Best channels to power amp for Denon AVR

Dobbyisfree

Active Member
I am looking at a 9 channel set up and I am wondering what the advice would be regarding which 2 channels to use for my external power amp. Or, indeed, if I am in need of further external power amplification.

I am proposing using the power amp, at present, for the surrounds. But frankly, after seeing @Mr Wolf amazing calculator, I am now unsure as the sensitivity and distance play such a part in this.

Mr Wolf has asked me for the following data:

1. Max. listening level (to reference)
Up to -15dB.

2. Speaker sensitivity ratings and distances

FL and FR
MLP 5.5m
6 Ohms, 89 dB
Crossover 80Hz

C
MLP 5m
8 Ohms, 91 dB
Crossover 120Hz

SL and SR
MLP 2.8m
8 Ohms, 91 dB
Crossover 60Hz

FHL and FHR
6.2m
4 Ohms, 88 dB
Crossover 120Hz

RHL and RHR
3.3m
6 Ohms, 88 dB
Crossover 120Hz

3. Amplifier power per channel on 2 channel and (if known) 5 channel basis. If the latter's unknown, we'll assume 5-channel = 70% of 2 channel like D&M guarantee

Denon AVR
125 Watts 8 Ohms 20-20,000Hz 0.05% THD
Power supply 710 Watts

Rotel power amp
70 Watts 8 Ohms 20-20,000Hz 0.06% THD
Power supply 250 Watts

4. Proposed allocation of amps to channels

No idea now! But was thinking to surrounds.

Thank you for your help!
 

Mr Wolf

Active Member
Thanks for the info.

Based on these assumptions I'd probably use the Rotel on the top fronts as they're potentially the most demanding after the LCRs. And I wouldn't use them on the LCRs as the Denon has more output plus I like to keep LCRs on the same power source.

Peak demand of 15W on the L/R gives 7.7dB headroom from 88W which is plenty.

1622544486395.png
 

Dobbyisfree

Active Member
Thank you so much for that, I will configure it that way exactly.

Fascinating...

So, due to their lower sensitivity and the distance away, it makes more sense to separately allocate that 250w power supply to the top fronts.

Funnily enough, double thanks, as this also works better regarding wiring and trunking provision!
 

Mr Wolf

Active Member
Well, this seems the best approach if you prioritise preserving peak power headroom on the LCRs which is what I generally favour.

There is however an argument to use the Rotel to power the surrounds instead on the basis that they will be far more active than the top fronts. There's also the fact that you cross the two tops to the sub at a higher frequency which in practice should reduce the peak power demand from them.

In practice, at your listening level I don't think you'd notice much difference either way due to the headroom levels under both options.
 

Dobbyisfree

Active Member
Yes, I think what is valuable is that your tool is a way of helping some members to realise that in the average UK lounge at normal listening levels, there isn't much need for a huge stack of power amps.

I'm not being cynical towards those people however, as I fall in exactly the same boat.

A black box called an AVR used to just amplify 5 channels. Now they amplify 7, 9, 11 or 13... the power supplies aren't much bigger. I think it sets off a natural panic that the thing isn't going to cope.

We all know that the channels normally don't all peak at the same time. We know some channels, e.g. rear height, can sit doing nothing or very little a lot of the time. But even still, the AVR geeks nightmare, it suddenly does a peak in many channels and we hear (sorry for swearing) DISTORTION!

Here's how I see it. My Denon AVR has a 710w power supply and can amplify max. 9 channels. Denon's (almost, except for the black interior why question) flagship x8500 has a 900w power supply for up to 13 channels.

Denon wouldn't charge you £3 grand and only give the extra 190w in the power supply for another 4 channels if they were not 100% that it was suitable. Which suggests to me that actually the 710w in my AVR is probably ample for most lounges full stop.

I'd like to mention on top of that though that I have AVR in open air very well ventilated - which can be a separate issue for people.

Thanks again for your help.
 

gibbsy

Moderator
I'm not even going to try and compete with Mr Wolf. However, I'll ask if there is going to be any serious music listening with the Denon as that could make a difference in the call as to which speakers need the external amp.
 

Mr Wolf

Active Member
I'm not even going to try and compete with Mr Wolf. However, I'll ask if there is going to be any serious music listening with the Denon as that could make a difference in the call as to which speakers need the external amp.
I agree but I'd assumed in this case that the Rotel is strictly a power amp and not an integrated stereo amp that might be able to offer superior 2-channel experience. If that were the case (as I know it is in your set-up) then I'd have modelled the option of it powering the L/R as 70W/channel would still be plenty at -15dB listening levels.
 

Dobbyisfree

Active Member
I'm not even going to try and compete with Mr Wolf. However, I'll ask if there is going to be any serious music listening with the Denon as that could make a difference in the call as to which speakers need the external amp.

Yes, music performance is very important too. Setting as stereo with Audyssey on but Dynamic EQ off. Subs on but at 60Hz crossover for fronts in music listening (using the "front speaker" setup in the menus).

The Rotel is just a power amplifier though, as in Mr Wolf's comment, would this make a difference?
 

gibbsy

Moderator
I agree but I'd assumed in this case that the Rotel is strictly a power amp and not an integrated stereo amp that might be able to offer superior 2-channel experience. If that were the case (as I know it is in your set-up) then I'd have modelled the option of it powering the L/R as 70W/channel would still be plenty at -15dB listening levels.
Should have read the original post a bit closer. A power amp is unlikely to make a difference to the stereo music performance of a Denon AV amp and so it becomes something of a moot point. The set up with a power amp added is always going to be a step forward as it's a win win situation for the Denon and any speakers attached.
 

gibbsy

Moderator
Yes, music performance is very important too. Setting as stereo with Audyssey on but Dynamic EQ off. Subs on but at 60Hz crossover for fronts in music listening (using the "front speaker" setup in the menus).

The Rotel is just a power amplifier though, as in Mr Wolf's comment, would this make a difference?
I run a different set up with my Denon. The fronts being powered by a HT capable stereo amp. I don't rate my Denon for music and need to cut the Denon completely out of the music circuit save for multi channel SACD, etc. You can only use a HT stereo amp to drive the front left and right as both set ups have to use the same front speakers which are themselves a difficult drive.

The benefit is the same as using a power amp for film and TV as the saved power is shared around the remaining connected speakers.
 

gibbsy

Moderator
The Rotel is just a power amplifier though, as in Mr Wolf's comment, would this make a difference?
Yes. A good power amp should not colour the audio signal of the Denon's pre-amp, just amplifying that signal. As I've said above using a HT capable stereo amp is to have all your music going through that stereo amp thus cutting the Denon out of the stereo music loop. A stereo amp is always going to outperform the Denon for stereo music playback.
 

Mr Wolf

Active Member
Yes, I think what is valuable is that your tool is a way of helping some members to realise that in the average UK lounge at normal listening levels, there isn't much need for a huge stack of power amps.

I'm not being cynical towards those people however, as I fall in exactly the same boat.

A black box called an AVR used to just amplify 5 channels. Now they amplify 7, 9, 11 or 13... the power supplies aren't much bigger. I think it sets off a natural panic that the thing isn't going to cope.

We all know that the channels normally don't all peak at the same time. We know some channels, e.g. rear height, can sit doing nothing or very little a lot of the time. But even still, the AVR geeks nightmare, it suddenly does a peak in many channels and we hear (sorry for swearing) DISTORTION!

Here's how I see it. My Denon AVR has a 710w power supply and can amplify max. 9 channels. Denon's (almost, except for the black interior why question) flagship x8500 has a 900w power supply for up to 13 channels.

Denon wouldn't charge you £3 grand and only give the extra 190w in the power supply for another 4 channels if they were not 100% that it was suitable. Which suggests to me that actually the 710w in my AVR is probably ample for most lounges full stop.

I'd like to mention on top of that though that I have AVR in open air very well ventilated - which can be a separate issue for people.

Thanks again for your help.
You raise some really good points but there's a lot of confusion in this area.

Firstly, the wattage ratings on the back of Denon AVRs is not a power supply rating at all (like you get with PCs), nor is it even an indication of the maximum possible power drawn from the socket. It is derived from a complicated formula which estimates the power drawn when a number of amps channels are run at 1/8 power. Gene at Audioholics did a whole article on this subject, even reworking D&M's calcs to prove them up. In practice the maximum power an AVR can potentially draw from the wall socket is much higher if they were pushed hard enough.

Secondly, the whole issue about AVRs needing more power for more channels seems to be completely misunderstood by most people. An AVR does not need power in direct proportion to its channel count at all. To maintain power per channel parity with an AVR with fewer channels, the extra power needed for the extra channels solely relates to the increase in power caused by having more amps idling at all times (bit like having a extra engines ticking over, still using fuel and generating heat). Think about what happens when the DSU upmixes a 5.1 soundtrack on a X8500 running 13 channels. The exact same sounds at the same SPL hit the listener, they just come out of different speakers. The same happens in reverse when you downmix a 7.1 TrueHD mix onto a 5.1 system, the back channel info comes out of the side surrounds instead. So in practice a X8500 will have more headroom than models lower in the Denon range due having a larger power supply and more powerful 150W amps.

The problem AVR designers have faced is that while adding extra on-board amps don't consume much more power they do take up more space and this has caused them to shift AVR cooling systems away from passive (e.g. heatsinks) to active ones (e.g. fans). Some have also robbed space for the amps by using smaller PSUs but IMO not many. Anyway, this accounts for why AVRs have generally got lighter over the last 10 years. The X8500 is a bit of an exception though as Denon just gave it a much bigger chassis, proper heatsinks and a massive PSU and bumped the weight - I like it a lot.

The point you make though is that most home HT systems do not need external power amps to run nicely. I'm a big fan of using fairly sensitive speakers up front though as, due to the 3dB higher (+20dB vs 17dB) dynamic peaks and the fact that most people sit further from them, they can often need >3x the power of the surround channels.

That all said, what many of the power amp members will be appreciating though is, to coin a phrase I've seen used by SVS's design team, is "the quality of headroom". Extra power headroom can, to a point, increase both fidelity and also give you that extra feeling of tightness and responsiveness that an AVR cannot deliver in some systems.
 

Mr Wolf

Active Member
Yes. A good power amp should not colour the audio signal of the Denon's pre-amp, just amplifying that signal. As I've said above using a HT capable stereo amp is to have all your music going through that stereo amp thus cutting the Denon out of the stereo music loop. A stereo amp is always going to outperform the Denon for stereo music playback.
I expect the improvement in quality you're experiencing is in superior DACs and pre-amp stage, not the power amp section.

Youthman (on Youtube) did a test a while ago between a standalone Marantz AVR, the same AVR with a power amp and a Marantz pre/pro with the same power amp. In blind testing listeners couldn't really tell the difference between the two AVR based set-ups but the Pre/Pro plus power amp was apparently streets ahead in SQ. I was quite envious.
 

Dobbyisfree

Active Member
@gibbsy Yes, I've seen in previous posts, you have a high model Rega I believe with HT bypass.

I would love to be able to do that but they are not cheap. I stream music from Spotify switched to its highest quality so that quite a lot if 320kbps. I'd need it to be able to stream too. And preferably to have a 12v trigger. The Audiolab 6000a Play seems to be the only one that does this at reasonable cost new but people say that the play function is not good (you can't just stream straight from Spotify Direct app).

Then, I've considered older used amps with HT bypass, e.g. Cyrus. Then I'd need a separate streamer to plug into it. Although I have just wondered if you stream Spotify whether the Denon outputs it from its optical out... a question that I should've asked ages ago. If it does, I could optical out to an integrated with HT bypass.

Anyway, I have kind of thought that for the quality of Spotify would it be worth it anyway. And now I'm just rambling again 🤣
 
Last edited:

Dobbyisfree

Active Member
You raise some really good points but there's a lot of confusion in this area.

Firstly, the wattage ratings on the back of Denon AVRs is not a power supply rating at all (like you get with PCs), nor is it even an indication of the maximum possible power drawn from the socket. It is derived from a complicated formula which estimates the power drawn when a number of amps channels are run at 1/8 power. Gene at Audioholics did a whole article on this subject, even reworking D&M's calcs to prove them up. In practice the maximum power an AVR can potentially draw from the wall socket is much higher if they were pushed hard enough.

Secondly, the whole issue about AVRs needing more power for more channels seems to be completely misunderstood by most people. An AVR does not need power in direct proportion to its channel count at all. To maintain power per channel parity with an AVR with fewer channels, the extra power needed for the extra channels solely relates to the increase in power caused by having more amps idling at all times (bit like having a extra engines ticking over, still using fuel and generating heat). Think about what happens when the DSU upmixes a 5.1 soundtrack on a X8500 running 13 channels. The exact same sounds at the same SPL hit the listener, they just come out of different speakers. The same happens in reverse when you downmix a 7.1 TrueHD mix onto a 5.1 system, the back channel info comes out of the side surrounds instead. So in practice a X8500 will have more headroom than models lower in the Denon range due having a larger power supply and more powerful 150W amps.

The problem AVR designers have faced is that while adding extra on-board amps don't consume much more power they do take up more space and this has caused them to shift AVR cooling systems away from passive (e.g. heatsinks) to active ones (e.g. fans). Some have also robbed space for the amps by using smaller PSUs but IMO not many. Anyway, this accounts for why AVRs have generally got lighter over the last 10 years. The X8500 is a bit of an exception though as Denon just gave it a much bigger chassis, proper heatsinks and a massive PSU and bumped the weight - I like it a lot.

The point you make though is that most home HT systems do not need external power amps to run nicely. I'm a big fan of using fairly sensitive speakers up front though as, due to the 3dB higher (+20dB vs 17dB) dynamic peaks and the fact that most people sit further from them, they can often need >3x the power of the surround channels.

That all said, what many of the power amp members will be appreciating though is, to coin a phrase I've seen used by SVS's design team, is "the quality of headroom". Extra power headroom can, to a point, increase both fidelity and also give you that extra feeling of tightness and responsiveness that an AVR cannot deliver in some systems.

Good point on sensitivity. Although, in my case, a sensible next upgrade could be the top fronts for something more sensitive (cheaper way to give more overall headroom). Except if I did that, I'd be asking you kindly to run the calculation again :)

My fronts are Mission/Cyrus 780SE, these cannot be changed as for some reason they simply are my favourite sounding speakers ever. Well, maybe if I won the Euromillions, I may audition something different.

My Dad has always said you know the real power of an amp by it's weight. Not fully accurate of course! But, he has a point, I'd argue it can be better than looking at the number sometimes :) I mean my first ever separates amp was a NAD 3030, apparently 30w RMS at 0.9%, weighing in at 9kg (not far off some AVRs).
 

gibbsy

Moderator
I expect the improvement in quality you're experiencing is in superior DACs and pre-amp stage, not the power amp section.
Bit off topic but no. I had a Marantz sa8005 linked by analogue to a Denon X6200. Awful. Same player into the Rega which is a pure analogue amp and it was night and day. The Denon would still put that analogue signal back into the digital domain, sucking the life out of the music.

I've obviously got the new Denon X6500 (with the Rega powering the fronts) for multi channel SACD, DVD-A, etc and it does a seriously good job. Best thing I ever did was cut the Denon AV amps out of playing stereo music. The X6500 (AL32 processor) is marginally better than the X6200 (AL24) but not for serious music listening.

It's horses for courses and there is no need for any additional power with the X6500 as it's more than adequate for film and TV and if I had a completely separate room for music then never the twain would meet. Saying that my wife would love me to have a soundproof music listening room.
 

Mr Wolf

Active Member
Good point on sensitivity. Although, in my case, a sensible next upgrade could be the top fronts for something more sensitive (cheaper way to give more overall headroom). Except if I did that, I'd be asking you kindly to run the calculation again :)

My fronts are Mission/Cyrus 780SE, these cannot be changed as for some reason they simply are my favourite sounding speakers ever. Well, maybe if I won the Euromillions, I may audition something different.

My Dad has always said you know the real power of an amp by it's weight. Not fully accurate of course! But, he has a point, I'd argue it can be better than looking at the number sometimes :) I mean my first ever separates amp was a NAD 3030, apparently 30w RMS at 0.9%, weighing in at 9kg (not far off some AVRs).
I'm sure all your speakers are sensitive enough for their current application as the headroom calculations support.

By the way, the PSU in the AVC-X8500 weighs 8.2KG alone, only 400g less than a AVR-X1600 - now that's meaty!
 

Dobbyisfree

Active Member
Far too 21st century for me. Nothing wrong with the little silver disc. My nod to late 20th century technology. :)

Darn it, so there's no point in me asking you nicely to connect a spare optical from the Denon out to the Rega in (assuming it has on-board DAC) and see what it does streaming Spotify then :)

You're not alone, I still have lived more of my life in the last century than this one!
 

gibbsy

Moderator
Darn it, so there's no point in me asking you nicely to connect a spare optical from the Denon out to the Rega in (assuming it has on-board DAC) and see what it does streaming Spotify then :)

You're not alone, I still have lived more of my life in the last century than this one!
The Rega is a pure analogue amp. No DACs, no headphone jack, can't even turn it on with a remote. If I were to ever venture into streaming it would have to be a standalone device.
 

Dobbyisfree

Active Member
I'm talking nonsense anyway, I've had a look and the AVR doesn't have an optical out, it's yet another thing they've taken away as time goes on.

Guess they used to have them as people had, e.g. CD or minidisc, recorders but now people don't use these things anymore.

If you have all the musical sources you want then no point in bothering with streaming is there. When we have visitors, we quite often play the "each person chooses the next track" game and this works well with streaming!
 

Mr Wolf

Active Member
The Rega is a pure analogue amp. No DACs, no headphone jack, can't even turn it on with a remote. If I were to ever venture into streaming it would have to be a standalone device.
Its DACs cannot be that good and it would probably sound totally rubbish compared to what you're used to but for streaming music I use the line-out on an Amazon Echo Dot (3rd Gen.) into the analogue inputs of the Denon AVR in my living room and I don't think it sounds too bad at all.

It's extremely convenient and was a bargain for £18 on the last Amazon Prime Day.
 

Dobbyisfree

Active Member
Its DACs cannot be that good and it would probably sound totally rubbish compared to what you're used to but for streaming music I use the line-out on an Amazon Echo Dot (3rd Gen.) into the analogue inputs of the Denon AVR in my living room and I don't think it sounds too bad at all.

It's extremely convenient and was a bargain for £18 on the last Amazon Prime Day.
Thank you for that I will check it out.
Some people use a Chromecast Audio which works with Spotify Connect then it has an optical out. So that could work with a bypass amp with a dac or get a 2nd hand dac too.
Problem is that in my opinion the dacs and the al32 in the Denon may just end up no worse than the alternative with the integrated. The Chromecast limits to 256kbps vs the Denon at full 320kbps too.
Also are the preamps in the cheaper integrated "better" than the Denons or do people just prefer the sound? Just like most of the audio world some things sound better to some people than others.
E.g. my 780se I compared switched with a mate's Kef r3 with some posh Arcam integrated amp at his house last year. Even he agreed that the Missions won on stereo separation and sound placement... but the sound he harped on for ages but I just preferred the Missions haha.
We all have different ears and brains!
 

Dobbyisfree

Active Member
Hi @Mr Wolf one last question on this sorry.
All over AVF people talk about some speakers having impedance levels across the frequency range that makes them "hard to drive".
The KEF Q900 show as 91dB sensitivity but it's said the impedance range needs power too, see below:
Is this something to also bear in mind or am I talking nonsense?
 

gibbsy

Moderator
Hi @Mr Wolf one last question on this sorry.
All over AVF people talk about some speakers having impedance levels across the frequency range that makes them "hard to drive".
The KEF Q900 show as 91dB sensitivity but it's said the impedance range needs power too, see below:
Is this something to also bear in mind or am I talking nonsense?
You're not talking nonsense. The figures to bear in mind is the obvious ohm loading and sensitivity. At 8 ohms and 91dB sensitivity then the Q900s are not a hard drive on the amp. I believe that the Q900s drop to 3.8 ohms, so again not a hard drive on the amp. If you look at the link you gave above then that is too complicated. You could easily go with the best figures available yet the speaker may not suit the amp, or your room. Don't over think things.

KEF speakers do have a reputation of being hard to drive but this is mainly from the R Series, LS50s and upwards. As for partnering then KEF do sit well with Denon amps of all description amongst others because the KEFs are quite benign in nature. I'm driving KEF R Series with a Denon AV amp and a Rega stereo amp. More than happy with the combination.
 

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