audio-talk

[SteveTheShadow]

I'm about to start rebuilding a Lenco GL78 and am writing up the rebuild here.

After a lot of thinking about CLD plinths, I suddenly hit upon a brilliant idea The main mass damping in my plinth is to be made up of electric storage heater bricks. These are 6" X 6" X 2", are colossally heavy and I have loads of them after taking out our electric heating.

Watch this space.

Steve

[SteveTheShadow]

Right

I've just weighed a brick on the bathroom scales and it tipped them at 7.5Kg. To make a TT plinth with enough room for a 12" arm will take 5, which makes 37.5Kg without the deck itself or the chipboard/MDF sandwich top and bottom plates.

This is going to be a two man lift job when it's finished at around 40Kg (88lbs) A wall shelf is completely out of the question.

Do we reckon I have enough mass there?

here's the scientific description of a storage heater brick:

Heat storage medium is produced by heating a mix of ferric oxide and an additive comprising a calcium compound to a temperature at which the additive reacts with the ferric oxide to improve its volumetric heat capacity, reducing the reaction product to particulate form, compacting the resulting particles, and sintering the compact.

They ought to be virtually the same weight as the equivalent cast iron brick judging by the stuff they are made from.

Steve

[Neal]

Why not just cast a cement 'tower' in the corner of you room and set the '78 into it while its still wet...should give you plenty of mass

[simon]

Steve,

I don't know anything about these bricks but it would be worth checking if asbestos was ever used in them - it can be difficult to track this down for sure though. The manufacturers have a duty to tell you if they did.

Just a thought from someone who lives their life paralysed by risk assessment and risk mitigation.

[SteveTheShadow]

[SteveTheShadow]

[simon]

Here I go again . Asbestos was used right up until the late 90s, much later than many think, not that I'm saying it's in your blocks Steve. That said, if asbestos is cementitiously bound and the surface is sound and not wearing then it's pretty safe. Which is why you don't have to be a licensed asbestos remover to take down asbestos sheets, provided they don't start breaking it up...

[SteveTheShadow]

Hi Simon
There is definitely no asbestos in my blocks. The Unidare WM range of heaters which is what I had can be found towards the bottom of this schedule http://www.aic.org.uk/Storageheaters.htm and are certified free of nasties. They came with a certificate of asbestos "freeness" from the YEB, who originally installed them but I've long since lost the paperwork.

Steve

[SteveTheShadow]

OK

I've got something working with the Lenco.
Before playing about with mass damping and giving myself a hernia, I thought I'd better make a test plinth to see what all the fuss is about regarding idler driven record players.

Hunting around for some materials that could be pressed into service, I came across some 1 1/2" laminated kitchen worktop in the cellar. This was reasonably heavy high density chipboard with a coarse-grained core so I figured it would work nicely to absorb vibrations.

First job after cleaning up the deck and polishing the top plate with Auto Glym car polish was to hack off the left hand corner. This would leave room to fit the Origin Live RB251.



In order for the Rega's armrest projection to clear the top plate, it had to be marked with an angled cut going to the edge.





Here it is all mercilessly hacked about.


After the top plate surgery, the worktop was cut out with a slightly modified template so as to allow for the angled cut on the deck top plate, otherwise there would have been nowhere to fix the arm.

With the deck firmly fixed to the chipboard plinth and a set of black tubular legs fitted, the RB251 arm was put in place. Because of the length of the arm I had to fit it at an angle to prevent the fingerlift fouling the on/off switch.



A couple of bits of pine strip to hide the chipboard edges and we are in business.

Steve

[al newall]

A very neat solution Steve, and probably what i should have done.
I can see myself ending up with a Rega arm or similar, if i decide to continue with vinyl.

The thing i 've made (although it works), does move around quite a lot when i'm trying to set it up. Doesn't inspire much confidence really.

[SteveTheShadow]

Hi Al

The work top solution seems to work very well indeed with this deck and the partnership with the Rega arm is very good.

I'm sure that the sound of the deck could be improved with mass damping but it sounds great as it is. I can't hear any of the rumble that idler decks are supposed to produce and I'm using two 12" bass drivers. There's no motor noise reaching the stylus either, none that I can hear at any rate

Interestingly, with the Rega arm mounted to the plinth, there is a lot less needle talk coming from the Stanton cartridge than there was on the Thorens, so the plinth must be working nicely to sink the vibes.

With the deck placed on my Ikea cabinet directly on its feet, there was some midband coloration coming up into the plinth through the support, but placing each leg in a felt bottomed castor cup (£1 per set from Poundland) got shut of that nicely.

The plinth itself is based loosely around jonathan Noble's Garrard 401 plinth, here [url]www.theanalogdept.com/diy'ing_a_time_machine.htm[/url]
I don't know what's up but I just can't get the above link to parse properly but it'll work if you paste it into your browser address bar

I've no doubt that it works well but there's one thing I've always wondered with mass damping, is that if it is supposed to sink the energy from the motor and in effect silence it at the stylus tip, then why can I, in a very quiet room, hear my neighbour's conversation from the other side of a ten ton, two brick thick party wall? Surely there is far less energy being put into the wall by a voice than any turntable motor would put into it. Therefore a pure mass alone has little damping.

Slate plinths can't be energy sinks, there must be something else going on to cause the fab sound they give to an idler deck.

Steve

[Mike H]

[SteveTheShadow]

Well
I've been playing records all day and am still going (listening to "The Best of the Doobie Bros-Vol 2" at the moment. After that it will be "Carly Simon - No secrets")
Considering how vinyl has pissed me off so much since 1972,
when my Dad ditched the family radiogram, this is nothing short of a miracle:lol:

Hell I'm even thinking about buying some new records

That a long forgotten idler drive motor unit from the early 70s, bolted
to a bit of kitchen worktop could do this to me is interesting to say the least.

Crazy man.

Steve

[simon]

Hi Steve,

I haven't played with my GL75 much but I thought it had a lovely sweet sound. Another project for another time .

Don't know about your 78 but my 401 is very sensitive indeed to how it's supported. I'm not sure about the merits of high mass TBH. I think it's probably a good thing, but I suspect it has to be done right otherwise it'll store energy, and I think the best thing to do is to get the energy out of the plinth. I wonder if this is why slate works well as the plinths are relatively light but the spiking gets the energy out of the plinth.

But vinyl has the potential of many complex interactions so that many things can happen - which why I say you've got to love vinyl to want to play with it .

Enjoy the ride .

[Lee S]

RE the link Steve - have you tried preceding the actual link with http:// ? It seems to be missing from within your URL tags. Just a thought.

Cheers,