Output voltage vs Output sensitivity - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 250 Old 06-18-2009, 01:18 PM - Thread Starter
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Anyone want to explain these in detail?

Any good links on them?

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post #2 of 250 Old 06-18-2009, 02:45 PM
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Power sensitivity = Volage sensitivity - 10 * log( 8 / Re )
in dB/1W @ 1m

the reverse....

Voltage sensitivity = Power sensitivity + 10 * log( 8 / Re )
in dB / 2.83V @ 1m

For an 8 ohm driver, the figures will be the same. For lower resistances, the figure for Voltage sensitivity will be higher.

Some manufacturers, notably Peerless and Mach5 audio, list their figures using Voltage sensitivity, which, for the unwary, suggest they are more sensitive than they actually are.

WinISD uses power sensitivity, so the figure for such drivers needs to be converted before entering the parameters into the database.
I don't know about the other modelling programs..
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post #3 of 250 Old 06-18-2009, 02:51 PM
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More colloquially, once upon a time, it was common to spec drivers as well as assembled speakers by their sensitivity at one watt, at one meter, at a specific frequency or frequencies. What many vendors of lower impedance drivers (and complete speakers) do is spec them at the voltage that would result in 1 watt to an 8 ohm load. But if it's a four ohm load the power required to get there is exactly double what it would be at 8 ohms. It is indeed a potentially misleading way to spec the devices, and I can't think of a reason that manufacturers adopted it except to confuse things for the consumer.
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post #4 of 250 Old 06-18-2009, 06:34 PM
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Quote:
Originally Posted by penngray View Post

Anyone want to explain these in detail?

Any good links on them?

Are the answers provide what you're looking for, or is it something else?

Just because there is a knob doesn't mean you should turn it.
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post #5 of 250 Old 06-18-2009, 07:33 PM - Thread Starter
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Quote:
Originally Posted by whoaru99 View Post

Are the answers provide what you're looking for, or is it something else?

Nope, I forgot to be specific. I know all the formulas (http://www.sengpielaudio.com/Calculations03.htm) and I know all about speakers sensitivity, Watt vs Volts and how they can be misleading too.

Im talking strictly about Pre-outs on Processors.

examply many will have sensitivity of .75V and but the AVR has max voltage would be maybe 5V RMS.

Pro Audio equipment have inputs that have sensitivity of 1V or higher.

This stems from many threads and discussions over the years about mismatch voltages, AVRs that can not driver pro amps to max levels, AVRs that can not give something like a DCX enough voltage to maximize SQ and so on.

I just want to get it all cleared up for once.

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post #6 of 250 Old 06-18-2009, 09:35 PM
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Is that possible...to get it straightened out, that is?

Guess I'm still not sure what you're after.

As I've said before, if you can drive the amp to clipping level with your AVR pre out, you have enough input signal to get full power out of the amp.

Just because there is a knob doesn't mean you should turn it.
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post #7 of 250 Old 06-19-2009, 12:43 AM
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The only thing I have to add is a bit anecdotal.

With my receiver, I can can reach a -0db input/output with my DEQ2496, so long as my source is at -0db and my subwoofer output on my receiver is at +4db. However, with my DEQ's output set to -0db, I have to turn my EP2500 down quite a bit becaues the clip lights will come on. With my receiver's subwoofer output at -0db, I still clip my EP even with it's attenuators a few db from all the way up.

So, consumer grade is .320v or -10dbv and Pro audio is 1.4v or +4dbv, but I can still clip my amp so I don't worry about it too much.

YID DIY
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post #8 of 250 Old 06-19-2009, 04:40 AM
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Quote:
Originally Posted by penngray View Post

Nope, I forgot to be specific. I know all the formulas (http://www.sengpielaudio.com/Calculations03.htm) and I know all about speakers sensitivity, Watt vs Volts and how they can be misleading too.

Im talking strictly about Pre-outs on Processors.

examply many will have sensitivity of .75V and but the AVR has max voltage would be maybe 5V RMS.

Pro Audio equipment have inputs that have sensitivity of 1V or higher.

This stems from many threads and discussions over the years about mismatch voltages, AVRs that can not driver pro amps to max levels, AVRs that can not give something like a DCX enough voltage to maximize SQ and so on.

I just want to get it all cleared up for once.



You are confused.

Outputs are measured in voltage & impedance.

Inputs have a sensitivity specification in voltage & impedance.


My consumer AVR has analog inputs with a sensitivity of 150 mv with a 50 k-ohms input impedance.

My outputs (tape, aux, etc) use an analog output level of 150 mv with a 10-k ohm output impedance.

My preamp outputs have an analog output level of 2 volts with an output impedance of 1-k ohms.

These levels are all maximum output / input levels.


All that you have to do is make sure that your AVR levels and impedance are a good match to the outboard equipment. As far as impedance is concerned, you want to have the input impedance of the external equipment higher than the output impedance of the circuit in question.


It is up to you to make sure that you know the input / output spec for all connected equipment when you mix and match consumer and pro equipment!
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post #9 of 250 Old 06-19-2009, 04:55 AM
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Quote:
Originally Posted by Looneybomber View Post

So, consumer grade is .320v or -10dbv and Pro audio is 1.4v or +4dbv, but I can still clip my amp so I don't worry about it too much.

I believe this is the root of all confusion in this deal. It seems they're being held as abolutes when, in fact, they're not.

And, AFAIK, or maybe it's IMO, those numbers actually refer more to line level input/output signals like between a tape deck and recording console or preamp, not the connection between preamp/mixer output and power amp input.

Just because there is a knob doesn't mean you should turn it.
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post #10 of 250 Old 06-19-2009, 05:08 AM
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Quote:
Originally Posted by whoaru99 View Post

I believe this is the root of all confusion in this deal. It seems they're being held as abolutes when, in fact, they're not.

And, AFAIK, or maybe it's IMO, those numbers actually refer more to line level input/output signals like between a tape deck and recording console or preamp, not the connection between preamp/mixer output and power amp input.


It is worse than that. Consumer equipment uses dBV, and pro equipment use dBu.



Link to dBu and dBV



"In the analog audio domain there are primarily 2 db scales of importance:
dbu and dbV. These scales describe voltage ratios. The difference are the reference points:


dbu: 0 dbu = 0.775 V (u means "unloaded")

dbV: 0 dbV = 1 V



Both scales can be found in the definition of standard reference levels of consumer and professional products. While the standard reference level for consumer products is -10dbV, the reference level for professional audio products in +4dbu."




Link to calculation of dBu and dBV levels


"A side trip -- "Professional" vs. "Consumer" Levels

There has always been a lot of confusion about the whole issue of the nominal operating level of "professional" gear versus the nominal operating level of so-called "consumer" gear.

You may have heard that professional gear is "+ 4 dBu" and consumer gear is "- 10 dBV." Because only professionals used this stuff back when it was new (and expensive!) technology, and the older dBu designation was all they had to work with, the original designation of operating level (expressed in dBu) has stuck. By the time consumer audio products were introduced in a big way, the dBV has been invented, and so dBV was used for consumer gear. (Remember, they are both simply ways of comparing voltage levels -- nothing more. That + 4dBu is somehow inherently "better" than -10 dBV is a big, fat myth, kept alive by the somewhat arbitrary labels of "professional" and "consumer" attached to them.)

I'll just bet that a lot of you have glanced at this "+4 / -10" thing, and just assumed that the difference between the levels is 14 dB. But now we know better, don't we?

The reason the difference isn't 14 dB is because the reference levels between dBu and dBV are different! Remember, dBu is referenced to a voltage level of .775 V, and dBV is referenced to 1V. Armed with the knowledge you now possess, can you figure out what the true difference in operating level is, between + 4 dBu and -10 dBV?

+ 4 dBu = 20 * log (voltage / .775 V)
voltage = 1.228 Volts

- 10 dBV = 20 * log (voltage / 1V)
voltage = 0.3162 Volts

20 * log (1.228V / 0.3162V) = 11.79 dB


You can confirm this by doing a little experiment. Plug a piece of consumer gear with -10 dBV outputs into a piece of gear with + 4 dBu inputs. If they both have VU meters, calibrated such that 0dBVU on each piece of gear corresponds to it's nominal operating level, you'll find that 0dBVU on the consumer gear causes a reading of -11.79 dBVU on the pro gear's meters."




.
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post #11 of 250 Old 06-19-2009, 05:13 AM
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Quote:
Originally Posted by J_Palmer_Cass View Post

You are confused.

Outputs are measured in voltage & impedance.

Inputs have a sensitivity specification in voltage & impedance.


My consumer AVR has analog inputs with a sensitivity of 150 mv with a 50 k-ohms input impedance.

My outputs (tape, aux, etc) use an analog output level of 150 mv with a 10-k ohm output impedance.

My preamp outputs have an analog output level of 2 volts with an output impedance of 1-k ohms.

These levels are all maximum output / input levels.

I agree mostly, but not necessarily about "maximum" in that very last line.

Is the 2V output really the maximum, or merely the maximum assuming 150mV input?

Just because there is a knob doesn't mean you should turn it.
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post #12 of 250 Old 06-19-2009, 05:25 AM
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Quote:
Originally Posted by whoaru99 View Post

I agree mostly, but not necessarily about "maximum" in that very last line.

Is the 2V output really the maximum, or merely the maximum assuming 150mV input?




I assume that you get close to the analog stage clipping level (input or output) when those levels are exceeded by a large amount.
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post #13 of 250 Old 06-19-2009, 05:38 AM
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Hmmm....curious.

Time for more measurements.

My Yamaha C-80 preamp is rated similarly to the example you gave.

150mV input sensitivity @ 47k ohms.
1.5V output @ 47 ohms.

This, to me, suggests about 20dB gain.

However, I just measured the analog outputs of my DVD player while playing a music CD and got 1.862V peak. So, assuming 20dB gain, that would mean a theoretical max of 18.62V output from the Yamaha.

Almost certainly the preamp won't put out 18.62V...at least not cleanly, anyway. But, I'm guessing it'll put out quite a bit more than 1.5V with clean output. I'll have to break out the Scopemeter and try that later.

Just because there is a knob doesn't mean you should turn it.
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post #14 of 250 Old 06-19-2009, 05:59 AM
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Quote:
Originally Posted by whoaru99 View Post

Hmmm....curious.


However, I just measured the analog outputs of my DVD player while playing a music CD and got 1.862V peak. So, assuming 20dB gain, that would mean a theoretical max of 18.62V output from the Yamaha.

Almost certainly the preamp won't put out 18.62V...at least not cleanly, anyway. But, I'm guessing it'll put out quite a bit more than 1.5V with clean output. I'll have to break out the Scopemeter and try that later.



Do you have the analog output spec of your DVD player?


My DVD player's analog line output is rated at 2 V RMS @ over 10-k ohms impedance. The AVR's preamp output levels are 2 V, so it looks like my Sony products are designed around a 2 volt RMS input and output level.


Maybe the input sensitivity specifications simply show the levels that are used when they calculated the S/N ratio. 150 mv, 50-k ohms, S/N of 100 dB are the full ratings of the inputs of my receiver.
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post #15 of 250 Old 06-19-2009, 06:15 AM
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Quote:
Originally Posted by J_Palmer_Cass View Post

Do you have the analog output spec of your DVD player?


My DVD player's analog line output is rated at 2 V RMS @ over 10-k ohms impedance. The AVR's preamp output levels are 2 V, so it looks like my Sony products are designed around a 2 volt RMS input and output level.


Maybe the input sensitivity specifications simply show the levels that are used when they calculated the S/N ratio. 150 mv, 50-k ohms, S/N of 100 dB are the full ratings of the inputs of my receiver.

Yeah, probably. I'll have to dig out the manual.

Thing is, all this stuff is relative to the upstream and to the internal gains of each device.

Sure, the DVD player output spec may be 2V, or what ever, but that's probably only when playing the passages that are burned at the max digital level, 0dBfs or what ever it's called.

Just because there is a knob doesn't mean you should turn it.
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post #16 of 250 Old 06-19-2009, 06:23 AM
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I checked my CD player's output level specification. 2 volts @ over 10-k ohms impedance with DSP set to OFF.

I wonder what the maximum output level is before clipping on all of these consumer rated devices? My old 2 channel receiver has preamp outputs rated at 500 mv, but there is a 4 Volt maximum rating noted. A 200 mv input level was listed to produce the rated preamp output level (500 mv).

My best guess is 2 volts is the expected nominal design voltage level for the analog inputs and outputs of my Sony consumer equipment. Maximum levels are another story!
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post #17 of 250 Old 06-19-2009, 06:28 AM
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Quote:
Originally Posted by whoaru99 View Post

Yeah, probably. I'll have to dig out the manual.

Thing is, all this stuff is relative to the upstream and to the internal gains of each device.

Sure, the DVD player output spec may be 2V, or what ever, but that's probably only when playing the passages that are burned at the max digital level, 0dBfs or what ever it's called.


Maximum is all that counts. Full volume is full volume!

Anyhow, does that mean that pro equipment is designed around a nominal level that is about 12 dB higher than 2 volts?
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post #18 of 250 Old 06-19-2009, 06:42 AM
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My external crossover has no input and output level specifications, but my NHT A-1 consumer power amplifier has a rating of 1.7 volts input to drive the amplifier to the full rated output.


Gain: +27dB (1.7V sensitivity) for full output


It looks like all of my consumer rated equipment is designed to work around a nominal input / output voltage of 2 volts.


If someone has a pro amplifier or perhaps some pro EQ product, perhaps they can fill in some blanks about pro equipment requirements.
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post #19 of 250 Old 06-19-2009, 07:04 AM - Thread Starter
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Quote:
Originally Posted by J_Palmer_Cass View Post

You are confused.

Outputs are measured in voltage & impedance.

Inputs have a sensitivity specification in voltage & impedance.


My consumer AVR has analog inputs with a sensitivity of 150 mv with a 50 k-ohms input impedance.

My outputs (tape, aux, etc) use an analog output level of 150 mv with a 10-k ohm output impedance.

My preamp outputs have an analog output level of 2 volts with an output impedance of 1-k ohms.

These levels are all maximum output / input levels.


All that you have to do is make sure that your AVR levels and impedance are a good match to the outboard equipment. As far as impedance is concerned, you want to have the input impedance of the external equipment higher than the output impedance of the circuit in question.


It is up to you to make sure that you know the input / output spec for all connected equipment when you mix and match consumer and pro equipment!

No you are confused on what the question is or you are not aware of how old specs where posted.

I guess Im still talking about different specs then all posts so far...


Here are examples of the exact specs I talk about.

Pioneer VSX-915

Pre Out .75V, Maximum Output 4V


Outlaw 970
Pre Out 1V, Maximum Output 6V

Now Pro amps like the QSC 1850

say this

Input Sensitivity at 8Ω 1.115V

The pioneer has a mismatch of .75 vs 1.115 and I know for a fact that I need a samson bump box to increase the signal. The 970 didnt need so much because of the 1V vs 1.115V.

The new AVRs seem to have different specs, this is the only thing I can find but is it for the line (REC) out and not the pre-outs?
Output (Level/Impedance)
REC. . . . . . . . . . . . . . . . . . . . . . 284 mV/2.2 kΩ


The Onkyo 806 says
Output Level and Impedance 200 mV/470 ohms

So how the specs are posted have changed over the past couple of years and I can not find the old "Sensitivity 1V specs".

Those specs have zero confusion to them, heck Im making zero conclusions period and Im asking questions so Saying Im confused is weird (annoying too) since asking the questions does indicate I do not know the answers

We also do not need want a running commentary on how to hook up AVRs to amps. We all know about it and this thread is not about that. I want to stick to discussing the difference between voltage sensitivity and maximum voltage output.

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post #20 of 250 Old 06-19-2009, 07:17 AM
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Quote:
Originally Posted by penngray View Post

Hre are examples of the exact specs I talk about.

Pioneer VSX-915

Pre Out .75V, Maximum Output 5V


Outlaw 970

Pre Out 1V, Maximum Output 6V


Now Pro amps like the QSC 1850

say this
Input Sensitivity at 8Ω 1.115V

The only confusion is that you are not reading what Im asking about. ...I think we want to stick to discussing the difference between voltage sensitivity and maximum voltage output.


Let's use the Pioneer for an example merely because it's first on the list.

To me, those specs imply that the Pioneer will put out 0.75V from the pre outs when the input signal is equal to the specified input sensitivity (for example, like the 150mV that J Palmer and I mentioned for some of our gear).

I think the maximum output of 5V comes into play when the input level to the preamp/receiver is higher than the specified input sensitivity, like in the example of my DVD player putting out 1.862V.

The input sensitivity of the QSC amp means that it requires 1.115V of input signal to produce its full rated output.

I think an hour or two with a good multimeter, or preferably oscilloscope, would clear up all the questions you have. Nothing beats a measurement or two to separate the theory and opinions from actual.

Unfortunately I don't have an AVR with pre outs to do these input/output measurements, but I could do some relative evaluation on that Yamaha preamp pretty easily. I'm not disconnecting all the crap from my AVM 20 to do these experiments.

Just because there is a knob doesn't mean you should turn it.
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post #21 of 250 Old 06-19-2009, 07:20 AM - Thread Starter
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Almost certainly the preamp won't put out 18.62V...at least not cleanly, anyway. But, I'm guessing it'll put out quite a bit more than 1.5V with clean output. I'll have to break out the Scopemeter and try that later.

They have to be able to put out more then 1.5V, we can not get high SPLs without it, correct?

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post #22 of 250 Old 06-19-2009, 07:23 AM - Thread Starter
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Quote:
Originally Posted by whoaru99 View Post

Let's use the Pioneer for an example merely because it's first on the list.

To me, those specs imply that the Pioneer will put out 0.75V from the pre outs when the input signal is equal to the specified input sensitivity (for example, like the 150mV that J Palmer and I mentioned for some of our gear).

I think the maximum output of 5V comes into play when the input level to the preamp/receiver is higher than the specified input sensitivity, like in the example of my DVD player putting out 1.862V.

The input sensitivity of the QSC amp means that it requires 1.115V of input signal to produce its full rated output.

I think an hour or two with a good multimeter, or preferably oscilloscope, would clear up all the questions you have. Nothing beats a measurement or two to separate the theory and opinions from actual.

Unfortunately I don't have an AVR with pre outs to do these input/output measurements.

Thanks....
I can find out the true difference....I just made a little wiring solution to measure the voltage on my sound card because Arta wanted it but my meter isnt accurate to below .1 Volts. I need to get different meter.

My question was more education on the topic though, I can test everything in the world and have all the numbers but still be confused (thats for JPC ) about what it all means.

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post #23 of 250 Old 06-19-2009, 07:26 AM
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Quote:
Originally Posted by penngray View Post

They have to be able to put out more then 1.5V, we can not get high SPLs without it, correct?

Depends.

If the input sensitivity of the power amplifier is 1.5V or less, full output could be produced.

If the input sensitivity of the power amp is more than 1.5V, then full output will not be achieved.

Just because there is a knob doesn't mean you should turn it.
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post #24 of 250 Old 06-19-2009, 07:27 AM - Thread Starter
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Quote:
Originally Posted by J_Palmer_Cass View Post

Maximum is all that counts. Full volume is full volume!

Anyhow, does that mean that pro equipment is designed around a nominal level that is about 12 dB higher than 2 volts?

Well, there are many of us that have EP2500 amps and commerical AVRs and we do not get full output from the EP2500, we had a Signal booster and we get full output.

The goal for me here is to get all the basics down so that we can explain this problem properly to people who wish to use a Pro products with Comercial AVRs

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post #25 of 250 Old 06-19-2009, 07:28 AM
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Quote:
Originally Posted by penngray View Post

Hre are examples of the exact specs I talk about.

Pioneer VSX-915

Pre Out .75V, Maximum Output 5V


Outlaw 970

Pre Out 1V, Maximum Output 6V


Now Pro amps like the QSC 1850

say this
Input Sensitivity at 8Ω 1.115V

The only confusion is that you are not reading what Im asking about. We also do not need want a running commentary on how to hook up AVRs to amps. We all know about it, I think we want to stick to discussing the difference between voltage sensitivity and maximum voltage output.



If you don't know the nominal output voltage of consumer / pro equipment, then the input sensitivity / maximum output of power amplifiers means nothing much at all.

The QSC 1850 needs 1.115V input to drive an 8 ohm load to full output.

The DEQ2496 mentioned above is rated at 1.23 V (+4.0 dBu) input to drive an 8 ohm load to full output.

My NHT A-1 consumer power amplifier is rated at 1.7 V input to drive an 8 ohm load to full output. This amplifier has no adjustable volume / gain control.


The way that I see it, the above listed pro amplifiers need less voltage input to drive them to full rated output than some consumer equipment.


So, if you use something like a digital crossover between a consumer AVR and a certain amplifier, then you have to be careful of how you set levels so the digital units don't drop their bits. I find it a bit curious that the pro amplifiers require less voltage to drive them to full rated output than my NHT amplifier. I thought that it would be the other way around!
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post #26 of 250 Old 06-19-2009, 07:29 AM - Thread Starter
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Originally Posted by whoaru99 View Post

Depends.

If the input sensitivity of the power amplifier is 1.5V or less, full output could be produced.

If the input sensitivity of the power amp is greater than 1.5V, then full output will not be achieved.

This is assuming the pre-out is 1.5V?


If the pre-out is .75V and the input is 1.5V then full output can not be achieved, correct?

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post #27 of 250 Old 06-19-2009, 07:31 AM - Thread Starter
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Originally Posted by J_Palmer_Cass View Post

If you don't know the nominal output voltage of consumer / pro equipment, then the input sensitivity / maximum output of power amplifiers means nothing much at all.

Older products did not list that information in the specs so we have to start with the specs we know, the specs meant something to someone or they would never have ben listed Its nice to see newer products giving better specs....just something new to understand because its the first time I have actually seen the new specs.

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The QSC 1850 needs 1.115V input to drive an 8 ohm load to full output.

The DEQ2496 mentioned above is rated at 1.23 V (+4.0 dBu) input to drive an 8 ohm load to full output.

My NHT A-1 consumer power amplifier is rated at 1.7 V input to drive an 8 ohm load to full output. This amplifier has no adjustable volume / gain control.


The way that I see it, the above listed pro amplifiers need less voltage input to drive them to full rated output than some consumer equipment.


So, if you use something like a digital crossover between a consumer AVR and a certain amplifier, then you have to be careful of how you set levels so the digital units don't drop their bits. I find it a bit curious that the pro amplifiers require less voltage to drive them to full rated output than my NHT amplifier. I thought that it would be the other way around!

Very interesting observation.

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post #28 of 250 Old 06-19-2009, 07:38 AM - Thread Starter
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I think maybe I will figure out dBU, dBV and Volts (RMS) that is definitely a starting point for understanding how it all connects.


http://www.sengpielaudio.com/calculator-db-volt.htm

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Originally Posted by penngray View Post

This is assuming the pre-out is 1.5V?


If the pre-out is .75V and the input is 1.5V then full output can not be achieved, correct?

Right.

But the reverse is also an assumption that 0.75V is the maximum, and Pioneer seems to indicate it is not.

Just because there is a knob doesn't mean you should turn it.
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post #30 of 250 Old 06-19-2009, 07:41 AM - Thread Starter
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Originally Posted by whoaru99 View Post

Right.

But the reverse is also an assumption that 0.75V is the maximum, and Pioneer seems to indicate it is not.

are you saying QSC1850 spec Input Sensitivity at 8Ω 1.15V (+3.4 dBu)

is maximum voltage? I have to learn what that means then.

What about the QSC1850 spec Input Clipping 10 Vrms (+22 dBu)

wouldn't that mean the maxium input voltage for the 1850 is 10V?

Im going to send Bob (QSC) a PM.

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