Dismiss Notice

Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Help! My new RBI is screaming like a banshee!

Discussion in 'Amps and Cabs [BG]' started by Monkey, Aug 8, 2003.


  1. Monkey

    Monkey Supporting Member

    Mar 8, 2000
    Dayton, Ohio, USA
    I just upgraded my rig from a Carvin R1000 to a Yamaha CP2000 power amp and a Sansamp RBI. I love the tone and punch of the RBI, but it is NOISY! I mean really noisy. I can't use the Presence knob at all; it adds hiss that is clearly audible over the tone. I'm running the rig through two Aguilar GS-112's; turning the tweeters down on the cabs don't help much.

    I used this pre- and power amps live just two hours after receiving it. I ran an XLR to the PA, and the noise was awful. I was using a well-shielded bass with humbuckers, and tried it at home with the same results.

    Any insights, or should I just send the RBI back?
     
  2. Mcrelly

    Mcrelly

    Jun 16, 2003
    Minnesota, USA
    I need more info. exactly what was connected to what inputs and outputs on the RBI and other components. where you getting high pitch feedback? buzzing, humming? what where the knobs set at for each knob? are you SURE You had a shielded cable between your guitar and the RBI AND between the RBI and the yamaha?

    "screaming" implies feedback to me. my tweeters on my swr were very sensitive and if I turned up the output to far above my actual signal level, the tweeters would start whistling. like a mic feed back.

    try starting with your guitar volume cranked the rbi gain at 9 o'clock and the level of the Rbi at minimum. slowly raise the "level" until you have a usable volume. if you can position the cabs or the tweeters so if your standing with your guitar in front of the cabs the tweeters are NOT nearby the pickups.
     
  3. HeavyDuty

    HeavyDuty Supporting Curmudgeon Staff Member Gold Supporting Member

    Jun 26, 2000
    Suburban Chicago, IL
    RBIs tend to be pretty quiet, but a small batch of them left the factory with a wrong transformer that causes a lot of noise - basically, the preamp is trying to run on too low of a supply voltage. Your symptoms are excactly the same as mine, particularly after the power company did the seasonal voltage drop.

    If you're comfortable opening it up, get the number off the power transformer and call/email Tech21 to confirm it's the right one for 120V.

    Mine had the correct power cord, but a 220V transformer. Replacing the transformer was a two minute job after Tech21 expressed the correct one out to me with their apologies.

    PM/email me if you want more info.
     
  4. Mcrelly

    Mcrelly

    Jun 16, 2003
    Minnesota, USA
    Heavy, I forgot to mention that my RBI occasionally, usually just when I turn it on, will emit a "tone" some kinda waveform (a constant irritating tone, kinda like a capacitor discharge) its seems to happen when I hook up to a P.A. with XLR. I usually shut it off right away and try to turn it on several times and then when it doesn't make the sound I leave the unit on. once it made the sound turning it off.

    its worked fine hundreds of other times, but 3-4 times its made that tone.
     
  5. Monkey

    Monkey Supporting Member

    Mar 8, 2000
    Dayton, Ohio, USA
    Screaming wasn''t the right word. The RBI isn't feeding back and in fact sounds great, but just has a really loud buzz when the TREBLE or PRESENCE knobs are turned up. I'm sure I have everything hooked correctly. Thanks for the advice, Mcrelly.

    HeavyDuty, it sounds like I may have gotten one with the wrong transformer. I will open it up and contact Tech21. Thanks a lot!
     
  6. Fishface

    Fishface

    Jul 26, 2002
    Denver, Colorado
    I also have had a lot of noise with my newly purchased RBI. I would like to use the presence knob (sometimes), but when I have it more than 9 o'clock I get a very noticeable hiss. So much that I got quite a few comments from bandmates and the soundman during its first use. I've since relegated myself to keeping the presence at about 8 o'clock all the time.

    It sounds like I also may have the wrong transformer in mine. With the correct transformer, how "hissy" is it?
    :confused:
     
  7. Schwinn

    Schwinn

    Dec 4, 2002
    Sarasota, FL
    I think with treble, presence, or drive turned up a little hiss may be normal. I'm not saying your hiss is normal though. But generally, those functions add high end (and thus noise). I think my RBI is fairly quiet, but I get noise when I turn up the drive, I noticed. Of course I've been using a SVP so anything will sound quiet compared to that :rolleyes: .
     
  8. Mcrelly

    Mcrelly

    Jun 16, 2003
    Minnesota, USA
    I run my RBI with the presence all the way off! I don't like finger noise and I don't slap. my friend who slaps and likes to play higher notes than I runs his presence very high 1-2 o'clock. if you have a bright cab/amp or piezo pick ups it might be too much higher frequencies that tne presence is turning up. presence will also accent you tube hisss through the tweeters.

    keep adjusting presence/blend/mids until yoou get a sound you like.
     
  9. Monkey

    Monkey Supporting Member

    Mar 8, 2000
    Dayton, Ohio, USA
    I think I am getting the hang of it now. I can only turn up the Presence to about the 8 o'clock position without annoying buzz, but I am getting a nice sound now.

    I am going to put my bass on the workbench and check my shielding. I was very careful when shielding it, but I think I missed something. Even if it turns out I can never really crank the Presence, I don't mind; the tone I'm getting now is really nice.
     
  10. Schwinn

    Schwinn

    Dec 4, 2002
    Sarasota, FL
    Is the noise exacerbated by florescent lights? If it is, I have that problem too.
     
  11. Fishface

    Fishface

    Jul 26, 2002
    Denver, Colorado
    I have just kept the presence at 8o'clock. That seems to take care of the hiss. I don't like much finger noise anyways.

    I do love the sound of the RBI. I don't even touch the EQ (it's all flat!!!). I just adjust the drive to taste (from 10 to 12 o'clock).

    I used it on a gig last week and I was in pure heaven. If it just had a mute button...