How much amplifier power do you really need?

[David A]

Because de Devialet is fully digital it is a bit different and in particular you can know exactly what is the peak power.

You will never exceed 0dBFS (if you except the pathological situations where the reconstruction filter moves above).

If you look at the configuration file of your Devialet, you find a section like this (in my case this is a D220):

"ADH_CONFIG":{
    "VOLTAGE_0DB":51,
    "PUISSANCE_0DB":220
  }

It tells your you that the peak voltage is 51volt which corresponds exactly to 440W under 6ohms or a pure sinus tone with a RMS power of 220W. (The crest factor of a sinus is 3dB in power).

Jean-Marie

I don't think the meaning of this code has ever been clarified.  @Antoine asked for clarification back when the Pro series debut.  How are we suppose to interpret what this is saying?

I have never seen an amplifier produce more than about 4dB of dynamic headroom to serve signal peaks. Many amplifiers are capable of producing between 1-2dB. The Devialets (all of them) have virtually no dynamic headroom (0dB) according to the tests I have seen.  So how is it the 220 would have a crest factor of 3dB?

I suspect the "VOLTAGE_0DB":51 statement only pertains to the 220 when it is in bridged mode (dual-mono configuration) and that the actual peak voltage it artificial limited somewhere else in the code that is not evident in the snipet above.  Would you agree?

I'm stupid but I'm going to make a guess at what is being set in those lines for Power and Puissance.

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.