BillFitzmaurice.info

im new to external amps, and my gear ive had is powered. this might be a stupid question but im not 100% sure. If I have a peavey ipr2 3000 which puts out 525watts rms at 8ohm. if I turn the gain knob on the amp up 3dB it would be like 1050watts rms and it would be safe?

The gain knob is not a volume knob in the traditional sense. It is there to match the input section of the amp with whatever voltage your mixer output signal is at. If your amplifier is only rated at 525 w rms into 8 ohms then that amp can only put that out regardless of your gain setting. If you have a very strong signal then the amp can put out maximum power with the gain turned all the way down. If your signal is very weak then the amp may never reach maximum power even if the gain knob is maxed out. However, once your amplifier output is at its design limits any increase in the gain knob will only clip the amplifier.

ok thanks for explaining

CoronaOperator wrote: If you have a very strong signal then the amp can put out maximum power with the gain turned all the way down.

Sorry.....but, that just ain't true. You turn the knob all the way down....there ain't no sound.

truitt wrote:im new to external amps, and my gear ive had is powered. this might be a stupid question but im not 100% sure. If I have a peavey ipr2 3000 which puts out 525watts rms at 8ohm. if I turn the gain knob on the amp up 3dB it would be like 1050watts rms and it would be safe?

Turn your amps up all the way...all the time....but, you must have a DSP of some sort to control limiting, EQ, crossover, etc...

Bruce Weldy wrote:


Sorry.....but, that just ain't true. You turn the knob all the way down....there ain't no sound.

You got me on that one Bruce, thank you for correcting me. I was trying to explain the theory of how the gain knob is not necessarily representative of the amplifiers output and that it could make full output wherever the knob is set (except zero). However I did say if the signal was very strong it would reach maximum power, I'm sure most people would consider lightning very stong

And yes, in the field operate with the gains set to maximum (with the processor turned down of coarse), that way nobody can turn them up higher on you by accident.

CoronaOperator wrote:I'm sure most people would consider lightning very stong

Doc perhaps, but not me. Now 1.22 gigawatts - totally different.

Bruce Weldy wrote:Sorry.....but, that just ain't true. You turn the knob all the way down....there ain't no sound.

In modern amps the "last click" is "-infinity". That will stop the signal from progressing out of the input stage of the amp.

One click above that.....and a sufficiently large input signal could drive the amp to produce full output voltage. While true in theory, there are not many musical applications for a setup like this.

SoundInMotionDJ wrote: One click above that.....and a sufficiently large input signal could drive the amp to produce full output voltage.

Perhaps, but it would likely also overload the input stage of the amp, resulting in very high distortion levels.
There is a reason to run attenuators at less than full, that's noise. If the source device is running at too low an output level then its S/N ratio may be low, and that can result in high levels of high frequency hiss and low frequency hum. You may have to do a balancing act between the output level of the driving device and the attenuation level of the power amp to get the best result. What's critical is that the amp attenuators be wide open when setting the limiter, which, BTW, should be the last element in the signal chain prior to the amp. That way even if someone fools with the amp knobs the maximum output voltage won't be exceeded.

Bill Fitzmaurice wrote:

SoundInMotionDJ wrote: One click above that.....and a sufficiently large input signal could drive the amp to produce full output voltage.

Perhaps, but it would likely also overload the input stage of the amp, resulting in very high distortion levels.
There is a reason to run attenuators at less than full, that's noise. If the source device is running at too low an output level then its S/N ratio may be low, and that can result in high levels of high frequency hiss and low frequency hum. You may have to do a balancing act between the output level of the driving device and the attenuation level of the power amp to get the best result. What's critical is that the amp attenuators be wide open when setting the limiter, which, BTW, should be the last element in the signal chain prior to the amp. That way even if someone fools with the amp knobs the maximum output voltage won't be exceeded.

Max voltage also wont be available. If you have to turn down 6-10 db to get rid of noise, you lose that much output too. The solution for that is tamper panels.

I keep all of my amps set to eleven, look right across the board eleven, eleven, eleven. That's one louder than ten.

But seriously, one of the nice things about a lot of the DSP amps is you can set the input attenuation and then lock the front panel knobs. Which comes in handy when using an external limiter.

BrentEvans wrote: The solution for that is tamper panels.

No. A baseball bat.

SoundInMotionDJ wrote: One click above that.....and a sufficiently large input signal could drive the amp to produce full output voltage. While true in theory, there are not many musical applications for a setup like this.

Sure there are. In car audio the main source for noise is the 20 foot long unbalanced RCA cable from HU to trunk along some very noisy electrical paths: Alternators, spark plugs, window motors, air cond fans, etc. Consumer grade RCA outputs can in theory output a 0.5 v rms signal although most are way below that. 8 volt line drivers (yes, 16 times the voltage, +24 dB's gain) have been employed in car audio for at least 25 years. Sound Quality competitors run their amplifiers as low a gain as possible with as strong a signal as possible for the highest signal to noise ratio possible over that run. I assume most recording studios would do the same.

Proaudio isn't the end all be all of sound reproduction.

BrentEvans wrote:Max voltage also wont be available. If you have to turn down 6-10 db to get rid of noise, you lose that much output too.

You don't lose any output, you just need a stronger signal to reach your amps potential. Ever hear of a Pioneer DJ mixer? They are just getting started at +6dB's

CoronaOperator wrote: You don't lose any output, you just need a stronger signal to reach your amps potential. Ever hear of a Pioneer DJ mixer? They are just getting started at +6dB's

No, you do lose output. The limiter threshold clamps based on input level. When you turn down the amp, you are reducing sensitivity AFTER the output stage of the limiter, which means voltage will be clamped lower than you anticipated.

BrentEvans wrote: No, you do lose output. The limiter threshold clamps based on input level. When you turn down the amp, you are reducing sensitivity AFTER the output stage of the limiter, which means voltage will be clamped lower than you anticipated.

Brent,
Can you explain some more please.
The schematics on my old iron (haven't ever had the need to get schematics for my new amps yet) clearly show the attenuator on the input side, almost immediately after the input XLR.
IIRC, it's correct to call it an attenuator rather than volume knob, and it's convention for a attenuator to lower input signal...