the home of the turntable

Tonearm wiring - help

snap, crackle and pop

Tonearm wiring - help

Postby PaulFolbrecht » 13 Nov 2010 19:35

I bought a phono IC with no connectors with the intent of wiring it directly to my SME 3009 because I hate their connector that comes loose (and didn't know about the RCA adapters at the time).

Now I realize I'm not quite sure how to wire the ground. I know how to connect the hot & neutral wires of each interconnect:

Red - right hot
Green - right neutral
White - left hot
Blue - left neutral

However, each IC has three wires, including the non-insulated ground - what do I do with that at the tonearm end?

Thanks!
PaulFolbrecht
junior member
junior member
 
Posts: 18
Joined: 22 May 2009 16:37
Location: USA

Postby analogaudio » 13 Nov 2010 23:35

Culd it be that what you have is a balanced IC? Was it described as balanced by the vendor? That would explain the construction you describe. How you wire it up depends on how they have made up the end with the RCAs, basically you copy what they have done at the other end.

But you may prefer to use single core shielded wire that is the conventional product used for phono IC and retain the balanced cable for some other purpose, though it is a little strange to combine twin + screen cable with RCAs, which cannot be balanced.

Ted
analogaudio
long player
long player
contributor
 
Posts: 2227
Images: 7
Joined: 06 Feb 2007 23:58
Location: Monroe NY USA

United States of America

Postby PaulFolbrecht » 14 Nov 2010 00:49

analogaudio wrote:Culd it be that what you have is a balanced IC? Was it described as balanced by the vendor? That would explain the construction you describe. How you wire it up depends on how they have made up the end with the RCAs, basically you copy what they have done at the other end.

But you may prefer to use single core shielded wire that is the conventional product used for phono IC and retain the balanced cable for some other purpose, though it is a little strange to combine twin + screen cable with RCAs, which cannot be balanced.


No, this is not a balanced IC! It's single-ended shielded. I am guessing that bare ground wire at the unterminated end is the shield termination. I will have to ask the maker. I soldered it today and also a separate ground wire attached to the arm, and am getting a good bit of 60 hz (I think) hum out of my TD124.
PaulFolbrecht
junior member
junior member
 
Posts: 18
Joined: 22 May 2009 16:37
Location: USA

Postby Ericus Rex » 14 Nov 2010 01:02

I believe your ground should be a third wire and not integral to the ICs. As for the 3-wire ICs, I've seen cable manufacturers solder together the neutral and ground wires at both IC ends. Whether this would result in noise in a phono setup I can't say for sure. If you're getting noise doing this then try totally floating the unshielded ground and see if that helps.
Ericus Rex
member
member
contributor
 
Posts: 114
Images: 1
Joined: 30 Dec 2009 20:20
Location: Boston

Postby PaulFolbrecht » 14 Nov 2010 01:59

It's floated now (at the tonearm) end, actually, and I do have hum - but I had hum before I went to this soldered-on IC.

It could be a ground loop. Or it could be the table doesn't want to be grounded. Chasing down these problems is always fun (not).

Thanks
PaulFolbrecht
junior member
junior member
 
Posts: 18
Joined: 22 May 2009 16:37
Location: USA

Postby zharca » 14 Nov 2010 17:42

Hi, the wire you have is probably the best way to make a tonearm cable. It's the way Isokinetik, Incgnito, Michell and many others do it. It's often called "pseudo-balanced".

Keep the shields isolated from the signal wires but connect them to the body of the tonearm and to a separate ground wire which you run to the grounding post of your pre-amp. Don't connect it to the signal wire -ve at any point.
zharca
senior member
senior member
 
Posts: 710
Images: 10
Joined: 13 Mar 2008 12:04
Location: Kent, UK

Postby PaulFolbrecht » 14 Nov 2010 17:59

zharca wrote:Hi, the wire you have is probably the best way to make a tonearm cable. It's the way Isokinetik, Incgnito, Michell and many others do it. It's often called "pseudo-balanced".

Keep the shields isolated from the signal wires but connect them to the body of the tonearm and to a separate ground wire which you run to the grounding post of your pre-amp. Don't connect it to the signal wire -ve at any point.


Here's what the cable maker told me about the shield wire: "That's the shield. Its tied to the ground on the RCA side of the cables. It should be tied into the ground on that end as well."

He tied it to the ground on the RCA side. Not what I'd really intended, although I wasn't specific enough I guess.

So, right now, I have the tonearm side of the shield wire unconnected - in fact I cut off the portion protruding from the insulator. Would having that wire connected on the preamp side but NOT connected on the tonearm side cause any issues - like the hum?

NOTE: I did run a separate ground wire from the arm to the phono preamp's ground lug.

I'm wondering if I should bother to open the RCA plugs on the preamp side and disconnect that shield wire. I actually think it's probably not related to the hum. Or hook the shield wire up to the arm on the tonearm side. But the hum is so bad I can't believe the cable being unshielded could be causing it. Especially because I've never gotten hum like this from any other table and I've never used a shielded phono IC before.

I should have just gotten an RCA adapter and used that.
PaulFolbrecht
junior member
junior member
 
Posts: 18
Joined: 22 May 2009 16:37
Location: USA

Postby PaulFolbrecht » 15 Nov 2010 00:18

I floated the ground on my phono stage and the hum is almost all gone.

And, WOW, does this Thorens 124 kick ass!!
PaulFolbrecht
junior member
junior member
 
Posts: 18
Joined: 22 May 2009 16:37
Location: USA

Postby zharca » 15 Nov 2010 03:13

How is your arm grounded now, that might be the source of the remaining hum.
The top drawing here shows how phono sockets with a separate grounbd wire are connected (the bottom one is the standard Rega wiring, which is often criticised though it doesn't hum!)

wiring diagram
zharca
senior member
senior member
 
Posts: 710
Images: 10
Joined: 13 Mar 2008 12:04
Location: Kent, UK

Return to Turntables and Tonearms