Tubes Asylum

• Try it without the GFI. You could be right at the edge. - Chris O 05:53:29 01/26/04 (3)
  In Reply to: Does a little hum indicate it is time to retube? posted by btrvalik on January 25, 2004 at 21:06:38:

  You could also have a ground loop.

  TO TEST. Do the usual, Disconnect everything from the amp, plug it into a conventional socket (non GFI) short the inputs and listen. If it hums, then it is something in your amp. Bad caps can cause hum as well as bad tubes. Is it both channels or one, swap tubes left to right. It is highly doubtfull that both channels would hum the same if the driver or output tubes were going bad. IF your hum is the same in both channels it is power supply related. Rectifier tube, if any, or caps, or noise on the power line (that GFI thing). Any dimmers?

  Keep adding components until the hum comes back. Trial and error you will find the cause, it will just take a little work.
  
  

  ---

  • Re: Try it without the GFI. You could be right at the edge. - btrvalik 13:28:48 01/26/04 (1)
    In Reply to: Try it without the GFI. You could be right at the edge. posted by Chris O on January 26, 2004 at 05:53:29:

    I did a little more searching at it seems like some of the power coverter that provide a balanced output use a GFI for safty reasons... I don't think it is the GFI... but still worth a test. I think the biggest difference is that my old knob and tube wiring did not have a ground. My preamp (CJ PV14L) and CD player (shanling t-100) are on one side of the room and my AMP (CJ MV60) are on the other. Both AC outlets are wired to the same circuit and then it does directly to the panel. I'm thinking the quickest test would be to use one of those 3-2 prong adapers and work my way from there...

    When I brought the power up to the room for the first time the biggest thing I noticed was a really loud hum from my Velodyne HGS-12 sub. I eliminated that by moving a line-level connector with sheilding that was touching a cold water pipe. Now the sub is quiet.. As I type this I'm thinking this is a groundloop issue and not a bad tube...
    
    

    ---

    • Re: Try it without the GFI. You could be right at the edge. - btrvalik 20:41:32 01/26/04 (0)
      In Reply to: Re: Try it without the GFI. You could be right at the edge. posted by btrvalik on January 26, 2004 at 13:28:48:

      I lifted the ground on the amp and no more hum... Definitely a ground loop... Given that the outlets are connected directly together with about 15 ft of wire I did not think I should have this problem.. I would have thought that a good ground at both the amp and preamp would be ideal. Good thing I have the GFI in case one of my kids touches a tube and something like a radiator...
      
      

      ---
  • When you ask 'any dimmers?' does that apply to any dimmer switches on the circuit, even if they aren't turned on? nt - PureAudio 10:46:05 01/26/04 (0)
    In Reply to: Try it without the GFI. You could be right at the edge. posted by Chris O on January 26, 2004 at 05:53:29:

    nt
    
    

    ---

This post is made possible by the generous support of people like you and our sponsors:

The Cable Cooker

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---