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midlife
08-15-2009, 04:57 PM
I have a Crown DC300 for my main power amp. It has L&R gain controls on the front of the amp. I have been told by some in order to get the maximum head room those gain knobs should be run full up regardless of my volume needs (listening levels should be controlled by the preamp gain). What would you do to have it "right"?...........:o::banghead::blah:

SEAWOLF97
08-15-2009, 05:55 PM
I have a Crown DC300 for my main power amp. It has L&R gain controls on the front of the amp. I have been told by some in order to get the maximum head room those gain knobs should be run full up regardless of my volume needs (listening levels should be controlled by the preamp gain). What would you do to have it "right"?...........:o::banghead::blah:

thats the same advise that I got to the same question .... been doing it that way with no problems.

many amps (including some very "high end" ) have no gain control, they just always run wide open.

midlife
08-15-2009, 06:14 PM
So too much might just be enough?

BMWCCA
08-15-2009, 08:17 PM
It's not correct. They aren't gain controls, they are input attenuators. The simplest explanation is you set them so at the loudest level you play your system your pre-amp volume control is in the "sweet spot" around the three-quarters point, and at "normal" level around the half-way point. This question got asked quite frequently on the Crown forum and was answered by a Crown employee and I re-posted it here. Let me see if I can find the thread:

Here's one mention: http://www.audioheritage.org/vbulletin/showpost.php?p=209737&postcount=19

But I think this is the one I was thinking of: http://www.audioheritage.org/vbulletin/showpost.php?p=128360&postcount=19

Here's the entire "gain structure" reply from the Crown Forum: http://www.crownaudio.com/forums/index.php?showtopic=1282&view=findpost&p=4628

midlife
08-15-2009, 08:58 PM
It's not correct. They aren't gain controls, they are input attenuators. The simplest explanation is you set them so at the loudest level you play your system your pre-amp volume control is in the "sweet spot" around the three-quarters point, and at "normal" level around the half-way point. This question got asked quite frequently on the Crown forum and was answered by a Crown employee and I re-posted it here. Let me see if I can find the thread:

Here's one mention: http://www.audioheritage.org/vbulletin/showpost.php?p=209737&postcount=19

But I think this is the one I was thinking of: http://www.audioheritage.org/vbulletin/showpost.php?p=128360&postcount=19

Here's the entire "gain structure" reply from the Crown Forum: http://www.crownaudio.com/forums/index.php?showtopic=1282&view=findpost&p=4628
I usually try to find the sweet spot among the source (when adjustable), pre-amp and the amp. However I do remember being told that the input attenuators on the DC300 should be run full up to offer the best protection from clipping. Is it a debate or a known quantity??? thanks, every little bit helps, no?

BMWCCA
08-15-2009, 09:33 PM
Is it a debate or a known quantity??? thanks, every little bit helps, no?Uhm, did you read any of the links? Personally, I think I'd trust the Crown rep. But you can do what you want. Pretty much all you can do is introduce more noise. It won't get any louder or produce any more power. :banghead:

Allanvh5150
08-16-2009, 04:09 AM
I heard the same argument a few days ago. No professional in thier right mind would run the Power amps attenuators any less than full. One of the linked articals even goes as far to say that if you run the amps on full you will not be able to get any more from the system....:blink: Regardless of the power that is being used, in a live situation there is ample control from a mixer that is running the masters from about halfway to 0. I have run all the amplifiers that I have ever used on full. If any one is worried about amplifier or mixer noise in a live situation they should get another hobby.

Allan.

Fred Sanford
08-16-2009, 05:12 AM
I heard the same argument a few days ago. No professional in thier right mind would run the Power amps attenuators any less than full. One of the linked articals even goes as far to say that if you run the amps on full you will not be able to get any more from the system....:blink: Regardless of the power that is being used, in a live situation there is ample control from a mixer that is running the masters from about halfway to 0. I have run all the amplifiers that I have ever used on full. If any one is worried about amplifier or mixer noise in a live situation they should get another hobby.

Allan.

So...why are there attenuators on pro amps, then? Shouldn't there just be on/off switches?

I generally do as described before- match it to the range I'm using on the fader controls, so that I can make the most of the fader/volume control while introducing the least amount of noise. Sometimes that's max, but here at home it's not (Yamaha P2100s at -16, Crown DC300A at ~7, JBL 6260 at -12, etc.).

But, I guess I'm a professional that's not in his right mind, so take that for what it's worth. :)

je

midlife
08-16-2009, 07:34 AM
Uhm, did you read any of the links? Personally, I think I'd trust the Crown rep. But you can do what you want. Pretty much all you can do is introduce more noise. It won't get any louder or produce any more power. :banghead:
I get it, in a home environment balance the pre and main gains to the desired output.

BMWCCA
08-16-2009, 08:38 AM
:dont-know
I get it, in a home environment balance the pre and main gains to the desired output.Yeah, but that's really a simplistic method because most home systems don't have the metering necessary to let you know when you've hit zero on the output meters. As Crown says, it's not the amp's output or power you're choking, you're just matching the input to the correct operation range of your pre-amp.

Sort of like the level-matching on a Soundcraftsmen EQ; you don't want to overdrive your pre-amp so you generally cut EQ rather than boost if you don't have level-matching controls and LEDs. With your Crowns you don't want to under-drive your pre-amp because it might not be as quiet in the lower volume-control positions or the highest positions and, since you don't have anything to measure the pre-amp output, you simply set the amp input attenuators to keep the pre-amp in its sweet spot to minimize noise.

Running your power amp wide open won't affect the power amp, but it might cause your pre-amp to run in a volume-control range that isn't optimum. I don't do this for a living and I didn't stay at a Holiday Inn Express last night, either. But I do know there's some reason Crown sells an anti-tamper knob set for their D and PS-series amps so the system engineer can set it where it should be and then keep prying little hands off those controls. $6 a pair, last I ordered any. :D

FWIW, I've worked with a pro SR engineer for a couple of years now, just helping out, setting up, and running the monitor board mostly. His biggest portable system runs five Crown MacroTechs and those knob positions are clearly marked, and the board's output is set so the main sliders can't go past zero. With the sliders at zero and the amps' attenuators set in the correct postion, the system gain structure is set and the noise floor optimized. You can do this in a rudimentary way for home use by following the instructions given above by the Crown technician. :thmbsup:

I'm no expert, obviously, but for all I know, the NZ method of setting gain structure (balls-to-the-walls) could account for why Opimax picked up noise from my Soundcraftsmen EQ using his down-under amps that I don't hear in my 4345 using the same front-end and my bi-amped Crowns with their attenuators set-up properly.

And yes, I'll take my punishment over the air, Mr. Limbaugh. ;)

hjames
08-16-2009, 09:40 AM
:dont-know I'm no expert, obviously, but for all I know, the NZ method of setting gain structure (balls-to-the-walls) could account for why Opimax picked up noise from my Soundcraftsmen EQ using his down-under amps that I don't hear in my 4345 using the same front-end and my bi-amped Crowns with their attenuators set-up properly.

And yes, I'll take my punishment over the air, Mr. Limbaugh. ;)

Yep, not only were they from a certain southern country,
but they were located in the basement,
with ins and outs cables run through small holes in the floor!

Literally Down Under!

SEAWOLF97
08-16-2009, 10:40 AM
I have tried both ways...

amp gain/attenuators wide open or half way ...big BGW is so quiet that I cud hear no difference. Same on the preamp volume control...so why not have access to all the power that you paid for ?

and on the gain/attenuator question....Phil is prolly right, BUT the manf labels them gain on the units and in manuals.

Fred Sanford
08-16-2009, 11:03 AM
I have tried both ways...

amp gain/attenuators wide open or half way ...big BGW is so quiet that I cud hear no difference. Same on the preamp volume control...so why not have access to all the power that you paid for ?

and on the gain/attenuator question....Phil is prolly right, BUT the manf labels them gain on the units and in manuals.

Most of my pro amps are labelled as attenuators- actually the Crown DC300A is the only exception, its labels run 1-8.

As to why not have access to all the power you paid for: I back them down to have more precise control from the fader- if 25% up on the fader is the loudest I'll ever play the very quietest tune on my system, why not bring down the amp's input so that 75% or more of the fader's throw is useful day-to-day? As an example, on my main monitors the amps are brought down -16dB, which makes my main volume knob settings ~2 for quiet, late-night use; 5 for most reference mixing, and ~7-8 for really slamming it. With the amps set wide open, I can't get past 2 or 2.5 and stay in the room comfortably. I much prefer a gradual, linear control.

Another part not mentioned so far is that many times in a pro situation you want hot levels coming out of your mixer (pre) in order to reduces the losses from sending the signal 100' or more to the stage & power amps. The power amp level controls would enable you to set the mixer running at its best range and still balance the house audio. There's also many other uses for the level controls, one being when a signal is split to multiple amps & speakers that you want differing output levels from (or, speakers of differing sensitivity ratings, that you want identical output levels from).

Dunno- I use them all the time, and they're helpful. :dont-know

je

SEAWOLF97
08-16-2009, 11:20 AM
There's also many other uses for the level controls, one being when a signal is split to multiple amps & speakers that you want differing output levels from (or, speakers of differing sensitivity ratings, that you want identical output levels from).
je

that is EXACTLY what I do with the 2nd BGW running rear of the room fill speakers (both are coming off the same preamp) ....I dont want them competing with the mains, only for rear fill and run that amp at abt 1/3.

BMWCCA
08-16-2009, 12:44 PM
...so why not have access to all the power that you paid for ?I do. You do, too. Remember, you're not limiting the power, at least in the case of the Crown's input attenuators, but I don't know what BGW calls them. Instead you're dialing back the input level.

There's no way anyone can stay in the room with my bi-amped 4345s if the volume control approached three-o'clock so running it in the normal range of nine-o'clock to one-o'clock I'm reasonably certain I'm not throttling-down the Crowns even with their attenuators at twelve-o'clock high! :D

Yet another opportunity for one of my well-loved ;) automotive analogies:
Throttle tip-in on most American and Oriental vehicles is immediate if not abrupt. Certainly non-linearómore of a bell curve on the downhill slope. You feel like you have all the power in the world off the line and in the first 25% of throttle travel. On the other hand, those fine German makes have near-linear throttles, or used to. You push the pedal half-way and you've gotten half the available throttle opening. The reason Lexus, among others, do it their way is the uninformed customer thinks the things are rocket ships when they first get in them. BMWs and Mercedes by comparison seem slow off the line unless you give them more "gas". Which one do you think actually allows more control in throttle modulation during cornering, applying power gradually, or in steering the car with the throttle, otherwise known as "driving" the car? GM even used an almost on-off brake application on their cars at one time. I used to scare myself to death driving my grandmother's Impala everytime I hit the brakes! And that was decades before ABS. Scary!!

SEAWOLF97
08-16-2009, 05:38 PM
Most of my pro amps are labelled as attenuators- actually the Crown DC300A is the only exception, its labels run 1-8.

je

But if you can attenuate from 11 they wud be much louder, than attenuating from only 8. :barf:


I don't know what BGW calls them.

Fred Sanford
08-16-2009, 05:46 PM
But if you can attenuate from 11 they wud be much louder, than attenuating from only 8. :barf:

Yeah, I figure with the DC300 only running up to 8, it's probably really a DC450 under the hood if I just modded the volume knobs to turn all the way to 10.

je

JBL 4645
08-17-2009, 02:38 PM
It's not correct. They aren't gain controls, they are input attenuators. The simplest explanation is you set them so at the loudest level you play your system your pre-amp volume control is in the "sweet spot" around the three-quarters point, and at "normal" level around the half-way point. This question got asked quite frequently on the Crown forum and was answered by a Crown employee and I re-posted it here. Let me see if I can find the thread:

Here's one mention: http://www.audioheritage.org/vbulletin/showpost.php?p=209737&postcount=19

But I think this is the one I was thinking of: http://www.audioheritage.org/vbulletin/showpost.php?p=128360&postcount=19

Here's the entire "gain structure" reply from the Crown Forum: http://www.crownaudio.com/forums/index.php?showtopic=1282&view=findpost&p=4628

This means input clipping? If set too low a level and the input signal music/movie was many times greater for the input it would start to distort. With the volume being at higher level there is less chances of clipping happening.

BMWCCA
Those links were very helpful.
:applaud:

But if you can attenuate from 11 they wud be much louder, than attenuating from only 8. :barf:



:D that is funny quote "11"

Nigel Tufnel (http://www.imdb.com/name/nm0001302/): The numbers all go to eleven. Look, right across the board, eleven, eleven, eleven and...
Marty DiBergi (http://www.imdb.com/name/nm0001661/): Oh, I see. And most amps go up to ten?
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): Exactly.
Marty DiBergi (http://www.imdb.com/name/nm0001661/): Does that mean it's louder? Is it any louder?
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): Well, it's one louder, isn't it? It's not ten. You see, most blokes, you know, will be playing at ten. You're on ten here, all the way up, all the way up, all the way up, you're on ten on your guitar. Where can you go from there? Where?
Marty DiBergi (http://www.imdb.com/name/nm0001661/): I don't know.
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): Nowhere. Exactly. What we do is, if we need that extra push over the cliff, you know what we do?
Marty DiBergi (http://www.imdb.com/name/nm0001661/): Put it up to eleven.
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): Eleven. Exactly. One louder.
Marty DiBergi (http://www.imdb.com/name/nm0001661/): Why don't you just make ten louder and make ten be the top number and make that a little louder?
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): [pause] These go to eleven.

I can’t find the old JBL cinema manual in pdf form for the 1993 edition which I have in paper form only.

JBL 4675
108db @ 1m
82db @ 20 meters

Noise floor
24db @ 1 meter
-2db @ 20 meters

The image is from the 2003 edition

Crown SPL db calculator
http://www.crownaudio.com/apps_htm/designtools/elect-pwr-req.htm (http://www.crownaudio.com/apps_htm/designtools/elect-pwr-req.htm)
SPL db calculator
http://myhometheater.homestead.com/splcalculator.html (http://myhometheater.homestead.com/splcalculator.html)

4343
08-20-2009, 04:31 PM
...

:D that is funny quote "11"

Nigel Tufnel (http://www.imdb.com/name/nm0001302/): The numbers all go to eleven. Look, right across the board, eleven, eleven, eleven and...
Marty DiBergi (http://www.imdb.com/name/nm0001661/): Oh, I see. And most amps go up to ten?
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): Exactly.
Marty DiBergi (http://www.imdb.com/name/nm0001661/): Does that mean it's louder? Is it any louder?
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): Well, it's one louder, isn't it? It's not ten. You see, most blokes, you know, will be playing at ten. You're on ten here, all the way up, all the way up, all the way up, you're on ten on your guitar. Where can you go from there? Where?
Marty DiBergi (http://www.imdb.com/name/nm0001661/): I don't know.
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): Nowhere. Exactly. What we do is, if we need that extra push over the cliff, you know what we do?
Marty DiBergi (http://www.imdb.com/name/nm0001661/): Put it up to eleven.
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): Eleven. Exactly. One louder.
Marty DiBergi (http://www.imdb.com/name/nm0001661/): Why don't you just make ten louder and make ten be the top number and make that a little louder?
Nigel Tufnel (http://www.imdb.com/name/nm0001302/): [pause] These go to eleven.


When I worked for Snell & Wilcox, one of the lads in engineering had hand-built a noise generator with a knob where the numbers rotated beneath a little window, 1-10 like normal. One day I had it on 10 and noticed that there was an 11 visible after the 10! The potentiometer would not turn that far, so I guess it would need a special "11" pot to get that far...

Fred Sanford
08-20-2009, 04:55 PM
I heard the same argument a few days ago. No professional in thier right mind would run the Power amps attenuators any less than full. One of the linked articals even goes as far to say that if you run the amps on full you will not be able to get any more from the system....:blink: Regardless of the power that is being used, in a live situation there is ample control from a mixer that is running the masters from about halfway to 0. I have run all the amplifiers that I have ever used on full.

Just as another example, I worked another show with the guys from Southard Audio yesterday(www.southardaudio.com (http://www.southardaudio.com)), and all of the amps in all of the many, many amp racks (football stadium show to a crowd of thousands) were specifically pre-set at less-than-wide-open, balanced to get the most from the mixer/crossover/loudspeaker management they were grouped with.


If any one is worried about amplifier or mixer noise in a live situation they should get another hobby.

Allan.

I don't think you'd get much work on Broadway with that philosophy. Professional-level dramatic & musical theater productions absolutely demand silent systems.

je

midlife
08-20-2009, 05:59 PM
As the original poster, I believe I get it, running the amps full up decreases the chance of a rare clipping incident while increasing the possibility of floor noise. However when I had my L300s (with a Crown DC300-home system) I was in the habit of running the amp full and having the pre at 1/3 to 1/2 when I was often impressing myself with the L300s punch and clarity. I am now using L166s with another DC300, generally running the amp at 2/3s with the pre at a little better than 1/3.

BMWCCA
08-20-2009, 06:12 PM
As the original poster, I believe I get it, running the amps full up decreases the chance of a rare clipping incident . . .No, running them at full actually has nothing whatsoever to do with preventing clipping. The amp will produce full power regardless and if you set the attenuators correctly you'll actually decrease the possibility of someone coming in and cranking the system into clipping, not the opposite. The noise floor isn't a possibility, it's a reality. Setting the amp correctly in relation to the pre-amp just keeps the noise floor as low as possible.

Allanvh5150
08-21-2009, 01:42 AM
A lot of the power amps that I deal with do not have attenuators. The only time I can think that I would use an attenuator is when I have an amp failure and I need to replace it with somthing larger. Most of the current generation rack gear and mixers have unbeleivable noise figures and so do the amplifiers. Feel free though to do as you wish. I have only been doing live sound reinforcement since 1981 so what would I know. I can't think why I would want any work on broadway though.......

Fred Sanford
08-21-2009, 04:28 AM
I can't think why I would want any work on broadway though.......

Lots more $/night than the concert work I've done, with lots less lifting. I've dated a few of the pretty dancers, too. ;)


I have only been doing live sound reinforcement since 1981 so what would I know.

Interesting- same year as me.

je

toddalin
08-21-2009, 10:07 AM
No, running them at full actually has nothing whatsoever to do with preventing clipping. The amp will produce full power regardless and if you set the attenuators correctly you'll actually decrease the possibility of someone coming in and cranking the system into clipping, not the opposite. The noise floor isn't a possibility, it's a reality. Setting the amp correctly in relation to the pre-amp just keeps the noise floor as low as possible.

Not necessarily so. It is not the amp output stages clipping that is of concern but the preamp overloading the input stages and this causing the clipping, just as the master volume is supposed to do on a guitar amp.

Taken it to the extreme, set the amp at "1" such that you have to turn the preamp up so far that its output will clip the input stage of the amp and the amp will never see its full power.

SEAWOLF97
08-21-2009, 10:35 AM
Setting the amp correctly in relation to the pre-amp just keeps the noise floor as low as possible.

Thats what I thot when I acquired the amp ....in reality, I find that it makes NO difference....its quiet anywhere that its set, and that is after a lot of experimentation.

The only benefit that I've found to setting the amp lower (more attenuated) is that there is now more granularity to the preamp volume control.

As for stray hands hitting the volume control on the preamp ?? There are only 2 of us here and she knows better than to touch the stereo.


A lot of the power amps that I deal with do not have attenuators.

dead-on right....many do NOT have more than just a power switch.

BMWCCA
08-21-2009, 12:45 PM
dead-on right....many do NOT have more than just a power switch.And many cars have only three, four, or five forward gears, too. Doesn't mean you won't use sixth gear in a car that has one.

I know we're picking at nits on this now but the original question was about the proper way to use the "gain controls" on a Crown amp. I believe that question has been answered. For those unfortunate enough not to have input attenuators on your power amps, you'll just have to muddle along in blissful ignorance, content that your life is so simple! :D

Allanvh5150
08-21-2009, 01:35 PM
And many cars have only three, four, or five forward gears, too. Doesn't mean you won't use sixth gear in a car that has one.

And the first thing one reaches for when they need to put the accelerator down? The gearstick/attenuator. If you are talking about using the attenuators in a home theatre system as safety devices I can see the merit but why not set the internal levels in your amp so that the masters cant run any harder than what you want to be a maximum level. I dont want to have to remember where poweramp levels have to be set when turning a system on and off and I certainly dont want to put marks on the gear where it should be set. I also never mark the desk so I know what channel is what, but that is another subject.

Allan.

BMWCCA
08-21-2009, 02:11 PM
And the first thing one reaches for when they need to put the accelerator down? The gearstick/attenuator. If you are talking about using the attenuators in a home theatre system as safety devices I can see the merit but why not set the internal levels in your amp so that the masters cant run any harder than what you want to be a maximum level. I dont want to have to remember where poweramp levels have to be set when turning a system on and off and I certainly dont want to put marks on the gear where it should be set. I also never mark the desk so I know what channel is what, but that is another subject.
I was referring to the fact that the Crowns have attenuators indicating one might want to actually use them. It's not a clutch-shift-throttle analogy, but if you want to play it that way, fine! But it doesn't work even if you consider different final-drive ratios, or whether or not the transmission is an overdrive box, or not.

And why would you have to move the input attenuators on the amp every time you turned it on? :confused: Are you just looking for reasons to disagree?

Again, the original question was about how to use the attenuators on a Crown amp. If your amp doesn't have them, then by all means don't waste your time contemplating your navel: You just don't have them. If a Crown owner doesn't want to use them properly, then just crank them wide open and have fun using that 1/4 of the range of your pre-amp's volume pot that you'll ever use. To each their own.

Now if you're just wanting to "buy and argument" in the best Monty Python manner, we'll just have to see how high up on that tree you can pee, won't we? ;)

http://www.youtube.com/watch?v=kQFKtI6gn9Y&feature=related

Robh3606
08-21-2009, 03:29 PM
I use my input attenuators to help manage the S/N in my active system. When you have compression drivers running at over 110db it certainly helps if you can adjust the amps sensitivity to help keep the noise down. It would be a problem for me if they didn't have them.

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSS

Rob:)

Allanvh5150
08-22-2009, 02:15 AM
And why would you have to move the input attenuators on the amp every time you turned it on? :confused: Are you just looking for reasons to disagree?


Simple fact being that not all power amps turn on and off as cleanly as they should. But you would probably know that anyway....

Fred Sanford
08-22-2009, 07:02 AM
And the first thing one reaches for when they need to put the accelerator down? The gearstick/attenuator. If you are talking about using the attenuators in a home theatre system as safety devices I can see the merit but why not set the internal levels in your amp so that the masters cant run any harder than what you want to be a maximum level. I dont want to have to remember where poweramp levels have to be set when turning a system on and off and I certainly dont want to put marks on the gear where it should be set. I also never mark the desk so I know what channel is what, but that is another subject.

Allan.

There are a number of options on how to manage signal levels and control ranges. Modern crossovers & speaker management systems can tweak what each power amp is seeing. Specific amplifiers can be chosen tailored to the applications.

I never doubted that you might be getting good results with all of your amps' dials at max...I don't doubt that I could get good results with that approach as well. I was just addressing the sweeping generalization/slandering in this line:


No professional in thier right mind would run the Power amps attenuators any less than full.

...and trying to balance your statement with real-world reasons/situations that professionals would and (usually, in my experience) do run at less-than-max.

je

JBL Dog
08-22-2009, 08:06 AM
When I worked for Snell & Wilcox, one of the lads in engineering had hand-built a noise generator with a knob where the numbers rotated beneath a little window, 1-10 like normal. One day I had it on 10 and noticed that there was an 11 visible after the 10! The potentiometer would not turn that far, so I guess it would need a special "11" pot to get that far...

The output pots on the QSC MX1500 (first generation, not the "A" series) go up to "11".

:applaud:

BMWCCA
08-22-2009, 08:43 AM
Simple fact being that not all power amps turn on and off as cleanly as they should. But you would probably know that anyway....For us laymen: Please explain how changing or even zeroing an amp's INPUT attenuators might affect the "dirty" turn-off signal sent through the amp's output? :dont-know

jcrobso
08-24-2009, 09:31 AM
Years ago I started attending this one Church, they had an on going problem of picking up a near by 50KW AM station in the sound system. After a few weeks of this I asked if I could look at how the system was setup. I found that the Crown amp inputs were at full and the Sound Craftsman mixer outputs were at 30bd down. I turned the Crown inputs down to the 2PM position and brought the mixer outputs up to 0db and the radio station went away. The radio station was still in the system since it was the wiring to the amps that was the problem, but now the level was so low that it was almost inaudible. After this they put me in charge of the sound system and I did fix the faulty wiring.

boputnam
08-24-2009, 09:06 PM
So...why are there attenuators on pro amps, then? Shouldn't there just be on/off switches? I've missed most of this so forgive if I don't catch all the opinions offered.

The input attenuators should be used to match the clipping levels at the pre-am and the amp. Unplug your speakers and drive the pre-amp to clipping; then, set the amp gains to clip at the same gain point. That way, you will know when you are getting close to overdriving your pre-amp that the amp is at the same point.

I don't understand the term "sweet spot" - that seems arbitrary / subjective and could put your speakers at risk. I prefer to use dB meters and match the gain structures throughout the signal path.

However, for home use, if you can be comfortable with no-one over-driving your pre-amp, then you can run your amps "wide open", but again, it is nice to know that the clip level is matched throughout the signal path.

BMWCCA
08-25-2009, 05:01 AM
I don't understand the term "sweet spot" - that seems arbitrary / subjective and could put your speakers at risk. I prefer to use dB meters and match the gain structures throughout the signal path. Exactly, but the "sweet spot" was simply an interpretation of the suggestion on the part of the Crown techs for how to set the amp gain in a home system that doesn't have meters on the pre-amp side, the exact scenario being dealt with by the original poster in this thread. :) The "pro" discussion was simply the sideshow that followed.


When working with a non-metered Preamp 3/4 of the way up, on the preamp output, is a good place to start as this is usually about the nominal output.

SEAWOLF97
08-25-2009, 10:39 AM
I ran across a "pre answer" (the answer b4 the question) from Dome on 7-07


I run my L250s (not 250Tis) with a Hafler SR2600 (600W/ch) and they can produce an immense amount of sound with no disortion. I usualy stop at around 1/3 rotation of the volume knob on the pre/pro, with the amp gains set at 0.

midlife
08-25-2009, 05:54 PM
Exactly, but the "sweet spot" was simply an interpretation of the suggestion on the part of the Crown techs for how to set the amp gain in a home system that doesn't have meters on the pre-amp side, the exact scenario being dealt with by the original poster in this thread. :) The "pro" discussion was simply the sideshow that followed.
How would meters help decide amp gain? I do have an OC150 with multi function meters? What would I set the meter biasing switches at and what would I look for from the meter readings to arrive at this much debated "sweet spot". Has anyone had good results by setting these dials where they simply sound right?

BMWCCA
08-25-2009, 06:49 PM
I ran across a "pre answer" (the answer b4 the question) from Dome on 7-07Which really didn't answer the question in this post, either, but instead was a testimony simply to at what level on the pre-amp volume control can drive you out of the room with the Hafler amps wide open. It answers nothing about noise floor or even suggests that that's the best setup for that system. That reply was in answer to underpowering 250Tis and causing damage. Comparing pre-amp volume pot positions versus sound-pressure level between systems is fun, but tells you nothing. I'd suggest any setup that reaches maximum volume at 1/3 of the pre-amp output control is possibly not making the best use of that pre-amp. But it does offer some ego-stroking consensual validation for the owner, in a Lexus kind of way. I know T-dome didn't mean it that way. He was just trying to get the point across about how much clean power the 250's could handle.

This discussion has gotten away from the original question and when answers from the manufacturer of the amp in that original question don't agree with the application of members here using other brands of amps, with or without input controls, everyone else is doing it wrong. I'm simply stating what Crown feels is the proper way to set the controls, refuting the claims that they are "output" controls, and answering the original question. No one's saying you can't do whatever you want with your equipment. :D

This thread outlived its usefulness after post thirteen. :banghead:

SEAWOLF97
08-25-2009, 07:44 PM
This thread outlived its usefulness after post thirteen. :banghead:

I know, BUT all the spinning is fun to watch.:D

Robh3606
08-26-2009, 07:24 AM
all the spinning is fun to watch.:D

Of what the knobs?? I wish I had a "dead horse" emoticon. http://fc01.deviantart.com/fs6/i/2005/064/c/0/Beating_A_Dead_Horse_by_livius.gifOpps found one. I know it's awful but.

Rob:)

hjames
08-26-2009, 07:32 AM
Of what the knobs?? I wish I had a "dead horse" emoticon. http://fc01.deviantart.com/fs6/i/2005/064/c/0/Beating_A_Dead_Horse_by_livius.gifOpps found one. I know it's awful, but.

Rob:)

Dang - I found one for you, but you are TOO FAST!
But ... these would be good to add to the collection!

opimax
08-26-2009, 01:59 PM
how come they al look like me? :banghead: :D:D

Mark

Robh3606
08-26-2009, 03:08 PM
LOL

Wow 3 of them!! Thanks, those can sure come in handy around here.

Rob:)

midlife
08-26-2009, 03:11 PM
I phrased the question wrong, the new thread asks; turn it down or not? Looking forward to any comments. :)

4313B
08-26-2009, 03:56 PM
I have a Crown DC300 for my main power amp. It has L&R gain controls on the front of the amp. I have been told by some in order to get the maximum head room those gain knobs should be run full up regardless of my volume needs (listening levels should be controlled by the preamp gain). What would you do to have it "right"?...........:o::banghead::blah:Trade it in on an amp without gain knobs and your days of fretting about it are over.

See how easy it can be?

Robh3606
08-26-2009, 04:10 PM
Trade it in on an amp without gain knobs and your days of fretting about it are over.


Now where's the fun in that??

Rob;)