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Denon AVR-4700 Preamp Mode Question

bigguyca

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Hi again ! Finally another question:p

With another setup,:
5.1.4 speakers
11.1 assignement
2 power amps, one for left and right, one for centre(purifie mono Block) .

I know that Denon centre preout Will clip at 1.4 vrms(internal amplifier still connected). My centre power amp has a 2.25 vrms input.
Can i compensate voltage difference by increasing output gain in denon setup?How?Is it worth it ? Will i still lose watts to power central speaker compared to internal amplifier capacity ?

Thanks again !

V not v for volt. You might as well learn to use the correct units.

If your power amplifier requires 2.25Vrms for full output, and the input to the power amplifier is 1.4Vrms, then you will lose about 4.1dB of output from the full output of your power amplifier by driving your power amplifier with 1.4Vrms.
 

batfunk

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Noted for Volt unit. As you noticed I'm a noob. Thanks again !
 

bigguyca

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Again, the pre out doesn't clip at 1.4 Vrms (the internal power amp will be clipping at that point). Take a look of the center channel of the X3600H, that obviously has the internal power connected:

That's almost as good as the AV7705 (a so called "separate" preamp processor.
Note that the dash board of the AV7705 measurements show about 4 V but that's XLR, had Amir used RCA for that measurement, it would have been 2 V and SINAD would have been about the same, again, as the AVR-X3600H that is an AVR, therefore internal amps would be "clipping" and degrading the SINAD at pre out.

So I really wouldn't worry about your center channel, unless you will be pusing the Purifi amp to output almost 400 W average (800 W peak) into 8 Ohms and you can hear the difference between 75 dB and 95 dB SINAD (I know I can't..).

- Omitted -

Denon/Marantz Preamp output limits and Gain Structure

I'm becoming less convinced over time that the 1.4V preamp limit is based on the associated power amplifier channel clipping. There may be a lot we don't understand about the Denon/Marantz AVR's/AVP's. This is a good subject for some future thread. Some items to consider concerning the 1.4V level and also the D/M gain structure.

(1) 1.4V into an amp with a 28.2x gain gives 39.5V or a rail voltage of 55.4V plus some extra for drops in the power stage. 39.5V into 8 ohms is about 200W.

With five channels driven the power output per channel may drop to 100W. This requires an output of 28.3Vrms with 39.6V as the rail voltage. At a gain of 28.2x the input from the preamp would be about 1V. Does this really mean that the preamp channels now essentially clip at 1V output since the associated undriven power amplifier stage will now clip at 28.3V output due to the drop in the rail voltage due to the load on the other channels?

This drop in preamp clean output suggests that the distortion performance of the preamp outputs will be modulated by the output of the power amplifier channel. This seems a mess and unacceptable. The 1.4Vrms value is such a common value in D/M gear that I wonder if it is set by gear and not determined by the clipping level.

(2) Based on my measurements of the AV7705, a 0dbFS input with 1.4V XLR output results in about -96dB THD and about -95dB THD+N. -6dBFS input with 1.4V XLR output with the volume control increased by +6dB results in about -104dB THD and -99 THD+N. Does Denon/Marantz make use of this relationship in the actual operation of the AVR's/AVP's? Output levels in the 1V to 2V range produce similar relationships in output performance.

Products like RME DAC's switch resistors to change gain to a take advantage of this sort of relationship. D/M could reduce the digital output in the DAC IC by 6dB and increase the volume control setting (internally, not seen by the user) by 6dB to get the better measurements noted above. The relatively low preamp output levels reported by many for D/M gear used in home theaters of -10dB to -25dB would allow a lot of room for adjusting gain to maximize performance.
 

bigguyca

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Noted for Volt unit. As you noticed I'm a noob. Thanks again !

It's "V" and "volt." The unit is named after Alessandro Volta.

Also, W and watt, named after James Watt.

You'll see Wrms. Wrms can be calculated, but is a meaningless value.
 

peng

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Denon/Marantz Preamp output limits and Gain Structure

I'm becoming less convinced over time that the 1.4V preamp limit is based on the associated power amplifier channel clipping. There may be a lot we don't understand about the Denon/Marantz AVR's/AVP's. This is a good subject for some future thread. Some items to consider concerning the 1.4V level and also the D/M gain structure.

(1) 1.4V into an amp with a 28.2x gain gives 39.5V or a rail voltage of 55.4V plus some extra for drops in the power stage. 39.5V into 8 ohms is about 200W.

In Gene's video on the AVR-X3600H, he mentioned that he talked to Denon about it, and it was the power amp clipping typically at about 1.2 V that resulted in the higher THD+N and that got fed back to the input that is connected to the preamp output. That seems quite logical and believable as an explanation. You seem to have the service manual of the X3600H, may be you can take a look and see if that makes sense to you.

With five channels driven the power output per channel may drop to 100W. This requires an output of 28.3Vrms with 39.6V as the rail voltage. At a gain of 28.2x the input from the preamp would be about 1V. Does this really mean that the preamp channels now essentially clip at 1V output since the associated undriven power amplifier stage will now clip at 28.3V output due to the drop in the rail voltage due to the load on the other channels?

That may be possible if all 5 channels are driven to output >100 W simultaneously.

This drop in preamp clean output suggests that the distortion performance of the preamp outputs will be modulated by the output of the power amplifier channel. This seems a mess and unacceptable. The 1.4Vrms value is such a common value in D/M gear that I wonder if it is set by gear and not determined by the clipping level.

Again, based on what Gene said about his discussion with Denon, I don't think if is "set by gear". It is better you see that video yourself as I may have missed or misinterpreted something he said.

You can start at the 25:20 minute point in the video linked belo:
Denon AVR-X3600H 11CH Atmos/DTS:X AV Preamp for $1,100?!? - YouTube

He talked about the same in at least another video too, but his review on the X3600H appears to be the first time he realized the "reason" for the pre out THD+N degradation at >1.2 Vrms level.

(2) Based on my measurements of the AV7705, a 0dbFS input with 1.4V XLR output results in about -96dB THD and about -95dB THD+N. -6dBFS input with 1.4V XLR output with the volume control increased by +6dB results in about -104dB THD and -99 THD+N. Does Denon/Marantz make use of this relationship in the actual operation of the AVR's/AVP's? Output levels in the 1V to 2V range produce similar relationships in output performance.

That's very interesting that you have much better results. Have you measured one of the Denon AVRs?[/QUOTE]
 

patoulol

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If I understood correctly, are we laughing at the 1.4v? can you buy the wattage amp you want?
 

patoulol

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I read this thread :cool:
So I can put external power amps on L- R- C on an x4700/x3700 without "fear" and asking 10000 questions? :)

goooooood !
 
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Lbstyling

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Hi all,
Problem with using pre amplifier mode. It doesn't apply audessey when I put it in this mode.

Any ideas what I can do?

I run audessey from the phone app. And it works well, but only in 11.1 channel mode?

Audessey isn't applying to 9.1 or preamp mode at all.
 

Golfx

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Hmmm, there are some spots in the process where it may not have been saved-depending on your level of experience. In amp assign during setup for instance or perhaps when completing the phone app process you must then send the completed measurements back to the denon. That last part is not that intuitive. Does it work when you just use the AVR’s audyssey without using the phone app?
 

Lbstyling

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Hmmm, there are some spots in the process where it may not have been saved-depending on your level of experience. In amp assign during setup for instance or perhaps when completing the phone app process you must then send the completed measurements back to the denon. That last part is not that intuitive. Does it work when you just use the AVR’s audyssey without using the phone app?
Do I have to rerun audessey from scratch and set it to pre amp mode first then? Very odd if this is the case!
 

Golfx

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This videos below will take awhile to view. It might help you discover some steps in your setup which might be giving you trouble. In denon setup wizard you will choose your “speaker setup”. Then ”amp assign” will let you choose which internal amps you will use or NOT use if you set it to pre amp mode. Then you can run audyssey using the internal AVR processor OR you can use the your phone’s app processor. If the latter you will have to then send the results back to the denon once you have completed the measurements. The app does store those previous measurements (called profiles) under the name you chose so you can just choose that name so you don’t have to remeasure.


 

amper42

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Hi all,
Problem with using pre amplifier mode. It doesn't apply audessey when I put it in this mode.

Any ideas what I can do?

I run audessey from the phone app. And it works well, but only in 11.1 channel mode?

Audessey isn't applying to 9.1 or preamp mode at all.

When you place the Denon 4700 in pre-amp mode you run Audyssey as part of that setup. The pre-out setup creates a file on your iPad or phone that can be reloaded later if you choose too. However, the first time you setup pre-amp mode Audyssey needs to run to properly configure gain levels for external amps and apply EQ as needed.

Each new setup will create an Audyssey file that can be saved on the 4700 (two presets) or as many presets as you want on the iPad/iPhone. You can have a stereo configuration, 11.1, 9.1, 7.1 or any combination allowed by amp assign. Once created they can always be loaded back on the 4700 should you change between them later.
 

MarcT

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So, still confused here, but my power amp for my front L/R speakers has input sensitivity of 2.7 Vrms and gain is 26.4 db. Is a Denon 4700/6700 a good idea or should I go with perhaps an Anthem MRX-740, about which Gene praised the pre-out performance up to 4 Vrms, or so?
 

tcipps

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1. If you are using Denon amp assign 11.1 - this is not "pre-amp only" mode.

2. If you use 11.1 amp assign and configure the Fronts as "pre-outs" then your Front pre-out RCA's lead to the external amp and the speakers connect to the external amp. Next, use the Center "Pre-out" RCA to the external power amp and then Fronts and Center will be powered off the external amp.

3. The Denon 4700 "pre-out" RCA's are always live no matter what amp assign mode you select. The difference between using "Pre-out ONLY" mode from any other Denon 4700 Amp assign mode is the internal amp power rails are disconnected in "Pre-out ONLY" mode which offers cooler operation and higher SINAD.

This is what your configuration would look like:
Fronts: Pre-outs:external amp channel 1/2:speakers
Center: Pre-out:external amp channel3:speaker
Question :
I got 9.1 setup

If I set to 11.1 with surround back .

Will the Denon put power to the surround back channels even if nothing connected?

Or is it already doing that regardless
 

bigguyca

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Question :
I got 9.1 setup

If I set to 11.1 with surround back .

(1) Will the Denon put power to the surround back channels even if nothing connected?

Or is it already doing that regardless

Unfortunately, you read and replied to a thread that has some bad information in item #3. That is, the #3 is wrong.

To quote #3:

"3. The Denon 4700 "pre-out" RCA's are always live no matter what amp assign mode you select. The difference between using "Pre-out ONLY" mode from any other Denon 4700 Amp assign mode is the internal amp power rails are disconnected in "Pre-out ONLY" mode which offers cooler operation and higher SINAD."

In "Pre-out only" mode the preamp outputs are disconnected from the power amplifier channel inputs. The power amplifier channels are always powered, that is, the power rails have power and are not disconnected. However, the voltage level of all the power amplifier rails is reduced to the level used in the ECO mode. This reduction in means that each power amplifier channel dissipates less power in the output transistors including when the power amplifier channel is not in use. This in turn means that the X4700H will run cooler.

Therefore, based on the above:

(1) Yes, but with a lower rail voltage.
 

superlupo

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Sorry to resurrect this thread from the dead, but maybe someone has an answer for me.
At which volume of the Denon AVR you are going reasonably to hit 1.4v on the pre-outs? At reference level (+/- 0 dB)? Or even below or only far above?
I am using active speakers as F/C/R (without preamp-only mode), and I don't know their sensitivity.
 

peng

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Sorry to resurrect this thread from the dead, but maybe someone has an answer for me.
At which volume of the Denon AVR you are going reasonably to hit 1.4v on the pre-outs? At reference level (+/- 0 dB)? Or even below or only far above?
I am using active speakers as F/C/R (without preamp-only mode), and I don't know their sensitivity.

In one of my posts from way back, I did to give some calculated numbers based on some assumed conditions. Without such stated assumptions, the volume can be anywhere, such as -10, 0, or even -15, 5 etc. What volume do you listen to now? You may not have to worry about the pre out voltage at all.

More related info on this topic has been posted many times, I wouldn't want to repeat those same points made, you can search for them if you are insterested in more details.
 

superlupo

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Thanks for your answer. I know it has been discussed, but I don't want to spend days reading through old threads.
I mostly listen between -20 to -10 dB, sometimes I use +/- 0dB. But never over this reference level measured by Audyssey. And my concern is only movies/series, not music.
 

peng

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Thanks for your answer. I know it has been discussed, but I don't want to spend days reading through old threads.
I mostly listen between -20 to -10 dB, sometimes I use +/- 0dB. But never over this reference level measured by Audyssey. And my concern is only movies/series, not music.

Actually, if it is for movies, then it is much simpler, no need for you to read too much.
Still, we have to assume the contents are recorded to the standard that at the highest peak, the signal is at 0 dBFS:

So since Amir measured the AVR-X4700H, and at volume 82.5, he had a little over 2 V.

index.php


So we can calculate that, roughly at 79.5, pre out would be at about 1.4 V.

79.5 in the relative scale would be -0.5. If you had run Audyssey, the number would likely be a little different but wouldn't likely be by much. Just keep in mind this is based on the maximum peak signal at 0 dBFS, movies obviously have peaks but not always at the maximum level. Most of the time, the pre out voltage would be much lower than 1.4 V at the same volume.

I hope that's the answer you are looking for.
 
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superlupo

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So we can calculate that, roughly at 79.5, pre out would be at about 1.4 V.

79.5 in the relative scale would be -0.5. If you had run Audyssey, the number would likely be a little different but wouldn't likely be by much. Just keep in mind this is based on the maximum peak signal at 0 dBFS, movies obviously have peaks but not always at the maximum level. Most of the time, the pre out voltage would be much lower than 1.4 V at the same volume.

I hope that's the answer you are looking for.
Thank you, that was the exact answer I was hoping for. So I should be good ;-)
 
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