Tonearm Internal Grounding - Better or Worse?

[Spider27]

Hello,

 

I see that tonearm wire has 5 wires. Red, White, Blue, Green and Black.

What happens if black ground wire connect to the two earth wires (green and blue) so they are internally grounded?  I was told that DJs use this type of grounding so they do not have to worry about external ground wire to be mounted onto preamp but connect direct to digital processor or active monitor.   Is this common practice and it can be as effective as external ground without causing hum or buzz?

 

I believe that this is how Rega tonearm usually grounded so they do not have external ground wire to be mounted onto preamp but I also heard some people experiencing issues with hum with Rega tonearm.

 

Any feedback or information would be greatly appreciated.

 

Thank you...   

[mloutfie]

There is no earth on a cartridge. It's signal ground, where your black wire is chassis ground. Good or bad of joining signal  ground and chassis depending the rest of your chassis ground wiring. Horses for courses

[Spider27]

3 minutes ago, mloutfie said:

There is no earth on a cartridge. It's signal ground, where your black wire is chassis ground. Good or bad of joining signal  ground and chassis depending the rest of your chassis ground wiring. Horses for courses

Thank you very much. Have I understood correctly that those green and blue wires are signal ground and black wire is chassis ground so it might be better to separate so chassis ground goes to preamp to be grounded? Not sure what would be Pros/Cons  of putting signal and chassis ground together can be.

Edited October 25, 2018 by Spider27

[Spider27]

Is Rega tonearm usually connected together between signal ground and chassis ground so there is no chassis ground coming out of the Rega turntable?

 

If I understand correctly, Rega tonearm does not have external ground wire. However, modified version from other companies such as J.A. Michell, Audiomods, Moth has black ground wire to be mounted on preamp.. Not sure why all of modified version of Rega tonearm has external ground wire to be mounted to preamp when original does not..  

[Batty]

Rega use the left channel screen as earth (ground). My RB250 is a Moth variant, in original configuration it had no black earth wire.

I have since had it modded by j7 at Audio Origami and it now has a totally separate earth.

[Spider27]

1 hour ago, Batty said:

Rega use the left channel screen as earth (ground). My RB250 is a Moth variant, in original configuration it had no black earth wire.

I have since had it modded by j7 at Audio Origami and it now has a totally separate earth.

Thank you for the great info.  When you change from Moth with original configuration to modded Audio Origami with separate earth, did you notice any changes such as blacker background or lesser hum?

[mloutfie]

@Spider27 Grounding is a hard thing to sort out in circuit design. All depending on what you have (Chassis, whether the rca connection is isolated etc) The only reason that rega can get away with it is because of their plinth material isolates the tonearm electronically from the motor. this is not the case for many other turntable and they actually do this out of convenience only no sonic reason to do this (At least that is what I believe). Most any other table motor hum definitely will seep in the signal if you link the chassis ground to signal ground on the tonearm side.

 

I assume your DJ reference also do this for convenience only one less connection to do. When you install a tonearm you can never know if that tonearm has buzz issue especially if its vintage and since there is no sonic advantage on linking signal and chassis ground in tonearm side I would stay using separate cable. Just FYI most phono will link them in the input side.

[Batty]

I can't recall, it was a long time ago (I bought the arm in 1986 and it was modded in 2010).

The only reason I had it modded is because I was getting intermittant dropouts on the left channel, so went the whole hog and had a full rewire, foam fill and earth mod done.

I had already done the Origin Live rear structure mod as the plastic stub had been damaged in transit when I emigrated from Uk in 2001.

Overall not much of the OEM left

[Spider27]

22 minutes ago, mloutfie said:

@Spider27 Grounding is a hard thing to sort out in circuit design. All depending on what you have (Chassis, whether the rca connection is isolated etc) The only reason that rega can get away with it is because of their plinth material isolates the tonearm electronically from the motor. this is not the case for many other turntable and they actually do this out of convenience only no sonic reason to do this (At least that is what I believe). Most any other table motor hum definitely will seep in the signal if you link the chassis ground to signal ground on the tonearm side.

 

I assume your DJ reference also do this for convenience only one less connection to do. When you install a tonearm you can never know if that tonearm has buzz issue especially if its vintage and since there is no sonic advantage on linking signal and chassis ground in tonearm side I would stay using separate cable. Just FYI most phono will link them in the input side.

 

Thank you so much    Yes, I now see that there is no merit combining signal and chassis ground together other than convenience. I was particularly interested in the option of using any RCA cable without ground wire and wondered if it is worth a shot and it seems that it is better to be separated.

 

I found that most of tonearm cable length is pretty short (1m or shorter) especially when it was rewired hence thinking of applying RCA female socket mounted under the tonearm base (as shown the photo on 1st post) or plinth such as some of Pro-Ject or VPI turntables do. Then, use external quality RCA interconnect cables and ground wire to connect between amp and tonearm. 

 

The issue of soldering tonearm wires to female RCA socket & Ground Screw then mount them at the back of the plinth is that it is hard to switch the tonearm since cables are soldered onto socket at the back of the plinth. 

 

Hence, I was thinking of mounting RCA female socket under the tonearm base so external RCA interconnect cables directly mounted to the socket and extend the black ground wire. Then, it would be much easier to change the tonearm without re-soldering the tonearm wire etc.

 

Not sure is this idea would work and if anyone tried this method previously. 

[Spider27]

38 minutes ago, Batty said:

I can't recall, it was a long time ago (I bought the arm in 1986 and it was modded in 2010).

The only reason I had it modded is because I was getting intermittant dropouts on the left channel, so went the whole hog and had a full rewire, foam fill and earth mod done.

I had already done the Origin Live rear structure mod as the plastic stub had been damaged in transit when I emigrated from Uk in 2001.

Overall not much of the OEM left

 Wow, that is a massive gap between 1986 and 2010 and it would be impossible to compare  

 

[Batty]

4 minutes ago, Spider27 said:

 Wow, that is a massive gap between 1986 and 2010 and it would be impossible to compare  

 

I was using it all that time, just not in use for about 2 weeks whilst it was away in Scotland.

John checked the bearings too, said they were like new.

Edited October 25, 2018 by Batty

[mloutfie]

1 hour ago, Spider27 said:

Hence, I was thinking of mounting RCA female socket under the tonearm base so external RCA interconnect cables directly mounted to the socket and extend the black ground wire. Then, it would be much easier to change the tonearm without re-soldering the tonearm wire etc.

 

most manufacturer will put a speaker screw binding post as a ground connector when they put RCA jack. that way you can use any sort of bare cable as the ground cable

[Batty]

On my Luxman TT I mounted a pair of RCAs and a screw terminal to the rear of the plinth abd wired the Hadcock tonearm to that and ran a wire from the arm to the eath screw if needed.

Phono leads are 2foot Blue Jeans LC1.

[Spider27]

6 minutes ago, Batty said:

On my Luxman TT I mounted a pair of RCAs and a screw terminal to the rear of the plinth abd wired the Hadcock tonearm to that and ran a wire from the arm to the eath screw if needed.

Phono leads are 2foot Blue Jeans LC1.

Great to know. Thank you.

[Spider27]

1 hour ago, mloutfie said:

most manufacturer will put a speaker screw binding post as a ground connector when they put RCA jack. that way you can use any sort of bare cable as the ground cable

 

I was thinking to have long black ground wire directly from tonearm all the way to preamp but speaker screw binding post at the back of the plinth would be neater solution.

 

Put female RCA socket underneath the tonearm base and black ground wire to be terminated with earth ring that can be screwed at the back of speaker screw binding post without soldering and mount binding post at the back of the plinth.

Then I can just unmount black ground wire from binding post and take the RCA interconnect cables from female RCA socket from tonearm base when swapping the tonearms. 

 

I will give it a go to see if it works nicely.  Again thank you very much for your suggestions.   

[GregWormald]

The fewer connectors the better.

I sure wouldn't be connecting signal grounds.

Some of my systems have preferred the turntable ground wire connected to the pre-amp, some have not. It's an easy change, so try it and listen.

 

[Spider27]

4 minutes ago, GregWormald said:

The fewer connectors the better.

I sure wouldn't be connecting signal grounds.

Some of my systems have preferred the turntable ground wire connected to the pre-amp, some have not. It's an easy change, so try it and listen.

 

 

Thank you. I will give it a go... 

 

I did a bit more research during weekend and found this upgrade service which is pretty much same as the one that I referred at the first post. If I understand correctly, this service person does putting signal ground onto left channel (similar to Rega?). Not sure where chassis ground went to though. Is chassis ground attached on screws of that black RCA plate?  

 

https://www.analogtubeaudio.de/en/service-and-repair/sme-tonearms/

The service for SME tonearms 3009/3012 includes:

• the complete disassembly and a professional 2-stage cleaning
• preparation and restoration of ball bearings
• repairing lift unit include refilling  damping fluid
• Cleaning, lubrication and precise adjustment of the horizontal bearing
• Rewiring of the tonearm wire inside with Pure Silver Hair Wire (exclude tonearm wire)
• precise mounting and adjustment of the tonearm
• the installation and adjustment of the bronze tweaks like bronze knife edge bearing, bronze groundplate, RCA Conversion Kit etc.

 

[GregWormald]

1 hour ago, Spider27 said:

<snips>

Thank you. I will give it a go... 

 

I did a bit more research during weekend and found this upgrade service which is pretty much same as the one that I referred at the first post. If I understand correctly, this service person does putting signal ground onto left channel (similar to Rega?). Not sure where chassis ground went to though. Is chassis ground attached on screws of that black RCA plate?  

 

I'm not an expert on this so take that into consideration.

 

I'm not sure why the signal grounds would be joined or whether it makes a difference but each RCA connector turntable to pre-amp (and right out to the speakers) has separate connections and I'd leave them separate.

 

The RCA mod adds another set of connectors onto each line and each set of connectors costs some signal at the expense of signal/noise ratio so I wouldn't have that done either. When I had Audio Origami upgrade my Linn Ittok arm I just asked for slightly longer leads from the arm to pre-amp so I could keep the t/t on separate shelving from the electronics.

 

The t/t chassis ground is a separate wire out of the Linn and as I said previously it's easy to check if your set-up likes it connected to the pre-amp or not. 

[mloutfie]

1 hour ago, Spider27 said:

Not sure where chassis ground went to though. Is chassis ground attached on screws of that black RCA plate?  

the metal pole is the chassis ground (Any sort of metal piece linked to the tonearm can be chassis ground) he link soldered the pole to the rca shield