Turntable Earth Issue

rtf posted:

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

exactly how mine is set up. LP12 to superline including earth lead. no connection from superline earth to 552 ground post.

enjoy

ken

Thanks all.

The SQ thing is very odd, Mike. Meantime, the importer suggested running the earth from TT to a mains plug connected to earth only. Any thoughts? 

My son had an issue with his Thorens 160 / NAC72 whereby he got hum with the earth connected to the 72. Fixed it by running the earth direct to mains plug bypassing 72 altogether. So that does work as a concept. But of course every setup is different. 

Is this correct?

NDX set to chassis and tone arm earth lead to 252 earth post gives no hum but odd sound quality?

NDX set to chassis and tone arm earth lead to P75 earth post gives hum But better sound apart from that?

eagle3333 posted:

Thanks all.

The SQ thing is very odd, Mike. Meantime, the importer suggested running the earth from TT to a mains plug connected to earth only. Any thoughts? 

I would not do that.    It needs the arm to be connected to or at least close to the phono or pre amp(s) which are connected to earth.   There is something going on that we don't understand & I would not be happy until I found out what,  I'm begining to think the pre-amp might not be earthed.

Yeti - yes, correct.

Ok MIke. Now I'm afraid. If the pre wasn't earthed wouldn't the TT hum still be there even after connecting earth the 252 earth post?

It seems to me that there's no signal earth from the p75 to the 252 via those custom leads. What happens if you connect tone erm earth to p75 and run a wire from there to the 252 earth post? Keep the NDX to chassis so the system as a whole has a signal earth there. I'm trusting neither the TT nor the p75 have signal earths through their power supplies. The versalex I tried diden't but not sure about the p75. You'll get a hum if there's a second signal earth.

Sorry Eagle,  I'm just thinking aloud, forget the pre-amp earth comment.    I don't understand whats going on,  fixing or not fixing the hum by the various & normal connection methods you've discussed,  all of which are attaching a wire from an earthed amp case to an isolated TT arm,    should not affect NDX sound 

Ian,

All connected now. Initial thoughts re: earthing etc. is: P75 connected to aux2 via RCA input, earth wire from tt to P75. No hum or untoward spurious sound. Will be making up an IC to use DIN instead of RCA in due course.

Sound? too early to judge but straight out of the box, no harshness evident. More to follow.

H

Eagle, Record player is earthed on the back of my P75 III. RCA phono to DIN i/c goes to unpowered AUX2 on the back of my NAC202. Works well. Sorry to read of your problem.

Chris

Morning Howard,

That's great! I'm sure you'll be listening at every available moment! You and Chris (thanks Chris) are obviously using the same earthing method. But, according to the P75 manual and John Burns, the UK importer, the earth post on the P75 is for earthing its own chassis. Not for earthing the tt per se. So the P75, I believe, is not itself internally earthed. So earth wire from tt to P75 should do nothing for earthing tonearm.  As is the case with my set up. This isn't my area of expertise! I could be wrong but if I've understood manual/John correctly, I'm not. And I think it's what Mike points out above. Also, both the manual and John recommend earthing tt to pre amp.

Did you cable the tt earth to P75 post because you had hum? Or did you do it because you were advised to do it? Unless Mike or other sees an issue with this, a really useful experiment (though only for my guidance and of little interest to you) would be to disconnect earth wire (from just P75 or tt & P75?) and see if you get any speaker hum. I'm wondering whether your set up is simply such that there isn't any and so earthing tonearm with outside cable is not actually needed. If that's so, then I have to find out why my Simplex tonearm induces hum and yours doesn't (H). Any chance of a quick test on that? 

Makes no difference if the earth wire from my Ittok is connected to the back of my P75, I've just found.

I'm now wondering how things would be if the Ittok's earth wire was connected to the back of my NAC instead. Might connect a thin wire to it sometime an try it.

C.

Thanks a lot Chris. Do you mean there's no hum whether the earth is connected or not? 

Ian

I do.

Chris

I removed earthing wire from P75. No difference. I wired it to preamp ground post. No difference. So I guess it just doesn't need it. 

Now all I have to do is find out what is pushing DC into the mains causing the NAP250 to buzz! 

rtf posted:

Now all I have to do is find out what is pushing DC into the mains causing the NAP250 to buzz! 

If  it buzz's at the same volume & tone all the time .........  if so thats the 250

If the buzz/hum tone & volume changes  ...........  what else is happening at the same time in your house or apartment block,  start with your wife/partner/significant others hairdryer,  next anything else that runs on half/full speed/heat/power,  next start searching this forum,  we have some good idea's.

Right - that's what I'd expect, Chris. The P75 does nothing for earthing unless you physically earth it - which you could do with a wire to pre'. Your tonearm set-up simply sounds like it doesn't need earthing. In which case, presumably, there will be no difference when cabling an earth to NAC. But no harm in trying and seeing whether it has an effect. Howard, I suspect your Simplex set-up, unlike mine, is just the same. So, how did you do that?! 

RTF - yep, another lucky non-hum tonearm set-up Thanks for testing.