PA / Amp setup Advice.

[scottishcammy]

Hi folks and merry Christmas! I've 'lurked' for a while and lots of interesting posts:-)

 

 

I play in a band called The BlackBeez, based in Edinburgh & looking for advice on an amp for our setup:

 

We've previously used active speakers (so no need for powered amplifiers.....just starting to get my head round using an amp!) however we've just bought some new gear. I setup is:

 

2 x Peavey Pro 15

2 x Peavey Pro Subs

W Audio DA 1300 amplifier

behringer 2222fx mixer

 

The Peavey Pro 15 specs are:

300 Watts RMS continuous, 600 Watts program, 1200 Watts peak

4 Ohms

 

The Peavey Pro Subs

300 Watts RMS continuous, 600 Watts program, 1200 Watts peak

4 Ohms

have a crossover which ensures the total load presented to the power amplifier is never less than a nominal 4 ohms.

 

So, unfortunately the amp we received in the package was knackered, and the seller has agreed to buy us a new one.

 

I've spoken to a lot of other bands on the circuit and I'm getting a lot of recommendations for the t.amp.

 

There are two for similar money.

 

http://www.thomann.d...0_amplifier.htm (2x700W @ 4 Ohms)

 

and

 

http://www.thomann.d...-amp_ta2400.htm (2x 1200W @ 4 Ohms)

 

I'm in a bit of a quandry as to which one to get. There's only £20 difference between the two.

I suppose I'm just a bit worried, if I get the more powerful one, it could overpower the system (though I realise it's better to have more power), but I suppose if I keep the controls on the amp to maybe half way it should be fine?

Sorry for the newbie questions, as I say, really starting out with the whole amp thing!

 

Appreciate taking the time to answer:-)

[paulears]

I've had at least 6 of the 2400s, and the only one that failed was full of water, so I'd recommend them without hesitation. As you say it's £20 more so a no brainer really.

 

For the price, they solve a lot of problems.

[scottishcammy]

Thanks mate

[mkfs9]

Keeping your amp at half way won't protect your speakers if you still turn your mixer high to get the sound required a amp puts out full power all the time, the control attenuators turn the input up and down.

[scottishcammy]

So, I'm thinking amp off, mixer set to unity gain as normal (singers sing as loud as they are going to, etc) master at 0db, then amp on and slowly increase the sensitivity controls for each channel?

I'm trying to read as much as I can about this!

[paulears]

It's fairly common to overdrive these Peavey cabs, and they start sound rather nasty before you get to the danger area - so you can turn down, but if you do abuse them, they're protected by lightbulbs that act as a fuse, and should protect the HF driver.

[scottishcammy]

Thanks for the answers chaps.

 

As I say, I'm really just getting into fully understanding gain structure using a separate powered amplifier.

 

I'm reading as much as I can, but I'm in the land of confusion...there's so much conflicting information out there on the correct way to do it.

 

So, I'd really appreciate some advice, I want to get this right. Does this seem the right way to set up a live sound mix:

 

Start with everything switched off.

 

Connect amp / speakers/ mics to mixer.

 

Switch on mixer first, then amp with sensitivity controls to zero.

 

Either play a cd/ipod through the mixer and or have the singers sing / instruments play & set each channel's gain on the mixer so it's at roughly zero on the mixer volume level meter.

 

Raise the master fader to zero, then begin to turn the amp sensitivity controls up until it clips slightly and roll them back off, or until the volume is right for the venue.

 

The volume can then be cut or boosted slightly at the mixer, either master fader or individual channel fader.

 

Does this seem right?

 

I've read folk saying you should have the amp channels 90 or 100 percent open (bearing in mind my amp is around twice as powerful in watts as the speakers rms this doesn't seem right??) and I've read folk saying to do it the way I've just suggested, starting with the amp controls at zero, setting the mixer's gain and then putting the amp controls up.

 

I'm confused, which is the correct way to do it?!

[paulears]

I think the oft promoted 'best practice' is flawed when it comes to non-skilled users, or the heavy handed operator. It's quite common for people to tweak their gain structure to not allow the mixer to overdrive the speakers, so some people will drive the desk as hard as they can, so all the lights come on, and then slowly up their amp controls until the danger level is nearly reached. The trouble with this is that those people who demand LOUD - simply use every trick to get extra volume, and a heavily distorted output from the desk is not kind to speakers. Other people, often owner/operators, line their desk up to give peaks that are realistic, and then line the amps up to match - so they have got some headroom for the occasional loud bit if they want. Others tend to set their channel gains properly, then the desk master at it's sensible working position, and then do the amps in the rack to suit the room. It's easy to get this all wrong so with the system very loud, the desk master is only 25mm from the off position. These different methods of adjusting gain all contribute noise into the chain, so finding a solution that produces the smallest amount of noise when there's nothing going through the system is the key - and if this means desk up and amps down, then that's ok. It also helps if you have amps with less than ideal noise figures. One of my old systems used to be like this, and with nothing coming in, the thing hissed quite badly. Reducing the input controls until the hiss was less annoying meant that the best signal to noise was with the mixer output quite hot (based on the meters) - but noise and distortion were fine.

 

Many people arrange their gain structure so the amps run fully clockwise. These people often have a set shut down procedure where they will return the amp controls fully clockwise before turning off the power and vice versa on power up. Maybe I'm just awkward, but my amp controls don't get touched. I bring the mixer output down, then turn the amps off with the switches. These rituals seem to work for some and not others - I don't let it bother me at all. All I do is find the maximum out for the lowest amount of noise/distortion and live with that structure.