Genz Benz amp problem ( Background distortion, loss of low end, possible loss of signal)

Discussion in 'Amps and Cabs [BG]' started by ChrisNoyesBass, Oct 14, 2018.

  1. Hey Everyone,

    Searched here to see if someone already had my problem, but haven't found a solution that works. Heres my issue.....

    I have a Genz Benz ShuttleMAX 9.2 (which I LOVE). On my last two gigs, I've had disturbing issues with a loss of low end/signal and background crackly distortion (seeming to be "underneath" my bass sound). I thought it was poor power, but it happened the same way at both gigs. Initially, the amp would seem to have a very weak sound, I would try to compensate by turning up the low end and gain. About 3 songs in, It would seem to get much louder and would be peaking. I'd turn it back down, and it would seem to be okay. I took it home and experimented. I'll share my results and see if it points to a solution.

    I switched out cables and basses and used the headphone jack in the amp, I tried both FET and Tube channels at various volumes. I got the exact same distorted background sound regardless. I would tap the top of the amp (as one does when you're diagnosing an issue) and the sound would go back to normal. I could then recreate the sound by tapping it again. Obviously, I want to fix the issue so I don't have to do that. One interesting side note: When the amp is distorting, the "signal" LED light on the front of the amp will stop working, (or stop being as sensitive). It usually comes on when there is any sort of playing, even light. I could get it to turn on, but only with heavy/hard playing. Tried twisting the cable on the input jack and there was no loss of signal at all, so I ruled out a dirty jack.

    Any ideas what it may be??

  2. Bim1959


    Apr 15, 2009
    Naples Florida
    Sales and electronic tech/piano tech: England Music Center - Clinton IA - now closed
    Hello and welcome to Talkbass!!!
    If you could please fill out your profile page it'll really help us all out.


    He can help you with your problem as he is still a tech for Genz Benz products
    wave rider likes this.
  3. Hi new guy! Welcome aboard.
    Couple or three things that are easy to check.

    Effects loop if you it... Plug a patch cable between the In and Out jacks ((Send, Return).
    The jacks can get corrosion from not being used.
    Sometimes just inserting the cable a few times might clear it.
    Other times you might have to leave the patch cord in.

    Are you sure it’s the amp and not the speakers?
    Running too much bass can cause the speakers to hit their mechanical limits.
    We call it -farting out- because the sound it makes kind of sounds like a farting noise.
    Try EQ-ing with a lot less bass. Sounds counter-intuitive but in many cases it can make your low end sound better.

    Are you running an active bass, one that uses a battery?
    If so try a new batt. When the batteries in an active get low, the preamp in the bass is starved for voltage and starts sounding crappy.

    Do you have dirty controls on your amp?
    When you turn them is there a scratchy noise coming from the amp?

    Try these things and check back in.

    Good luck.
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    There are many possible causes, though the first thing I would double check is that it's not a failing battery in an active bass.

    Your amp is covered under a factory supported service program. PM me and I will get you the details.
  5. I know my original post was kinda long, so just to clarify....

    I used two different basses, same exact results, so I ruled out a bad battery.

    I got the same result through the headphone jack in the back of the amp, and got the same result regardless of gain and master volume changes, so i ruled out anything to do with speakers.

    I just try closing the effects loop in the back with a cord, and it seems to have worked? as in I can't recreate teh sound like i did last night. I'm going to let try the amp a bit more to see if that "solved" the issue, or if I'm just too tired to be properly testing this thing yet (my original post was from 3:30am EST)
    yodedude2 and Old Garage-Bander like this.
  6. OK. Get some sleep then check back in.
    In the morning, or afternoon, whever you rise and shine...
  7. jnewmark

    jnewmark Just wanna play the groove. Supporting Member

    Aug 31, 2006
    Stax 1966
    Third St. Cigar Records staff musician.
    Sounds like the old effects loop/distortion problem.
    wave rider likes this.
  8. catcauphonic and jnewmark like this.
  9. FronTowardEnemy

    FronTowardEnemy It is better to go unnoticed, than to suck Supporting Member

    Sep 19, 2006
    Chicago Illinois
    GB ShuttleMax 9.2 owner here. I love this amp, I would clean all the jacks and see if that works.

    I had a crazy little crackle going on with mine a few months ago. No matter what, it sounded like a bowl of rice crispies was being played through it. It wasn’t loud but it was audabile. I had to clean and reseat the preamp tube pins then all was good.

    If you still have issues send it off to agedhorse for repair, I know I would.

    These amps are the GOAT in my opinion.
    ChrisNoyesBass likes this.
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Just don't hack a repair or spray anything in it, that increases repair costs.
  11. I can't agree more!!! This has been my baby for years (just after they got bought out :( and I got one for cheap with an uber bass 210 and 115). That's why I got so nervous when it started giving me issues. Like when you see your kid fall off the swing set for the first time.

    UPDATE: the dirty effects loop might have been it. Hasnt given me a problem at all. Fingers crossed!
    Last edited: Oct 14, 2018
    catcauphonic and FronTowardEnemy like this.
  12. BadExample


    Jan 21, 2016
    For peace of mind, you can complete the troubleshooting process by removing the bypass and see if the issue returns (if you haven't already).

    You can use it with the jumper in place as long as you want, but it might be best to get it back to the aged horse when it's a good time to do so. You'll get a full checkout and it's not expensive.

    Just don't spray anything into the 1/4" jacks. It will get all over inside and cause trouble.
    catcauphonic likes this.
  13. BassmanPaul

    BassmanPaul Inactive

    If the normalising contacts on the Effects Loop jacks are the problem, spraying contact cleaner into the jack will do nothing as the contacts will not be touched.
  14. I took the chord out of the effects loop, seems to be working fine. One thing I noticed was the problem appeared only when I first plugged the amp in, so I'm gonna let it cool down and try again.

    Thanks everyone for the support!
    eff-clef and BadExample like this.
  15. BadExample


    Jan 21, 2016
    Opening and closing the contacts with the jumper may have cleaned them up enough for now. I'd leave the jumper out, but keep it handy. If it returns, mute the amp and insert the jumper again, un-mute. If the problem goes away again, it's likely to be the contacts.
  16. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Often, cycling a plug into the effects return jack a few times will re-establish the normaled connection.
    eff-clef, Bim1959, JMacBass65 and 3 others like this.