) between the pan the plinth (complete surface area) might be more beneficial. I'm planning another plinth design for the latest incarnantion of My Reference Lenco and this is something I'm looking in to.

Btw. I did some recordings to see the effect of idler arm damping - I previously already had put a pass of electrical tape around the arm, so I added some bits of blu-tack and another round of electrical tape and rumble was further reduced from 1 to 3 dBs - the initial damping had a similar effect, so it does pay off to damp the idler arm (I've seen this one debated). If you have already replinthed and gone over the deck, I don't think damping the idler arm would make for a very obvious improvement since the noise floor should be sufficiently low already, but all the little noises do add up.

I've done some more listening and this skeletal thing seems to work OK, and the way it is now it's already better than the modified stock plinth (but I didn't bolt the deck through the bottom plate for that one). I think I'll move on though, mainly because I'm not sure how to tweak this plinth further without making it uglier (most thing I could do would be very visible) and since I'm not a big fan of the looks to begin with, I'll be happier with something that pleases the eye more.

This is another area that I discounted as a possible modification but your mods seem to suggest that it's beneficial. Again something I could try on the new build.

Many thanks for the discussion thread so far, Its been an interesting read so far and a welcome distraction from my own Lenco ramblings.

[helma]

Well, the deck went through a test drive with the two boards simply bolted together with the mounting threads and at least like that it was nowhere as good as the double decker. Had to do a cutout for motor and tonearm on the bottom board of course, so a little less mass (and the bolts I used in the double decker weighed about half a kilo in total as well). Out of necessity feet were also a bit different. Bit too much variables for my liking Now the boards are glued together with little bits of wood as support in the cavity area, and 620ml of acrylic mass was used to fill empty cavities. Ran out of the acrylic, it could take another 310ml tube easily. I will give the glue at least some hours to dry under pressure, but I guess later tonight I could do a test drive and see where I'm at.

It would've been interesting experiment to try to find out resonant frequencies for the boards, I guess miking them up for recording and doing some knuckle raps might have done the trick, maybe. I'm starting to come to a conclusion trying to make an effective relatively low mass plinth like this is probably more trial and error than most people are willing to suffer. It's just everything affects everything, but I also think with some clever engineering and better understanding of all the theory involved, it would be possible to make a relatively lightweight plinth which in many ways would out perform a heavy affair. But then again going for the mass is a tried path with good results and anyone can glue pieces of plywood together So it's starting to look like it might end up so I'll just keep throwing more mass at this thing until I'm satisfied with the results

How you mount the deck to the plinth has an effect, whether you support the pan or not has an effect, how you support the pan has an effect, what you use for feet have an effect, and probably some other things that haven't yet even crossed my mind have an effect on what happens with the energy. And those are only variables that don't even take into account anything about plinth construction, materials, shape, mass etc. etc.

Still, a lot has been learnt already but I'm also starting to get fed up with the experimenting, time to choose a direction and follow it through. I know it won't be a bad sounding TT but it might not be anything like what an optimised Lenco/plinth combination is capable of. Yeah, I'm getting just a tad impatient and perhaps a bit frustrated as well Probably the thing to do would be to let this thing sit in bits until I feel like more trial and error, but that's something I have trouble doing, when I start something I need to see it through. I guess I'd rather just finish this and perhaps someday I will cross paths with another Lenco and do another build with more knowledge going in.

[helma]

Lowered motor voltage from 240V to 220V (which is what it was designed to run), some reduction in vibration that translated into a dB or two of less measurable rumble. I've played with voltages before, as I recall going lower than 200V started to increase vibration again and loss of torque became very obvious. Going from memory anything from about 205 upwards is fine. I wouldn't fuss about the voltage, 240V is good, 220 maybe slightly better overall. But I realized I have a spare 220 -> 110 step-down transformer, so I'm gonna try the motor wired for 110V because the word on the street seems to be this lowers vibration by quite a lot because the coils are wired in parallel instead of series. I'll just need to find a US mains plug or travel adapter somewhere...

[Wakefield Turntables]

Lowered motor voltage from 240V to 220V (which is what it was designed to run), some reduction in vibration that translated into a dB or two of less measurable rumble. I've played with voltages before, as I recall going lower than 200V started to increase vibration again and loss of torque became very obvious. Going from memory anything from about 205 upwards is fine. I wouldn't fuss about the voltage, 240V is good, 220 maybe slightly better overall. But I realized I have a spare 220 -> 110 step-down transformer, so I'm gonna try the motor wired for 110V because the word on the street seems to be this lowers vibration by quite a lot because the coils are wired in parallel instead of series. I'll just need to find a US mains plug or travel adapter somewhere...

Your findings seem to mirror my own. I've messed around with lower voltages and came to the conclusion 220V was best for my ears. I've also been planning the 110V motor rewire but just havent had time so I'm really looking forward to seeing how this turns out.

[helma]

I've got a 45W rated transformer sitting unused and a cheap travel adaptor should arrive here sometime next week. The rewire for 110V is as easy as loosening a couple screws and moving two wires around.

I managed to squeeze 3 more tubes of the acryl stuff inside the middle layer of the plinth, also added some support pieces of wood so the top layer can't flex. It was an improvement of about 2-3dB but at least in terms of measurements my new plinth still falls a bit short of the first one in terms of noise from the deck. It probably just doesn't have enough mass to be as effective in making motor vibrations "disappear" as the bigger plinth. Based on my experiments with this one, I really lucked out with the first plinth with some of the design choices I made by just winging it and going by gut feel. This new Lenco is gonna be one sleek looking mofo though I really like the proportions of a thin plinth with the deck positioned just right. Haven't yet done much real listening which will be the final judge of course.

I also experimented with supporting the pan again, this time around I actually managed to make it measure as good and even slightly better than without the supports, but I'm still not convinced by the sound. On a quick listen it sounds to me like bass is perhaps a bit more taut and controlled, but somewhere higher up things sound a bit 'strained'. I've yet to reach a conclusion if this is just a more accurate and drier presentation (and perhaps highlighting a setup issue like VTA or something) or somekind of resonance. Will need more listening and I think I'll try adding even more support to see what direction that takes things. I have to say I'm a bit disappointed because I secretly hoped for supporting the pan to be some kind of magic bullet since it seems such an universally accepted improvement. It was something I hadn't tried because the plinth of my first Lenco would make experiments difficult - the cutouts were originally for a Connoisseur BD-2 and I just enlargened them at appropriate places and stuffed the empty places with all sorts of "stuff", mainly the aforementioned acryl mass and some rubbercork mat for 'coating', not really leaving any surfaces that would work easily for pan support.

It seems to me for minimal amount of mass a double decker configuration is very effective and yields better results more easily, not sure why but some sort of magic damping must be going on

I also bought a can of Maston "Rubber Comp" which is a rubber coating spray, I guess similar to something called PlastiDip which seems to be popular in some parts of the world. The can suggests 4 layers 15 minutes between each layer and the final coating should be easy to peel of if you desire to get rid of it. I plan to try it on the platter at least and see if it makes a difference for better or worse. Should be easily reversible if the stuff works as advertised...

[helma]

Well I tried the rubber spray on the platter, only two coats though because I didn't want to over do it and well, it had next to no effect on ringing of the platter. Interesting looking finish though. I opened up the main bearing finally, was going to check / change the thrust plate, but it seemed previous owner had already been there, changed the thrust plate to a metal one and sealed the bottom plastic plug so tight with something I couldn't even get it off Since the bearing always was very silent and felt good in use, I just changed the oil. The bearing is definitely better than on my first Lenco, everything looks and feels very smooth and tight. I used some pretty light oil which seems pretty much identical in viscosity and color as the one that was there previously and platter takes over 5 minutes to spin to a halt from 33rpm. Seeing this example certainly made me think higher of the stock bearing. It is sort of small diameter and skimpy for such a heavy platter, but machining tolerances on this one at least seem as tight as any vintage TT I've come upon, as far as you can judge by feel and eyeballing (which might not be very far...)

Run into some trouble with finished the plinth, I was putting too much faith on the wood filler I'm using to get the front cavity even with the bottom and top layers, so it has kept collapsing and I've had to add more and more of it... I think I'm on my 4th fill now, but it looks like this one might finally do it. I could always craft a piece of veneer or something for the front, let's see how this turns out. I have to admit I'm not big on fine details and don't mind some DIY look and feel on my turntables as long as the basics of the aestethics are right. Fine for me, but if I ever decide to sell either of my Lencos (don't think I will though) it'll probably come bite me because on both all the fine detail on finishing, top plate paint etc. are really half-assed to put it bluntly. Oh well

Can't wait to get the plinth to a stage where I can put everything back together again, wanna see how it all looks now and get spinning some tunes.

[helma]

Life got in the way and I had to take a week off from the Lenco Got back to it yesterday, I've had some trouble with the woodworking and finishing side of things, part of it because of not taking enough time to do things properly, part of it because of somewhat loose tolerances and sloppy construction of the Ikea chopping boards and mostly because of doing all the tests and trying different things meant it just wasn't possible to know what exactly I was going to do when starting out. Got that sorted now except for final touches to make it look right.

I rewired the motor for 110V, can't say anything completely conclusive about it because between running the deck at 220V and rewiring it I also filled the old tonearm hole in the top plate and that is bound to have some slight effect on vibration damping characteristics I believe. However it does seem it vibrates a bit less and in terms of measurable rumble it's maybe another dB or two down, except for the peak I get at 23Hz which went down by a whopping 8dB or so. But this is something that is also greatly affected by all sorts of things like how tightly the top plate is bolted down to the plinth, how the pan is supported or not etc. so some of it might be just that the bolts and screws I have holding the thing to the plinth are fastened with somewhat different torque than before. Still, it seems like a worthy tweak but I wouldn't deem it a really necessary one - it's probably about similar in effect to dropping the voltage from ̃240V to 220V or so - now I'm running the motor with some series resistors at about 107V which is better than the 115V or so I get from the step down alone.

In putting things back together I ran into a weird issue with bearing and it seems I have to find a way to take that very tightly sealed (by previous owner) bottom plug off after all, it might be I have to just break it and use something else as a cap or seal the bottom with some candlewax or something. Like I mentioned in my previous post after cleaning and reoiling the bearing the spin down time was something like 5½ minutes - but now it's only 30 seconds! I cleaned and oiled it again but no change, even removed the side screw just in case, have made sure the platter doesn't rub into anything on the top plate but to no avail. The puzzling thing is spinning the bearing without platter it feels very smooth and free, so my suspicion is something is happening at the thrust pad / ball bearing interface under load. It doesn't make any noise and is still very silent in use, but this needs to be investigated and sorted out because running the bearing like this can't be good. From 5½ minutes to ½ a minute just isn't right. I have a spare POM thrust pad identical to the one I've been using in the other Lenco with good success. I guess the oil I used could be another suspect, but I've used the very same oil in about every turntable bearing I've ever had and never had a problem before. In the other Lenco I'm using 5W/30 syntetic motor oil though, mainly because that bearing is just a tad looser than some other and for it the motor oil seemed a good choice because it's a bit thicker than the very runny stuff I've used in most bearings.

[helma]

Well that was pretty fast in the end, some big pliers did the trick for removing the bottom cap. Still no clue what was wrong and the trust pad seemed fine - maybe it just wasn't somehow properly seated or something, in any case I added the POM plate on top of the existing metal one (which was in some fashion glued to the bottom support cap) and we're back to healthy spin down times, 2-3 minutes, which seems about right for these POM plates. The metal plate looked quite nice, I wonder where it was sourced from and when all was just right the bearing was crazy free running, so I might revisit this at some later date.