Phono Interconnects

I am 64 years young and have worked in the electronics field, for most of my life. I recently made some phono interconnects, but get a low level hum, when using them. I have some store bought upper level brands and they are silent, when tonearm is at rest.
The cables I made are two conductor, with a wire mesh ground. I have tried connecting the ground on the phono side, while leaving it open on the preamp side and leaving the ground open on both ends. I still get like a tube rush sound, using my home made cables. All connections are pristine and plugs, although are not a name brand, are good. I purchased some Furotech connectors that I didn’t use. I’ve been doing this a long time and can’t see how the Fufutechs can make a huge difference. Any advice?

 

When you say "two conductor, with a wire mesh ground", do you mean in each L and R cable there are two conductors, one for signal and one for return, with a wire mesh shield? Or you made unshielded cables with two conductors in each, and are using the wire mesh just as a ground connection between turntable chassis and preamp chassis? Twisted wires? Or maybe make a quick sketch of the connections and post it. Most phono cables are heavily shielded, usually coax construction with center conductor for signal and then close to 100% coverage on the shield, which is used for the signal return, so you have to be pretty careful if not using a shield.

 

Get some Belden 9271 and be done with it!

 

I too am thinking shielding is the problem with interconnects.

 

Are you by chance trying to use Mil-Spec twisted pair?

 

No-simple two conductor with ground.

 

I am using 2 conductor with wire mesh ground. Just like any microphone or phono cable, except two “hots” plus a ground. I bought this, because all my cables are balanced using xlr connectors. I thought it would be good for phono interconnects, but was wrong. Guess I’ll get the Belden. After all, they’re only about one meter long.

 

Agreed. Hum from cables is nearly always shielding related. IMO

 

Plus, phono cables should be really low capacitance. Not just any interconnect cable wire.

 

Guess I’ll get some good quality plain shielded cable and use my Furutech 110’s. Searing 75- you suggested using the Belden 9271. Can you suggest the proper connections of the cable? I’ve read where it recommended to use the shield and ground together, at the source, then leave the shield open at the amp.

 

It needs to be twisted wire, best way to avoid low frequency pickup. Most likely, this is the "hum" you are hearing. Shielding (in the traditional sense, like foil or braid) will to NOT effect 60 Hz hum unless its a mu-metal shield. Traditional shielding will be very effective to reduce high frequency interference/pickup.

 

That is right you want to have it open on one end, this way no ground loop.

 

Shielding

 

Not to doubt your soldering skills, but a cold solder joint will often result in noise as well.

 

The Belden 9271 previously mentioned is not going to be good for phono interconnects either; it's two 125 ohm insulated conductors in a single foil shield.

What you want is ideally a single RG6 coax cable for each RCA (nominally 75 ohm, but the characteristic impedance doesn't matter so much for audio), where both left and right are inside their own double-shield or better. If you are going to be soldering, Belden 1505F is a good choice, with a stranded center conductor that is more flexible.

The better end terminators are RCA compression fittings that need a special tool, (not crimp fittings as a certain "blue" company uses), and work with solid conductor cable. For this, Belden 1694A is a go-to dual-shield cable. Quad shield RG6 might be even more overkill, but also needs quad-shield compatible connectors.

Cable length is important to phono because of its capacitance. Keep either of these cables to 2 meters for a standard value.

For the trouble, you can just buy a set of KAB phono interconnects for under $20 which work well. Don't forget the extra ground wire from the turntable chassis to the phono preamp and/or amplifier ground lug, without which you get hum.

 

I may have misrepresented the actually “hum” I’m hearing. It’s almost like tube rush, as I do have tube phono and line stage preamps and have to turn the gain up to at least mid-level to hear it. However, using my Verastarr Silverstream interconnects, my system is pretty much dead quiet, at the same level, with tonearm at rest.