Mono preamp into a stereo amp

Discussion in 'Amps and Cabs [BG]' started by jive1, Mar 31, 2003.

  1. jive1

    jive1 Moderator Staff Member Supporting Member Commercial User

    Jan 16, 2003
    Owner/Retailer: Jive Sound
    I'm considering going to a more modular rig, and I was wondering how you can use a mono preamp into a stero power amp, and use both channels of the stereo amp. I guess I could use a Y cable, but I don't know how much sound degradation that would cause. I guess I could use the XLR direct out and the line out of the preamp, but I am not sure how effectively that would work either.

    Any ideas?
  2. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    Use a Y cable. Unless you are using some wierd power amp with ridiculously low input impedance, you won't have a problem.
  3. Touch


    Aug 7, 2002
    Boulder, CO
    For many power amps you can also "bridge" the two channels of the power amp together. This effectively combines them together which can give you more than twice the power of the two channels (crazy laws of electricity).

    I do this on a QSC-RMX-850. My preamp is a Rane AP-13 (I'm over here from the DB dark side). I bridge the two channels together and deliver ~800W to a 4 ohm Acme B-2.

  4. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    You can also run a single line from the preamp to channel A of the power amp. Then use a jumper from the output of channel A into the input of channel B.
  5. LJW


    Feb 8, 2002
    northeastern pa.

    Do NOT feed the output of one amp to the input of another.

    Set the amp to parallel mode.
  6. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado
    Not everyone has an amp that has a parallel mode option. And, doing it as I've described works just fine. See below....


    Above is a likeness of the back of my amp. Just to the left of the fan on the right are 4 XLR type connections. Channel A input is on the lower right and channel B in put is on the lower left. The top two are the outputs (channel A on the right & channel b on the left). All you have to do is either make or buy a short cable with a male XLR connector on one end and a female on the other. The male go to the input on channel B and the female to the output of channel A. Simple.
  7. LJW


    Feb 8, 2002
    northeastern pa.


    Instead of setting the amp to parallel mode you are using a set of parallel inputs to acomplish the same thing. Although they may be labeled 'output' they do not carry the higher power of the amplifier output intended to drive loudspeakers. My concern was for the poster since many amplifiers (my QSC included) label the loudspeaker connections 'output'.

    The error may well be mine for making such an inference.

  8. This amp has a pass-through input which allows you to daisy-chain amps. The "output" he refers to is actually just parallelled to the input connector. Many amps do not have this feature.

    Do NOT connect the speaker output of one channel to the input of the other!!!
  9. ebozzz

    ebozzz Supporting Member

    May 17, 2001
    Denver, Colorado

    I figured that you probably misunderstood what I was getting at. I have a way of doing that to people. ;)

    You and Bill are dead on regarding the speaker outputs. I'm sorry that I was not clear with my initial description.
  10. LJW


    Feb 8, 2002
    northeastern pa.
    No apologies are necessary.