Hum and other stragne stuff with my Omega HotRod Deluxe

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Mike9, Apr 4, 2008.

  1. Mike9

    Mike9 Supporting Member

    Messages:
    10,355
    Joined:
    Sep 26, 2006
    Location:
    Ghent, NY
    My Omega modded Hot Rod Deluxe has developed a hum while idling. Also when I turn on a pedal like the Lovepedal 200#'s of tone the buz is over the top. I'm running NOS tubes in the preamp V1 - 5751, V2 - 12ax7 & V3 - 5751. Power tubes are SED 6L6's, or RCA black plates depending on my mood. I took the PI out and it's dead quiet so I'm thinking the preamp is buggy - question now is - where to start looking?

    I'll email Jim and see what he thinks in the mean time - great sounding amp when I'm playing it he really nailed the BF clean tone.
     
  2. Sparky6string

    Sparky6string Member

    Messages:
    3,527
    Joined:
    Aug 22, 2005
    Location:
    Thither
    One good way to rule out preamp tubes is to use a spare 12ax7 or similar preamp tube (5751 etc) that you know is good and swap it for the preamp tubes one at a time to see if you can eliminate the possibilities. Since you have 2 pairs of power tubes do the same with those.
     
  3. alltone

    alltone Member

    Messages:
    257
    Joined:
    Apr 4, 2008
    Location:
    Huntsville, Ontario, Canada
    Sounds like a bad ground.Check ground connections at the input stages( input jack etc.).I am not familiar with the amp,I assume it has a printed circuit board? These are notorious for bad connections due to the sonic vibrations they endure form the close proximity to the speaker.Any large caps that filter the preamp section that were not properly glued down to the board will also come loose at the solder points.I believe the board is a pain to get out ( pot nuts and the like)??If it is going to be removed to re-solder a bad connection,it might be a good idea to use a magnifying glass and look at the rest of the board for loose joints or solder pockets where the resin is present at the connection.Might as well hit anything suspicious while you've got the board out.
     
  4. Mike9

    Mike9 Supporting Member

    Messages:
    10,355
    Joined:
    Sep 26, 2006
    Location:
    Ghent, NY
    Thanks Doug - I was hoping to avoid removing the chassis, but looks like I'll be doing it now. The preamp tubes I have in it are very quiet - the ones they replaced were noisier. If that doesn't do it I'll ship the chassis down to Jim Price for upgrades. It's a damn good sounding amp so I'm hot to keep it for as long as I can.
     
  5. Mike9

    Mike9 Supporting Member

    Messages:
    10,355
    Joined:
    Sep 26, 2006
    Location:
    Ghent, NY
    This is interesting - I took the amp to work to pull the chassis and tank for packing. I figured what the hell - and plugged it in - dead quiet. I must have dirty power at the house. Has anyone else had this problem? I'm thinking about looking into a power conditioner - anyone experience these?
     
  6. Blue Strat

    Blue Strat Member

    Messages:
    30,036
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    It's possible that flexing the chassis is opening an intermittent ground connection. I would try it out of the cabinet at home and in the cabinet at work to see if the condition changes.

    When you first received the modded amp was the hum ok?

    Also, does it hum with nothing plugged into the input jacks or only when you plug a cable or cable AND guitar in?
     
  7. alltone

    alltone Member

    Messages:
    257
    Joined:
    Apr 4, 2008
    Location:
    Huntsville, Ontario, Canada

    :D
    I agree.. Save your money on a line conditioner! Chances of bad A.C. compared to mechanical vibration making and breaking poor contacts..100 to 1. The only time you might hear noise from bad A.C. (60-120cps) is when you have your amp plugged into a duplex that shares a branch line with a solid state light dimmer or the like, reverse polarity in the duplex etc. and the noise will be consistent.
     
  8. Mike9

    Mike9 Supporting Member

    Messages:
    10,355
    Joined:
    Sep 26, 2006
    Location:
    Ghent, NY
    Funny - I plugged it into the outlet at home and it's quiet now with nothing plugged in. I get a standard hum with input cable plugged in and a little more with my FX, but nothing like it was.

    I started swapping out my Bill Lawrence Low Capacitance cables and turns out they contribute a lot to the buzz factor. I know they allow more high frequencies through, but who knew?
     

Share This Page