External amplify front & center speakers Denon x3700h.

[PABZ]

Wondering if anyone has used an external amp to power the front and center Channels on a Denon AVR x3700h receiver and still used 4 height and 2 surround speakers (powered by the receiver)?? I have read in the manual that you can select all chanels as pre outs or the zone 2 pre-outs for external amplification and in one instance after a lot of digging I found if you select 11.1 setup you can select the 2 fronts for pre-outs but I don’t have that many speakers, (I have 9- 2 front, 2 surround, 4 height, & 1 center) and still would not get to the center. Any thoughts?

 

[Golfx]

I have not used the 3700h for this purpose but have used Marantz AVRs and other Denon AVRs. The use of amp assign to change to pre out “only” (my phrase) allows a few DB of lower distortion for that channel as it unattaches the channel from the internal amplifiers. The internal amps are however still on and not turned off.
But all the channel pre outs, even if you do not change amp assign to turn off your front L&R or All channels, will still send out a signal that you can use for an external amplifier. If your concern is will the center be able to use an external amp too. Yes, it will just have the internal amp still attached to the channel signal which will likely add some extra (probably inaudible) distortion.


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[j_garcia]

Was just typing the same thing. Preouts are still preouts regardless of what you've done to the assignment of the internal amps. Particularly for the front 3, it should not be an issue.

 

[lovinthehd]

Yeah the slightly better spec in that pre-amp only mode has been misinterpreted a bit. Might affect your choice of external amp as far as sensitivity goes I suppose....

 

[PABZ]

Thank you ALL for the very quick responses on my first ever post!! I was afraid about using the pre outs without assigning the amps but now I’m ready to get started! I will be using a 5 channel Rotel amp and was thinking I would biamp my front Klipsch RF7’s and use the last channel for the Klipsch RP-450C or should I power the front stage and the Klipsch RP-402S surrounds? (this is mainly for a 20 x 25 living room home theater)

 

[Golfx]

Which 5 channel rotel the 120w or the 200w per channel?


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[PABZ]

120W

 

[Golfx]

Well, hmmm, you are using 4 heights. And you have pre-outs for height 1 and height 2. But I believe one of those height pre-outs are the mandatory pre-outs you would need to biamp your fronts. If you try just splitting the front pre-outs with y-cables to allow the external amp use of four channels then you likely would NOT have enough signal to allow the 4 rotel amps to work. If the 3700h isn’t used as the manual states then you will not get the proper signal sent to the proper speaker and room correction and codecs will not work. So I do not think you will be able to bi-amp. Maybe someone else might know a way?


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[PABZ]

Thanks for the quick responses, I am happy to get you insight! Did not think of the signal drop off with the use of a splitter. It appears as though I will end up going with the second option then.…

 

[Golfx]

Yeah, the rotel has more power per channel than the denon. But, If you are concerned your fronts could use more than 120, you could get another more powerful 2 channel ext amp just for those later on. There are some VERY reasonable class d amps from hypex that would work well.


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[PABZ]

Looking them up now! thanks!

 

[Golfx]

In the US there is Buckeye and VTV that build and sell reasonable priced hypex amps. Overseas there is March Audio (Australia) and Nord Audio (England) that provide well built hypex modules. I own March and Nord. Nord offers XLR and RCA input switch. The US versions are fine they just didn’t have the builds I wanted at the time. ATI in the US also offers hypex but is easily 2-3 times as expensive as everyone else for the SAME sound quality.


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[PENG]

Wondering if anyone has used an external amp to power the front and center Channels on a Denon AVR x3700h receiver and still used 4 height and 2 surround speakers (powered by the receiver)?? I have read in the manual that you can select all chanels as pre outs or the zone 2 pre-outs for external amplification and in one instance after a lot of digging I found if you select 11.1 setup you can select the 2 fronts for pre-outs but I don’t have that many speakers, (I have 9- 2 front, 2 surround, 4 height, & 1 center) and still would not get to the center. Any thoughts?

As Golfx mentioned, you get better pre out quality in pre amp mode but that's only at higher output voltage. If you don't need more than 1.4 to 1.5 V, pre amp mode or not would make no difference in performance except energy consumption.

In pre amp mode, you won't be able to use any of the 9 internal power amps.

So if you want to use the X3700H with a 3 channel ext. power amp then you cannot use pre amp mode. However, even when not in preamp mode, you can still get better pre out performance by disconnecting the the front left and right channel internal power amps. Again, that will be of benefit (in terms of THD+N) only at output voltage higher than 1.5 V, say up to >3 V by using the amp assign feature. To do that you have to use the amp assign trick. If you are serious about doing it I can post a link to some screenshots that will save you time trying to figure it out.

 

[PABZ]

Thanks Peng, sounds like it could be over my head! I do have a question about using pre outs and two external amps (I.e. a 2 channel driving fronts and another external amp driving center and surrounds) while the receiver drives the four height speakers, how does the volume equalize between the speakers with the different amps and just the receivers volume control?

 

[lovinthehd]

Thanks Peng, sounds like it could be over my head! I do have a question about using pre outs and two external amps (I.e. a 2 channel driving fronts and another external amp driving center and surrounds) while the receiver drives the four height speakers, how does the volume equalize between the speakers with the different amps and just the receivers volume control?

Running Audyssey or manually setting levels with your spl meter. Wouldn't bother with the passive bi-amping, tho.

 

[Golfx]

When you run Denon’s setup program and room correction it will properly adjust all your speaker volumes regardless of the amps powering the channels. You are using the Denon’s preamp and therefore its master volume control. Not each external amplifier. Most power-only amplifiers do not have adjustable power outputs for this reason.


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[PABZ]

Thanks lovinthehd! ahhh so that’s how! That totally makes sense!! I will not biamp the RF7’s now, Just going to use 200w external amp to drive them. Thank you for sharing you knowledge with a newbie!

 

[PABZ]

Thanks golfx, just saw your explanation and it totally answers my question!

 

[lovinthehd]

Thanks lovinthehd! ahhh so that’s how! That totally makes sense!! I will not biamp the RF7’s now, Just going to use 200w external amp to drive them. Thank you for sharing you knowledge with a newbie!

Even with differences in gain on each amp, that routine of level matching at your seat will make appropriate adjustments in the pre-amp section. With 200wpc on the RF7s I think you're fine without passive bi-amping (the conclusion of an article here on AH is essentially to do just that, just use a more powerful amp). Most of the passive bi-amping features in avrs and on the backs of speakers are largely about marketing, not performance. Do you know what the sensitivity spec for each amp is to see how well it will match up with the pre-out levels?

 

[PABZ]

I have the Rotel amp already and its 27 k ohms/1.0 volt. The Denon x3700h preamp is 200 mV/47 k ohms. I have not selected a two Chanel to drive the RF7s yet