XPR-5 Gain Question

[ninjahifi]

Just looking for some input on something I read.

I came across this article on Audioholics that talks about Amplifier Gain and what one should look for in pairing an amp to a preamp. www.audioholics.com/audio-amplifier/amplifier-voltage-gain

If I understood the article correctly it essentially states that depending on the Input Sensitivity/Gain of a given amplifier there is a minimum amount of Voltage needed from the Pre-amp to drive the amplifier to full power.

I have the Emotiva XPR-5 that has an Input Sensitivity of 1.875 V. So that implies that the Pre-amp needs to provide 1.875 V in order to get the full stated 400 W of power from the amp, correct?

I use the Marantz AV-8801 which is listed as having 1.2 V output through unbalanced connections.

So obviously my question is, if I'm using this setup am I not using the full capability of my amp? Should I switch to balanced connections since the Marantz outputs 2.4 V through that method?

Also something about all this doesn't seem right, I have to be missing a piece of information. Using the math in that article I linked to, using unbalanced connections would mean I am only using about 140 watts of my amp per channel before it can potentially start clipping the signal?

Again, this doesn't seem right so what am I missing?

[garbulky]

Well you are correct in way. You are not getting all the power. But I think your 140 watts per channel is incorrect. It's likely more than that. The XPR-5 has the same gain as the other X-series gen 2 amp. it just has more power on tap so it can pump out more. So basically you won't be getting lower volume at the same volume setting at the AVR than the other x-series amps.

[ninjahifi]

Thanks for the response. But not sure I understand. It sounds like your saying that the noise floor will be higher?

I used to have the XPA-5 Gen 1 and I upgraded to the XPR-5 to have more power "on tap." Even though I don't listen very loud my understanding was on movie passages where it is suppose to get loud the XPR-5 would provide plenty of reserve for my speakers. However now I'm doubting that is correct. The article specifically states "Suppose you have a receiver that can deliver 1 volt RMS from its preamplifier outputs before clipping; if you pair this receiver with a high powered amplifier expecting a huge boost in headroom, you might be sorely disappointed if its voltage gain is a below average 27dB. A gain of 27dB equates to a ~22.6x increase in voltage, meaning our amplifier will be putting out 22.6 volts RMS, or a whopping 64 watts into an 8 ohm load before our AVR’s pre-outs run out of gas. Even if the amplifier is rated to deliver 1,000 watts, all you’re going to do when you push harder is get garbage as your AVR clips the signal to the amplifier or potentially trip its protection circuits. "
My numbers are a little higher than those but it appears that the same would hold true, no?

I'm ordering a set of XPR cables to switch out my RCAs and see if I can hear a difference. I've had my XPR about a year now and have been pretty happy with it but it's disappointing finding out I may not be fully using it's potential.

[garbulky]

Jun 7, 2014 14:27:55 GMT -5 ninjahifi said:

Thanks for the response. But not sure I understand. It sounds like your saying that the noise floor will be higher?

I used to have the XPA-5 Gen 1 and I upgraded to the XPR-5 to have more power "on tap." Even though I don't listen very loud my understanding was on movie passages where it is suppose to get loud the XPR-5 would provide plenty of reserve for my speakers. However now I'm doubting that is correct. The article specifically states "Suppose you have a receiver that can deliver 1 volt RMS from its preamplifier outputs before clipping; if you pair this receiver with a high powered amplifier expecting a huge boost in headroom, you might be sorely disappointed if its voltage gain is a below average 27dB. A gain of 27dB equates to a ~22.6x increase in voltage, meaning our amplifier will be putting out 22.6 volts RMS, or a whopping 64 watts into an 8 ohm load before our AVR’s pre-outs run out of gas. Even if the amplifier is rated to deliver 1,000 watts, all you’re going to do when you push harder is get garbage as your AVR clips the signal to the amplifier or potentially trip its protection circuits. "
My numbers are a little higher than those but it appears that the same would hold true, no?

I'm ordering a set of XPR cables to switch out my RCAs and see if I can hear a difference. I've had my XPR about a year now and have been pretty happy with it but it's disappointing finding out I may not be fully using it's potential.

No the noise floor will not be higher.

The good news is that the XPR amp is 29db gain not 27 db gain. So in terms of gain it's actually right about standard. The other thing is that your AVR pre-outs aren't necessarily going to "clip". What that means is that when the current is demanded from the pre-amp section of the AVR, it cannot muster enough oomph and therefore clips.
But most AVR's aren't going to be clipping like that. Usually they'll simply top out unless it's a crap one. THe redbook standard RCA voltage is 2V. But a lot of AVR's do just over a volt. Emotiva used to make their amps 32 db gain specifically for this lesser voltage. But honestly I'm glad they went with the lower 29db gain.

What I was saying is that your figure of just over a 100 watts of power being put out is probably not accurate. I would guess it's more than that. I just don't know how to do the calculations....

Also the other part you may have been confused about is this.
Let's say you have an XPA-200 and an XPR-5.
If you connect your AVR to the XPA-200 and crank the pre-amp outputs to say 1V. Assuming that's not more than the maximum capable amplifying power of the XPA-200, it will put out say a specific amount of power.
Now connect your XPR-5 and crank the pre-amp output to 1V. You will get the SAME AMOUNT OF power.

[redog]

Get the balanced cables and be at peace knowing nothing is being left to the wayside.

[ninjahifi]

I'm going to get the balanced cables but isn't this sort of a big deal or do I have a major misunderstanding of how amplifiers work electrically? Its very likely I do.

My take is that the Pre-amp (AVR) actually creates the required voltage signal it then transfers it to the amplifier and the amp "amplifies" the signal. However, based on the input sensitivity of the XPR-5 the Pre-amp (or AVR) would have to provide a 1.875 V signal for the amplifier to "amplify" it to the rated 400 watts. Doing some more digging I guess the 1.2 V of output that my Processor is rated at putting out is an average so it could presumably be more. The problem is I don't like that the average is so much below the input sensitivity of my amp.

[garbulky]

I get what you are saying. Like I mentioned Emotiva used to have 32 db gain to help out. Not everybody was thrilled with that. But they switched to 29db gain. It's not really their fault though. The AVR's don't put out 2V. Their 29 db gain is pretty standard.

The more important question:...is the volume loud enough for you? Because if it is and you aren't hearing any kind of wierd nastiness then the pre-amp is more than capable - for your needs.
For instance did you know that your normal listening volume which is around 75-85 db at couch takes up about 2 watts of power (no joke). That doesn't actually require much pre-amp drive at all. It's the peaks that can take an exponentially large amount of watts. Something to do with an exponential or logarithmic increase but that's a bit beyond my head.....

Now see there are people (N8dogg comes to mind) who routinely runs his setup and +6Db over reference volume high efficiency HORNS!! and at least four huge subs about 45,000 watts of amplification power . As you can imagine that's VERY VERY loud. And well he's probably not going to be satisfied with the AVR. Maybe he has a solution for this. As I know he runs pro-amps and they all have rather low gains if I recall correctly.

Did you know that higher priced stuff like this passlabs.com/products/amplifiers/xs/xs-300 uses gains that are pretty low. Like 26 db gain and below. A lower gain does help a little with the noise. 29db I think has been mentioned on the forum as the THX standard.
Now all is not lost. For instance Emotiva's XDA-1 had a standard 2V RMS line level out but could generate peaks of 9 to 12 V of power. So maybe (I don't actually know the how it works) your pre-amp may do all right.