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ZP3 phono pre hum problem! (Read 7840 times)
rmcfee
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ZP3 phono pre hum problem!
12/02/12 at 01:34:22
 
 Has anyone had trouble with hum in these amps?  It is as loud as the quiet passages in any album making it unusable.
 I tried grounding the tonearm to the Zen, grounding the Zen to the amp, grounding both to the amp or no ground.
  I gave the Zen a dedicated outlet instead of the isolation transformer I usually use.
   I replaced the Decware interconnects with shielded ones.
    I tried swapping tubes in case a tube had a problem.
  Still a loud hum.
  Any advice would be great since I really wanted to like this amp. Thanks.
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Lon
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Re: ZP3 phono pre hum problem!
Reply #1 - 12/02/12 at 03:55:47
 
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. . . .
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rmcfee
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Re: ZP3 phono pre hum problem!
Reply #2 - 12/02/12 at 04:37:20
 
 When I disconnect the ZP3 the noise goes away so it is not the table/tonearm.
   When I turn the ZP3 off it is still making a faintly audible hum through the channel.
   The previous preamp (Rega Fono) was dead silent so it is not the channel on the amp. Very frustrating.
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SteveC
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Re: ZP3 phono pre hum problem!
Reply #3 - 12/02/12 at 05:54:28
 
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.
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rmcfee
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Re: ZP3 phono pre hum problem!
Reply #4 - 12/02/12 at 05:58:16
 
I may have to send it back which would suck after waiting so long to get it!
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EdGuY
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Re: ZP3 phono pre hum problem!
Reply #5 - 12/02/12 at 07:36:37
 
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
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Lon
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Re: ZP3 phono pre hum problem!
Reply #6 - 12/02/12 at 12:54:13
 
rmcfee wrote on 12/02/12 at 05:58:16:
I may have to send it back which would suck after waiting so long to get it!


I agree that would suck. I waited three months for mine and have had it just over two weeks, I love it and would hate to send it back.

You should both call Steve!
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SteveC
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Re: ZP3 phono pre hum problem!
Reply #7 - 12/02/12 at 16:03:26
 
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).
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Lon
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Re: ZP3 phono pre hum problem!
Reply #8 - 12/02/12 at 16:37:01
 
Great news!
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rmcfee
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Re: ZP3 phono pre hum problem!
Reply #9 - 12/02/12 at 16:56:30
 
 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.
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jpv
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Re: ZP3 phono pre hum problem!
Reply #10 - 12/02/12 at 20:46:54
 
There are two oher things you could try.
1) Use a cheater plug on the ZP3. Thay may remove the ground loop.
This is not the best solution but it may work.

2) I cured my hum problem by grounding the motor on my VPI Scoutmaster. I took a thin wire and ran it from the mounting screw on the motor assembly, wrapped it around the bearing assembly , then attached it to the phono grounding post. Why a stand alone motor not even attached to the turntable causes a hum is a mystery.
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rmcfee
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Re: ZP3 phono pre hum problem!
Reply #11 - 12/02/12 at 21:17:55
 
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 .
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rmcfee
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Re: ZP3 phono pre hum problem!
Reply #12 - 12/02/12 at 21:43:00
 
  One thing I forgot to mention - the rectifier tube supplied was a different one than listed in the manual (5Y3GT) It was an equivalent 5U4G.
    Also the other tube OA3 looked different than the pic in the manual - it looked like a rectifier bottle shape.
   If I installed them in the wrong place the amp wouldn't work at all would it?
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Lon
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Re: ZP3 phono pre hum problem!
Reply #13 - 12/02/12 at 22:32:28
 
rmcfee wrote on 12/02/12 at 21:43:00:
† One thing I forgot to mention - the rectifier tube supplied was a different one than listed in the manual (5Y3GT) It was an equivalent 5U4G.
† † Also the other tube OA3 looked different than the pic in the manual - it looked like a rectifier bottle shape.
† †If I installed them in the wrong place the amp wouldn't work at all would it?


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 itís 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.
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« Last Edit: 12/02/12 at 22:41:58 by Lon »  

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Lon
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Re: ZP3 phono pre hum problem!
Reply #14 - 12/02/12 at 22:34:08
 
rmcfee wrote on 12/02/12 at 21:17:55:
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 .


I would try running a ground wire from the ground lug by the RCA connections to the ground lug on the ZP3, as well as the wire coming out of the table.
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