Garrard 401 plinth project

[Greg.]

I've started work on my 401. Initially I'm using an experimental plinth made out of recovered 45mm thick Mahogany laboratory bench top. Thinking about the sinking of vibration, do you other 401 users fit rubber washers (I would imagine tap washers would do) between the plinth and chassis as per the original mounting instructions, or do you leave them out and screw the chassis rigedly to the plinth? If anyone has actually experimented on this point, I'd be interested in the conclusions reached. Thank-you.

Best wishes,

Greg

[John T]

Hi Greg,

Here's the 401 Manual. Have a look at page 11, that is how I fitted mine.

http://www.arrakis.es/~igapop/Garrard.htm

Hope this helps.

Regards,

John.

[Greg.]

Hi John,

Thank-you. I do actually have the original manual. My question is prompted because it appears the original Garrard recommended method of mounting the chassis into light-weight box plinth or onto a cabinet panel is now considered flawed and much of the renewed interest in the 401 and the Lenco's is because the benefit of high mass plinths or the decoupled Johnothan Noble type is now recognised. It seems to me that if these designs are proving to be successful, this is much to do with the sinking of unwanted energy coming from the deck. Therefore using the original mounting method with rubber washers could influence the sinking of this energy and it might be more appropriate to screw the deck hard down to the plinth. I'm hoping someone has experimented with this and would like to share their findings.

Best wishes,

Greg

[John T]

Hi Greg,

I remember asking a Garrard rep. the best way to mount the 401. He said it must be mounted in a heavy base in order to soak energy to earth. He said they'd just installed some for the BBC in a basement studio in order to enable concrete bases to be built!

In the instructions I attached, you'll see that mounting on at least a 13mm baseboard or a "substantial metal plate" is recommended. I should think your manual is a very early one that was soon superseded

Regards,

John.

PS. I was advised to "tighten the mounting nuts until they break and then loosen them off a bit!" I have tried all ways and found the "dead tight" method the best.

[Greg.]

Hi John,

Yes, that's exactly what my manual says, but current thinking is that a thickness of at least 36mm is needed and some are building plinths that are well in excess of 100mm.

Have a look at http://www.theanalogdept.com/garrard_gallery.htm

Thanks for the info on your own experience.

Best wishes,

Greg

[IslandPink]

I'M BACK !!!!

( the poster formerly known as Mark J )


Greg,
Definitely in my tests, I found that with a big, rigid plinth , it was better to mount the 401 unit hard onto the plinth . I suspect when I had rubber or fibre washers between unit and plinth , some vibration motion ( relative ) shows up as a spurious 'music' signal on the arm/cart, since the arm is bolted to the plinth .

Mark

[NealG]

Greg, is the arm on a seperate arm board or mounted on the same top plate?

I would have thought you would need some sort of rubber under the 401 if the arm was on the same top plate?

If you are trying to 'sink' vibration then bolting it as tightly as possible onto a heavy mass plinth would be my choice then spiking it onto another heavy mass object with the arm board mounted on this second mass. IE a split plinth similar to the diag I sent you a while back.

Edit: thinking about it do as Mark says, bolt it down hard either way, I would still try to use a seperate armboard if possible to limit any resonance being transmitted to the arm.

[Greg.]

Thanks Mark, that's useful. I'll be interested to hear Clive's experience as he's decoupling with ball bearings the Jonno Noble way, and I thought I'd have a go at that style of plinth.

Best wishes,

Greg

[david counter]

I don't know if my 401 is typical but if I mount it without rubber washers the bottom of the front panel fouls the base and it rocks,

I only mention this as it seems to me perhaps Garrard always meant the deck to be decoupled on the washers,

[Greg.]

David, yes I also wondered if the rubber washers were intended for decoupling which rather prompted the question originally. It does seem to me however that if owners are bolting the chassis down tight, their presence is superfluous. Your observation is interesting, so I suspect I'll have to experiment for myself.

Neal, I'm using a one piece plinth at present as discribed above. I go with your seperate arm board suggestion as we've previously discussed, but as I'm experimenting at present, I want to keep things as cheap as possible to start with. I am going to make a seperate arm board similar to an SME mounting plate out of MDF which I intend to decouple from the plinth with 'O' rings. I will also 'O' ring the VTA adjuster onto the board.

My other plan is to decouple the plinth from the table using ball bearings. I've found Ikea sell very small 50 x 20mm glass bowls called 'Blanda'. £1.99 for four. The base of these bowls is just 12mm. You need to check but the base on most of the bowls is concave, readily accepting a marble sized bearing. I'll be filling the bowl with something to damp them and sticking three of these to the underside of the plinth and have another three mirrored to support on the table. I'll also be doing a full service on the deck and trying the cheap voltage reduction method of a 40 or 60W lightbulb wired in series in the power lead. I'm hoping that after that I'll have some clear indicators as to whether the project is worth pursuing further which would then mean spending a bit of money.

Best wishes,

Greg