input sensitity

[gearheadgene]

I've been investigating input sensitivity levels on amplifiers (mostly integrated amps). Talk about being all over the map! I can tell you what line-level is defined as (sort of). Then I can show you some examples that just don't seem to make sense.

Look at these input sensitivities:
Creek Audio EVO integrated amp : 415mV (rms or peak? specs don't say)
Creek Audio 5350 integrated amp : 559mV
Creak Audio Destiny integrated amp: 450mV
McIntosh MA6300 : 250 mV
Rotel RA-1062: 160mV
Denon PMA2000: 135 mV.

The manufacturers seem to indicate these values are for full scale output. Not even close to one another, are they? Further adding to the confusion, they don't indicate RMS or peak. I suspect it's mixed - at least that would make them somewhat comparable (6 dB, perhaps - although that's not very comforting).

Next, I looked at a number of DVD players, and they typically specified analog output of 2.0Vrms. Well that doesn't match very well to the input specs of the integrated amps, does it?



One A/V receiver I found has a user selectable reference for the analog input source (1V, 2V or 4V - again, not clear if it's rms or peak). Clearly, they solved this problem by adjusting the system for maximum dynamic range by input type. Nice idea.

BTW, stand-alone amps also seem to have varying input sensitivities.

Can anyone add some insight? Seems to be pretty universal problem. Why do all these manufactures have such divergent specs? Is there no standard? Other than the adjustable sensitivity method, how could anyone design equipment that is anything other than a compromise, under these conditions?

gene

[soongsc]

If the power rating is defined in terms of rms, then the sensitivity is most likely to as well. Integrated amplifiers have an additional volume control stage, depending on the gain of that stage, you will have different sensitivities. Most common is additional gain of 10, some might have less.

[sreten]

Hi,

Input sensitivities on hi-fi amplifiers almost standardised to 150mV.

Then CD players came along and outputs of tape players and tuners
and the like started to increase to match CD, something like 500mV.

Generally not a major problem if you attenuate the CD players output.

Note a lot of preamps are now passive, the power amplifier itself
having high sensitivity, negating the need for any line stage gain.

/sreten.

[soongsc]

I always though power amp sensitivities were more or less 1V. Some kits that I looked at were around 1~1.5V.

[gearheadgene]

Originally posted by sreten
Hi,

Input sensitivities on hi-fi amplifiers almost standardised to 150mV.

Then CD players came along and outputs of tape players and tuners
and the like started to increase to match CD, something like 500mV.

/sreten.

go back and read my notes on input sensitivity. I found 'real-world' integrated amps with sensitivity that are very inconsistent with one-another.

Where is the attenuation you talk about?

[Pano]

I think that is what sreten is saying; at one time the amps came close to having a standard, 150mV. But things never really settled down.

In the real world it "doesn't matter" because you can always turn down the volume - that's the attenuation.

Of course you usually want an amp to have more gain than you need, so that weak signals can be played loud. But that comes with trade offs, E.G. added noise. Most amps have far more gain then most of us ever need - that is also true in the pro audio world.

When I build an amp I try to keep the gain as low as practical - so often end up around 1V rms for full output. I like my normal listening to be at about 1:00 or 2:00 o'clock on the volume knob.

[gearheadgene]

I got some feedback from a couple of manufactures. Also, I looked deeper into the McIntosh data sheet. Here's how it works:

1. They spec input sensitivity as the minimum voltage level (rms) to produce the rated output power. This would have to be with the gain (volume knob) at maximum.
2. They spec the maximum input before overload. This must be the largest input level, rms, the still produces the rated output power without distortion. This would have to be with the gain set to mimimum (0 dB?). I think the amp would have to also have -gain as well, so the volume can be reduced

Yeah, I've often read 1Vrms input - seems like a decent rule of thumb. Yet, many of the integrated amps I listed earlier spec the overload at 5Vrms or more! Pretty big range.

[Pano]

Originally posted by gearheadgene
many of the integrated amps I listed earlier spec the overload at 5Vrms or more! Pretty big range.

Headroom!


Think about #2 in your post above. Doesn't really make sense, does it?

[gearheadgene]

Originally posted by panomaniac


Headroom!


Think about #2 in your post above. Doesn't really make sense, does it?

I've said stupid things before, too Which part sounds wrong?

[koolkid731]

There're some other considerations for input sensitivity. Say you want to bi-amp. Thus you want all amps to have same gain. Thus a 1000W amp would have different sensitivity from a 100W amp.

Even when a mfg advertises 26dB gain, the actual gain may be different, for commercial reasons.

I'd say since the Tower of Babel, standardization is tough. Why can't the Chinese speak English so we understand what they say? In my area schools are offering classes of Chinese because they're 4 times more numerous than USA.