regarding shielding

You are referring to a "floating shield" (one end 'floats' -- is not connected.) This is exactly to PREVENT any curent flow, which would result in hum and RFI being mixed with the audio signal (and thus winding up in your speakers!)

Having the shield connected at one end only does not prevent intercepted hum and RFI from draining to ground at the connected end.

In the old days ;~) single ended interconnects contained only one (center) conductor (+) and the shield carried the (-) signal, so it had to be connected at both ends. Then Bruce Brisson (owner of MIT cables) invented the "shotgun" single-ended interconnect while working for MonsterCable, which is what put MonsterCable on the map! It is called "shotgun" because it contains TWO signal conductors (double-barreled shotgun ;~) surrounded by a shield -- but since the shield no longer has to carry the audio signal, it can be 'grounded' at just one end, and can do its shielding job even more effectively.

Mr. Brisson provided these shotgun cables with ARROWS, which point to the end of the cable where the shield is connected to ground (no, the arrows have NOTHING TO DO WITH SIGNAL FLOW!) He did this specifically so that all interconnects could be installed with the grounded end of their shields connected to the preamp (yes, EVEN THE ONES BETWEEN THE PREAMP AND THE AMP!) That is because such a configuration is what's called 'Star Grounding' -- with the preamp at the center of the 'star'.

Star Grounding provides the quietest system; and in order to prevent ground loops, the preamp should be the ONLY component actually grounded to the wall. In the old days ;~) we generally put 'cheater plugs' on the (three prong) power cords of all other equipment, to prevent additional grounding points (which will always produce ground loops.)

Unfortunately, installing 'cheater plugs' can produce a, shock hazard if you are working on your system and remove the interconnects (and thus the ground connection) from a piece of equipment that has a cheater plug on it (for example: if you were adjusting the bias on a tube amp, which requires removing the input interconnects ;~) So be careful! Much of today's equipment (especially amplifiers) have switches on the back that allow you to 'float' (disconnect) that piece of equipment's audio circuits from ground, and thus eleminating the need for cheater plugs (the equipment's chassis is still grounded) and preventing you from accidentally electrocuting yourself!

Okay, I'm using unshielded cables from both, my TT and preamp. The phono preamp is plugged into the wall using a c-7 cable. It's very quiet, no RFI. I did the star grounding with other cables and it worked okay, but why with non-shielded cables do I get better sound without them acting like antennas? Also, I have four dedicated circuits which everything is plugged into.

mt10425, could you provide a little more detail:
What is the construction (or brand) of your (single-ended?) interconnects? Just because cables are unshielded doesn't necessarily mean they will be noisy if they don't pass near power cords (or equipment transformers) and if there is no strong RFI coming from your system (usually digital gear) or from fluorescent lights or dimmers in your home, or broadcasting stations in your area.

What is a c-7 power cord? Is that a brand?

Dedicated circuits are good, but you still have to observe the same grounding techniques as with any wall citcuit.

thx

Sure. The cables are Music Metre with a single silver wire in a semi-flat transparent tube. 1m from TT to TTVJ Hybrid phono stage - 1/2m from phono to Sophia Baby amp. With the amp turned all the way up there is no tube rush or any noise.i thought phono cables had to be shielded against RFI. Apparently not. C-7 is the two pronged end of some power cords. I use Furutech outlets on my dedicated circuits. Let me know if that's enough info.

Hi Mt10425:

I checked and found that the Music Meter cables are constructed of TWO wires in a "twisted pair" configuration. This works well for rejecting RFI (with no shield) but not so much for 60Hz hum (although hum is more easily controlled by careful cable placement.) Twisting the + and - conductors together though, creates other issues that might negatively affect performance (or not) depending on the cables' application.

The Vinyl Junkie phonoamp is actually solid state for the first gain stage (first and second gain stages if you're using a MC cartridge.) That's where tube hiss would happen if tubes were used there.

The unit's power supply is a (transformerless) "switching" power supply providing high voltage to the tubes, and the 12V DC is provided by a wall wart transformer. Neither of those devices require a third ground conductor, as would be required for a more conventional power supply which is often housed in a separate chassis away from the sensitive phonoamp circuits.