Who tried Class D only to return to S/S or Tube



And what were the reason you did a backflip back to S/S or tube.
As there are a few pro Class D threads being hammered at the moment, I thought I'd put this up, to get some perspective.

Cheers George
128x128georgehifi

George, the answer is... Yes, the current switching frequencies of approximately 500KHz in the power conversion modules are sufficient for some OEMs to implement some marvellous-sounding amps.... Kuribo and several others have already mentioned some example brands and models.


Having said this, and knowing how things proceed in technology, the word "enough" hardly ever applies, no matter where one stands in the evolutionary curve. Whether a switching frequency increase of 5X or 10X yields an audible enhancement or not, such featture will eventually be introduced at some time in the near/medium/long term future by module and SMPS manufacturers.


And with such next gen component parts, some OEMs will create even superior amps... While other ones will persist to develop "Creatures From The Black Lagoon", and all in between.


'Tis all in the handle, George!


G.

Kijanki, in your zeal for Class D I'm afraid you mischaracterize linear power supplies. Not all are cap input.

Choke input linear supplies do NOT draw power in "huge narrow spikes". In fact they draw power continuously throughout the conduction cycle, resulting in smooth, fast and clean power delivery. No "huge amount of capacitors" are needed since choke input supplies have very good inherent regulation.
I use choke input in everything I build, including amps, preamps, DACs, even for DC IDHT tube heaters. Best feature though is no RF nasties flying around the room, which are inevitable with high frequency switchers.
Ait, Choke at the input as well as choke and big capacitor in my Furman Power Factor correcting conditioner serve as filter. Charging Linear PS capacitors is still done in narrow spikes of high amplitude - no escape from that.  Current is switched on  and off when voltage is the highest (worst possible moment). Choke filters out spikes from the power cord but problems inside still exist.  Switching noise propagates thru the circuit affecting sound.  The only linear part in "linear supply" is that it is unregulated.  Output voltage still depends on the load while line regulation is zero.  I wrote about "linear" supplies, to show that switching can be done smarter in SMPS that has very tight line and load regulation - usually not possible in power amps linear supplies because of power dissipation in voltage regulators.  There are great sounding amplifiers with linear supplies, even without any input choke.  I’m only stating that it can be done better with quiet SMPS.  Switching supplies designed by Jeff Rowland are extremely quiet.  FAQ on his website explains why he abandoned traditional "linear" supplies.

http://jeffrowlandgroup.com/kb/questions.php?questionid=145


Kijanki,
I believe you misunderstand what a critical inductance choke input supply is. The input choke serves to smooth the current draw - I have attached two simulations of the power supply I use in my amps showing the current draw in the first power supply capacitor. The left half of the picture is the supply as-is (with choke input); the right half is the same supply set up as cap input.

http://i1243.photobucket.com/albums/gg559/Quagmire22/Choke%20vs%20Cap%20Input%20Supply_zpsnywzj0ww.p...

Notice that with choke input the draw is a smooth sinusoid. With cap input the draw is as you describe - sudden sharp pulses. The energy storage of the input choke smooths the current draw and also contributes to the very good regulation of the choke input supply.