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How much amplifier power do you really need?
#71
@Jean-Marie

I don't think the extra power you have with a single 220 has any real benefits apart from the fact that if you really want to turn things up to 0 dB on the volume setting you'll get 2 dB louder peaks than you got with the 120 :-) Of course, since your current volume setting is -8 dB, those extra 2 dB mean that your peaks will be 10 dB louder than you're getting at a -8 dB volume setting and a 10 dB increase in volume, not only on the peaks but on all of the music regardless of level, means everything would actually sound a bit over twice as loud to you. Do you want to listen to music that's twice as loud as what you're currently listening to? Obviously not or you would be listening at higher levels right now.

If you were using SAM before with the 120 and had power in reserve and you're using it now with the 220 and have 2 dB more power in reserve, then it's a bit hard to say that upgrading from the 120 to the 220 has made an "appreciable difference" for you with SAM. You're not doing anything more with SAM now than you were before. If there is an "appreciable difference" then it's going to have to be in areas other than peak volume or SAM functionality for you because you're still listening at the same level and using SAM in the same way. Note that I'm not saying that there are no benefits from using a bigger amp. All I'm saying is that you're not getting any benefits in relation to peak volume or SAM functionality because you had enough power for both before given your needs and you're not using any more power now, the extra "headroom" you gained going from the 120 to the 220 has just been added to the headroom you had in reserve with the 120.

In terms of peak volume levels alone, ignoring whatever extra power SAM requires, I can easily see some people needing a 220 rather than a 140. Someone with a taste for louder music than you or I have, less sensitive speakers than you or I have, and a bigger room with a longer listening distance could easily need more power than a 220 provides and be looking at a 440. A 440 would give you 3 dB more power than you currently have, giving you 11 dB of headroom. You could run through that 11 dB easily and end up needing a 1000. A desire for 3 dB higher peaks, 5 dB less sensitive speakers than yours (there's more than a few 83 dB sensitive speaker options available) and larger room and a 5 metre listening distance would eat up all of your 8 dB peak volume reserve and the extra 3 dB that a second 220 would provide and have you running the 440 at a 0 dB volume setting to deliver the peak levels you wanted.. Go for an 82dB sensitive speaker rather than an 83 dB sensitive one and keep the same peak listening level and listening distance and you'd be looking at a 1000 because a 440 would deliver 1 dB less than what you needed.Every extra dB you need to meet your requirements chews up an increasing number of watts. Going from a 220 to a 440 only gets you an extra 3 dB to deal with higher peaks. lower sensitivity, or greater listening distances and going from a 440 to a 1000 probably only buys you another 4 dB. Infinite power may not be necessary but every time your power requirements increase they increase by bigger and bigger amounts. No one needs infinite power but with the right speaker choice (should that be the wrong speaker choice?), a taste for louder music, and a big enough room it's possible to create a need for more than a kilowatt of amplifier power and outgrow the 1000.

The fact that I'm happy with a 140 and you're happy with a 220 doesn't mean that there aren't people with a legitimate need for a 440 or 1000 or greater to meet their needs. 1000 W or more may not be infinite power but it's still something that easy for someone in our positions to shake our heads at in disbelief until we start looking at just how many more watts every extra dB we need over what we currently need is going to cost us in watts.
Roon Nucleus+, Devilalet Expert 140 Pro CI, Focal Sopra 2, PS Audio P12, WireWorld Starlight ethernet cables, Cisco SG110D-05 network switch, Kimber Select speaker cables, Shunyata Alpha NR and Delta EF power cables power cables, Grand Prix Audio Monaco rack, RealTRAPS acoustic treatment.

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#72
(14-Jul-2019, 09:34)thumb5 Wrote: Purely in the interest of science, you'll understand, I extracted the audio track from the YouTube video in the original MP3 format.  Here's Audacity's frequency analysis:



ETA: according to the relevant page in the Audacity manual, this is an amplitude spectrum.

Incidentally Audacity says that the track has full scale (0dBFS) samples and the RMS value is about -13 dB, which I believe means a crest factor of 13 dB.  The waveform diagram shows the samples in dark blue and the RMS value in light blue:



At the risk of stating the obvious, it's worth pointing out that this is not the exact same audio the guys in the video were actually playing (unless they've also invented time travel); presumably they were using an original, uncompressed version of the track.
I am completely new to Audacity, I have just downloaded a copy this morning.  So I have not yet worked out the significance of the various parameters and similar.  However, I did manage to get this from the native Laptev Sea track:

   
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#73
(14-Jul-2019, 08:53)Confused Wrote: @Stefan - Thanks for posting the measurements, good stuff.  As I mentioned in another thread, I often consider myself to be a frustrated objectivist.  That is, I rely on subjective observations simply because there is not enough objective data around that corelates with what I am hearing, in many areas there is no decent data at all.  

As a general point, it is always good to see some measurements.  It might be useful if between us we collect all the available Devialet test data relating to power.  It would be good to have it together in one thread, so if anyone knows of any power related measurements, please post!

@David A - Lots of detailed information as always.  With respect to your post #66, please note that I was not complaining about the "how much power does a Devialet produce" posts, quite the opposite, I fully agree that these are related topics.  There is some interesting reading there on many related topics.  My take from it is that what you have stated is more or less in line with my estimate that the SPL in the video was maybe 90 to 95dB(a), and certainly less than 100dB(a).  You make no view on this, I am guessing you position is that it is impossible to say with any certainty?  (you strike me as a cautious man who prefers not to speculate)  OK, there is some speculation here, but from about the 6:00 min mark in the video you can just about make out the voices, not what they are saying, when the camera and microphone are about three to four metres away from those talking.  After 7:00 min when the camera closes up on one attendees smart phone to show the track name, you can clearly hear his voice, it does not sound like he is shouting, and the camera is maybe half a metre away.  So based on your comments, would you be happy to estimate SPL's below 100dB(a)?  I would be interested in you view here.

Regarding your post #67, you make this statement:

Let's say you had 85 dB sensitive speakers and a 4 metre listening distance. We still need to get 101 dB at 1 metre for 92 dB at 4 metres so that's an extra 16 ddB. You still need less than 100 W. 100 W would deliver a 20 dB increase in level so a pair of 85 dB sensitive speakers would deliver a 95 dB level at 4 metres with 100 W.

I fully agree with this in terms of your calculations.  If my earlier assumptions re SPL are about right (if), then what you describe above is more or less in line with what we find in the video, in terms of the SPL's, the sensitivity of the speakers and the listening distance.  Yet, the amps are not showing 100 w, nothing close, they are showing 700 w.  OK, there are assumptions here and a fair margin or error, but the end result is a factor of 7 different.  I think there are some "real world" complexities here that the basic calculations do not fully address.

As am open question to all.  I have been thinking a bit about audio reproduction and the dB "A weighted" scale.  I have attached a dB weighting graph here for easy reference.  What I am thinking about is the fact that human hearing is far less sensitive to sound at lower frequencies, so with equal energy, a sound at 1000Hz will sound to a human a lot louder than a sound at 100Hz.  This is well known.  To me, the obvious consequence of this is that to produce a sound at very low frequency that sounds reasonably loud to a human will take considerably more power than to produce something equally loud at around mid range frequencies.

This is relevant to the Pan Sonic track.  It has a lot of low bass content, right down to frequencies more felt that heard, so not just below 100Hz, but dipping below 20Hz.  (maybe someone has software that can analyse this aspect the track?)  Looking at the a weighted scale, these low frequencies sound -30dB down to human hearing at say 40Hz, even more as you drop to 30 or 20Hz.  -30dB is a lot!  So if you take the power needed to reproduce 1000Hz at 90dB(a), then you would need fully 1000 times the amplifier power for an equally loud sounding sound at 40Hz.  I am thinking aloud a little bit here, but could this be a factor in what we are seeing in the video?

I haven't watched the video. I'll try to do so and comment.

Re the dBA scale: Don't use it!!! The dBA weighting scale was designed specifically for assessing the risk of hearing damage. The bass rolloff is there because our ears become less sensitive at lower frequencies and noise at those frequencies provides less risk of hearing damage than the higher frequencies where the curve is flat. If you want to know whether you're likely to get hearing damage at your listening levels use dBA weighting with an option that averages the levels being measured and calculates a noise dose based on 8 hours continuous exposure to those levels. That's the way dBA weighting is intended to be used.

If you want to know about how much power your amplifier is putting out then ideally you'd use a Flat measurement, ie no weighting curve at all, because low frequencies are important in terms of their impact on power needs so you don't want to downplay their contribution by using a weighting scale that rolls the bass off. A lot of the meters that get sold for use by non-professionals only offer 2 options, dBA or dBC weighting scales. If they are the only options you have, use dBC. It still has a roll off in the bass but it's a smaller roll off than the dBA weighting uses so it gives a more accurate result for the purposes we've been discussing here but it's still neither accurate nor the best option for our sort of purpose.
Roon Nucleus+, Devilalet Expert 140 Pro CI, Focal Sopra 2, PS Audio P12, WireWorld Starlight ethernet cables, Cisco SG110D-05 network switch, Kimber Select speaker cables, Shunyata Alpha NR and Delta EF power cables power cables, Grand Prix Audio Monaco rack, RealTRAPS acoustic treatment.

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#74
(14-Jul-2019, 12:52)Confused Wrote: ...
I am completely new to Audacity, I have just downloaded a copy this morning.  So I have not yet worked out the significance of the various parameters and similar.  However, I did manage to get this from the native Laptev Sea track:

I noticed that your FFT uses a larger number of frequency bins, which is a good thing as it gives much better resolution in the low-bass region you're interested in. In retrospect I should have done that in the spectrum I posted earlier. Having tried it I don't see any obvious difference between the native track and the MP3 I used before.
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#75
(10-Jul-2019, 09:44)RebelMan Wrote:
(10-Jul-2019, 00:40)David A Wrote: Since they occur in the section for ADH config, I'm going to guess that the line for Voltage defines the setting for the class A amp which supplies the voltage and the 51 V that it shows for Jean Marie's 220 equates to the voltage for 220 W output per channel for a 220 in stereo mode. 

"Puissance" seems to translate to power. There's a setting in the configurator's speaker section where you can set maximum power output and the maximum you can set is your amp's specified power (that's also the default setting) but you can limit to to a lower output. I suspect that the 220 shown in Jean Marie's file indicates that he has chosen to leave that setting at the maximum for his 220. If you have a dual amp setup I suspect the maximum/default will be the mono output so for a 440 which is comprised of 2 220s the figure shown would be 440 which would be the power output from 51V for bridged mode for the amp.

If you limit the power output I think you'd see a lower number for Puissance reflecting the lower wattage limit you've set and that the lower output would be reached at a 0 dB volume setting. Maximum power output, whatever you set it to, will always be reached at a volume setting of 0 dB. I don't know whether the voltage value will also change if you limit maximum volume but it may also.

Basically, taken together, I think those 2 values control the settings for the Class A and Class D amps respectively given the maximum power output you choose in the speaker settings in the Configurator.

Just a guess as I said but there''s no reason to specify ADH configuration if you don't give the user the option to vary maximum power output and given the fact that the Devialet is a Class A/Class D hybrid it would seem to make sense to have separate values for the Class A and Class D stages if you are going to be able to vary output.

I've got a 140. That section of my config file shows 41 V and a Puissance of 140. I think if I added a companion to make a 210 the file would show 41 V and Puissance 210.

The logic behind your hypothesis follows but some of the math is still elusive.  Looking at the 220, max voltage is set to 51V at 0dBFS and the corresponding impedance at this voltage is 6 ohms.  Power in this case computes as 434W which is almost twice what the 220 is rated for.  @Jean-Marie suggests this to be peak power.  If we apply the math to the 140 using your figures power computes to 280W peak which is exactly twice what the 140 is rated for continuously.  If power from the Devilet 140 and 220 are not artificially limited (somewhere in the code) then where did the peak power go?

According to HiFi World the Expert 220 Pro reached a peak power of 190W into 6 ohms which is nowhere near the 434W computed from above.  @Jean-Marie suspects this is due to the evaluation unit being tested with SAM enabled. However, Audio was unable to measure the peaks of the Expert 140 Pro because the sophisticated power protection circuits prevented it...   

"It is worth mentioning the presence of a special protection circuit, which, after exceeding a certain input voltage (sensitivity), does not allow distortion of the terminals, so distortions do not increase, but stop at a level even lower than the standard THD + N = 1%. Hence, our results concern such conditions, because it is the highest power that can be obtained."

It would seem peak power may never be reached regardless of the amplifier's ability to produce it because it's trying to play it safe.  If this is true then the 220 has a major handicap.  I confirmed with Devilalet that continuous power of the 140 and 220 is as follows...

                 Expert 140 Pro            Expert 220 Pro
8 Ohms      105 W                        165 W     
6 Ohms      140 W                        220 W
4 Ohms      210 W                        330 W
2 Ohms      420 W                       330 W

If peak output power is limited to continuous output power (as multiple tests have shown) because of the protection circuits then that can be a problem for people with speaker impedances that dip below 3 ohms and mine do.  For the people that still believe more power sounds better than less power, have some crow.

I have asked Devialet about the 2-ohm continuous power of 220 Pro in two different occasions before and got two different answers: 660W and 500W respectively. Not that I think the answers I got are more accurate (I shouldn't have got different answers in the first place), but I can't understand how a 220 Pro could do worse than a 140 Pro for a 2-ohm load, given that they have the same chassis and the power supply of 220 Pro should be no worse than 140 Pro (if not better). I am curious to know if the above power figures quoted for 140 and 220 were all provided by the same person? 

BTW, just for additional information, I found another review from the Stereo magazine ( https://stereo-magazine.com/flipview/epaper/stereo-magazine-20-2019-20/ which posted somewhat better measurements for the 220 Pro than what Hi Fi World did: 173W at 8ohms and 343W at 4 ohms. Not sure which review is more correct, but to me the differences are not night and day and could be just due to different test conditions.
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#76
David A Wrote:Re the dBA scale: Don't use it!!! The dBA weighting scale was designed specifically for assessing the risk of hearing damage. The bass rolloff is there because our ears become less sensitive at lower frequencies and noise at those frequencies provides less risk of hearing damage than the higher frequencies where the curve is flat. If you want to know whether you're likely to get hearing damage at your listening levels use dBA weighting with an option that averages the levels being measured and calculates a noise dose based on 8 hours continuous exposure to those levels. That's the way dBA weighting is intended to be used.
Agreed.  I did a little bit of reading up re the dBA scale and it appears to only be relevant to "relatively quiet" SPL's.  There might be some debate about how loud the music was playing in the video, but I suspect we can all agree that it was most likely not "relatively quiet".  Fletcher Munson might be more relevant I think, but maybe drifting off topic here.

(Some kind of Fletcher Munson widget might be a nice use for all this new Devialet DSP power that is going spare in the CI Board? - but that's definitely off topic here)
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#77
(10 hours ago)Confused Wrote: Agreed.  I did a little bit of reading up re the dBA scale and it appears to only be relevant to "relatively quiet" SPL's.  There might be some debate about how loud the music was playing in the video, but I suspect we can all agree that it was most likely not "relatively quiet".  Fletcher Munson might be more relevant I think, but maybe drifting off topic here.

(Some kind of Fletcher Munson widget might be a nice use for all this new Devialet DSP power that is going spare in the CI Board? - but that's definitely off topic here)

Actually, when it comes to hearing protection concerns which is what the dBA scale was designed to be used for, it's high volume situations that it's relevant to. "Relatively quiet" SPLs aren't going to damage your hearing but high SPLs will. Our hearing is most sensitive in the mid-range frequencies (that's what the Fletcher Munson curves show) and that's where noise related hearing damage occurs first, not in the bass and high frequency regions. The dBA scale gives a measurement which is dominated by the loudness in the frequencies where the ear is more sensitive and therefore more easily damaged and gives progressively less emphasis to those low frequencies which present a lower risk to hearing.

Normal hearing protection recommendations tend to take effect at levels equivalent to an 85 dBA average for a continuous 8 hour period. If you have an environment in which the sound reaches that level and you measure the SPL using the dBC scale you'll get a higher reading, and if you measure it using a flat scale (no weighting) you'll get an even higher reading. If you use the dBC or flat measurement as a measure of the risk of hearing damage you'll overestimate the risk. The dBA scale gives a more accurate idea of what the risk of hearing damage will be.

Re your idea of a "Fletcher Munson widget" to make use of the DSP power in the CI board, it's not necessary. What the Fletcher Munson curves show us is that you have to play notes in the bass range louder than notes in the mid range if you want them to sound as loud as the notes in the mid range. If the bass player plays his notes at the same SPL as the singer/guitarist/pianist is playing their notes, the bass player will sound softer than those other musicians and you'd need to either turn the bass up, or raise the level of the music overall, or a bit of both in order to make the bass player sound as loud as the other musicians. In practice you don't have to do that because the bass player knows how loud he/she wants to sound relative to the other musicians so he/she plays at a level that produces the level balance the musicians want you to hear. Basically all musical groups are effectively delivering EQ to compensate for the frequency differences in our hearing sensitivity when they play because each of them plays loud enough to proceed the balance of sound they want the listener to hear. We want our amps and speakers to have a flat frequency response so they don't exaggerate one part of the frequency band and minimise other parts. The music being played doesn't have a flat response, it has a response with some notes louder than others at a given moment so that the balance of those notes "sounds right" for what they're trying to do, and they determine what "sounds right" based on how loud each musician's notes sound. They're automatically compensating for the hearing behaviour the Fletcher Munson curves show as they play and equipment with a flat response ensures we hear music as the musicians intended us to do.

That's why when it comes to any of the concerns about sound pressure levels we have when assessing equipment, we need to use a flat measurement rather than a measurement made using a weighting scale like the dBA and dBC scales. Flat measurements tell us what we need to know when it comes to assessing power requirements because they tell us how loud the sound being produced is and that allows us to calculate how much power we need in order to get the levels we want.

Actually, if I'm correctly guessing what you would want your widget to do, your Devialet already has 2 widgets that do what you want, the bass tone control and SAM. If you can't get loud enough sound overall with the amount of bass you want when you have your volume set to 0 dB and your bass tone contol and SAM, you need a bigger amp. If the bass doesn't go low enough at peaks with your bass tone control and SAM adjusted then you need speakers with more bass extension.
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