Lenco L75 Replinth

Goodness, 8 months since my last blog. The Google servers must have thought I'd given up. Life just gets in the way sometimes. And even this isn't a blog about something I've done, it's about a rather special plinth that Anthony Cresswell made for my Lenco L75. And here it is, playing REM's New Adventures in Hi Fi, rather appropriate but completely unintentional.

I've had a Goldring Lenco for a few years waiting for the right moment to be redeveloped. I'd been leaning towards a solid replacement plinth, either slate or constrained layer damped with various timber sheet materials, which would do away with the slightly tinny top plate. Something along the lines of Pieter's Top Plate looks to have some merit in its approach to me.

So I was starting to do a little more detailed research about the Lenco itself and how it would need taking apart, chopping down and rebuilding when Ant posted on the Audio Talk forum that he'd just done something very similar. Given my somewhat glacial timescale for audio projects commissioning Ant seemed a pragmatic choice. Besides, he knows what he's doing and I knew he'd make a much better job than I would...

The Lenco is an idler drive turntable - it doesn't use a soft belt around the rim of the platter, and doesn't drive the spindle directly. It's a mechanically sophisticated method of spinning the platter, but can be affected by poor setup, just like any turntable.

Unlike Garrards, like a 301 or 401, which drive the inside of the platter rim with a horizontal idler wheel, the Lenco uses a vertical idler wheel which drives the underside of the platter top. Idler drive proponents will discuss at length pros and cons of different drive systems, the quality of the motors, and even whether a grease bearing 301 is better than one with an oil bearing. I'll leave that discussion to others with more time and inclination, but those that have taken these things apart are impressed with the build quality - they're Swiss and the build quality shows.

Here are a series of photos that Ant took during the build, for which I'm very grateful. The first is when Ant had initially stripped the deck down. It's nearly as old as I am and cosmetically in excellent shape, much better than me. In a way it was a shame it was going under the angle grinder, but some things have to be done.

No going back now...

I think this is something akin to the PTP mod mentioned earlier (with apologies to Pieter if it isn't!)

And now with the idler wheel, spindle and linkages refitted.

Next job was the plinth with lots of routing of a sandwich of a number of layers of mdf and plywood. The theory of constrained layer damping (CLD) is that a different layer of material is used between others materials to damp vibration that the outer materials can't. Rubber is often used, but as we know, audio is a mysterious beast with many different ways to succeed.

Here we can see the differing cutouts in each layer - just enough is removed to house the mechanism, this way the mass is maintained.

Those with a keen eye that know their Lencos will have noted that Ant has been rather clever in the way he's mounted the mechanics. One of the biggest drawbacks with the L75 for me is that the on/off lever is located virtually under the cartridge. I can't imagine how many styluses have been destroyed by unfortunate accident over the years. So Ant reoriented the mechanism with the on/off lever at the back - this is a compromise as it doesn't want to be too close to the arm collar either. This puts the variable speed lever at the front, and the idler wheel at the opposite side of the platter from the arm, which is probably a good thing.

And here it is with my old Linn Ekos mounted. I'd wanted to try an Audiomods arm but Ant suggested trying the Ekos - it has a very slightly different effective length than the Rega-derived Audiomods so will need an arm board should I change in the future, but using the Ekos was a "zero cost option", additional cost anyway, as it was sat on a shelf unused. And for that matter I had a Kontrapunkt b with low hours also sat in a box, so why not use that too.

Next job was sanding. Lots and lots of sanding, after the plinth was cut roughly to shape.

Next was paint time, starting with the underside.

Just 5 coats of black on the rim. It does look good I have to say.

It turns out the mechanics weren't quite as good as thought. Somehow it had seized "on" - even though the platter wasn't turning the motor was turning. Must have been like this for some time before I obtained it. Previously I'd only listened to about a side of one record - I'd lashed up an old Linn K18 just to try it and was surprised by just how "together" it sounded. Enough to know a full rebuild was worthwhile ;-). So at least I didn't make it any worse. So Ant stripped it down, which saved me a job.

Note the pit the spindle has worn in the bottom plate. Ant simply turned the plate over. Testament to the Swiss build quality really.

Back to the plinth, and it was veneer time - a simple English oak. It's difficult to see but Ant managed to salvage the original Lenco sticker for provenance - it's located on the left hand side of the remaining part of the platter.

And here it is with a couple of coats of danish oil (I think)

And finally at home with the the Kontra b fitted, this time playing the Living Stereo release of Reiner's Chicago Philharmonic performance of Pictures at an Exhibition.

I must say I'm very pleased with how it's turned out. I'm always a little reluctant to wax lyrical as one day I'll probably look back and think I was talking rubbish, and well, we've all read those oh-so fawning reviews that mean nothing.

But Ant's done a terrific job, much better than I would. It strikes an excellent compromise - it has the drive of an idler (obviously), and the effortlessness of a good direct drive. Compared to my 401 in twin deck slate plinth with 12" ebony Schroeder-a-like arm and Denon 103pro cartridge this has the edge. The bass is firm and controlled, and better balanced than the 401 I think, which tends to tank-on. Coupled with the fluid mid that reminds me of direct drive this is an excellent turntable.

One day I should try an alternative arm and cartridge as I've never been a huge fan of the Kontra b - at least the 103pro should get a run out. That might squeeze a little more musicality out, but for now I'm very happy with it as it is.

I should add that I have no connection with Ant other than as an audio friend through Audio Talk. We live about half an hour away which makes it easier too. But I have no financial interest. With that said, make no mistake - in the crazy world of audio, if you were to find yourself a half decent Lenco (cosmetics aren't important) and get Ant to build you a plinth you'd have a killer turntable for pretty cheap. Ant has a website where you can read his own thoughts. Cheers Ant.

Alpair 12P MLTLs - Part 5

Day 5 - 5 hours

As is customary let's start with temperature-watch - much cooler today, 6 degrees.

The first job was to finish off the holes for the pseudo tweeter and port for the second baffle. And then rout the holes for the Lpad and speaker terminal in the rear panels. Here's the front baffles with the finished holes.

With all the holes complete the next job was to rout 45 degrees chamfers around the holes for the 12Ps on the rear of the front baffles. This allows the driver cones to "breathe" as the front baffles are quite thick.

Then it was time for a trial fit to make sure the 12Ps and Monacor RBT-95SQ pseudo ribbons fit okay. First a sand with 70 grit to clean things up a touch before mounting the drivers. Only one of the pseudo ribbons was tried as they needed unsoldering from the Quasars as well as unscrewing.

And then it was back to sanding. All surfaces are now sanded to 120 grit both inside and out, I'll finish with 240 grit when assembled. I did test a patch that will eventually be inside with the finer grit and finish was lovely and smooth.

It's taken a while but the speakers are starting to come together now.

Alpair 12P MLTLs - Part 4

Day 4 - 4 hours

Goodness, it's over 7 months since my last blog, and over 10 months since I last had chance to play with the speakers. It's fair to say audio has been on a back burner for much of this year, but today I made a little progress with the MLTL speakers :-). But first let's have a look at temperature-watch.

Parts of the country are experiencing terrible flooding, no doubt made worse by the unseasonably mild weather which is probably retaining a lot of moisture. 12 degrees C, mild for the end of December.

So first job was to have a quick tidy, then remember where I'd got to. I'd made a start on routing the first hole for the 12P at the end of the last session, but I was rushing and hadn't noticed that the template had slipped slightly and was no longer centred. Fortunately I noticed in time before serious damage was done. So I marked out the circles with a compass to be sure, then carefully reset the template and clamped well.

More haste less speed. Lesson learnt - measure twice cut once.

The first hole needed three phases. The first was to rout the inner hole for the driver to pass through, 170mm diameter. The plunge cutter only reaches part of the way through the baffle though, so needs cutting from the other side too - the third phase.

The second phase is to rebate the driver, 203mm diameter and 11mm deep. This was a bit of a laborious process as there was a lot of wood to cut away. Here's the finished hole. Note the misalignment from cutting from the front and then the back. This was largely due to the initial cut that had slipped. It shouldn't be a problem though, as long as the driver passes through and the driver makes an air tight seal.

Next was the hole for the Monacor pseudo ribbon I'm going to use to fill the treble out over 12k Hz. I started to cut away the all the wood so the unit sits within a cavity...

...but then decided that I was probably going over the top so then cut full depth before turning over and finishing the cut. Ideally I guess I would have preferred to isolate the driver from the main chamber and the air pressures within, but hopefully it shouldn't make too much difference. I might even add a plate to the back just to seal it.

And here's the two holes viewed from the rear.

Next the 3" port, which requires a 79mm diameter hole. This is perhaps just a little slack, but probably better than being too tight and struggling to insert the port. I can always use a bit of glue or silicon to secure them.

From the rear

And here's the first baffle with the initial holes made. It needs a good clean up and a rear 45 degrees chamfer cutting on the rear of the hole for the 12P. And a check to make sure everything fits of course.

For the second baffle I fully marked out all three holes both front and back first, now I had a little more confidence with what I was doing.

And started with the largest hole for the 12P. Here's the first 170mm diameter hole cut and the start of the wider 203mm rebate.

The finished hole from the rear.

And from the front.

And that was the end of the today's audio fun.