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How much amplifier power do you really need?
#21
@David A Your points are well taken, except for the fact that this discussion has always been about peak power rather than continuous power (ref. your item (3)).  Whether the amp can deliver a factor of 100 peak power (vs RMS power) will depend on its design.  For example if it's driving music with a 20dB crest factor into a resistive load, by my maths it would need power rails with at least seven times -- that is, 10 divided by the square root of 2 -- higher voltage than it would need to deliver a sine wave with the same RMS power.  Likewise the amp would also have to be able to deliver seven times higher peak current for that music than for a sine wave at the same RMS power.  With a non-resistive load like a real-world loudspeaker I'd expect those ratios to increase: of course I may well be wrong, as I don't design amplifiers for a living.

As you said, we don't know what the peak power capabilities of the Expert series are compared to their rated continuous power which may or may or may not be something that keeps you (one) awake at night.  If you listen to sine waves, probably not Smile  If you listen to loud electronic music via low-efficiency speakers, possibly so.

To follow up one of your earlier points, albeit slightly provocatively: how can you be /really/ sure that your Expert amp is not clipping?  That might very well be the case of course depending on what music you like listening to and how loud you listen to it, but the question still applies in principle.  While I'm sure we'd agree clipping is very easy to hear in traditional transistor amps when it's happening frequently or continuously, there are two factors relevant to this discussion that might make it harder to be sure.  Firstly, clipping on short transient peaks might not be so easy to hear and secondly, the Expert amps implement soft (so-called "elliptical") clipping which is supposed to be less obvious to the ear -- and I guess also less potentially damaging to tweeters.  Given that, you could reasonably ask why are we even discussing it, but I think in the more general case it's still a valid thing to talk about.
Roon (Mac Mini), Wilson Benesch Full Circle, Expert 1000 Pro CI, Kaiser Chiara
Warwickshire, UK
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#22
Thinking out loud: one way to be sure that you're not likely to be running into a peak power limitation on the Devialet is presumably to keep the volume control below about -20 dB.

(Assuming the volume control is such that 0 dB means full power output and -20 dB means 1/100 of full power output, both with maximum input level. And that the input level peaks approach maximum.)

Maybe an interesting poll: what is the maximum volume control level you regularly use on your Devialet?
Roon (Mac Mini), Wilson Benesch Full Circle, Expert 1000 Pro CI, Kaiser Chiara
Warwickshire, UK
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#23
After reading my post to RebelMan, I'm embarrassed for display such an inappropriate rant. My apologies to the members. It supplied nothing to the ongoing discussion.
Jim
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Roon for life, VPI Aries 3D le/Dynavector XV-1s, 1000 Pro, KEF Blade Two
Okanagan, British Columbia
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#24
Sorry, missed this earlier.

(07-Jul-2019, 23:25)RebelMan Wrote: I'll start with the second question first.  Power is not power.  Power is the measure to do WORK or the potential to do WORK.  In the strictest sense (as it applies to electronics) power is the amount of work that is needed to move electrons through a given medium.  When fewer obstacles are present electrons are more free to move and thus more work is needed to keep them moving.  The converse is also true, when more obstacles are present electrons are less free to move and therefore less work is needed to keep them moving.  So unless the system requires large amounts of power less will do.  How can anyone tell how much power they need unless they measured it?

What you have defined is energy.  Power is the capacity for work per unit time.  Never mind, it doesn't have that much bearing on the discussion.

One of the interesting points of the video was that it did indeed measure instantaneous power delivered to the load.  To be really explicit, the meters on the amplifiers showed the amount of power needed to drive the speakers with a faithful (undistorted) signal at the set volume level.

(07-Jul-2019, 23:25)RebelMan Wrote: GOOD, power that is sufficient in supply at any given time for any given load.

CLEAN, power that is free from artifacts inherent of the architecture's design and components.

LINEAR, as the demands for power increase (instantly or continuously) the supplies of power also increase in lock step.

None of those qualities are inherent to power in itself (where do they appear in the definition of power?).  Of course I agree that they are desirable characteristics of an amplifier.

(07-Jul-2019, 23:25)RebelMan Wrote: The problem with the video is that it does not indicate what the conditions are at that "instant".  What is the load when the amplifier displays 350W?  My example amplifies the problem when snapshots of power are taken out of context.  I made the assumption that the load was 6 ohms the instant 350W was needed to prove a point.

The video shows that the amplifiers are delivering up to 600 W per channel peak power into the load at some points.  Assuming the amplifier knows how to properly measure the peak power it's delivering, the power is just what the meter shows it to be whether it's into a 1-ohm, 3-ohm, 6-ohm or any-other-ohm load.  You don't have to make any assumptions whatever about the load -- or any other "conditions", for that matter -- if you believe that the amplifier is designed so that the peak power meters are accurate.

(07-Jul-2019, 23:25)RebelMan Wrote: How can you conclude that an amplifier needs 100 times more power available for peaks when we don't even know what those peaks are?  That's purely conjecture.  You cannot solve what you do not know.  Again how do you know?  You need to measure.

It's not my conclusion.  It follows directly from the definition of crest factor, as explained in the article I linked to, without any interpretation or assumptions on my part.  Neither is it conjecture, unless you disagree with the values of crest factor that are quoted by that article and other independent sources.  I am not trying to "solve" anything, in your words.

I suspect our conversation has gone beyond the point of being interesting or useful.  You're welcome to continue if you wish but I will bow out here.
Roon (Mac Mini), Wilson Benesch Full Circle, Expert 1000 Pro CI, Kaiser Chiara
Warwickshire, UK
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#25
(08-Jul-2019, 12:27)thumb5 Wrote: Thinking out loud: one way to be sure that you're not likely to be running into a peak power limitation on the Devialet is presumably to keep the volume control below about -20 dB.

(Assuming the volume control is such that 0 dB means full power output and -20 dB means 1/100 of full power output, both with maximum input level.  And that the input level peaks approach maximum.)

Maybe an interesting poll: what is the maximum volume control level you regularly use on your Devialet?

Your question in the previous post about how we would know if our amp was clipping on transients is a valid question and there's really no way, short of using something like an oscilloscope in real time, to tell. Most of us don't listen to music that way.

The volume control goes higher than 0 dB if I remember correctly. I'm forced to rely on memory since my amp is somewhere between France and here on it's return from repair for a faulty SD card slot. You know you're not in the world you grew up in when you need to get your amp repaired because it no longer reads SD cards. It should be back tomorrow and I can check then unless some inquiring mind wants to check in the meantime. I didn't just grow up in a world where amps didn't have SD card slots, I grew up in a world without SD cards.

Probably over 50% of my listening is done with the volume control at -20 dB or lower. I rarely go above -10 dB and usually that occurs with DSD files which seem to be 6 dB lower in level than PCM. I tend to only use higher levels with music with a high dynamic range which may mean that I could run into clipping given that I'm turning things up then because the average levels are low on many of the files I have with dynamic ranges of 15 dB or higher according to Roon. Most of the music I listen to has a dynamic range of 10-12 dB or so according to Roon but much of the more popular music I listen to, rather than my usual jazz, has a dynamic range of 7-8 dB or lower and I find myself reducing the volume level for much of that music.

It would be interesting to know how crest factor relates to the dynamic range measurement Roon uses. From reading what Roon have written about the dynamic range measurement in their user guide and other documents, it defines the range in which something like 95% of the music occurs, excluding the loudest peaks and the softest passages. It's not a measure of the range from silence to maximum peak level of the recording.
Roon Nucleus+, Devilalet Expert 140 Pro CI, Focal Sopra 2, PS Audio P12, Keces P8 LPS, Uptone Audio EtherREGEN with optical fibre link to my router, Shunyata Alpha NR and Sigma NR power cables, Shunyata Sigma ethernet cables, Shunyata Alpha V2 speaker cables, Grand Prix Audio Monaco rack, RealTRAPS acoustic treatment.

Brisbane, Qld, Australia
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#26
I vaguely remember hearing a while back that the volume control was arrange so that 0 dB was full rated power when the input levels were at max - for a digital input at least I suppose that's pretty well defined.  (I don't think I'm making that up...)  Maybe it has some additional gain available to handle lower-level inputs?  Another question to add to the growing list for Mathieu, perhaps.

Yes, I also usually listen with the volume control in the range -40 dB to -20 dB, with rare exceptions usually for orchestral music, and I don't think I've ever ventured above -10 dB.  My speakers are meant to be 87 dB at 1 m for 2.83 V input and have nominal 4-ohm impedance.  If I've got the maths right that means 84 dB at 1 W.

Interesting thought about whether/how the dynamic range indication in Roon might relate to crest factor. It makes me wonder what the DR value would be for the PanSonic track used in the video.
Roon (Mac Mini), Wilson Benesch Full Circle, Expert 1000 Pro CI, Kaiser Chiara
Warwickshire, UK
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#27
(07-Jul-2019, 22:27)MRebelMan Wrote:
(07-Jul-2019, 14:41)Confused Wrote:
(07-Jul-2019, 13:56)RebelMan Wrote: It puzzles me why you found the 170 so lacking as compared to the 240 when driving the Kef Blades.  I suspect the conditions between listening sessions differed significantly.

The amps were swapped in front of me, with everything else left unchanged, the same music was used too.  The D170 went first, and had been powered up and running for some time, so arguably it had an advantage over the "swapped in" D240.

Someone once said if you eliminate the impossible whatever remains however improbable must be the truth.  The 170 and 240 are bred from a similar (nearly identical) architecture.  Applying the aforementioned rule it would be impossible for the 170 to sound anything short of similar to the 240.  All that remains is the conditions of the test environment.  Nothing else changed?  How can you be so sure?  How did you confirm everything?  Surely you took level matched measurments before and after the swap?  Surely you measured the SPLs at the same position using the same sources before and after the swap?  See where this is going?

https://youtu.be/hmJiZ8VcfD4
1000 Pro - KEF Blade - iFi Zen Stream - Mutec REF10 - MC3+USB - Pro-Ject Signature 12
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#28
Joking apart (sorry, I couldn’t resist), I think Antoine’s post #20 is the most likely reason there was an obvious difference between the D170 and 240, with the Blades at least. In other words, the reason the amplifiers performed differently was due to the known technical differences between the amplifiers. No need for Sherlock Homes. In terms of level matching, we pushed the 240 as loud as I would ever want to listen, so irrelevant in this case.
1000 Pro - KEF Blade - iFi Zen Stream - Mutec REF10 - MC3+USB - Pro-Ject Signature 12
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#29
(08-Jul-2019, 04:03)Jim_Anderson Wrote: What I've gotten in moving up in the horse power range is more clarity - not limited to but predominantly with the lower registers.  When the dial is turned to the left, the music isn't getting louder - its bringing out hidden gems in harmonics, voicing, transients. 

So Mr RebelMan, as for the Devialet D1000 - you and I will have to disagree on it being a bragging rights thing.  I am very fortunate to have my current system. Is it the best - hell no, but it makes this old soul happy and for that I'm quite thankful.

I can appreciate the toe tapping feeling and the need to drive up the volume, it happens for me too.  It just doesn't take large amounts of power to get me there.  I typically listen at a continuous 76dB with spikes in the 84dB region.  When I feel like pushing the throttle I can reach a steady 85dB with peaks into the lower 90dB region usually between 92-93dB.  My 140 is capable of delivering 101dB to the listening position without breaking a sweat so there is plenty of headroom left in the tank should something more arise.

My speakers are pretty sensitive but the demands they place on current reserves given the low impedance they present (below 3 ohms)  requires a very linear amp to pair with.  Thankfully, the 140 is up to the challenge because it is capable of doubling down to 2 ohm loads making for a very robust and powerful "little" amplifier (420W for those that are curious).  Power figures for the 1000 have been all over the board (and much lower than they probably should be) so it is unclear just how linear it really is.  If we give the 1000 the benefit of the doubt and say it produces 1500 W into 2 ohms (like the Original d’Atelier) this would add an additional 5.5dB of headroom (round up to 6dB to keep the figures simple).

Would the extra 6dB the 1000 could muster sound any better than the 140 in my system?  Depends.  As long as nothing else changed with my system, my room and my listening habits, no.  In this example more power would have absolutely no impact on sound quality (which goes against the grain of popular belief).  However, if my speakers were swapped with some more difficult to drive and/or my room was over treated to sound lifeless and/or I played my music much louder than before would the 1000 sound better then?  Again NO!  Why?  Because the 1000 is doing what it did before only without clipping and distorting the signal.  The 140 may perform less competently in this example because it maybe clipping or distorting the signal and that could deteriorate sound quality.

In summary, a lesser amplifier will not sound inferior to a greater amplifier when doing the SAME work.  If a lesser amplifier is driven to work harder than before a greater amplifier will not sound better but the lesser amplifier may sound worse because it is doing MORE work. The ONLY way you can know for certain how much power you actually need is to measure how much power you actually use (or trying to use).  ANYTHING else is just placebo effects and/or misplaced expectations and/or bragging rights.

NOTE: These remarks are based on the 140 and 1000 having a similar architecture.  Other architectures may vary.
"Dream as if you'll live forever. Live as if you'll die today."
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#30
(08-Jul-2019, 04:49)David A Wrote: I've got a different take on peak levels and how much power you need.

I do think bigger amps can deliver benefits with many speakers and those benefits may sometimes be related to avoiding clipping at peak levels but I do think more often the benefits of a larger amp are simply related to a bigger and better power supply rather than the ability to deliver more watts without clipping. If I were still listening to the kind of music I listened to in the '70s and 80's at the level I listened at then and were still using lower sensitivity speakers like Dynaudio and/or I had a bigger room then I would definitely be running a bigger amp than the 140 but I'm not and so far the 140 is meeting all of my needs and delivering the best sound quality I've ever had. YMMV.

You bring up some good points, but those points are related to amplifier architecture not power in the manner that is being discussed in this thread.  There are differing philosophies on amplifier architecture that you somewhat perhaps unknowingly touched on.  Some implementations use a few large capacitors where reaction times are slower but the headroom is greater.  Some use a lot of small capacitors where the reaction times are quicker but the headroom is lessor.  Still others use capacitors that are a mixture of both where the reaction times are maxed but headroom is nil. The Devialet tends to fit the last of these.

Bigger amps do not deliver better benefits than smaller ones just because they are bigger.  I replaced two comparatively massive mono blocks with one slender Devialet and the benefits were just as good if not better.
"Dream as if you'll live forever. Live as if you'll die today."
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