# setting up an amp



## zac850 (Dec 9, 2004)

So, my school is getting an amp that should be showing up tomorrow.
We are getting a BEHRINGER EP2500. I know Behringer isn't the best equptment, but it was cheep enough, so, oh well.

Anyway, this amp is 500 watts at 8 ohms and the speakers we're going to be using are 400 watts at 8 ohms. So, would I need to turn the gain down on the amp or will it only put out 400 watts for the speakers.

I assume that it is the second, but I'm not sure. I've never set-up an amp, so I am just unsure of what to do with the gain settings.

I hope this makes sense. I'm coming off 3 weeks of back to back shows, and its 11:30, so my brain isn't really working right now. 

I just don't know what to do with the left and right gain settings on the amp, everything else I can do. I hope that makes sense.

Good night all, thanks very much.


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## RelativeMischief (Dec 10, 2004)

Oi, thats a toughie. I would've recommended checking your speaker specs before buying an amp  You could've gotten a better quality amp matched to your speakers for the same amount. However, for what you've got, the amp is gonna put out 500W at 8ohms no matter whats hooked up at the other end. Best thing to do would be turn your amps down by 6dB or so. That should give you some breathing room. You have to bear in mind however, that your amp is gonna be running a little cool now, so don't judge anything by the LED's on the amp. Don't attempt to get it running at nominal, you'll just fry your inputs.

Hope I helped!


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## Mayhem (Dec 10, 2004)

For what it is worth Zac, I always run my amps at full gain and control my overall volume from the board. 

The reason that I do this is because I find the lower frequencses sometimes get lost or are lacking if the amp is turned down.

Just keep an ear out for any distortion and keep your eye on the clip meter and you should be fine.

With your speakers being suited to your amp (ie the amp output is greater than your speakers) you will (should) hear any distortion, in which case you drop the gain a little. On the other hand, were your amp underpowered, you are more likely to damage the speakers by clipping the amp in order to drive them.

If you are unsure. Wind the amp back to begin with. I know some people who just cannot stand having the master out on their board sitting at 30%. Even though the sound is good and at the right level.


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## zac850 (Dec 10, 2004)

I k now that the speakers are 400 watts at 8ohms and for the price, that was the closest we could do. It is better then our old amp, that only put out 250 watts at 8 ohms. 

So, if I keep the gain on the amp turned way down, that will help save the speakers? I assumed this, but I just want to make sure.

Thanks guys,
-Zac


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## ccfan213 (Dec 10, 2004)

my only problem with turning my master up to 30 is that if someone else uses my board they may do something dumb, or if someone sees that i have that much power @ a concert they may try to make me turn it up.


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## ccfan213 (Dec 10, 2004)

my only problem with turning my master up to 30 is that if someone else uses my board they may do something dumb, or if someone sees that i have that much power @ a concert they may try to make me turn it up.


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## zac850 (Dec 10, 2004)

OK, so...
1) I assume that the extra 100 watts is harmful for the speaker and will cut down on speaker life, correct? Also, I assume that the excess power will cause clipping and other nastyness in the speaker... Also, is this correct?

2) Now that we're going to have an amp, I was wondering about power in the booth. The amp will be sitting under the table in the booth, pluged into the same circuct as a projector, a computer, the sound board, a mini disk player, a CD changer, and 2 desk lights. I can (if needed) change most of this stuff over to the lighting side of the desk, with its own seperate circuct without overloading anything (we have 2 20 amp circuts to the booth, one for lights and one for sound). 

How much of this stuff should I move to keep speaker hiss to a minimum. I assume that it would be OK to keep the sound board on the same circuct, but what about the mini disk player and the CD changer. Also, is it even worth it, will there be enough hiss heard at the speakers to warrent this extra work?

Thanks a lot guys!
--Zac


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## disc2slick (Dec 10, 2004)

zac,

as far as I know, having the Amp on the same circuit won't create lots of hiss. so long as you don't have lots of power cables running along side your sound cables you should be fine


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## Peter (Dec 10, 2004)

The only time I have have to worry about where things are pluged in at my auditorum is the fact that we have two different sets of plugs, (one white and one orange). The orange ones are dedicated computer plugs, and have a seperate (longer) ground rod then the other circut does. The only problem is, two ground rods usualy means that there is a small bit of current wanting to get from one rod to the other, and that can make a bit of hiss, so i just make sure all my sound equipment is pluged into one or the other. (there are horror stories floating arround the internet about guitar players who's amp is pluged into one circut and the mic system is on a differnt ground, and them getting zapped through the mouth singing into the mic. I kinda doubt that the difference in voltage/amperage is that much... but.... i dont really see how it can hurt to be safe. 

PS for more info on this, look up "ground loop" or "ground loop hiss" or something similar on google


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## zac850 (Dec 10, 2004)

Well, we hooked up the amp and it is WONDERFUL!

We have the gain somewhat lower then normal, to compensate for overpowering the speakers. The nice thing is, the speakers don't hiss anymore! Before we were running the outputs of the main board as 2 mic inputs of a powered board, and from that to our speakers. Now, however, main out is going to the amp, and it is silent now.

We are using the old soundboard/amp as a monitor for the keyboard, and listening to the difference between the two is amazing.


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## tjbaudio (Dec 10, 2004)

Some things to keep in mind:
how Beringer specks there amps compaired to QSC or Croun is not the same. But you have the amp so I wont come down too hard. Just know that the B stuff is just like the real thing with out paying for R&D and with cheeper parts that may not protect the speakers when it failes.

Now the real problem with the preveous posts in the thread. Gain at the amp is just that, gain. That knob is not a limiter or a power controle. It is there to match the signal leve in the reast of the system to the speakers and needed volume. You can still clip an amp that is only 1/4 of the way up. By lowering the gain at the amp your console has to provide more level to reach the same volume in the room. This is not a bad thing because it also reduces the amount of hiss (as you found) There is a balance between too much gain (lots of hiss) and not enough (clipping and distortion before the volume is loud enough.) Clipping the console is just as bad as clipping the amp.


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## zac850 (Dec 10, 2004)

Yes, I know that Beringer isn't the best company. The problem is, the purchase was donated, and I was told $300, it ended up being $370 for this amp. It was either this or an American DJ, so I decided that Beringer would be the better buy. 

The Beringer manual said that at 8 ohms we shouldn't use a speaker lower then 400 watts, so, yes, I know its bad, but its better then what we had, under-powering the speakers by 150 watts.

Also, just out of curiosity, what is the negative thing with overpowering an amp? I understand the hiss thing, but as long as i keep levels low enough and don't do that, what is the problem with putting an extra 100 watts into the speakers?


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## mbenonis (Dec 11, 2004)

You should be fine running the speakers with the amp at full gain - I'm not sure how mathematically, but it all works out fine. Search the Theatre-Sound list-serv archives for some interesting reading on this topic.

http://www.brooklyn.com/theatre-sound/index.html

As far as the mains distribution, I would make sure that *all* audio equipment is plugged into one circuit, and preferably the other equipment is on a different circuit - this will reduce noise on the power line. Note that the important thing is that all sound equipment is on the same circuit, not that other stuff is moved to a different circuit.

Btw, this may sound unimportant, but I'm glad to see that the amp requires a balanced input - don't defeat this with a cheap, unbalanced cable and some funky adaptors (believe me, I've seen some weird wiring at my school).

Enjoy the new amp!


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## Radman (Dec 11, 2004)

I reccomend the "Sound Reinforcement Handbook" to anybody here who hasn't read it and works with sound. The edition I have is ancient and it is still a treasure trove of info. 

In matching speakers to an amp, there are many ratings that can be given. Contonuous, Program, and Peak are common for speakers. The amp should generally fall around half the peak rating for the speaker. 

Continuous is a worst case scenario rating, peak is what it can handle for periods less than 1/10 a second, and program is average usage.


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## tjbaudio (Dec 11, 2004)

Somthing to consider is that the rating of an amp is how many watts it is capable of delivering. The rating of a speaker is how many watts it can electricaly disipate or how much abuse it can take. There are many ways to mesure what an amp can produce and what a speaker can take. Speakers are the most trouble some to mesure. There are many ways to mesure the ratings that Radman mentioned. Some manufatuers are conservative some are not. Many dont give the sircomstances of there raitings. Some are mesured with full sprectrum noise (conservative raiting) some are mesured with a 1K tone (easy teast for most speakers.) 

I tend to run an amp with an RMS raiting around 1.5 to 2x the RMS raiting of the speaker. That gives some head room for peaks. Just because an amp is capable of 1000 watts does not meen it is delivering it all the time. I have used a 1000W amp on a 3W speaker as a booth monitore. How hard you are pushing the amp deturmins how much power is deliverd to the speaker. Most of the time you are only pushing a few watts any way. 

I also recomend the yamaha book, probably the best reference there is for PA.


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## mixsa (Dec 11, 2004)

zac850 said:


> 2) Now that we're going to have an amp, I was wondering about power in the booth. The amp will be sitting under the table in the booth, pluged into the same circuct as a projector, a computer, the sound board, a mini disk player, a CD changer, and 2 desk lights. I can (if needed) change most of this stuff over to the lighting side of the desk, with its own seperate circuct without overloading anything (we have 2 20 amp circuts to the booth, one for lights and one for sound).



how close is your amp to your speakers. i dont know where youve got your speakers placed, but if they are down by the stage its best to have the amps as close to the speakers as possible - as the voltage loss over speaker cables is a lot more than over a balanced xlr.
so if your speakers are by the stage it would be best to have the amp under the stage or somewhere close.
and its best if you can keep all the sound stuff off one circuit, even if this means running an extension lead back to the booth to run the amp


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## zac850 (Dec 11, 2004)

mbenonis said:


> Btw, this may sound unimportant, but I'm glad to see that the amp requires a balanced input - don't defeat this with a cheap, unbalanced cable and some funky adaptors (believe me, I've seen some weird wiring at my school).
> 
> Enjoy the new amp!



Yea, it requires a TRS or XLR input, which was good. I was kind of surprised, because I thought it had a TRS output, but ended up having only Speakon output (which was almost bad, considering that the snake we just installed 3 days ago has only TRS returns). Of corse, then I realized that I had 2 speakon to 1/4 inch adaptors, so its all good now.

Anyway, thats very reassuring to here. As I'm sure you all can tell, I'm not to much of a sound guy, so I'm just sort of probing in the dark to make this work. I'm not going to be pushing the speakers or the amp very hard, so we should be safe for all of that.

Thanks a lot guys!


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## sound_nerd (Dec 11, 2004)

zac850 said:


> mbenonis said:
> 
> 
> > Btw, this may sound unimportant, but I'm glad to see that the amp requires a balanced input - don't defeat this with a cheap, unbalanced cable and some funky adaptors (believe me, I've seen some weird wiring at my school).
> ...



ITs kind of vaigue, but PLEASE tell me that you are not running the output signal from the amp into an audio snake back to the stage. The wire used in the snake is not meant to carry such a signal. The length of leads that you need, and the output of your amp require at least 14awg speaker cable, if not 12awg. There is no way you should ever run an amps output through the returns on a snake, and then to the speakers. Thats a major problem just waiting to happen. The returns on the snake are meant to be used for fx racks /monitors and such. I hope I just read what you said wrong, and you are actually running seperate speaker cables from the amps output to the speakers input. 8O


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## zac850 (Dec 12, 2004)

Erm, well....

Yes, that is what we're doing.

OK, well, here is a question. Is this a very very big bad thing that will break things now, or is this a "well, in theory this is bad, but ya know, in practice it isn't that bad." I know that it is best to keep the amp close to the speakers, but we are in a gym, with the booth in the back, and no safe place to put an amp near where the stage is set up. 

I don't know where else we could put the amp besides the booth. The only other thing that I could think of would be to buy 100 feet of 1/4 inch speaker cable or XLR cable and run it through the conduit and snake it up and around the way we did with the snake. The problem is, this is a BIG hassle, and I would like to avoid this if it can be avoided.

So.... is this a big concern or is this one of those "well, in theory this is bad, but in practice you will still be OKay"


I'm a bad sound guy ::hangs head in shame::

EDITS::

MISTXA, well, as I said above, we're in a gym, so there is really no other place to put the amp besides in the booth, because, well, its a gym and bad things would happen otherwise.

I was also reminded by the sound guy to ask about running 4 JBL speakers (250 watts at 8 ohms) as opposed to the 2 Peavey Cabinets (400 watts at 8 ohms). We would run 2 JBL's on each circuit of the amp, in parallel I think the term is. We would be taking the output from the amp into one JBL, and then output from that JBL into the second. I thought I remembered hearing at some point that the load on the amp would still be 250 watts. Is this true? Any opinions on this or that?


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## mbenonis (Dec 12, 2004)

This is a bad thing *now*, and it's akin to running a high current appliance off a puny little extension cord. It could be dangerous. Not only that, but it may cause interference on the mic inputs.

However, there is a simple solution: don't put the amp in the booth as you originally planned, but rather at the other end of the snake, and send the signal to the amps over the returns. This will avoid the problem and actually give you slightly better performance from the speakers. As far as power, if possible, run a *heavy duty* extension cord from the amp back to the booth. In a pinch, if you don't get any hum, you're OK, but it's always better to get the amp on the sound circuit.

Edit:

Well, if you can't put the amp by the stage, you need to buy appropriate gauge speaker cable and run that to the stage along with the snake for safety.

As far as the wiring of the speakers: no matter which way you wire the speakers, you always add up the wattage for the total power output of the amp. However, you do need to worry about the resistance, which is measured in ohms (forgive me if you already know this stuff - I'll say it anyway for the benefit of those who don't know). When speakers are wired in series, you simply add the resistances for the total. For example, two 8-ohm speakers in series total 16 ohms. However, if they are run in parallel, you have to use a nasty equation or memorize some values. The equation is as follows:




There are some values you can simply memorize:

Two 8-ohm speakers in parallel total to 4 ohms, and two 4 ohm speakers (or 4 8-ohm speakers) in parallel total 2 ohms.

Absolutely make sure that the total resistance on the amp is not lower than the rating of the amp, which is likely 2 ohms (but check this!). From your description, it sounds like you will be fine with the JBL's.


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## sound_nerd (Dec 13, 2004)

well, see, you're trying to run power from an amplifier down what is at the most, 18awg wire, maybe 22awg. That is BAD NOW. Bad in theory, bad in practice. If you already set it up, unplug it asap. In a pinch, you can run 14awg extension cord with speakon ends from the booth to the speakers. That would be cheaper than 100 feet of professional speaker cable.


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## tjbaudio (Dec 13, 2004)

You will damage the snake by using the returns with speaker level. The wire in most snakes is closer to 22 or 24 awg (think phone line) That is unless the returns are built to take speaker level. If it is ment to do that the wire for the returns will be thicker. However you still need to check the specks on the snake. Even if it is rated for speaker level you are still better off running the amps at the stage by a long shot. Keep in mind though that if by chance the snake is ment to run speaker level through then the speaker lines are not good for line level.


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## zac850 (Dec 13, 2004)

Well, I talked to some people, so we are not going to use it until we get some 12 gauge 1/4 inch TS cable... a bit over $100, but it will be done.

Thank you so much for catching that mistake everyone. It will be dealt with, and until that happens, we won't be using sound in that room.

Thanks again!


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## m4g1cky (Dec 13, 2004)

zac850 said:


> Thank you so much for catching that mistake everyone. It will be dealt with, and until that happens, *we won't be using sound in that room.*



 Thanks for catching _his_ mistake, I didn't either, but of course, I was just testing him.

Now, time for one of my questions: Since you all are saying to have the amp at the other end of the snake, I was wondering if it would be feasible to have a sort of wooden road case to house the amp, as it has rack mounts? To illustrate, I have included a happy mspaint: 
[mspaint]


[/mspaint]
Now, one of my motivations for suggesting this is that I believe it would save us some time and money as we would just roll the amp out, plug it into the returns, and the speakers, and have the cables stored in the road case. Is it feasible for us, or would it just be easier to have it run from the booth.

zac850 disagrees, and will be responding with a rebuttal soon (Heh, butt.)


ps. I'm the sound guy he is always referring to. .


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## zac850 (Dec 13, 2004)

My rebuttal--see, its only a little funny...

Anyway, my point of view is that it will not save us more time. If we are running the amp from the booth with a 12 gauge cable, we have about 97% efficencty. Since we have a 500 watt amp and a 400 watt speaker, so the 19 watt's that are lost in the cable arn't all that important.

If we do it the way m4g1cky sugests, we would have to run a 100 foot power cable next to the snake, down the counduit so that the amp and the rest of the sound system are on the same circuct. 

To set up we would have to wheel out the amp (which would be kept in the back closet with the all of the cleaning equptment and chairs and stuff) plug it into the power, plug in the returns from the snake and the speaker output. 

If we have it run from the booth, we just have to purchase 2 100 foot 1/4' 12 gauge speaker cable and run it down the conduit. The cost of this is just over $100 (about $50 somad each from PSSL). The ends would sit right next to the breakout of the snake, and when needed we would just use 2 adaptors that we already have to plug another 1/4" TS cable in and run it to the speakers

One thing that m4g1cky reminded me: the booth is sitting right infront of a hot air vent from the heating system. While I am trying to get some wood to block this off, it is fairly hot (i don't know the tempature, but it would be about 90' up there). As I said, I am trying to get this off, but this could be a factor.

Anyway, we leave it to you CB, which do you sugest we do, and why?


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## tjbaudio (Dec 13, 2004)

I personaly like the idea of having a cart with all of the cabling in it. As has said having the amp closer to the speakers is better. However I do understand having the amp in the booth where it is safer. I will admit that in the system I just installed I put the amps in the booth, but I used heavy wire to the main cluster (1 12 awg run for each of 3 speakers) and I used better ends than 1/4" (hard wired to the amp and NL4's at the cluster) Using the 1/4" ends and the cheep adaptors is asking for problems. They tend to short the amp as they are conected and the 1/4" to 1/4" adapters tend to just short out all on there own. The 1/4" ends are called "PHONE" plugs because that is what they were ment to do, hook up phones at a switch board. Get some heavy Nuitric NL4panel mounts and run some 12-4 or 2 runs of 12-2. for your speakers run NL4 to 1/4" cables from the wall. 

Also as for havign a 500 watt amp on 400 watt speakers, stop worieing about it! At 500 watts of beringer power you are probably still under powering the speakers if you want maximum performance. The extra power in the amp is headroom. And using long cables to "reduce" the power the speakers see is just a bad idea. With longer cables you reduce the dampaning factor of the system. The dampining factor is the amps ability to controle the speaker movement. With poor dampining the speaker driver can flop and bottom out easyer than with a good short cable. The speaker will also sound better with shorted (or thicker) cables.

TJB


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## zac850 (Dec 13, 2004)

Well, if I buy the cable it will be 12 awg. 

Someone here (i forget who) made a power-loss calculator

When putting in all the information I get 96.15% efficiency, a loss of 19.23 watts. That still gives me 480 watts getting to the speakers, so we still have some headroom for that.

The thing is, I am really worried about the amp getting damaged if it is placed in a movable cabinet in the back closet. Things could get dropped on it, someone could not know what it is and put it out in the rain, etc.

Any other opinions?


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## tjbaudio (Dec 13, 2004)

Running a 12 awg cable for each speaker is fine. BUT please make it NL4 for as many conections as posible. I thing a 1/4" jack is only rated for 50 watts. The contact area is tiney and like I said before, they short the out put of the amp if they are pluged/ unpluged. THe worst is if it is 1/2 unpluged and no one notices. The amp is then just sitting there driving a dead short.
TJB


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## The_Guest (Dec 13, 2004)

You'll eventually fryout your snake returns, that's not good. Leave your long runs to your balanced siginals, leave your short runs to your inbalanced. In just about every portable applacation (Even though this in your facility, you still have to strike your amp and speakers. Therefore, it's portable) the amps belong at the stage. You're washing your signal down the drain with such long runs like that. It's okay to put amps in the booth just as long as it's an install, you're using top notch wires, it's hardwired, and the wires will be wired away from nasty things in the walls that will cause buzzing ahd hums. I have found more interferance problems in systems with longer amp runs than shorter ones. Those high powered inbalanced lines are just asking for interferrance. If you can consider converting your speakers input jacks to speakon (neutrik NL-4), you really have no idea how much it will improve your system.

Poor connections and cabling often are responsible for the largest problems and lag on computer networks. Thousands each day are spent fixing these problems, and in reality good cables cost so little.


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## zac850 (Dec 13, 2004)

Well, the way it is run now keeps the cables away from power, so I'm not worried about hum that way. What my mind keeps coming back to is that I do not trust my school to keep the amp's safe. things get thrown around, little kids run around, and people throw things around without knowing what there doing (the speaker's are constantly used as a table for water, soda, chips, etc.)

OK, so, what if I got 2 100 foot speakon cables, and then when I got to where the snake ends used an adaptor of some sort to get to 1/4 inch? or... I believe that the speakers also have an XLR input. If I used an adaptor at the amps and got the speakon over to XLR (3 pin, so balanced, right?) and then ran the XLR down to the back of the gym where the normal snake ends, would that work? What gauge is normal XLR cable? I remember seeing speakon to XLR adaptors somewhere for like 5 or 10 bucks, so that would be easy....

I'm just really scared about keeping the amps where anyone could touch them and spill soda on and break....


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## The_Guest (Dec 14, 2004)

zac850 said:


> Well, the way it is run now keeps the cables away from power, so I'm not worried about hum that way. What my mind keeps coming back to is that I do not trust my school to keep the amp's safe. things get thrown around, little kids run around, and people throw things around without knowing what there doing (the speaker's are constantly used as a table for water, soda, chips, etc.)
> 
> OK, so, what if I got 2 100 foot speakon cables, and then when I got to where the snake ends used an adaptor of some sort to get to 1/4 inch? or... I believe that the speakers also have an XLR input. If I used an adaptor at the amps and got the speakon over to XLR (3 pin, so balanced, right?) and then ran the XLR down to the back of the gym where the normal snake ends, would that work? What gauge is normal XLR cable? I remember seeing speakon to XLR adaptors somewhere for like 5 or 10 bucks, so that would be easy....
> 
> I'm just really scared about keeping the amps where anyone could touch them and spill soda on and break....



First of all you'll need a quick cable lesson...

XLR-3 pins, low z, balanced. Great for microphones and interconnects between audio components (ie: mixer to processor, processor to amp, or mixer to powered (active) speakers, etc). Not to be used with passive speakers.

TRS-3 contacts (pins), low z, balanced. Stands for Tip, Ring, Sleeve. It's basically XLR but in a 1/4" form. Great for audio interconnects (CD players, auxilaries, mainouts, snake returns, effects units, balanced compressors, etc) It is a balanced signal it can be ran long distances. Because of it's 3 pins I can also run an unbalanced stereo signal, which many headphones use. Even though TRS is balanced it can be ran unbalanced by bypassing the "Ring", thus functioning like a TS cable.

TS-2 contacts (pins), hi z, unbalanced. Stands for Tip, Sleeve. It's just basically guitar/bass cable, often used for unbalanced inserts for compression. This is not something you'd want to run down a snake because of it's unbalanced siginal. In theory these cables can be used for speakers, but regular TS is not insulated or strong enough to handle heavy power loads from an amp.

1/4"-2 contacts (pins), hi z, unbalanced. Even though 1/4" often refers to TRS, TS, 1/4" loudspeaker, etc. We'll refer to 1/4" as a hi z, unbalanced, loudspeaker cable. Even though they're unbalanced they should not be used with guitars, compressors, or other unbalanced audio devices. This cables have more insulation and a tougher guage wire. As with all loudspeaker cables, try to cut down on length to generate a cleaner signal.

Speakon-the poles (pins) vary from connector to connector. I've seen everything from 2 poles, to all the way up to 8 poles. Often reffered to as (neutrik) speakon NL-2, NL-4, NL-8, BSR-WR, etc. Speakon is much more robust cable/connector than 1/4" loudspeaker. Speakon cables lock when mating to prevent any disconnections, which definitely can prevent some nasty noises and even protect your loudspeakers. Another reason to go speakon is it's just simply a different cable, it avoids the 1/4", TRS, TS confusion. Which you can really benefit in your high school environment you speak of, it will definitely avoid mistakes. Things will get done the right way, the first time, definitely an educational plus.

Now that you've learned a thing or two about cables you now know it's impossible for a speaker to have both 1/4" loudspeaker and XLR. XLR is an balanced lo z signal that could not handle the force of an amplifier. 1/4" loudspeaker is suited for linking a power amp and a passive (non- powered) loudspeaker together. However powered speakers (in which the amp is built into the speaker) can accept an XLR cable.

Personally I would ditch the 1/4" loudspeaker jacks on your speakers and install speakon jacks. This is not hard to do at all, the connectors are cheap too. It's just basic soldering skills, if you can't do it I'm sure someone around could do it for you if you showed them which wires go to which. Just by doing this your already running a cleaner signal, is definitely smart thing to do if you plan on running the amp from the booth.

Now I have a quick question...where do you store all of your other equipment? If your worried about losing an amp, I'd be losing sleep wondering if your express 125 was safe and sound. If you have to run a snake and setup everytime (since your in a gym), why not just run the amp on stage and lock it up with rest of your gear when your done. I personally really like the idea of getting a rack with a bunch of storage and putting your amp in there. Think about it, when it's time to setup and start working you just take the rack from the booth and roll it to the stage. You'll have all your stage cables/supplies with you, no need to make trips back to the booth. And you won't have to tape down two extra cables ALONG with your snake.

This reminds me of the last system I designed. I put the mixer/processing all in one main rack. I had this rack put on a seperate dollyrack where the amp and drawer would go. This allowed me to roll in only one rack, but I could split the FOH rack and amp rack up. So if I needed to mix a longer distance from the stage I could split it up. Or if it was not necessary to mix far away I could still have the amp and FOH racks together.

Hope this helps.


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## Mayhem (Dec 14, 2004)

Jeff - you raise some pretty valid points here but I think there is some confusion between the connectors and the cable.

For example, some of the older amps and speakers left the factory with 3pin XLR connectors on them. Only one of my 3 main amps has Speakon connectors. The important thing is the cable that is used in between the connectors.

As you correctly point out, speaker cable is different to signal cable. Not only in the conductor gauge, but in the fact that speaker cable should not be sheilded. When you think speaker cable think of power cable.

The main difference between say a mic lead and a speaker lead (appart form the cable) is that the speaker cable will have two female xlr connectors on it and the mic cable will have one male and one female. 

I agree that where ever possible you should use speakon connectors for the visibility factor but it is the application not the connector in my view that makes the difference.

Again - I agree with Jeff and everyone else that has recommended keeping the amp as close to the speakers as possible and I certainly run my amps on stage. As for the power thing, the important factor is reducing noise and one way around this is not to have lights on the same circuit or even use a line filter. Many amps now have an ground lift switch on the back that will disconnect the signal ground from the chasis ground, and in most cases this will remove the hum.

Many good points raised in the posts on this topic and when running an amp on stage I still prefer to run it flat out and control the volume from the desk. I know a few people have commented on the inability to know what setting to use if other people use the desk. My response is that who ever uses the desk should do a sound check and besides, if you decide that you need to turn the amp up, do you really want to have to run to the stage to do it??

Just my thoughts after a long hot day!


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## zac850 (Dec 14, 2004)

Well, the snake is permanently run in a conduit under the gym, and that is where any additional cables will be run as well. It is permeant, and it is never leaving. 

The express 125 is safe, because it is in the booth, where I want to keep the amp.

So.... what if we ran speakon under the gym through the conduit and once we're there, switched it to 1/4' for the speakers? The speakers are 1/4 inch, and I would like not to spend the however much to change them over. 

I understand what everyone is saying, and at every theater (excecpt 1) that I worked at, the amp is back stage. However, I just can't get over my fear of the amp getting broken/destroyed.


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## m4g1cky (Dec 14, 2004)

Just a clarification for my own state of mind, if we keep the amp backstage, we would use the returns on the snake to go from Amp to Soundboard correct? I'm just a little confused about this. 

Also, would it be easier to make a roadcase or buy one($$$?) and if so, would it be safe in it? Since that is Zac's main concern, and mine as well (Though not as much), it would probably be the deciding factor in using a road case.

If we were to run it back stage, it would be off a different circuit than the lighting.

edit: On another note, does anyone know of any sound system design software. Similar to Lightwright for lighting? I'm interested to do this in my spare time, to save time actually working with the equipment.


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## sound_nerd (Dec 14, 2004)

here is a simple solution, that is very cost effective. Also, its a method that I used when wiring the portable student council sound system at our school. Go to your nearest pro audio dealer. Buy 4 Speakon NL-4 connectors, or whatever connectors you need. Go to Home Depot (or lowes, or wherever) and buy 200 or more feet of 12/2 power cable or 12/3 might be easier to find. Make sure it has thick insulation, its much cheaper than standard speaker cable, and for an application like yours, it will do just fine.


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## Mayhem (Dec 15, 2004)

m4g1cky said:


> Just a clarification for my own state of mind, if we keep the amp backstage, we would use the returns on the snake to go from Amp to Soundboard correct? I'm just a little confused about this.



Yes - the returns from the snake would join the output from your sound board to the inputs of your amp. That is what they are designed to do.


m4g1cky said:


> Also, would it be easier to make a roadcase or buy one($$$?) and if so, would it be safe in it? Since that is Zac's main concern, and mine as well (Though not as much), it would probably be the deciding factor in using a road case.



Depends upon your application and for security you might see if your manual arts teacher can make up a steel frame to which the amp can be bolted in to and then locked in place.

Or you could get a conventional rack and leave one of the top bolt holes empty and place a padlock through this hole and the rack frame. The rack can them be chained into position if needed.

Although, as long as the amp/rack are stored in a secure position before and after each show I fail to see a problem. 

If the sound goes out during the show, just look for the guy with your amp in his hands and head him off before he gets to the door!!


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## len (Dec 15, 2004)

I was always one of the "open it up all the way" type people. However, the people at QSC say it's not a good idea. According to them you should run an amp at about 70% as a baseline, and then make minor adjustments from there.


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## mr_sound (Dec 15, 2004)

I well built roadcase will protect it from the abuse you're worried about. The amp itself is probably tough enough to take the occasional bottle of windex falling on it....but not IN it...that's another story. If you pack it up in a decent quality rack (like SKB, or even make your own flight case..hell check ebay), it'll be fine for most abuse. What exactly do you think is going to be done to it? This can take being moved around and bumped into and such....but it's not going to take a fall down a flight of stairs well (though if it weren't a behringer, it just might live).

Now you've been warned by everyone else about behringer....but take it from me...I bought a lot of behringer stuff for my sound rig and over the years most of it has decided to stop working in some ways. I got the digital board with the mic pre's screwed up. I got the 32 chan analog board with noise problems, and half the auxs are dead. I've got feedback destroyers where a connector goes bad....and these are things that haven't seen much road abuse either. I've got a behringer compressor/limiter that is just not causing me problems. Here's what hasn't stopped working though: My QSC amps, and even my Mackie board and speakers. Behringer is crap...they fall apart much too easily, and the cheap cost in my opinion doesn't make up for all the time you'd spend fixing their stuff. If you're on a tight budget go with makie or peavey. They're not top of the line either....but for the money it's good. I've had my mackie board for 5+ years now, and it still keeps ticking...whereas the behringer digital board lasted almost a year.


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## mr_sound (Dec 15, 2004)

I well built roadcase will protect it from the abuse you're worried about. The amp itself is probably tough enough to take the occasional bottle of windex falling on it....but not IN it...that's another story. If you pack it up in a decent quality rack (like SKB, or even make your own flight case..hell check ebay), it'll be fine for most abuse. What exactly do you think is going to be done to it? This can take being moved around and bumped into and such....but it's not going to take a fall down a flight of stairs well (though if it weren't a behringer, it just might live).

Now you've been warned by everyone else about behringer....but take it from me...I bought a lot of behringer stuff for my sound rig and over the years most of it has decided to stop working in some ways. I got the digital board with the mic pre's screwed up. I got the 32 chan analog board with noise problems, and half the auxs are dead. I've got feedback destroyers where a connector goes bad....and these are things that haven't seen much road abuse either. I've got a behringer compressor/limiter that is just not causing me problems. Here's what hasn't stopped working though: My QSC amps, and even my Mackie board and speakers. Behringer is crap...they fall apart much too easily, and the cheap cost in my opinion doesn't make up for all the time you'd spend fixing their stuff. If you're on a tight budget go with makie or peavey. They're not top of the line either....but for the money it's good. I've had my mackie board for 5+ years now, and it still keeps ticking...whereas the behringer digital board lasted almost a year.


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## zac850 (Dec 15, 2004)

I'm not worried about things getting bumped, what I'm worried about is someone setting an open soda on it, goes off to play basketball, the soda falls over and gets all over the amp. 

Yes, yes, I know, behringer is crap, I know. However, we had a very small price range to choose from and it was between behringer and american DJ, and I have personally have a horrible time with some American DJ lighting gear, so I choose the Behringer. We just really need to make this last for about 3 or 4 years, and then we will hopefully getting a theater space that is not a gymacafatoriam and the sound can get a well deserved face lift.


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## Radman (Dec 15, 2004)

If you run the cable through the conduit, you are most likely going to be running raw cable, so you can just put the right connectors on the right ends. You could also just put gang boxes.


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## cutlunch (Feb 1, 2005)

Hi Zac850. I was wondering if you could post what you did with the amplifier install in your gym. Like for instance where did you put the amp - near the speakers or in the booth etc. Did you use convertors or wire the correct plugs straight onto the speaker cable? Which speakers did you use in the end?
Thanks, it always interesting to findout what the final solution to a problem was.


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## jammers (Feb 5, 2005)

500 watts going into 400watt cabs (rms im working on?) is NOT underpowering them! In fact the ideal power you want goin to them is about 800watts per cab - so in fact your JUST giving them enough power. A long as you dont run into clip, that 500watts will never damage your cabs. In our turbosound floodlight system we run one stereo qsc pl2.0hv (2k amp) per four 75watt comp drivers and never had any probs.

Setting your amp gains at different levels does not effect the amount of power that can go to your speakers, it just affects the amount of signal you have to put into it to get the same power.

Jammers


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## EPAC_Matt (Feb 5, 2005)

It's always better to overpower your speakers than to underpower them. You wouldn't want to be driving 400 watt speakers with a 300 watt amplifier, as you may drive both the speakers and amplifier into clipping.

Just keep the volume down a bit on the mixer, if it sounds like your speakers are clipping, then back off the volume a bit.


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## jammers (Feb 6, 2005)

EPAC_Matt said:


> It's always better to overpower your speakers than to underpower them. You wouldn't want to be driving 400 watt speakers with a 300 watt amplifier, as you may drive both the speakers and amplifier into clipping.
> 
> Just keep the volume down a bit on the mixer, if it sounds like your speakers are clipping, then back off the volume a bit.


Sorry, i said 500w going to 400w cabs is not underpowering them. Now what i meant to say is its NOT OVERPOWERING them. Its just giving them enough!

If you decide to install your amp in the booth, why dont you use the screw terminals for the outputs? Saves on the connector cost and IMO it gives the best install connection. 

As for the JBL's vs Peavey. Well it depens what despersion you want. if you just need it quite narrow use the peaveys, however if you need to cover a wide area use two of the JBL's a side. Also usng the JBL's close to each other you will gain 3dB and bring the load down to 4ohms so you draw more power frm your amp (parallel). Using the JBL's you could gain some 'free' power in your system, obviously this depends on the sensitivity of the jbls v peaveys (but working on them being the same - most prob not). But its definatly worth a play, see what it sounds like!

One other point, you said that people use your cabs as a table? Does this mean that there on the floor? Im sure you know that isnt a good idea - get 'em above peoples head so's the mid/high energy isnt being wasted throwing into peoples knees.

Hope sum stuff here helps.

Jammers


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## EPAC_Matt (Feb 6, 2005)

jammers said:


> Sorry, i said 500w going to 400w cabs is not underpowering them.


Ah, I know, I was just giving an example of underpowering. :wink:


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