Maxing out power amps..??

[Zooberwerx]

Im familiar with gain structure and unity and the ideal zone. The distortion end of things is what concerned me along with pushing at maxed output when it was unnecessary. I guess in a nutshell I want maximum headroom with maximum signal to noise.

example...at a recent show I had our main power amp ( 500w x2 4ohms) going to our 2 main speakers....I had the amps at about 75% of full power. After going through the gain structure and such I couldnt push things past about a 3 or 1/4 of the way before the audience was holding their ears. Granted they were close but still...no where close to unity or 0 in the main level

So my mind thinks that pushing the amp back to 50% and then pushing the master closer to 0 makes more sense.

...hmmm, I missed this part. What's your procedure?

Riis

 

[LightGroove]

Well most of out equipment is very standard.

Typically I go channel by channel and slide each respective channels slider to unity. I then turn up the gain to clipping and then back off slightly. I then have the singer or guitar hit some louder or more involved passages and look for any further clipping on that channel and back off a touch more. I do this for each channel working left to right.

Our board is all in one with onboard effects etc and I adjust those accordingly..typically send the effects out to just short of clipping.

Thats about all I do...crank the amps on and adjust the main volume accordingly which as mentioned can be really low.

 

[Zooberwerx]

Well most of out equipment is very standard.

Typically I go channel by channel and slide each respective channels slider to unity. I then turn up the gain to clipping and then back off slightly. I then have the singer or guitar hit some louder or more involved passages and look for any further clipping on that channel and back off a touch more. I do this for each channel working left to right.

Our board is all in one with onboard effects etc and I adjust those accordingly..typically send the effects out to just short of clipping.

Thats about all I do...crank the amps on and adjust the main volume accordingly which as mentioned can be really low.

You can also set your mic trims by soloing the respective channel and activating the PFL (pre-fade listener). I've seen directions which address both methods.

Here's the process I use...check out pages 37 & 38:

ftp://ftp.dbxpro.com/pub/PDFs/Manuals/English/DriveRackPAPlusManual18-0483-B.pdf

I had to re-read it several times but it starts to make sense when you pull it off. You'll need a CD player and pink noise CD (lots of free downloads online) but its worth the effort and you only have to do it once! The speakers do not have to be connected.

JOOC, if you run all your channel and master sliders to -0-, does anything clip....and I mean the mixer, amps, etc? Disconnect your speakers and give it a try sometime.

Riis

 

[walterw]

Our board is all in one with onboard effects etc and I adjust those accordingly..typically send the effects out to just short of clipping.

Thats about all I do...crank the amps on and adjust the main volume accordingly which as mentioned can be really low.

if you're running the main volume fader on the board "really low", then you probably should back down things elsewhere.

on a lot of budget boards (and apparently even some higher end ones) if every channel is running right at the "correct" unity level, then the summing amps in the master section of the board can peak out. it's OK to run that stuff a little lower.

it's also OK to back the amps off a little (or to back off the EQ and crossover between the board and the amps) so that the master level hangs out closer to the middle. you get more fine control in the middle of the fader's range, as opposed to running it way down where the slightest bump will make the volume jump up.

(oh, and you really don't need to crank the effects levels to "just short of clipping".)

 

[LightGroove]

Thanks Walter...that clears it up a lot.

This is def. a budget board and setup. No PFL .

I'll focus a little more on the main signal next week and back off the respective channels. Sounds like you may be discussing what is happening.

Ive never paid attention to the amps clipping. Something Ill put more emphasis on. I will say we played a show about a month or so ago and had this weird clipping phenomenon going on...actually had to stop the show...board was clean but after backing the amps a 1/4 turn it went away and actually why I started this thread. This cat came in and instantly cranked things and tried selling the point. Which on some levels I agreed with him but if it has negative effects.

I'll also ease back on the effects as well.

Things are starting to make much more sense...

 

[Zooberwerx]

Any way you can list your components (mixer, xover, amps, etc.)? I have a list of default amp attenuator settings (Crown, QSC, and others) that may get your pretty durn close. The suggested setting for my QSC 1450 is...get this...40 % / 11:00. When I read this, I thought "no way...they must be &*%#@ kidding". Turns out it was spot on and corroborated by the lengthier gain / headroom procedure linked earlier.

Sounds like you have more on the ball than some of these so-called experts you run into occasionally.

Where exactly are you located in Virginia?

Riis

 

[LightGroove]

Hey Zoober,

Im in Central Virginia near the city of Lynchburg...about 3 1/2 hrs southwest of Chesapeake.

As mentioned our setup is extremely modest.

Main mixer : Peavey PV 14
Some kind of powered behringer board as a submixer for drums. I just bypass the power amp section and hard pan to form a submix.
Power amp for monitors : Behringer EP1500
Power amp for mains: Crown xls802d we just got this and its in shipping and not the amp Ive been working with.

Pro co sound snake 12x4

Mains: 2 Peavey 2x15 4ohm each
monitors:2 Peavey 1x15 8ohm each

Thats all for now. Ive been suggesting a dual 15band eq for vocals and possibly some subs/crossover for future growth. Nothing in the budget right now

 

[Zooberwerx]

Hey Zoober,

Im in Central Virginia near the city of Lynchburg...about 3 1/2 hrs southwest of Chesapeake.

As mentioned our setup is extremely modest.

Main mixer : Peavey PV 14
Some kind of powered behringer board as a submixer for drums. I just bypass the power amp section and hard pan to form a submix.
Power amp for monitors : Behringer EP1500
Power amp for mains: Crown xls802d we just got this and its in shipping and not the amp Ive been working with.

Pro co sound snake 12x4

Mains: 2 Peavey 2x15 4ohm each
monitors:2 Peavey 1x15 8ohm each

Thats all for now. Ive been suggesting a dual 15band eq for vocals and possibly some subs/crossover for future growth. Nothing in the budget right now

Nice...we have a Roberts Home Medical office in Lynchburg.

I pulled up manuals for both the Peavey mixer and Crown en route. Looks like the mixer has bargraph LEDs (with clip indicators) located directly above your main sliders You can pick up used EQ's for less than $30 if you keep your eyes peeled. I have two that were given to me. An inexpensive limiter would be handy but, then again, I worked for years without one.

Riis

 

[Wes Whitmore]

You should set the gains on your amp to hit a target voltage to your speakers with a test tone or pink noise, with the channel set at unity and the master out set at unity. Live material will be less "hot", so you will be able to turn the sensitivity up a few clicks after you hit your target. You set it up once, and you should be good to go. Your S/N will be as high as it can be. If you feel that you want to subject your speakers to more voltage, then give it another click. I feel that if you keep finding yourself clicking it up more and more (before clipping lights), then you need more amp to do what you need.
Wes

 

[walterw]

Ive never paid attention to the amps clipping. Something Ill put more emphasis on.

the usual thing at this level is to put the amps where you can see them while you're mixing, so the clip lights on the amps become your final "speed limit" warning.

 

[LightGroove]

Thanks Walter... I need to pay you guys a visit...its been awhile since Ive been in the store...I remember a solid selection of Roscoes there about 2 years back....

Anyways...Im going to attempt to have the amps within sight. Right now Im using the sends out of our snake directly into the amps so they are a distance away.At some shows 60-75 ft. I should be able to see the light flashing however. I debated on having the amps back at the mixing desk but then had the drawback of extra wires in the middle of the crowd. Also starting to find solutions so the crowd doesnt step on the snake too much. Its fairly small wire and a weekend warrior type setup.. Ive seen a few recommendations but we are limited at 100ft

Anyways I think I have a LOT more clarity now...pretty excited to testdrive and play next Tues.

 

[Zooberwerx]

Thanks Walter... I need to pay you guys a visit...its been awhile since Ive been in the store...I remember a solid selection of Roscoes there about 2 years back....

Anyways...Im going to attempt to have the amps within sight. Right now Im using the sends out of our snake directly into the amps so they are a distance away.At some shows 60-75 ft. I should be able to see the light flashing however. I debated on having the amps back at the mixing desk but then had the drawback of extra wires in the middle of the crowd. Also starting to find solutions so the crowd doesnt step on the snake too much. Its fairly small wire and a weekend warrior type setup.. Ive seen a few recommendations but we are limited at 100ft

Anyways I think I have a LOT more clarity now...pretty excited to testdrive and play next Tues.

Walter wasn't in the shop today but I was. Had to pick up a power amp. Alpha had two really nice Roscoe Century's...a 4 and a 6...with nice figured tops. No fivers....blasphemy!

BTW, if you follow the set-up procedure described earlier, you won't have to watch the the amps' clip LEDs. This is where a limiter comes in handy: when adjusted correctly, you'll see it kick in before the amps come close to clipping.

Riis

 

[walterw]

BTW, if you follow the set-up procedure described earlier, you won't have to watch the the amps' clip LEDs. This is where a limiter comes in handy: when adjusted correctly, you'll see it kick in before the amps come close to clipping.

sure, but i suspect tone generators and output voltage calculations might be a bit above the OP's pay grade at this point.

also, system limiters aren't "free". like anything else in line, they will affect the tone a little. if the system is just run properly, they won't be needed. (i'm all about compression for vocals, though.)

as a general rule, proper deployment beats relying on another gadget every time.

 

[Zooberwerx]

sure, but i suspect tone generators and output voltage calculations might be a bit above the OP's pay grade at this point.

also, system limiters aren't "free". like anything else in line, they will affect the tone a little. if the system is just run properly, they won't be needed. (i'm all about compression for vocals, though.)

as a general rule, proper deployment beats relying on another gadget every time.

The only tone generator required would be a CD player and a pink noise CD. I swiped my wife's Koss DVD player off her TV and downloaded 20" worth of pink noise. Cost?...the price of a blank CD. The built-in amp limiters and proper set-up will probably be more than adequate.

Riis

 

[LightGroove]

So I tracked sown some free pink noise via truerta (went the free route)

So...do I simply plug and play into the pa... what am I looking for and doing specifically....just sounds like an obnoxious hiss

Thanks guys

 

[Zooberwerx]

So I tracked sown some free pink noise via truerta (went the free route)

So...do I simply plug and play into the pa... what am I looking for and doing specifically....just sounds like an obnoxious hiss

Thanks guys

Obnoxious hiss? That's exactly what we're looking for. Pink noise encompasses the usable sonic spectrum (high freq's, low freq's, and everything in-between). We're halfway there.

I strongly encourage you to check out the link on post #23 and check out / print pages 37 & 38. Read it over a few times. This is a rough procedure outline but a little too involved as it rolls an external limiter into the equation, gear which you don't have and probably won't need for the moment. If you'd like, I can draft an abbreviated step-by-step process which addresses just the mixer and power amp. But first, some preliminary tasks:

*Disconnect the speakers. Most modern power amps have disconnect protection so you'll be okay.

*I'll assume you've connected your CD player to the L & R RCA inputs. You should be able to select the CD for source / monitor and watch the LED bargraph to indicate signal strength. I don't have the manual in front of me but if you need assistance, let me know. Make sure your main volume sliders are all the way down.

*Defeat any clip limiters and/or high pass filters on your power amp. We're not running any speakers so no big deal. We'll re-engage when done.

On second thought, I'd hold off on all of the above until I get the rest of the plan in order. I imagine you'd like to do this in one fell swoop.

Riis

 

[Wes Whitmore]

So I noticed that the "big" sound company here in columbus provided audio support for a festival here in Columbus. They had their amps turned all the way up...makes me question either the theory, or the practice in real life a little more. Regardless, it works for me to set them based on a particular voltage because we purposely bought a huge amp with enough headroom to shred our every-day budget system, and use the sensitivity controls to help keep some of the power from going to the speakers. It sounds night and day better to have the reserve power compared to our old amp, which was constantly hitting the limiters. It just sounds much better than it should.
Wes

 

[Zooberwerx]

Hmmm....looks like the Crown has no user-defeatable clip protection or HPF's which makes life a whole lot easier. Sames holds true for the PV 14 mixer...very straight-forward. Well, here goes nuthin':

1) Connect CD player to L & R Tape inputs. Depress "Tape > Mains" button to the left of the main faders. Faders should be off.

2) Connect mixer's L & R main ouputs to Crown's inputs. Make sure speakers have been disconnected.

3) Turn both attenuators to -0- or fully CCW. No two manufacturers use the same numbering system which is a real PIA.

4) Play pink noise CD and slowly advance the mixer's main faders upward. You should see the signal indicated in the LED bargraphs. Continue to advance the faders until you see the red LED clip indicators begin to flicker. I would imagine this occurs in the +5 to +10 db range but your results may vary slightly. Not to worry.

5) Slowly pull back both faders to the point where clipping stops and no further. If we've done this correctly, the signal should be bouncing around in the yellow LED region with maybe an occasional clip indication. Again, I would guess this will be in the -0- to +5 db range.

6) Slowly turn up the amp attenuators until you start to see flashing yellow signal LEDs. Continue to advance until both channels begin to clip (red LEDs). You may want to mark the knob locations with a piece of tape, whatever, for future reference. Slowly back off the attenuators until clipping stops. Mark these positions, as well. Sidenote: normally, this is where we fold in limiters to reign things in but we'll improvise later with a "real" CD or live performance.

7) Pull your faders down, reconnect your speakers, and pop in a Steely Dan CD (I recommend AJA). Slowly advance your faders to the desired volume...and above if you can get away with it. We should be 95% there but if you're still seeing occas. clipping, turn down your attenuators by a cat whisker or two.

Let me know how it works out.

Riis

 

[LightGroove]

Thanks Riis,

I actually had to leave the pink noise at home last night but plan on making it a priority at an upcoming practice. I did get th enew amp setup last night...as a previous poster stated this bigger amp has given us GOBS of what I associate with headroom. I actually did a quick run through from those pages listed and its a fantastic solution. I was able to reach unity across the board including my main outs. The crown made it to high noon and then the clipping kicked in on the amp. Ive got things just short of yellow, with the occasional peak into yellow for loud snare or vocal hits..otherwise ..it was sweet.

Side note..do the guitard begins to instantly talk about how things were sounding like mud again(funny thing, i didnt touch anything from previous week). I guess im the mud guy...lol....at the very end of practice he took some of my advice (a 1st)..one of which was to get away from his amp (which is mud to me) and run di and use his amp as a monitor...wouldnt you know it he wanted to play for hours more because it sounded so good... I was like dude...you were the mud the whole time...how bout that.... Anyways...I dont have all the answers but a general understanding..for some reason this guy has all the answers...I know Im not alone ayay aya

Sounding good..this advice has been wonderful folks...

 

[Zooberwerx]

Sounds like you're 95% there. Its amazing where the attenatuators end up, isn't it? My QSC's are all in the 10:30 - 11:00 postion....a far cry from the 5:00 full-on position. Now you have an idea as to how and why things work, its time to throw in a two channel limiter. C'mon....I know you can do it! LOL!

If you've pulled this off correctly, you should have a smooth near-linear volume response from -off- all the way to -0- with no clipping and extra horsepower to spare.

Riis