Turn it up or not?

[Allanvh5150]

And why would you have to move the input attenuators on the amp every time you turned it on? 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]

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]

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".

[BMWCCA]

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]

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]

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]

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]

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]

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]

I ran across a "pre answer" (the answer b4 the question) from Dome on 7-07

Which 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.

This thread outlived its usefulness after post thirteen.

[SEAWOLF97]

This thread outlived its usefulness after post thirteen.

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

[Robh3606]

all the spinning is fun to watch.

Of what the knobs?? I wish I had a "dead horse" emoticon. Opps found one. I know it's awful but.

Rob

[hjames]

Of what the knobs?? I wish I had a "dead horse" emoticon. Opps 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]

how come they al look like me?

Mark

[Robh3606]

LOL

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

Rob