The ONLY purpose of a trim pot (gain knob) on a mixer is to match the input signal to the internal working range of the mixer. Too much gain and the signal will clip, which is a very obnoxious sound in a PA system. To little gain and you amplify the noise floor. The rules are the same for your harp as they are for any other mic'ed instrument.
If the gain is set properly, the channel fader will have a useful sweep of your signal, from low to high. If not, it will be impossible to get your signal to "sit" in the mix.
Set your channel and master faders to unity gain (minus zero). Set your EQ knobs to zero. Have the band (including you) play a loud passage. The sound guy should advance your channel gain until it clips (an LED will flicker) and then back it off about 10 percent. After that don't touch the channel gain because changing it can foul up any downstream processing, causing a real mess.
EQ settings on PA for harp are a lot like the settings on your amp: Roll off the highs a bit and maybe boost the mid bass. Or, use a preamp or pedal chain before the PA mixer, and then properly set the gain on your processed signal. Remember, clipping distortion sounds great in your tube amp but it sounds terrible in a PA. The only place to control it is the trim pot. That is what it is for.
-Rick Davis The Blues Harp Amps Blog http://www.bluesharpamps.blogspot.com/
On Tue, Sep 16, 2008 at 6:27 PM, John F. Potts <hvyj@xxxxxxx> wrote:
I'm not a sound tech, but this is what I've learned from my own experience playing harp through PA boards with low impedance non-bullet style mics: The most important controls are volume, gain (sometimes called pad or trim) and midrange. Typically a harp player will roll,off some treble and pump the bass up a bit. But the most interesting and helpful variations over tone control for harp are a product of where you set the gain relative to the volume and how much or little you pump the midrange. Paying attention to the bass and treble settings, is, of course, important, but that's not where the action is--real control comes from the relationship between the gain setting and volume setting and where you put the midrange, Btw, don't assume all feedback problems are treble related--too high a bass setting can cause feedback, too. Also, too much bass can make your tone muddy, and too little treble may take away "cut" and also result in a muddled tone. Much of this depends on the particular mic that is being used. Considerations for bullet mics are different, but I'm not a bullet mic guy. BE CAREFUL when you turn up the gain, it can cause immediate feedback and keep in mind that a little increase in gain goes a long way. When you turn up the gain, you must lower the volume control to compensate because increasing the gain gives you a "hotter" and also louder signal. The mic will be more sensitive with the gain turned up and therefore more responsive to hand and breath technique, which may or may not be a good thing depending upon whether the player knows what he is doing.
I hope this made sense
JP
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