Mesa Boogie Express power stage hiss

Discussion in 'Glowing Bottle Tube Amp Forum' started by JL_LI, Sep 29, 2020.

  1. JL_LI

    JL_LI Friend of Leo's

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    I hope I'm in the right place. I got hearing aids back at the beginning of the year and finally got them adjusted to eliminate phasing that made my guitars sound like they were being played through a chorus pedal. So now I can play with the aids in. Tone, timbre, and balance between strings are all improved. That's great but I hear something unpleasant with my hearing aids in.

    My amp is a Mesa Boogie Express 5:25. The problem I'm noticing is hiss from the power stage. I never noticed it before I began using my hearing aids. The hiss is loud enough to bother me at bedroom volume. It gets louder when I turn the volume up and decreases when I turn the volume down. The hiss is independent of the volume setting on my Stratocaster. The hiss is not 60 cycle hum. I can hear that if I listen for it, but my FCS Strat is shielded well enough that it isn't bothersome. I use only one pedal, a BOSS EQ-200 and the hiss is independent of the pedal or pedal settings. I can reduce the hiss by reducing the volume on the amp and raising the gain but that puts the volume at about 9 o'clock and I loose harmonic richness with the volume that low. I replaced the power tubes with new tubes from Mesa Boogie about 6 months ago. The last ones lasted years, not months so I don't think the power tubes are shot.

    Is there something I can check? How much hiss is normal? Can low noise power tubes be had anywhere? Mesa Boogie makes a big deal about selecting tubes that don't need biasing. What are the risks of using matched tubes that may need a different bias from the preset? I love the amp. I want to keep it. I don't want to go solid state. Am I just overly sensitive to this? Somebody tell me there's a way out of the maze. Thanks in advance.
     
  2. MuddyWolf

    MuddyWolf Tele-Meister

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    Tube amps with gain stages for distortion have hiss. It was always there. Now your hearing is bionic like steve austin so now you are hearing it. There probably is enhanced eq and compression in the hearing aid also that brings noise up to be more noticable. If you can reduce the compression and flatten the eq of you're hearing aid it would help help. You probably cant adjust that. I dont think you can do anything to the amp that will work the way you want. Maybe turn down the treble and presence.
     
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  3. Lef T

    Lef T Tele-Holic

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    The Mesa 5:25 and 5:50 Express both have a little bit of hiss.
    I've also heard others complain of this.
    You could try different preamp tubes.
     
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  4. bftfender

    bftfender Poster Extraordinaire

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    In my recent Mesa binge. Ended up putting all Mesa tubes in them.. 1 was fussy, .f100, I used to put Ruby 12AX7AC7 HG in my Peavey's in V1 & it really tamed some hiss but did not hurt gain, if anything, fuller sounding. Tried it in the f100..instant fix. The amp became so good. Have 3 more kicking around & will try them in the others if needed. Also noted in all of them..there is that place on MV where it is there.. the fullness, just a tiny nudge from the thins & agitating to 'the sound" Do have el84 DC3 & its a bit hotter & wound up to begin with in comparison to the 6l6's
     
    Last edited: Oct 2, 2020
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  5. JL_LI

    JL_LI Friend of Leo's

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    My amp is an Express 5:25 that I use clean with a little bit of an edge to the sound at indoor volume. Playing with it a little more, I find that the Blues channel quieter than the Clean channel. I guess I can be OK with that. I need to increase Treble to get my sound. What's curious to me is this. I can increase loudness using Gain, Volume, or clean boost from a BOSS EQ-200 equalizer pedal. At as close to the same volume as possible, The Blues channel has less hiss than the Clean channel, increasing loudness using the volume control adds more hiss than increasing it with gain, and using the equalizer for a few dB boost doesn't add too much hiss but it's harder to quantify. I just replaced the power tubes a few months back with tubes from Mesa Boogie and have been using the Mesa Boogie low noise 12AX7SPAX tubes for V1 thru 5. A Ruby 12AX7AC7 HG is cheap enough and maybe worth a try. I also may just leave it alone if I find a good balance point with what I have. With my hearing aids set up for music, playing as opposed to listening, I like the differences I hear from the wound strings and I really like the overall tone. I think what I'd done over time is change my amplifier, guitar, and EQ settings so it sounded good with my hearing loss. I have to start the process over again now that I have my full frequency hearing range restored. Thank you for the suggestion @bftfender . $25 shipped is cheap enough to try a tube.
     
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  6. hotraman

    hotraman Tele-Afflicted

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    I, too, own a first generation 5:25.
    Yes, there is a hiss, but mine comes and goes.
    Its not there all the time.
    Once you get to playing, the hiss is not noticeable on my amp.
    I've read over at the old Boogie forum, that changing out tubes may help.
    I'm just staying with what I have.
     
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