Sea Blue EQ w/acoustic question

Discussion in 'Effects, Pedals, Strings & Things' started by scottcw, Oct 10, 2005.


  1. scottcw

    scottcw Low rent hobbyist Silver Supporting Member

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    Yesterday I played at church with the following rig:

    Gurian acoustic w/FRAP pick-up > Analogman BiComprossor > BJF Mint Green Minivibe > BJF SBEQ > board.

    I had the BiComprossor set on the Juicer side for a slight compression/boost. The SBEQ was set for unity gain, Bass at 1:00, treble at 10:00. We were having trouble getting enough output from the mains without feedback, so I was mostly lost in the mix.

    My question is... how should the input trim pot on the board be set when being fed by the SBEQ - min, max, or somewhere in the middle? We had it set around 10-11:00 with the channel fader in the middle of the shaded zone showing recommended setting.

    I am thinking that we should have turned the input trim to minimum and turned the SBEQ output up to feed the board a hotter signal. Is this correct? any other suggestions?

    Thanks.
     
  2. Don Rusk

    Don Rusk Gold Supporting Member

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    Well of course you want to have your gains up high enough to keep the signal to noise ratio at its lowest without causing distortion by overloading the input ............. but too much gain can also make a Piezo too dynamic, but it sounds like that wasnt your problem.....;)

    does the guitar have any onboard EQ/level control or is it that what your using t he SBEQ for ??

    I would probably set the guitar/sbeq at unity and then find the sweet spot on the board input where its full sounding but not easily overloading then maybe tweek the SBs tone controls ......

    the Pale Green Comp would be very useful there as well, it matches up really well with an acoustic and the SBEQ.... many comps can make an acoustic sound fake but BJ took that click/ping at the beggining of the compression out, so it sounds natural......and that would give you a more consistant signal to t he board.......

    does the board have any comp available ?? insert or otherwise ??
     
  3. Don Rusk

    Don Rusk Gold Supporting Member

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    ...well I just reread the question !!:D

    Actually the problem sounds like an EQ problem that could be fixed with a parametric EQ, targeting t he offending frequency so you can turn the rest up to useful gain level......

    and forgot you already had a comp going..... tho comping at the board post EQ might be a better Idea sometimes...
     
  4. scottcw

    scottcw Low rent hobbyist Silver Supporting Member

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    No onboard guitar controls, just pick-up > output jack. So I am using the combination of the Juicer and the SBEQ as a pre-amp/booster.

    The board does not have comp available. There may be insertion points that I can put the compressor inline at the board.
     
  5. Don Rusk

    Don Rusk Gold Supporting Member

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    is the piezo active at all or fully passive....


    also you might try the SBEQ first then the comp, tho Juicers can get noisy
     
  6. scottcw

    scottcw Low rent hobbyist Silver Supporting Member

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    AFAIK, the pick-up is completely passive. BTW, it is not a piezo pick-up. It is a contact transducer.
     
  7. Don Rusk

    Don Rusk Gold Supporting Member

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    did it come with the preamplifier ???


    but again feedback is usually an EQ problem best resolved with a parametric so you remove the least amount of signal to get the job done....
     
  8. BJF

    BJF Member

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    Hi,

    I would agree that feedback is an eq problem most often and that you'd really need a sharp parametric eq to swap out the offending frequency.
    Now the pick up in itself has a lt to do with tendency towards feedback- often if one has a parametric to check the frequency- because feedback is usally just a spot frequency where system resonates- one can sometimes reduce tendecy with a mere capacitor if the pick up is choke based...
    It is interesting: you know PA sytems as used in churches in the 60's- well at least in Sweden- often had tuned notchfilters to swap out just the least needed to make sound manageable.
    SBEQ would help to some extent but in stubborn cases more to the exact point tools must be used.
    There is of course a crux in that an EQ section cabable of swapping out feedback in a system like this would either have to be big enough to allow total control or tune to perfect spot.
    It would help a lot if the relative height in frequency could be pinpointed.

    At your service if possible
    Bjorn Juhl
     
  9. OOG

    OOG Member

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    a preamp wth a high input impedance, say about 10 meg ohms,
    would really help too
    i haven't tried one yet, but the Baggs unit, seems to be a favorite
    i think it has a parametric EQ
     
  10. scottcw

    scottcw Low rent hobbyist Silver Supporting Member

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    No preamplifier. I have a Tube MP pre-amp that I could use, but no parametric EQ. I will have to look around for something.
     
  11. Don Rusk

    Don Rusk Gold Supporting Member

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    scott email me if you can, might have something for you...;)
     
  12. thelionsden

    thelionsden Member

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    The Baggs has gain, treble and bass, a sweepable mid and a notch filter. This notch filter is very useful for removing a narrow band of offending frequencies and the mid control can cut as well but the bandwidth is wider and is good fro removing honk. The Frap is a very high impedance pickup and requires to be plugged into a pre with an extremely high input impedance to sound its best. I don't know the input impedances of those pedals but they are probably not as high as a dedicated acoustic pickup preamp. On the Tranceaudio site (they make the latest iteration of the Frap, the Acoustic Lens), they recommend that their preamp is the only one with an input impedance high enough. I am not sure of the specs required offhand.

    Anyway this may be a part of your problem due to an inferior frequency response due to the mismatched impedances, but obviously gain before feedback is the ultimate problem that you have. Some frequencies are obviously reaching the feedback threshold sooner than others. The console trim has nothing to do with this other than overall level. If you turn your signal level up with the pedals and down on the trim or down on the pedal and up with the trim it is the same thing basically. You just don't want to set the pedals or pre so high that it gets into the area of instability or high noise but once you have the pre to a reasonable level where it is operating comfortably you trim the input on the console using the solo or cue meter if you have one, or using the main meter with nothing else playing. It is good to trim all your sound sources to say minus 6 or minus 8 VU so when you sum everything together it does not add up to something excessive in the mix buss.

    Now as to the feedback issue. You can minimize this as much as possible by the proximity of the guitar to the offending speakers whether it be the monitor or the house speakers. Obviously you want to minimize the sound coming from any speakers from re-entering your guitar pickup. When you have optimized this then you can begin to cut frequencies with EQ that are reaching feedback threshold before others enabling you to increase the gain before feedback till you get to the next offending frequency and then cut that one and so on. You can do this either on the pre like the Baggs or with the console EQ. A notch filter like on the Baggs has a narrow bandwidth and can zero in tighter without removing desired content along with offending frequencies. If your console has a bandwidth or Q control you can set it only as wide as needed to do the job. A good way to find an offensive frequency is to crank the gain of the mid eq band all the way up (while riding the trim with one hand so as not to blow anyone away :) ) then sweep the frequency control til you find the one that is feeding back then turn the gain to the left of 12 OClock to cut that frequency a bit. Repeat if you have another band available to you and you will be able to get it louder and louder but keep in mind that if you start to notch too many freq's the sound will begin to get lifeless and strange. Piezos and soundhole pickups like a Sunrise are less prone to feedback than a Frap I think. If you put an undersaddle or soundhole in there and blend you may be able to get louder as well while still having a good bit of the natural tone that the Frap provides. Only sending the Piezo or soundhole pickup if you had one to the monitor but both to the house cuts down on monitor feedback if you have a problem there.

    Too much to type, hope I made some sense, but it would be easier to talk about by phone. I would be open to that if you want. Let me know and I will PM you my number.

    Dennis
     
  13. scottcw

    scottcw Low rent hobbyist Silver Supporting Member

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    Great stuff. What other high impedance preamps should I be looking at?

    Thanks.
     
  14. thelionsden

    thelionsden Member

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    The one I like the best which I have is the Pendulum Audio SPS1...the Caddillac! It is a rack unit and a bit cumbersome and overkill at times but it is great. Fantastic EQ. One thing that is good about it is that it has the first preamp stage right at the jack. There can be a lot of loss in the cable before it even gets to the pre due to the low level output of the pickup. ...this takes care of that. Also a lot of guys like the Raven Labs stuff like the Professional Master Blender ll but it is no longer made. I have one of those too. But for a single source quick and easy I like the Baggs. With the Baggs though you have to use a cable and don't know how much that will effect the sound of the Frap..I think they are really low output. Trance audio offers the Inducer for a single mono element. Here is the Tranceaudio.com Inducer pre manual:

    http://tranceaudio.com/manuals/Inducer-Manual.pdf

    They recommend no more than a 10 foot cord of some Low capacitance cable.

    Here is Pendulum Audio.

    http://pendulumaudio.com/SPS-1.html

    Just to double check, your guitar has no pre inside, true? No battery, right?Do you have two Frap elements inside or one? If you have two, did you ever check if they are wired with a TRS Jack for stereo operation?

    Dennis
     
  15. scottcw

    scottcw Low rent hobbyist Silver Supporting Member

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    No pre inside, no battery, one element. I prefer to buy something that can run on a battery and clip to my strap or belt, so I am leaning toward the Inducer. I just wish it did not cost so much. I may also look at the KK stuff.
     

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