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Matching amp to pre-out question

ciotime

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With regards to choosing an external amp to power the Denon X3700H I've been told that it's very important to get one with a specific sensitivity that will match the Denon's pre-out voltage gain. Saw this review and I quote " As you see, peak performance with the amplifiers off is around 1.1 volts with SINAD of 101 dB which is excellent for an AVR. With the amps on, you are OK up to 1.4 volt output before it nose dives. So when selecting an external amplifier for channels beyond fronts, make sure it can output its maximum power at or below 1.4 volts (usually specified as "sensitivity"). " I never knew this until I asked someone if getting the Rotel RMB1585 was a good idea to use as an external amp. The INPUT SENSITIVITY is as follows: Line Level Inputs (RCA): 1.9V / Line Level Inputs (XLR): 3.8V. 1.9V is WAY above the recommended 1.4 volt. Am I correct that I should choose a power amp with an Input Sensitivity of 1.4V or lower? IF an input voltage to an amp is less than it's rated sensitivity, the amp will not come close to amplifying the signal to it's rated wattage. SO, if I use the Rotel, it most likely will make less output wattage per channel than just using the Denon alone and there is no point in spending money on an amp that actually makes less power than the AVR that it's connected to. Or will the Rotel RMB1585 paired with the X3700H be fine? I plan to externally power just the 3 front speakers and just let the Denon handle the other surround speakers. Setup is 7.2.4.
 

mdsimon2

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To me 1.4V vs 1.9V is not a huge difference (~2.6 dB) but it may be to you. If you limit the output to 1.4V that would effectively cap the output of the Rotel at ~110 watts at 8 ohms. Now you could make the case that power from the Rotel will be cleaner than the AVR but the distortion specs they provide are very limited and only state THD+N < 0.03% (70 SINAD). Imagine actual performance is better than that but it is difficult to tell. Amir's review definitely showed that AVR performance increased with less amplifier channels in use so you would still get that benefit.

I guess the ultimate question is how often do you listen at a volume level above -3 dB? If the answer is never then you will never have a preout voltage above 1.4V and it doesn't matter.

Michael
 
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ciotime

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To me 1.4V vs 1.9V is not a huge difference (~2.6 dB) but it may be to you. If you limit the output to 1.4V that would effectively cap the output of the Rotel at ~110 watts at 8 ohms. Now you could make the case that power from the Rotel will be cleaner than the AVR but the distortion specs they provide are very limited and only state THD+N < 0.03% (70 SINAD). Imagine actual performance is better than that but it is difficult to tell. Amir's review definitely showed that AVR performance increased with less amplifier channels in use so you would still get that benefit.

I guess the ultimate question is how often do you listen at a volume level above -3 dB? If the answer is never then you will never have a precut voltage above 1.4V and it doesn't matter.

Michael
Thanks for the advice. I do need an external amp coz though the X3700H is capable of processing 11 ch it's only a 9.2ch 8K AV Receiver meaning one needs to externally power 2 channels to do a 7.2.4 setup. I had only planned on using my old Denon AVR as the external amp. But then I saw an offer of the Rotel RB1585 at less than $2000 used but good as new ( MSRP is about $3500 ). I'd imagine it'll be better but the question is will it be $2000 better?
 
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