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.

preamp --> poweramp --> cabinet (connection problem)

Discussion in 'Amps and Cabs [BG]' started by Mara, Oct 23, 2002.


  1. Mara

    Mara

    Jan 11, 2001
    Finland
    Hi guys,

    So I've managed to gather my new gear under the same roof. Today I tried connecting them all together. Doesn't work like in the movies...

    My set up with the "problem":

    Bassguitar --> Peavey MAX preamp --> Phonic XP2000 poweramp (1920W@4 ohms on bridge mode) --> Peavey 4x12" TVX bass cab (4 ohms/450W RMS).

    I connect the Peavey MAX preamp to the Phonic XP2000 poweramp via a cable which has a 1/4" mono-plug leaving the preamp and a balanced XLR male entering the CH1 input on the XP2000. With the XP on bridge mode, I connect it to the basscabinet with a thick speakercable. The cable leaves the XP2000 from the CH1 Speakon output (with the cable wired to the male speakon so that the blue wire is connected to pin 1+ (bridge +) and the brown wire to pin 2+ (bridge -)). There are not other wires in the cable. The cable is connected into the 1/4" jack of the cabinet (blue wire of the cable (bridge +) is connected to the tip of the 1/4" plug and the brown wire (bridge -) is connected to the ring of the 1/4" plug).

    Are these connections right?

    The problem is that with the system "on" and the pre and post gains on the preamp, both on 5, I have to turn the CH1 volume on the poweramp all the way up to 6 to get the same volume which I get when running an old Peavey MkVI (400W@4ohms) basshead with the 412TVX cab. The XP2000 is rated 1920W @ 4ohms on bridge mode so there should be plenty of headroom in the amp.

    Where could the fault be? Is it the cable and/or it's + and - wiring between the XP2000 and the cabinet? Should I not use a cable with Speakon and 1/4" connectors? Or is it the connection/cable between the preamp and the XP2000?

    Thanks for your help!

    Mara

    Edit: powermap changed to poweramp
     
  2. ldiezman

    ldiezman

    Jul 11, 2001
    Nashville
    ok.. I could be wrong.. but on my power amp I cannot use a regular 1/4' male connector.. I had to split the wire to connect to my carvin Power amp...

    Its was either that or use a speakon connector.. But I don't think that, when running in bridged mode, you can use plain speaker cable connection.... at least thats how it is with my PA
     
  3. geshel

    geshel

    Oct 2, 2001
    Seattle
    I don't know if there's anything wrong at all.

    Turn down the preamp all the way, then turn UP the CH1 on the power amp all the way. Slowly turn up the preamp, and note the volume.

    In a head unit, the "power amp" section gain is always all the way up. I don't know what the gain of the new amp is on 6 (6 out of what?), but it could be substantially less than full.

    The new amp, when putting out 2kW, would only be 7dB louder than the old Peavey at 400w was. So, if by having the power amp setting on "6" it's set to more than -7dB (it's likely a lot lower than that), it won't be as loud as the old Peavey.

    It could also be the Speakon wiring - I don't know enough to say if that will work for that amp in bridge mode.
     
  4. zoran

    zoran

    May 10, 2002
    croatia
    on my hafler amp on the bridge mode i have to boost ch2 to the end , and regulate volume with ch1
     
  5. I agree. I don't think there is anything wrong. Numbers on a knob don't really mean that much on a bass amp. It is where it sounds right that matters. Howmany times have I told a guitar player he was too loud only to have them tell me "I'm only on #3" For best results turn the power amp up all the way and then adjust you pre-amp volume. But, don't worry too much about knob numbers.
     
  6. malibu

    malibu Guest

    Dec 26, 2001
    what jumped out at me was that 1/4'" mono to XLR "balanced" connection, which won't be balanced (unless you go through something like a DI box to convert unbalanced to balanced - can't do it by just wiring the same signal from the mono plug to the two opposites on XLR)
    that cable could wire the signals in a couple ways to the XLR -- one of which might cancel out signals instead of being balanced -- (hope I said that in a way that makes sense)
     
  7. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    I agree with geshel and GreyBeard:
    To compare the Peavey and your new rig you should set the poweramp at max.
    But also make sure that the preamp volume is set high enough to drive the poweramp to full power.

    Matthias
     
  8. Mara

    Mara

    Jan 11, 2001
    Finland
    Will do that.

    When dealing with almost 2 kW of power, I just want to be sure what to do.

    Lets see if I can beat the noise of the tunnel work behind our cellar wall...
     
  9. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    Just don't overdo it!
    2kW into a 450W cab is a bit much. Turn up the volume step by step and see what happens!
     
  10. Mara

    Mara

    Jan 11, 2001
    Finland
    That's for sure! Maybe I should run it on stereo and use the CH1 only. The amp is rated 660W per channel @ 4 ohms.

    Maybe this thread would fit in the "headroom vs. overkill" one, few weeks back....
     
  11. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    I'm willing to bet you have an impedance mismatch with the 1/4" to XLR cable. If you have a 1/4" input on yhour power amp, try that instead and see if there is a difference.
     
  12. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    I run the signal from the full range 1/4" output jack of my MAX to my power amp which accepts an XLR or 1/4" input. I have all of the volume that I can handle. I may be mistaken but wouldn't the balanced XLR output be more useful for recording or sending a signal to a mixing board? :confused:
     
  13. FalsehoodBass

    FalsehoodBass

    Jul 22, 2001
    Denver, CO
    I agree with this...

    also.. if you max the volume on your preamp, and control the volume with your poweramp, it minimizes hiss and noise coming from your preamp and surrounding RF interference sources.