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!  

preamp help

Discussion in 'Amps and Cabs [BG]' started by Blind owl bass, Dec 4, 2019.


  1. Blind owl bass

    Blind owl bass Supporting Member

    Apr 13, 2018
    Hello TB
    just bought (from here on TB) a crest ca9 power amp because I want to try the pre/power amp combo thing. I currently double with a radial engineering tonebone OD 2 channel preamp. upright 4 string bass (Fishman full circle pickup) into the A side (piezo boost engaged), and a 5 string fretless with active emgs on the B side.

    a guy from radial said I can't power the crest with the sends/outs from the radial because they are not at line level (or mic level, I'm not super techy here). said I would need a di or something to bring the level up for the crest ca9 to power.

    so my question. what preamp or di or gizmo do you think would work best to feed the radial into. I have been thinking about trying a radial firefly or summit audio tube preamp. the ART stuff seems cheap and good too.

    so again goal is to have ability to use both basses, have separate eq for each bass (radial tonebone od), run both basses in ca9 power amp, and run that into one Audiokinesis cab. and no cable swapping.

    any help or opinion is greatly appreciated
    cheers
     
  2. How are you planning on connecting the ‘stereo’ amp to a ‘mono’ speaker system? Let’s start there. :)
     
    mcnach and agedhorse like this.
  3. Blind owl bass

    Blind owl bass Supporting Member

    Apr 13, 2018
    it can be bridged for mono
     
  4. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    I replied over on your other thread too...Do you really need to bridge that? Amp itself has enough juice that you probably can be running off of a single channel, or run dual-mono into two cabs.
     
    Fuzzbass and Arthur U. Poon like this.
  5. Blind owl bass

    Blind owl bass Supporting Member

    Apr 13, 2018
    I am not the most tech savvy. I plan on using just one audiokinesis thunderchild 2x12 cabinet. 4 ohm 900watt. if the amp is stereo out, can I use just one side?
     
  6. Blind owl bass

    Blind owl bass Supporting Member

    Apr 13, 2018
    I agree bridging to mono would be alot of power and i would turn the gain down alot. but if there is another way, please let me know tb world
     
  7. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    I'm not one to tell someone not to bridge if they really want but transient spikes (lookin' at you upright) could well exceed safe operating power. The Crest CA9 can do 900w per channel at 4ohms. To me that says don't bridge, run it standard and use only one half of the amp. If you find that not enough, then bridge. It'll be pretty easy to suss out as you set it up. Get a 3 or 4 space rack grab a reasonably priced preamp of your choice and have at it.

    And yes, you can use one channel safely. :) Back in the 'old days' I would sometimes run my whole rig off of one side of my power amp then if needed power monitors or part of FOH with the other side if we really needed it.
     
    wave rider, zon6c-f and Wasnex like this.
  8. Use one side of the amp. It's plenty. As far as the other issue-the concern seems to be that your pedal preamp won't output a large enough signal to drive the Crest properly. I say go ahead and try it. Might be fine. Worst-case it's not loud enough. I'm not familiar with that amp's input requirements situation.
     
    Fuzzbass likes this.
  9. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
    First of all, one channel of a CA-9 will be sufficient for your cab, and there's no harm in running the amp with just one channel being used. I definitely wouldn't recommend bridging it for mono. But you need some kind of real pre-amp to get the drive level from the pedal up to the input level the amp needs to see. It would seem that a rack-mounted one would be easy to deal with, given that you've already got a rack-mounted amp. If the Radial is giving you a tone you like, then you really don't need too much more in the way of a preamp than just a gain stage...so almost anything would work well enough. It seems like a groovy preamp like the Summit would be over-kill in that situation...but it would certainly get the job done.
     
    Last edited: Dec 4, 2019
  10. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
    OK...I looked at the specs for the Radial device on their web page and I'm puzzled...it doesn't appear to be any sort of preamp at all. The specs say specifically it's a unity gain device. What are you doing with it now? Plugging your instruments into it and then running it's output into a conventional bass head? If so, you really are going to need an actual preamp of some sort.
     
    Last edited: Dec 4, 2019
    mcnach and agedhorse like this.
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    With that amp, bridged mode could easily destroy your cabinet if you happened to have an unfortunate accident (like partially unplugging a cable of power supply of a pedal) resulting in a large transient noise. Turning the gain down doesn't limit the power, it just changes the input level required for rated power. You would be MUCH better using only one channel of the amp IMO and IME.

    Also, I don't think the Radial device is going to be suitable to drive the power amp. Even though it's capable of +10dBu, by the published specs it doesn't appear to have the gain needed to go from instrument level to line level.
     
  12. Wasnex

    Wasnex

    Dec 25, 2011
    The 1/4 output is instrument level and the XLR output is mic level, so you need another preamp to bring the signal to line level to drive the power amp. The CA9 requires an input signal of 0.775V RMS to reach full output power. So whatever preamp you get must be able to produce the equivalent output to 0.775V RMS. The level may be listed in other units such as dBu or dBm.

    Here's a handy page you can use to convert from one type of units to another. dB dBu dBFS dBV to volts audio conversion digital - calculator volt to dBu and dBV dB mW SPL dB decibels 0 dBFS - convert dB volt normal decibels relatioship relation explanation analog audio absolute level true rms convertor converter decibel to dbfs converter calculation online attenuation loss gain ratio reference audio engineering sound recording dBFS dBVU 0 dB audio logarithm level converter peak to peak p-p impedance voltage pro consumer audio digital analog recording level - sengpielaudio Sengpiel Berlin

    You could use a small cheap preamp like an Art Tube MP to amply the output of your Tonebone to line level.
    Tube MP – The Original – ART Pro Audio
    Handles mix and instrument level, and the XLR output maxes out at +28dBu, which is significantly above 0.775V RMS.


    There are also a variety of full featured Preamp DIs that provide a line level output sufficient to drive the CA9.

    For example I believe a Grace Felix is designed to push a power amp.
    FELiX – Grace Design
     
    mikewalker and Jim Carr like this.
  13. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    IMO, if 900 Watts RMS isn't enough, there's not enough speaker for the task required. Bridged is (IIRC) ~2000 watts RMS into 4 ohms, doesn't leave much margin for accidents or lapse of good judgement...
     
  14. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
  15. Blind owl bass

    Blind owl bass Supporting Member

    Apr 13, 2018
    you are correct, I called up radial today and they confirmed that the radial wont be able to drive the crest as is. I've been looking at the grace for a while. but dang its pricey. my mandolin player has one, it's pretty great.
     
  16. Blind owl bass

    Blind owl bass Supporting Member

    Apr 13, 2018
    prob start with the cheap ART. maybe move to something better if I like the results.
    can I use one output and not bridge the amp?
     
  17. Blind owl bass

    Blind owl bass Supporting Member

    Apr 13, 2018
    sorry saw this after. thank you all for the great info!
     
  18. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Be sure it has adequate output level. It really needs a minimum of 3dB and better 6dB beyond .775VRMS drive level which is between 1V and 1.6V RMS in order to drive the amp to rated power without clipping the output (or not having adequate margin). Many pedal preamps, unless designed specifically for driving power amps, have an instrument level output.

    Also, the level control on the amp's channel that you are using will need to be all the way up in order to achieve rated sensitivity ofthe amp.
     
    BasturdBlaster and Wasnex like this.
  19. Wasnex

    Wasnex

    Dec 25, 2011
    FYI, the ART Tube MP specs +28dBu. The unit converter I linked in post #12 says +28dBu is over 19V RMS.
     
  20. Blind owl bass

    Blind owl bass Supporting Member

    Apr 13, 2018
    so the cheap ART works. def will start there. again thank you all so much
     

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.