Backline amp issues

[baddog]

Hi there.

We've just started gigging and have now got quite a few bookings. We've got by on the stage technicalities more by luck than knowledge, but wonder if someone may be able to help with this technical problem.

We've got a few bookings coming up outdoors and we've only got a basic set up - essentially a 60 Watt PA from which we mix vocals, guitar bass (we've never used mics on the drums as the volume from them has always been adequate.

 

Now we've got the problem of output - I play guitar and up to now managed quite well with my 15 Watt valve amp in pub venues, but I'm getting hold of a larger amp in anticipation of doing slightly bigger gigs (looking at 40Watts). But I've always been confused about the placement of backline amps in relation to vocal mics. I know you site a monitor speaker directly behind a vocal mic so it doesn't pick up much sound, but backline guitar amps sit at the back of the stage and seem to pump out all their sound straight into the vocal mics ? Is this right - how come there's not loads of feedback ?

 

This is probably obvious to most people, but It's got me confussed?

 

Cheers ;)

 

 

Moderation: A good topic but I've moved it to sound as you may get more of the mixing specialists dropping by in here, especially as the consensus...which I agree with...is that you should invest in your FOH system rather than your guitar amp.

[Shez]

My preference (others may disagree...) would be for you to keep your current backline & let a bigger PA take the strain. The louder your backline is, the higher the overall on-stage volume is, the less clearly any of you can hear anything, the louder monitors have to be, and the quicker you go deaf.

 

The reason you won't get feedback between vocal mics & guitar amps is that the signal from the vocal mic isn't being amplified by the guitar amp. Feedback is caused by a signal going around a loop with greater than unity gain e.g. vocal mic -> monitor wedge -> vocal mic etc. However, really loud backline firing straight at the vocal mic, whilst not a feedback causing issue, is still an issue. There comes a point where the mic can "hear" the backline at the same level as the vocals. When this happens, trying to turn up the vocals results in the backline being turned up in the PA by the same amount. Obviously not a good thing.

[revbobuk]

And a nice 15W valve amp turned up so it begins to crunch is beautiful, whereas a more powerful amp may be altogether too clean until turned up to a point past the onset of pain. There are plenty of nice sounding and powerful amps - but if you like the sound you have now, you'll do everyone a favour by not adding more volume onstage.

[Dmills]

15W is fine on any size stage, let the PA do its job.

 

In fact, even at the 15W level there may be something to be said for having the amp (assuming a combo) up on a flight case pointing across the stage rather then toward the front, again, less spill into the vocal mics and a cleaner mix out front.

This trick is especially useful on smaller stages where the amp is a significant contributor to overall stage volume (and to spill out into the audience).

 

Regards, Dan.

[Killyp]

I agree with others RE amp size. It's not so much the volume but the tone you get out of the amp. Even most practice amps will produce enough volume to fill over the top of a small PA system when positioned correctly.

 

Just to note, you said the volume the drums produce at the moment is fine, but do bear in mind that indoors, most of the drum sound the audience is hearing is reflected sound. You'll be amazed how outdoors, the drums seem to disappear as there are no reflections at all. I was amazed how, when I did my first outdoor gig a few years ago, the drums seemed to completely disappear (and this is jazz, where drums aren't exactly at the front of the mix anyway). Sticking even my cheap 'n cheerful Behringer C2 pair on top of the drums pointing at the high and mid toms improved presence and definition of the drums hugely.

 

As for the PA system, a 60 watt system is probably going to struggle outdoors. Watts are generally a little meaningless when comparing say, 400 watt systems with 900 watt systems as they can be measured completely differently, or produce 'more sound per watt'. However, a 60 watt system would suggest it's one of the many 'PA in a box' systems on the market, which I've found can often struggle with decent amounts of vocals.

 

It may be worth considering your budget, and looking at renting a better PA off a small rental company with someone to run the sound for you and also considering what the return may be from the gig. If you make little profit from said gig, but in return get a handful of bookings, you may be better off spending a little more.