To DPM or not? That is the question.

[Jean-Marie]

I am home today, and the Devialet has been running most of the morning.  I am listening at a reasonable volume level, but not that loud, the amp is on about -30dB.  About an hour ago I checked the temperatures, all high 30's to low 40's, except the companion power supply at 46.  I tuned DPM off, checked an hour later, still high 30's to low 40's.  Ummmm.   The highest temp I have is still 46deg on the companion power supply, the A amp temps are 42 master, 40 companion.  I have turned DPM back on, and after 10 minutes or so the temperatures do not appear to be dropping at all.  Another 20 minutes, still no change.  Maybe I need to try this another time what I'm pushing the system a little harder?

This does beg the question though, when exactly is DPM doing whatever it does?  Some have reported better SQ with it off, but many report no change.  Perhaps in some systems, some volumes, music types, speaker efficiencies etc. it is not actually doing very much, if anything at all.  I have been trying to find the appropriate Devialet white paper that covers DPM, but can't find it on line now.  It would be nice to remind myself of exactly how it works.

One use I have found for DPM is when using the Devialet in pass-through mode for the front stereo channels in a surround system.  This is one way of using a Devialet that can yield very high temperatures, so having DPM available for this is most welcome.

If I understand correctly what DPM does, it shall not greatly affect temperature when listening at low volume.

From what I understand, if you are listening at let's say -30dB on a D1000, (and with no SAM on for the simplicity of the explanation), it means that the Devialet will deliver at max 1W under 6 Ohms at 0dBFS. Even with DPM off, the Devialet already knows that it will never need to deliver more than 1W and adjusts its internal power and voltage accordingly.

My understanding of DPM is that it does the same kind of adjustment of its voltages and internal power, but dynamically according to the content of the music. 

Now let's imagine that the record you are listening to is having a 3dB Headroom, with DPM on, the D is able to divide his power by two.

if you are listening at -30dB, going from 1W to 500mW shall not change much of the temperature.

On the other hand, if you are listening at 0dB, the difference will be 500W with DPM on vs 1000W with DPM off. The difference if terms of temperature shall be much more noticeable.

best regards,
Jean-Marie