Daft prefix question time...

Posted by: Top Cat on 07 April 2004

Hi folks.

Daft question time: when connecting a Prefixed LP12 to a 52, should the earth Y-leads be connected to the 52's earth connector or not? I'm assuming that they do, but am suffering occasional static pops and wondered if perhaps something about the way the Prefix is wired might be doing away with the need for these earth leads.

FWIW I've checked that the earth leads are connected to the right places (they are) and that there's nothing else about the setup which could be causing the static pops (can't see anything).

Also, can't seem to find my Aro setup manual. I do have it, just can't lay my hands on it right now. I can't find it in the main NA site - does anyone know where it lives?

Thanks,

John

Posted on: 07 April 2004 by Laurie Saunders

quote:
when connecting a Prefixed LP12 to a 52, should the earth Y-leads be connected to the 52's earth connector or not?

the best rule is: use whatever works. If disconnecting the earth does not induce hum, then you can probably get away with not using it

BTW isn`t the arm earthed via the prefix anyway?

Two earths are not generally a good thing fro my experience

Laurie S

Posted on: 07 April 2004 by Top Cat

quote:
BTW isn`t the arm earthed via the prefix anyway?

My question, really... dunno.

Can anyone confirm?

I've still got the K-boards in the 52 for now - but will remove these once I get some straight-through boards (NeilW, never heard back from you - are you going to send these up to me?

)

Hmmmm... and I thought going Prefix was going to be easy...

John

Posted on: 07 April 2004 by Hermann

quote:
BTW isn`t the arm earthed via the prefix anyway?

No it isnt. The wire is the earth for the arm. The prefix is earthed thru power supply either 52/552 or a *cap.

If a Naim CDP is in use the earth for the TT shouldnt be connected to the back of the pre.

Hermann

Posted on: 07 April 2004 by Top Cat

OK, so now I'm confused. Should I connect the earth wires to the back of the 52 (for the moment I'm powering the Prefix from the 52 rather than via a dedicated PSU) or should I leave them unconnected?

Also, Hermann, can you explain that last bit about the Naim cd players - I'm using a non-Naim cd player but it has a DIN output so I'm using a Naim DIN

IN and was connecting it to socket 2 but have now moved it to socket 3. I wasn't experiencing any static problems before I did this - but now I am.

Really confused...

John

Posted on: 07 April 2004 by Hermann

Ok let me try

The earth wire from TT is the arm earth and should go the back of the 52.

The prefix (if used) is earthed thru the 52/552 itself or by a *cap.

The TT (w/o Naim CDP) is the central earth point of the system and should have a connection to the earth via TT power supply. There has to be a wire from the TT (chassis) to the earth point of the back of the pre. This wire provides the earth of the system then.

If a Naim CDP is in use then the CDP is the central earth point of the system. The connection from the TT to the back of the 52 has to be removed.

In your case you have to find out if there is an connection between the earth and signal neutral into the CDP. If thats the case you have to remove the connection from TT (chassis) to the back of the pre to prevent earth loop.

I hope thats correct.

Hermann

Posted on: 07 April 2004 by Rockingdoc

My dealer insists that the Prefix is just 52 boards in a box. Can anyone confirm or refute please.

Posted on: 07 April 2004 by Laurie Saunders

quote:
My dealer insists that the Prefix is just 52 boards in a box. Can anyone confirm or refute please.

My understanding is that the circuit is, as you suggest, identical

However, the layout of components is "improved" (i`m told) and the other big benefit is the much reduced length of armlead.

Notwithstanding all the above, I am as certain (as much as I can be) that installing a prefix is a very definite upgrade over the 52 boards

Laurie S

Posted on: 07 April 2004 by hungryhalibut

John - My prefix has two wires coming our of it that go to the amp - a Snaic which plugs into the powered socket on my 252, and a black wire with a spade connector which attaches to the earthing post on the 252. Then there are the thin signal wires - four that join via the Aro to the cartridge and a slightly stiffer one that is the arm earth. So the arm earths to the Prefix and the Prefix earths to the 252. The turntable chassis earth is taken care of via the Armageddon.

Hope that helps

Nigel

Posted on: 07 April 2004 by Top Cat

quote:
John, you sing the paises of Robert Richie, and the man needs your custom I'm sure, so why not take it into him and have him update your prefix and sort it all out?

Patrick, that's beginning to look like a very attractive option. Fact is (was?) that I didn't want to be without the TT for too long, but I may have to just bite the bullet.

I inspected the deck again last night and noticed that one of the screws in the armboard was slightly loose (a remnant of fitting the Prefix no doubt) - since tightening this up properly I've not noticed any static pops, and whilst I still can't get my cartridge to track the difficult 'third' track (+18dB) on my borrowed setup LP without a lot of distortion, the first two are fine.

Musically all seems well but I have a nagging suspicion it should sound better than this as moving from the 52 with K boards to the Prefix K into the 52 hasn't noticeably improved the music.

Perhaps in fitting the prefix I've moved from an optimal pre-Prefix setup to a sub-optimal Prefix setup, if you know what I mean.

Robert!!!! Robert!!!!

John