Audio Science Review of Expert 200.

[whatmore]

Stereophile also measured the 140 Pro:

THe 140 pro article states (my bold)
The spectrum in fig.9 was taken at 8Wpc into 4 ohms, the highest power the amplifier would deliver continuously without its protection operating

[ogs]

Amir has reached out to Devialet for a response.
There are questions that could easily be cleared up but I wonder if they will be as woefully uncommunicative on this as they are with pretty much everything else….

I'm sure we can depend on Devialet. They'll be just as silent here as we have become used to. If they do respond I'll be surprised

[petrik]

Does anyone know what kind of configuration was used when taking these measurements? Like were DPM, ICM, and SAM all disabled? I have understood that these should be disabled when taking measurements.

How was the analogue input configured?

[Antoine]

Does anyone know what kind of configuration was used when taking these measurements? Like were DPM, ICM, and SAM all disabled? I have understood that these should be disabled when taking measurements.

How was the analogue input configured?

He mentioned in the comments he disabled all DSP functions though some doubts did arise. The analogue input was set to 96kHz input sampling rate.

[petrik]

Does anyone know what kind of configuration was used when taking these measurements? Like were DPM, ICM, and SAM all disabled? I have understood that these should be disabled when taking measurements.

How was the analogue input configured?

He mentioned in the comments he disabled all DSP functions though some doubts did arise. The analogue input was set to 96kHz input sampling rate.

I continued reading the comments there and found out that he did not disable the DPM. It would be interesting if he could run the measurements again with all these three features disabled.
https://www.audiosciencereview.com/forum/index.php?threads/devialet-expert-200-amplifier-dac-and-streamer-review.12286/page-5#post-361325

[Bwaze]

Anyone knows why the Expert line has such a low protection threshold? I mean, I'm surprised that approximately 140W amplifier (at 6 ohm) switches off when outputting continuous signal at 5W or 8W at higher frequencies?


From Stereophile Devialet Expert 140 Pro review:

"I ran into problems when I tried to test for intermodulation distortion with my usual mix of 19kHz and 20kHz tones. The amplifier went into protection with sustained high-power, high-frequency tones, reducing the output level. The spectrum in fig.9 was taken at 8Wpc into 4 ohms, the highest power the amplifier would deliver continuously without its protection operating. "

Audio Science Review:

"My frequency response testing is at 5 watts as that is what I use in my dashboard. Turns out this amplifier cannot reproduce high frequencies reliably at 5 watts! It has some kind of limiter that kicks in and pulls power back. It also does that at low frequencies but at or past maximum power. That I can sort of understand but not the high frequency hold back. "

Are these tests so long that they trigger thermal protection? Is it a safety feature, a high frequency signal so strong would fry most of the tweeters?

[Confused]

With reference to a number of posts on page 2 of this thread, and latterly @Bwaze 's post above, I was interested in making a few "real world" measurements myself, just because I wanted improve my own understanding of these measurements, and what might going on in the tests.

I do not own an Audio Precision analyser, or anything remotely similar, so I am not able to repeat or challenge the measurements made by ASR, Hifi News or anyone else. But I do have a multi meter.

So, I connected some speaker plugs the cables on my multi meter, plugged it into the spare terminals on one speaker, ran a continuous 10kHz test tone, and checked the voltages at different gains on the Devialet. Initially I checked the voltage at very low gains, and then calculated the wattage this equated to. Reasonably confident that power levels were low enough, I then increased the gain. The first thing I discovered is my multi-meter is not that accurate with low voltage. You can set it for different voltage ranges, I used the 2V range and 20V range. As an example, the reading with 10Khz at -30dB was 0.1V using the 20V range, or 0.38V using the 2 V range. So one thing I have learnt is that I probably need to buy a better multi-meter, although my old one has served me well for what I need. I then repeated the above using a 15kHz tone. (which I was quite please to note that I could hear very clearly)

What I was particularly interested in understanding was exactly how much power a 10kHz or 15kHz test tone would require at anything up to 0dB gain.

To calculate the power, I needed to know the resistance that the Blades are presenting at the particular frequency. I do not have an impedance curve for the Blade, but Stereophile have published one for the Blade 2, which I think has the same HF driver, so this should be near enough. Here I conservatively took the impedance at 10kHz as 5 ohms, and at 15kHz 4.5 ohms.

These are the results:

10kHz tone:

-30dB gain, 0.08V, approximately 0.001W
-20dB gain, 0.38V, approximately 0.03W
-10dB gain, 1.44V, approximately 0.41W
0dB gain, 5.8V, approximately 5.8W

15kHz test tone:

-30dB gain, 0.02V, approximately 0.0001W
-20dB gain, 0.21V, approximately 0.01W
-10dB gain, 0.88V, approximately 0.17W
0dB gain, 4.0V, approximately 3.6W

In an earlier post @ogs made the point "Your Blades are quite sensitive at 91dB (2.83V/1m). 90dB SPL at your listening position would be around 2 watts..." In terms of normal listening, I agree with ogs here. Normally I use HQPlayer with upsampling, and run HQPlayer at -4 dB to prevent issues with inter-sample clipping. Even with this, I am usually at -20dB or lower, and rarely go above -10dB even with "quiet" recordings played loudly. I mention this because with the above figures, HQPlayer was set to 0.0dB, so even with a level of gain way above what I would ever normally use, the highest wattage I have measured is 5.8W for the HF tone. In normal use, running my system with 0dB gain would lead to very high volumes, certainly enough to cause hearing damage, possibly enough to cause speaker damage.

This makes me think that to get higher wattages during the kind of tests ASR and Stereophile are doing, you would need to run a very high voltage, equivalent to huge positive gain, into the Devialet's analogue input. This is the only way I can see how you could get to 20 or even 10 watts. Have I got this right? If so, I assume the Devialet sees the high voltage on the analogue input, it thinks this is wrong, and shuts down. I am speculating a little here, so would be interested in the views of others here.

In practical terms, say if you wanted to use your Devialet for something like listening to music at a reasonably high volumes, I would say the above numbers suggest this testing anomaly is not of too much concern. Thankfully, trying this test did not cause my Devialet to shut down, and it has not fried my speakers. For this I am very grateful (I was a little worried about trying this) and I shall now proceed to using my Devialet for the above mentioned purpose.

[thumb5]

@Confused - Firstly, well done for taking the bull by the horns and for avoiding any accidents in the process!

Interesting results.

On the face of it, the numbers show that the power output is increasing more or less linearly as you increase the volume in fixed logarithmic steps, which is good to see.  There are some fairly wide variations but it's possible that these are as much due to the meter and assumptions about the load as to the amp itself, I guess.

However the fact that there's no sign of limiting might be because the input level was too low to push the amp into that mode even when the gain was turned up to full (0 dB).

Do you know what input level you were pushing into the amp, either in dBFS or volts RMS -- and if the latter, what's the configured maximum level of the corresponding input?

It might be interesting to see corresponding numbers for (say) a 1 kHz input at the same input level.

I tend to agree with you that for all practical purposes if there is an output power limit that affects high frequencies it probably doesn't affect music much because there isn't much power at 10 or 15 kHz anyway.  But there is still something niggling away at me asking: if it can output 1000 Watts at 1 kHz, why can't it also output 1000 Watts at 15 kHz?  Is the output power limited to protect the load, or to protect the amplifier itself?  Maybe there is something inherent in the ADH design that limits the power output at high frequencies?

Now I start to think about it: perhaps the digital (PWM) output section is less able to dump current into the load as the frequency increases.  It does have a ton of inductance in series with the load, after all.  In the extreme case if the frequency is high enough, perhaps only the class A part of the ADH section might be able to drive the load.  (I'm just thinking aloud here, and could be on completely the wrong track so don't take it too seriously.)

I remember hearing -- but never seeing -- that Devialet used to demonstrate the ADH section of the amp by removing the class D output section and just running it as a class A amp. There's a very vague memory that the output power in that mode was about 5W. Hmmm.

[Cylob]

A.f.a.i.c. Armir lost all credibility in the EtherREGEN discussion. Measuring, not listening and jumping to negative conclusions is bad form. Not even going to bother reacting to his 'review'. Hope nobody from the Devialet scene does. That is just what he seems to hope to achieve.

Isn't measuring and not listening exactly what the Devialet engineers claimed to do at some point?
Not sure where I read this on this forum, but I was gutted to hear that.

[David A]

A.f.a.i.c. Armir lost all credibility in the EtherREGEN discussion. Measuring, not listening and jumping to negative conclusions is bad form. Not even going to bother reacting to his 'review'. Hope nobody from the Devialet scene does. That is just what he seems to hope to achieve.

Isn't measuring and not listening exactly what the Devialet engineers claimed to do at some point?
Not sure where I read this on this forum, but I was gutted to hear that.

I guess that there's at least 2 types of "measuring and not listening". One type is done by people who believe that a certain type of result gives an improvement in sound quality so, when designing a new device, they measure to see whether they're getting more or less of the thing they're interested in. That, I think, is the way Devialet works but, if I remember correctly, the comment made said that having got the kind of results they were looking for in their measurements, then they did listen to make sure that it sounded right.

The other sort of "measuring and not listening" is done by people who believe that measurements predict how something will sound. They measure what they believe is critical to good sound, which may not be what other people measure or think is critical to good sound, and assume that the measurements they have are sufficient to tell them how the component will sound. Listening is an afterthought for some of these people.

There's a difference between measuring in order to help you reach a certain desired result and then listening to see whether that result gives you what you want, and measuring in order to find out how things are going to sound because you believe that the sound of the component will be revealed by your measurements, and then listening to confirm your belief.

I thought that Devialet comment was interesting when I read it but I definitely wasn't gutted. I thought it was a quite different way of developing a product and quite different from the way I would go about it if I knew enough to be able to design an amplifier but then different people do work in different ways. Given my own personal approach to things, I find it interesting and perhaps even reassuring to find that I can listen to and find a lot to like in an amp designed by people with a very different approach to me. I find it reassuring because it indicates that, despite the differences in approach, we're all still interested in getting a sound we like.

How meaningful are measurements when it comes to predicting how something will sound? Well, you might well be able to predict some characteristics of the sound from a given set of measurements but, when one considers how different the measurements from a Devialet and from a single ended tube amp are, it's actually very apparent that the results will tell you nothing at all about whether an amp will be assessed as good or bad by a particular listener. I'm very happy with my Devialet and I doubt I would ever want to go down the very high sensitivity speaker and low wattage single end tube amp road but over the years I have heard a number of such systems which I really liked. I think measurements are valuable for a lot of reasons but I don't think they're always predictive of the final sound and I've never found them predictive of whether or not I'm going to like a product.