When I first plugged my ZP3 in I thought I had some hum, turned out the hum was not from the ZP3 at all but the CSP2+ I think, it didn't persist anyway. I'm not having any problem at all. Mike (tgarden) has related to me he had problems with his first ZP3 that turned out to be the ground wire not attached internally in the ZP3, sounds like you describe. . . .

I have the same problem.  Don't remember all the troubleshooting I've done.  Haven't listened to vinyl for a while.   Like you said. hum is at quiet level between tracks.  no problem during a song.  plainly humming between them.  my speakers are 96db efficient, so I don't know if that was allowing me to hear a small amount of hum.   I put shielded wires on instead of the decware silvers like you.  helped.  Everything is on same isolation xformer.  if I disconnect zp3 from Torii, the torii alone is dead silent.  adding the zp3 to torii, powerered on, without turntable hooked up, I get hum.  adding the turntable, I get a bit more hum, so it's more than one thing involved.  trying to ground everything to everything else has made zero difference.

have to use power from same outlet for all your hifi equipments to prevent ground rounding (and all your sources as well also turntable). I had no problems after that. Not hard to try

Well, my zp3 made a liar out of me.  Because of the hum, I haven't been listening to vinyl for a while... and it clearly used to hum.     I  just opened my zp3 to see if the ground wire was there, and it was.  put it back together.  put tubes back in,  connected everything... guess what. I don't have hum anymore.   now, when I play a track at the higher end of my normal listening level, and lift the needle... it's quiet. no audible hum.  There is hum if I turn the volume all they way up (20 out of 20 steps on the attenuator) but that's to be expected.  The high end of my listening level is 10~12 steps on the tori with HDT's.  at that point, I cannot hear hum.  So... I don't know what happened.  But I don't have the hum problem anymore.  (And yes, everything is powered out of the same isolation transformer, and thus out of the same wall outlet).

 I tried using the same outlet (with an isolation transformer ) and also using a dedicated outlet for the ZP3  but no effect on the hum.

Thanks. My table is a Scoutmaster 2 so I will try that. However the table has a ground lug where the rca outputs are and a wire coming out of the table.
  I attached that wire to the ground lug to see if that would work but it did not .

rmcfee wrote on 12/02/12 at 21:43:00:


I received a 5U4G as well. I prefer the sound of the 5Y3GT in this preamp, but the 5U4G should work and not be causing your hum situation if the tube is new and healthy.

(It's funny, it says this in the ZP3 manual: "The rectifier is a 5Y3GT and should not be substituted unless it’s a different brand of 5Y3GT." And yet the web page references a 5U4G and Steve ships a 5U4G.)

The OA3 regulation tube is made in both bottle-shaped and straight sided versions, and they both work and that alone would not be causing you hum if the tube is functioning properly. That OA3 should be the tube furthest back in the chassis, right in front of the power and standby switches.