1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

No pre-amp, no feedback

Discussion in 'Amps, Mics & Pickups [DB]' started by Pierre Boucher, Apr 2, 2018.


  1. Pierre Boucher

    Pierre Boucher

    Apr 28, 2017
    Montreal
    Hi to all,
    When I bought my used DB, it came with accessories and a Fishman BII among others, but no amp. So I bought a Rumble 25 and always believed a DB needs a pre-amp for amplification, unless I misunderstood something.

    I play at church (large venue of course), but the musicians' corner is rather tight. So I had some problem with feedback. After juggling with the B, M and T buttons, I suppressed the feedback, but I could not pump the volume too high.
    Now, recently, I went to church for a sound check. The pre-amp didn't work. So, I gave it a try and plugged the DB directly into the amp. BINGO.
    I could max the volume, set my sound (no difference with no pre-amp). Feedback and hum problems resolved, being close to or away from the amp.
    Can someoine can explain why it works with no pre-amp?

    Thanks
     
  2. What pickup do you use, Pierre?
    The input impedance of the Rumble 25 is not optimized for most piezo pickups.
    Did you replace your preamp battery?
     
  3. Pierre Boucher

    Pierre Boucher

    Apr 28, 2017
    Montreal
    New battery. I could hear the electric contact when I plugged the guitar cable jack.
    Pickup : 1 piezo sensor slipped on each side of the bridge.
     
  4. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    The Fishman BII is optimized for the
    Fishman Full Circle pickup. Depending on what pickup you have, it can actually make it sound less than optimal. The Rumble 25 is bassically a practice amp. It’s quite possible that the output of the BII is overloading the amp’s meager 25 watt power output. So, even with the 10 Meg Ohm impedance benefit of the BII
    your feed back issues could be the result of overdriving the power amp. Just my take.

    Ric
     
    Lee Moses likes this.
  5. Do you know the brand of the piezo?
    Can you try with just one sensor, with the preamp?

    When you don't use the preamp, do you notice the sound to be thin and you have to boost the lows or engage the contour switch?
    This shouldn't be the case with the preamp.
    It should thicker and need less, if any, lows boost.

    Do you have the V3, like this one?:
    Fender Musical Instruments - Rumble 25 - Rumble Series 25 Watt Bass Amp (V3)
     
  6. I had one and used it with several piezos and it made all of them sound better, actually.
    The overloading is an interesting idea.
    If you reduce the volume of the BII to, say, 1/3 or 1/4, this should verify this hypothesis.
     
  7. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    That’s been my experience with
    with a Ibanez Promethian 20 watt. The Ehrlund Preamp just pushes the
    input of the Ibanez pre to hard, so it will start to feedback, as soon as you
    increase the Ehrlunds volume. I have the original Fishman Model B Preamp
    it does the same thing. It’s to much of a good thing, I guess.:) :woot:

    Ric
     
  8. Pierre Boucher

    Pierre Boucher

    Apr 28, 2017
    Montreal
     
  9. Pierre Boucher

    Pierre Boucher

    Apr 28, 2017
    Montreal
    Don't know the piezo brand. I can use only one sensor.
    No pre-amp : The sound was not thin, on the contrary. Nice sound to me. No gain, no contour, no overdrive, etc. Just plain B, M and T adjustments.
    There was always a kind of feedback when I enabled overdrive function. So, no overdrive.
    What suprised me was that even playing close to the amp at high volume, there was no feedback nor interference whatsoever.

    Yes, this is the amp (Long McQuade).
     
  10. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    Seems that the Rumble 25 just can't handle the increase in gain.
    The larger Rumble's get high praise for DB.
     
  11. The BII has an input gain control on the back of the unit. Unity to +12 dB gain, according to the manual. Back it off, start with the BII volume control low and try again. You shouldn't have to max the input of the Rumble. The input impedance of the Rumble is not specified, but it may actually be detrimentally loading your piezo; the BMII's input impedance is 10M. So, YMMV.
     
    Ric Vice likes this.
  12. It's now 1Meg (was about 200K in previous version) so it may explain why it works well for Pierre.
    Manual attached.
     

    Attached Files:

    Ric Vice likes this.
  13. Good info. Unless the OP needs any of the features, i.e. volume control on his person, I'd leave the preamp out of the equation. Less stuff to go wrong on the gig.
     
    Ric Vice likes this.
  14. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    The exception would be if his pickup
    is a Fishman BP-100 or something that needs a higher input impedance than 1 Meg Ohm. Ye Olde BP really needs a higher input impedance
     
    Francois Blais likes this.
  15. Indeed!
    Pierre, can you take a picture of the bridge showing the pickup, please?
     
  16. dhergert

    dhergert Gold Supporting Member

    Jan 17, 2018
    Blue Zone, California
    So, I've experienced this now also, but plugged into a sound system mixer rather than an amp. This is for four different on-stage bluegrass performances with different sound systems and no pre-amps... I have been pleasantly surprised, especially because I wasn't even planning to use the piezo setup and was expecting to just use a mic.

    This is with Vic's Pickups Model C single-bridge and slap piezo combo. I believe the cables and mixer inputs were mono, so they're probably only picking up the bridge piezo. Extremely clean sound, proper non-boomy acoustic tone for these bluegrass venues, and no feedback. And none of the sound guys had any trouble mixing in the bass.

    So, please excuse my ignorance, but what are the circumstances where a preamp is preferred?
     
  17. When plugging direct fails?
     
  18. dhergert

    dhergert Gold Supporting Member

    Jan 17, 2018
    Blue Zone, California
    Hmmm, thank you, I'm still confused, but listening...

    I'm guessing a bass preamp provides an EQ and amplification and maybe some voicings. My experience with direct connections and no preamps so far is basically plugNplay. Am I just not getting the value of a preamp because my current understanding is of bluegrass venues that tend to under amplify compared to other venues?

    When is a preamp absolutely required?
     
  19. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    There are no staid and fast rules for using a preamp into a FOH system. It depends on system used in a particular venue. Generally, piezo pickups Fishman, Realist, & Underwood need at least a 1 Meg Ohm Load to sound decent. The HPF Buffer Preamp built by Francis Deck is a very economical box that works very well provided you are using a pickup.

    Ric
     
  20. dhergert

    dhergert Gold Supporting Member

    Jan 17, 2018
    Blue Zone, California
    Thank you. It sounds like I'll need to run into a situation where I need a preamp before I buy one. When that time comes, I'll ask here for recommendations.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Mar 1, 2021

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.