Acoustic preamp to DI to TRS balanced mixer input - active or passive? | The Canadian Guitar Forum

Acoustic preamp to DI to TRS balanced mixer input - active or passive?

Discussion in 'Recording and PA Lounge' started by Greg Ellis, Oct 30, 2019.

  1. Greg Ellis

    Greg Ellis

    Joined:
    Oct 1, 2007
    Location:
    Newmarket, ON
    I'm working on a possible house jam, and trying to figure out if I can make it work with gear on hand.

    I have a Mackie PROFX8 that has 4 mic inputs, a stereo channel with full eq, and a "stereo return" channel that is just a slider (no eq, no adjustable preamp).

    I will probably need all four mics for vocals, so I need to figure out if I can run the acoustic guitars (at least 3, maybe 4) into the remaining inputs:

    left and right sides of the stereo channel
    left and right sides of the stereo return.

    Not ideal, I know, but it would save me buying a bigger mixer.

    My question is how to get a signal from an acoustic preamp into a balanced TRS input.

    Is this as simple as a guitar > passive DI > XLR to TRS cable > TRS mixer input?

    Or would an active DI be more useful in bringing the signal level up to a usable level?

    I know how to make the connectors fit. I'm not so sure about the signal levels.

    Any thoughts?

    Thanks in advance
     
  2. Kerry Brown

    Kerry Brown Gold Member

    Joined:
    Mar 31, 2014
    Location:
    Squamish, BC
    Milkman and Greg Ellis like this.
  3. Greg Ellis

    Greg Ellis

    Joined:
    Oct 1, 2007
    Location:
    Newmarket, ON
    I hadn't considered that, but it's a good idea.

    I still don't understand the passive vs active DI part of things.

    Most mixers have a very minimal number of hi-Z inputs.
     
  4. cbg1

    cbg1

    Joined:
    Mar 27, 2012
    Location:
    elliot lake.ON
    Active di has a preamp in it. Powered by an internal battery or phantom power from the mixer via the xlr connection


    Hope the jam goes well
     
  5. Granny Gremlin

    Granny Gremlin Gold Member

    Joined:
    Jun 3, 2016
    Location:
    Toronto - Riverside
    DI outputs mic level (balanced LoZ) so you need a preamp before going into a line level ( balanced HiZ) input or it will just be too damn quiet/noisey/some signal loss at extremes.

    If you have anything else with a mic pre ( even if the output is not balanced -that mixer will take TS or TRS) then use that ( e.g. your computer interface or an actual stand alone mic preamp).

    Simpler still, the active circuit on tour acoustic may already be HiZ ( if not sure google the model) in that case just go straight i to the mixer - forget the DI).

    I know you said 3-4 guitars - do you have that many DIs anyway? Renting a larger mixer may be the best option. Or if one of the other jammers has another similar small mixer, take the main outs of that into the teturn on yours ( legit thing to do - google submixer or sudecar mixer).
     
    Last edited: Oct 30, 2019
  6. KapnKrunch

    KapnKrunch Gold Member

    Joined:
    Jul 13, 2016
    Location:
    Yes
    Four mic's plus three acoustics, into four channels plus left and right stereo.

    "Do the math". Seven equals six. Nope.

    You need another cheap mixer or rental.
     
    Greg Ellis likes this.
  7. Greg Ellis

    Greg Ellis

    Joined:
    Oct 1, 2007
    Location:
    Newmarket, ON
    Chuckle, I'm getting more confused by the minute...

    Sound source is an acoustic guitar with an onboard preamp, probably under-saddle pickups but maybe fancier stuff too.

    I'm assuming those are looking for a Hi-Z input, and there might only be one or two of those available on a given mixer.

    Using a DI box, I can convert that signal to a Lo-Z mic-level signal and plug that into a mic preamp on the mixer.

    I hope I've got all that right.

    Does it make a difference if I use a passive DI or an active DI for this?

    Are there advantages one way or the other?
     
  8. KapnKrunch

    KapnKrunch Gold Member

    Joined:
    Jul 13, 2016
    Location:
    Yes
    Your mic channels are OK for mic or acoustic guitar. Any type.

    Your stereo input is good for two preamped acoustics (left and right).

    Still leaves one acoustic out? Just use a guitar amp?
     
  9. High/Deaf

    High/Deaf Gold Member

    Joined:
    Aug 19, 2009
    Location:
    LM,BC,CAN
    Do you need the PA?

    I jam with multiple acoustic guitars and multiple vocalists all the time - and no PA support. Levels are better controlled, a good mix is easier to obtain. KISS. We also usually have an amplified bass and acoustic drums. The drummer has to be good and able to play within the environment, but other than that, this is my preference for an acoustic jam.

    Acoustic gigs are different, but depending on the size of the room, I'd still do that without PA if possible. PA just adds complication, which if it isn't necessary isn't worth the trouble. IMO.
     
  10. marcos

    marcos Gold Member

    Joined:
    Jan 13, 2009
    Location:
    Canada
    I am assuming your guitars have on board pre-amps correct? Powered by a 9 volt batt? If so, you can go directly to the stereo inputs left or right no problem. The signal would be better with a DI for sure and i would use a powered DI but again, a non powered will work fine just need to bump up the volume. We do this all the time at my house when we have an acoustic jam. Works fine. best of luck
     
  11. Chito

    Chito Gold Member

    Joined:
    Feb 17, 2006
    Location:
    Ottawa, Ontario
    If it was me, I'll just rent a mixer that can handle all the inputs you need. Less complications and not an expensive solution either.
     
    gtrguy likes this.
  12. bw66

    bw66

    Joined:
    Dec 16, 2009
    Location:
    Uxbridge, ON
    Another solution might be to run the acoustics into stand alone amps. Ideally acoustic amps, but a clean electric amp will do in a pinch.
     

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