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Amplifier Specs: Input Sensitivity Question

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Luke Geis:
yes.

Tim McCulloch:

--- Quote from: Douglas Cyr on July 06, 2021, 11:38:00 PM ---So what happens if more voltage is fed to the input than the rated sensitivity? Does this cause input clipping?

--- End quote ---

Maybe. It will fo-shizzle clip the outputs.

Brian Jojade:
Either will get the job done. You simply need to know what you're actually dealing with regarding the levels needed to get the job done.  Simply match your output with the input the speaker needs and go about your way.

Having the higher input voltage sort of protects the speakers.  Most non DJs will resist driving their mixers into full redline.  With a speaker rated at +4, that means the speaker will have maximum performance plugged directly out of the mixer.

But throw a DJ into the mix that likes all red lights all the time and that speaker rated at +4 will have an unhappy life.  The speaker that is happy with a +18 input will be ok with a redlined mixer.

The downside is if you don't realize you need such a strong input to get the most out of it, you may think it just doesn't have the capabilities it really does.

Douglas Cyr:
Thank you everyone! This is very interesting stuff. So is it safe to say the "volume knob" is actually just scaling the input sensitivity, not adding gain to the signal?

Sensitivity pot all the way to the right = 0 dB attenuation?

What does it mean if my digital amp goes from a -dB value to +dB value on the inputs? (Powersoft T302 - input sensitivity 2.57 Vrms)

John Roberts {JR}:

--- Quote from: Douglas Cyr on July 06, 2021, 11:38:00 PM ---So what happens if more voltage is fed to the input than the rated sensitivity? Does this cause input clipping?

--- End quote ---
In a typical amp design it should cause output saturation (clipping) unless the amp has an internal limiter. With enough voltage gain and enough input signal, the output signal will at some point run out of power supply voltage to cleanly go higher.


--- Quote from: Douglas Cyr on July 07, 2021, 09:13:29 AM ---Thank you everyone! This is very interesting stuff. So is it safe to say the "volume knob" is actually just scaling the input sensitivity, not adding gain to the signal?

--- End quote ---
I can't say without inspecting specific schematics but in general the typical amplifier stage will be designed with a higher than needed total gain (because that is most stable configuration), and then an input attenuator pads down the input signal coming in to a level that will not overload or saturate the amplifier output. Historically amplifiers used passive input attenuators to deliver good signal to noise ratio. Around the 90s inexpensive op amps were quiet enough to put active balanced input stages ahead of the "attenuator" without compromising S/N. Of course factored in with the gain of this active input stage the attenuator could result in some additional gain.

--- Quote ---Sensitivity pot all the way to the right = 0 dB attenuation?

--- End quote ---
perhaps, but don't overthink this... the net affect is the this amplifier control adjusts the total effective gain of the power amp and should be adjusted to avoid output saturation (IMO) for clean signal reproduction.

--- Quote ---What does it mean if my digital amp goes from a -dB value to +dB value on the inputs? (Powersoft T302 - input sensitivity 2.57 Vrms)



--- End quote ---
I don't know and am too lazy to look at that specific amp model.

JR

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