Turntable Earth Issue

I did suspect an earthing issue with your 252,

If the NDX is set to chassis, no further earthing is required.

Naim preamps need one, and only one, source to be earthed.

Let this be the NDX and leave it at that. 

It seems your turntable does not have signal earth connected to mains earth. In your scenario, you needed to run the turntable earth cable and connect that to mains earth, but since the NDX does this a lot more elegantly, you have solved the problem. 

Hope this helped.

Thanks Analog' - as mentioned on other thread I have to apologise for forgetting to act on your last advice. I'd have got here faster! 

I'm not completely clear re: t/t. I get NDX set to chassis. But what do I do about the earth cable with the t/t? 

..I mean - yes, I've solved the problem - by disconnecting the t/t earth from the 252. But it has to go somewhere or I get hum.  Connecting to phono amp, previously, also induced hum. I'll try again tonight but if same happens I'm not sure what to do with it. (The earth wire looks like a v cheapo, thin twin-wire thing fyi..)  I'll post results later. 

what does your retailer suggest?

enjoy

ken

that is strange because my turntable is floating (it is a 2 pin charger) and I get no hum, and I do not connect any earthing between the TT and the 282.

Can you please let us know what kind of charger/Power supply your TT uses is it 2 pin or 3 pin?

Do you have any Switch mode power supply in the same circuit as your Naim

Shouldn't you connect the turntable earth to the back of the 252 and set the NDX to floating?

That was precisely how I've had it for weeks, HH. That was the scenario that caused the knackered SQ. I'll reply back on others when back from physio'.

Ah, ok. That's how I did it when I had an LP12. It must be different in your case because you have a different turntable setup. 

Not all LP12 have signal earth connected to mains earth....

The TT is itself not earthed,  its arm needs to find earth & this is normally done by connecting the arm earth lead to the amp,  or if it does not have a separate earth wire such as Rega & others,  one of the signal return (-) is connected to the arm & provides the earth connection via the arm cable RCA plug to the amp -ve.  The NDX needs to be set for chassis

As Mike says above, set the NDX to chassis - this will give best performance for the system.  The issue is with the T/T and DV75 phono stage.  Not all decks need the arm earth lead attached, you should do whatever gives best sound.  Trouble is, there are many things in the cart/arm/turntable that can cause hum.  Even a poor contact between cart body and headshell can be a cause of hum and noise.  I assume your dealer has experience, so in this case I'd make best use of it as these things usually need to be solved in situ with hand on...

Analogue - tt psu is a 3-pin wallwart. When not earthed to 252, by process of elimination I can hear what each item in the tt chain does through the speaker - either as hum or varying degrees of electrical (?) interference. I switched the wallwart for the Russ Andrews psu which I recently put on the P75 and there's less interference noise at speaker so I'm going to get another one to replace wallwart. But the hum remains unaltered - unless tt earth goes to 252, in which case it disappears leaving only bgd hiss (which my dealer said was inevitable with a phono stage) The extension block for the Naim kit shares only with wireless hub power lead. I'll move latter away when the new power blocks arrive but that isn't the cause, I'm sure. As Richard (thank you) says - it's in the TT/P75 chain.

Mike - I was hoping you'd comment. But I achieved a 'U' grade at physics o-level so don't understand how to translate your remarks into any kind of go forward action! I can tell you I'm using Mogami IC's made up in USA from tt to P75 and P75 to 252. I recently tried a Chord Chorus Ref. from P75 to 252 but it banged and popped, especially when adjusted about and needed very careful dressing. You might see something in that.. The Mogami didn't at all. The tt has an earth stub on the back which is precisely for connecting a lead to run to earth elsewhere. Original dealer told me to connect to the P75 - which did nothing. (Howard - are you doing something I'm not since you mentioned doing same and having no hum issues with your near identical set up?) Only connecting to pre amp removed the hum. 

Ken - good point. Current dealer advice is, given my 'epiphany', to simply unplug any source not being played. This isn't practical. Nor should be necessary, surely? 

What I'm struggling with, Richard, is that earthing the tt to 252 - which is what the earth stub is for? - gets rid of the tt hum but seriously compromises SQ. (I'm sure you've read my saga..) Should that happen? I'm overjoyed to have solved the SQ problem but can't solve the tt hum in the way I should be able to? Do I really have to disconnect the tt earth every time I go digital? And I wonder if the tt SQ is also compromised by this earth problem? If it is, what's the solution? Help!

Adam - that's how I've always played it until an argument recently surfaced to switch NDX to floating (which didn't actually seem to make much difference, btw) It's simply this - tt earth cable to 252 removes phono stage hum but compresses and hardens SQ from NDX. Disconnect tt earth lead from 252 and open, smooth SQ instantly returns. 

Eagle, I understand the frustration here, but I'm afraid I'm just not familiar (i.e. I've never set up) your Simplex T/T combination and Dyanvector phono stage to give you precise answers.  In theory any connection by the arm earth lead should be made to the earth post on the phono stage, not to the pre-amp itself.  What is the interconnect between Dynavector phono stage and Naim pre-amp? Are you connecting via DIN or RCA?  Is the hum present on both or just on one?

Sorry, Adam, not my intention to appear frustrated at all. I'm more relieved to have solved a bigger problem than I am frustrated with this one. Yes, a fellow Forumite has done as you describe and has no problem. So I'll see if Howard can offer any further insight. All Mogami IC's. TT to Dynavector is rca to rca; Dyna' to 252 is rca to din. I don't have a means by which to test Dyna' to 252 as rca to rca but it's an interesting point. I'll contact the Well Tempered UK importer and feed back any solution which works.

Eagle, you may have confused Richard Dane with Adam Meredith 

I'm not familiar with Mogami's interconnects - I know that they make and supply pro cable assemblies and some cable brands use their cable (i think I have a couple of T/T DIN-RCA tonearm cable assemblies that use Mogami), but I didn't know they made their own interconnects. Perhaps they are damaged in some way?  Have you tried substituting other interconnects - in the past this has often solved such issues...

First thing - STOP - be very careful swapping PSU's around.  My alarm bells rang very loud when I read "I switched the wallwart for the Russ Andrews psu which I recently put on the P75......."    The P75 has changed its PSU polarity,  the MkI & Mk-II's require a negative centre pin,  the M-III has a positive centre pin.   So my concerns are that you might be using the wrong polarity & causing damage.

The RCA IC's between TT-P75 & P75-252 are nothing to worry about,  From what you say about the Chords it sounds like a connection defect of some sort.      Do you know what cable number the Mogami's are made from ???  

The earth terminal on the TT should be connected to whatever earth the preamp is connected to.  I don't  know the schematic of the P75 but it is not connected to earth - the earth pin on wall wart PSU's are invariably plastic & no earth connection is made with the wall wart - It might be the 252 RCA -ve connects to the P75 -ve & that is case grounded,  but whatever that is supposition.   I would try the following 2x connection experiments   (1) by-pass the P75 TT earth terminal & go straight from TT to 252.   (2) connect to P75 & then another connection P75 to 250.

Analog' - thank you; yes I did! Apologies. That's what comes of trying to respectfully personalise many replies whilst on high dosage codeine. I probably needed to apologise to Adam for something as well as Richard.  

It's a fair point but Mogami didn't make-up the interconnects - a pro' USA cable company did that. But I'm not sure it's cables. The hum has always been there, originally with yet different cables. One thing, though, is that process of elimination shows the hum to be absent when TT is not connected to Dyna' but latter is connected to 252. Whatever that implies..

Many thanks, Mike. Yes, I did check that power requirements of TT and P75 were compatible - 12V DC, >100mA and centre positive. The last thing I want to do is blow something up!

Mogami is 2549. When the guys made it they wanted the exact configuration of the - and + sockets in the 252 which was reassuring but I don't know what they ultimately did other than they're shield-connected at both ends. (I'm going RCA to DIN at 252.)

I've always by-passed the P75 on the earth route from TT to pre'. Zero hum but have made this new discovery of what it's been doing to SQ from NDX. Many thanks for the suggestion to go to P75 and from there to 252. I'll absolutely try it.

To be clear, I'm not trying to lose the hum per se - I've already done that. I just need to lose it in a way that doesn't kill my SQ - which wrapping the earth cable around the 252 earth post is currently doing. 

Ian,

Don't forget my 'no issues' with tt earth is with my current Dyna' L200 preamp. I get home tomorrow night and the 252 will hopefully be waiting for me to unbox and get connected. I'll report back as soon as I have it all wired up. PS I don't have an NDX.

H

Ah, right. Thanks Howard. Well I'll be very interested to hear whether your earth connection to P75 still works with the 252 in situ. If it does, I need to understand what you're doing that I'm not. If it doesn't, we're in a similar position. Except, for you, it's solvable without having digital source SQ issues to worry about! Very exciting for you - I bet you're counting down the hours

I

Yep, I sure am. I've waited a long time to be able to stretch to a 252. For info, my ICs are hand made by dealer using Mogami and bullet RCA / DIN as appropriate. I will have to get out the soldering iron to adapt the P75 to 252 IC if I want to use DIN, but will start out using the RCA input. Interestingly, I looked at the Naim Connection guide and there is a scenario with 252 and SuperLine and they show the earth connected to the SuperLine, not the 252, which has the ground post unused. I'm not about to get a SuperLine to test it mind!! Also, I confirm the walwarts for WT Simplex and P75 are interchangeable.

H

..yes interesting. And spookily similar set-up path! The P75 is brilliant. Maybe RCA to RCA with 252 will be a better result than my din.. I've written to the UK importers with the problem, too. Just now I'm looking for some earth cable to chop up and daisy chain

eagle3333 posted:

Many thanks, Mike. Yes, I did check that power requirements of TT and P75 were compatible - 12V DC, >100mA and centre positive. The last thing I want to do is blow something up!

Mogami is 2549. When the guys made it they wanted the exact configuration of the - and + sockets in the 252 which was reassuring but I don't know what they ultimately did other than they're shield-connected at both ends. (I'm going RCA to DIN at 252.)

I've always by-passed the P75 on the earth route from TT to pre'. Zero hum but have made this new discovery of what it's been doing to SQ from NDX. Many thanks for the suggestion to go to P75 and from there to 252. I'll absolutely try it.

To be clear, I'm not trying to lose the hum per se - I've already done that. I just need to lose it in a way that doesn't kill my SQ - which wrapping the earth cable around the 252 earth post is currently doing. 

OK Phew,  for the P75 polarity check

Mogami 2549 is an excellent cable,  I use it.   The fact that they have the screen connected at both ends is normal  to adapt it for RCA-DIN.  I expect the 2549 two cores are designated ch1 & ch2  & each will go to the individual RCA centre pins & they add a screen (or 2nd wire) to connect to the 2549 screen & then to each of the RCA outer's.

This should not affect the NDX s.q. as its not adding or making an extra earth/ground,  its just extending the 252 earth to the TT's isolated arm tube & arm base.