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Author Topic: Amplifier Specs: Input Sensitivity Question  (Read 771 times)

Douglas Cyr

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Amplifier Specs: Input Sensitivity Question
« on: July 06, 2021, 07:35:01 PM »

Hello everyone,

Just curious about the meaning of amplifier input sensitivity in general as well as how it applies to a couple examples:

DAS Event 210 - https://www.dasaudio.com/en/products/systems/event-series/event-210a-115/#dt

Input Sensitivity = +18 dBu

RCF HDL 20-A - https://www.rcf.it/products/product-detail/-/journal_content/56_INSTANCE_2MT9qNpeXdu4/20195/234252

Input Sensitivity = +4 dBu


Why do these similar products have such different input sensitivities? Does this spec mean the speakers will be at their maximum output when the input voltage reaches the stated input sensitivity? Does this mean the Event 210A would require a higher input voltage to reach it's maximum output?

Thanks for any info, just curious to learn more about the meaning of this specification.

Doug
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John Roberts {JR}

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #1 on: July 06, 2021, 09:11:23 PM »

Just off the top of my head, input sensitivity means input level needed for rated power output (IIRC).

If those two amps make similar rated output power at full scale, the different input sensitivity suggests the two amps have different voltage gain.

JR
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Bob Faulkner

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #2 on: July 06, 2021, 09:37:04 PM »

The DAS speaker shows it needs 6.2v   The RCF needs (from what I recall) 1.8v  Yes, the input voltage shown would be needed to drive the amps at their rated full power.
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Dave Pluke

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #3 on: July 06, 2021, 11:00:48 PM »


Why do these similar products have such different input sensitivities?

Differing philosophies related to noise/hiss at idle, I believe. You'll find this in rack mount power amps as well. Neither is right or wrong, but this needs to be considered - especially when running amps from multiple manufacturers.

Dave
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Douglas Cyr

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #4 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?
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Luke Geis

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #5 on: July 07, 2021, 12:00:32 AM »

yes.
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Tim McCulloch

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #6 on: July 07, 2021, 12:52:26 AM »

So what happens if more voltage is fed to the input than the rated sensitivity? Does this cause input clipping?

Maybe. It will fo-shizzle clip the outputs.
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Brian Jojade

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #7 on: July 07, 2021, 01:26:09 AM »

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.
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Douglas Cyr

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #8 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?

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)

« Last Edit: July 07, 2021, 09:27:08 AM by Douglas Cyr »
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John Roberts {JR}

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Re: Amplifier Specs: Input Sensitivity Question
« Reply #9 on: July 07, 2021, 09:50:23 AM »

So what happens if more voltage is fed to the input than the rated sensitivity? Does this cause input clipping?
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.

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


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

JR
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Re: Amplifier Specs: Input Sensitivity Question
« Reply #9 on: July 07, 2021, 09:50:23 AM »


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