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Powered Mixer and Amp DI question

Discussion in 'Live Sound [BG]' started by Remyd, Jan 4, 2017.

  1. Remyd


    Apr 2, 2014
    St. Louis, MO
    One of the projects I have going right now is a contemporary acoustic trio and the BL just sprung a PA on me at rehearsal tonight. It's a Yammy EMX640 powered mixer with a couple passive mains and a powered monitor. I have a TCE BG250 112 combo, which has been doing just fine in the loudness department.

    We were doing a dress rehearsal type setup tonight and he asked me to plug in so they could hear me in the monitors. This should not have been a problem; there's a balanced out from my amp.

    But, when the DI out was set to "pre" the PA sounded like liquid crap and when the DI out was set to "post" it sounded like solid crap. When the amp sounded good, the PA was all farts except when there was no low end at all. When the PA sounded good, the amp was shrill and harsh with crunch and hum taking the place of actual bass notes. I had maybe 10 minutes to twist knobs and couldn't find ANYTHING. No matter which switch I flipped, no matter what knob was where to which part of the whatsis - YUCK.

    I've never been in this particular situation before where it was just not possible for me to get an eq that didn't sound like an unsound kind of sound, if you know what I mean ;)

    There are factors:

    I'm a hired gun, so no room to complain. I'm also really, really broke, so no new gear.

    The gig is a 3 hour cover set at little wine bar in an affluent part of town, maybe 100 people total, half seated, no giant volume levels required. My amp would cover this no sweat, but the man pays, so he gets what he wants.

    The instrument is a DB, piezo pickup with a 1M output impedance, no preamp. I use synthetic strings for extra old-timey thump and no mwah in sight. Thus, plugging directly into an instrument jack on a PA is out. I have sent DI out from the amp a bunch of times before and never had a problem, although SE were running the board. And the board didn't suck.

    There's some gear in the cabinet that might be useful. There's a SM57 for micing, and a little powered monitor with a 3 channel mixer, and a laptop. I also have a Zoom B1on which I have formerly used as a filter to HPF, remove a measure of crappyness, and buffer pre-DI to get the impedance right, before I got this amp. It does not do a good job. I really, really, REALLY prefer the tone that comes out of the amp (and that I think is supposed to come out of the DI set to post eq).

    TL;DR So, now the question: How do I get a good house tone out of my amp and still have something that isn't embarrassing on the not very adjustable mixer?

    Should I just dump all the lows from the PA and carry with the amp? Could it be crappy signal path or low strength or something? Maybe split the signal with clever routing and send the PA something run through the Zoom for preamping? Or just use the Zoom in front of everything to get a little shaping and gain but which is impossible to really test until sound check before the gig on Saturday?

    Is there a trick or magic frequency or anything?
    Last edited: Jan 4, 2017
  2. derrico1

    derrico1 Supporting Member

    Apr 12, 2005
    Charlottesville, VA
    Solutions first (in descending order of preference):
    1. Just cover the gig from your amp (familiar, simple, sufficient, tested, and uncompromised sound)
    2. Mic the cab (this is essentially a personnel-management solution to help you deal with the bandleader. The 57 is not my choice for DB, but it'll likely be better than your current results from the PA; gets you around potential impedance mismatch problems)
    3. Spend an unpaid hour+ troubleshooting how to get less terrible results from this particular pairing of gear—a pairing that you might not deal with a 2nd time.
    If you get down to troubleshooting, I'd start w/ a few basic diagnostics:
    • Do you know that your amp's balanced XLR output sounds good into other mixers? (I'd start here and then decide whether to go further. Once you confirm that your rig's DI works correctly, you're spending time troubleshooting downstream problems in the bandleader's gear.)
    • Does the channel assigned to bass work with other XLR sources in your DI's ballpark (probably ~600 Ohm, but check the manuals)? Does using the TRS input (w/ an adapter) rather than the XLR change your results? Plug the bass amp DI into a different mixer channel. Same result? (Here, you're trying to rule out a bad mixer channel, shorted mixer input, or mismatch b/w DI output and channel input)
    • Does the PA sound good with a known full-range source? (If a well produced recording sounds bass-starved, etc, when played through the PA, then the job ahead is flattening the PA response.)
  3. Remyd


    Apr 2, 2014
    St. Louis, MO
    Just wanted to drop an update here. I had a really long time to sound check because there was almost nobody in the café. Finally came to the conclusion that I could take 75% of the bass out of the mains and cover with the bass amp. Sounded good all the way to the back.

    It was my first sideman gig in quite a while. Still fun.
    derrico1 and Grumry like this.
  4. John Hobson

    John Hobson

    Dec 13, 2016
    Sounds like you found a fix, so you can ignore my advice, but.....

    My suggestion would have been to just go straight into the PA. I get that you preferred your tone, but it seems like there was a conflict between the power mixer and your head.

    For a 3 hour "hired help" set in a bar I would have just tried to get the best tone out of his PA possible with its built in EQ knobs. Ultimately I could see where the guy who hired you is coming from, he wants to control the mix.
  5. derrico1

    derrico1 Supporting Member

    Apr 12, 2005
    Charlottesville, VA
    Straight into a mixer combo-input channel can work with electric bass. Results going straight in with an upright (like the OP's) aren't likely to be stellar.

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