Amp to sound board problems

Strat_dude · 08-30-2003, 03:53 PM

Hey,

I've just started trying to use my amp at church (I used to just plug straight into the system), but we've been having problems with it and I can't figure out why. The first problem was the signal at the soundboard was peaking really badly (even though it's a 25 watt amp and I only turned it up to like 1 or 2). So I turned it way down and the signal was ok (i think), but it came through really buzzy and distorted even on a clean channel.

Any ideas on why this would happen? If not, it's not a big deal (I can just keep plugging in straight), but I was just curious since I don't know much about this kind of stuff.

Thanks,
Strat_dude

Major Tom · 08-30-2003, 05:04 PM

Probably need to turn down the TRIM (also called GAIN) on that channel of the mixer. It is the knob at the very top of each channel, its purpose is to compensate for (cut or boost) the relative strength of the signal before hitting the rest of the preamp circuitry. Turn the TRIM all the way down, set the slider on 0db, and slowly bring the TRIM up while playing until you are at the volume level you need. Sounds like its up too high, and saturating the channel's preamp causing clipping distortion. when you turned down the amp, that brought the signal down enuf to keep from peaking, but most amps won't sound right set at "1". Does the amp have a knob for the direct out signal? If so turn that down.

If its an electric guitar, mic the amp's speaker, (even if it is a solid state) - this will give the "true" electric guitar sound, since the power amp and speaker also "process" the sound, and a direct out from the amp is just the preamp signal. If it is a modeling amp, it should have a separate volume for the direct out, turn that down.

Brent · 08-30-2003, 05:24 PM

What are you plugging into the board from on your amp? If it's an external speaker jack then that's a no-no. It needs to be a direct out jack. A headphone jack will give you problems as well, but not as badly as an external speaker jack would.

Major Tom · 08-30-2003, 06:09 PM

Wow, I didn't think about the speaker output thing...Strat dude, if you're doin' that, then stop it right now young man! Before you blow the channel on the board.

Strat_dude · 08-31-2003, 05:05 PM

Quote:

If it's an external speaker jack then that's a no-no. It needs to be a direct out jack.

Well I'm glad you mentioned that, since no one at church seemed to catch it. What's the difference between the two?

Major Tom · 08-31-2003, 06:24 PM

The direct out's signal will be approx 1 volt (line level) which the board's input is designed handle, the speaker out will be more like 20 volts which is way beyond what the board can handle. If it has both, put a piece of duct tape over the speaker out so no one will make that mistake....

Strat_dude · 08-31-2003, 06:28 PM

Quote:

If it has both, put a piece of duct tape over the speaker out so no one will make that mistake....

No, it's only got the ext. speaker jack. I'll just leave it home from now on

Major Tom · 08-31-2003, 07:07 PM

Just mic it, sounds better than any direct out anyway...

Maestro_dmc · 09-05-2003, 11:51 AM

Direct for electric guitar sounds bad bad bad!

You need an SM57, or an EV 635a, or another vocal mic right in front of the speaker. This way you can hear yourself from the amp itself, and what you hear will be what the congregation hears. Turn the amp sideways to the congregation so the sound man can really mix. With a 25 watt amp you may not need to, but it's still a good idea to give more control to the F.O.H. mix.

If your dead set on going direct, there are direct boxes that will allow you to put a speaker level signal into a mic level send. The Behringer DI100 active will do this I believe. Behr also has an Electric Guitar oriented direct box with a speaker "simulator" circuit, but I don't have any experience with it. It is called the Ultra-G GI100. I think they go for under $50.00
http://http://www.behringer.com/02_p...GI100&lang=eng