Tube Watts vs. Solid State Watts - Any credence?

Hi Mapman,

In your last sentence you probably meant to say "drawing" rather than "delivering," the former (referring to AC **input** power) being consistent with class D's very high efficiency. While dynamic headroom, of course, has to do with the difference between short-term and long-term **output** power capability.

I don't have a great deal of familiarity with class D designs, so I'm hesitant to comment. But I seem to recall reading that some class D modules have limitations (measured in minutes) with respect to how long they can sustain their rated maximum output power. And also that amplifiers from different manufacturers using the same class D module will often have considerably different max power specs. So it seems to be a different ballgame when it comes to class D, that may be hard to pin down with respect to dynamic headroom. Not surprisingly, given the radically different technology.

Best regards,
-- Al

Geofkait,
You are either autistic(which happens to many Americans for known reason) or didn't grow up yet.

To be more specific, my tube amp has a 1040 joule power supply. In my "un-technical" way, I interpret that as "head room" because my amp presumably can handle short term power demands that exceed its rated power output of 150 wpc, subject to FR, speaker impedance and tap output impedance. Am I mixing and matching terms and concepts here??

Yes.

Its important to understand that the concept of 'dynamic headroom' and the resulting spec was entirely 100% marketing on the part of the manufacturers of inexpensive amps and recievers during the 1970s.

A worse amplifier has higher dynamic range? Worse how?

I did explain that in my prior post, here it is again: the amp has a small power supply that will not allow it to operate at full power continuously. On top of that, it would probably overheat if it did due to poor heatsinks. Further, it is biased class AB and likely exiting the A region with less than 1/2 watt output. These properties will allow the amp to put out brief spikes of power that otherwise its design does not allow in a steady state condition. The higher the headroom number (in db) the cheaper the amp.

Class D FWIW is not an exception to this rule of thumb- the best class D amps will make about the same power whether continuously or not.

"And also that amplifiers from different manufacturers using the same class D module will often have considerably different max power specs. "

I know that often different manufacturers interested in optimizing performance use customized power supply circuits to that end. Bel Canto with their M series amps is an example. Accountings I have read support the notion that the power supply used makes a big difference in class D amp performance as well, but given the nature of Class D switching technology, these can be much smaller and lighter than what is required to power comparable Class A or A/B.

I have also read of some high end Class D amp vendors using more traditional larger and heavier power supplies with their Class D amps to help assure the nth degree of performance I would assume.

Have a nice Day, Andrew.