Class D is just Dandy!

One thing I'd like to see for the nCore modules which I can't find is output phase angle. If anyone can point me to a doc which has this I would appreciate it.

I notice that the ICEPower units do have some phase shift involved. It is minor compared to what your average multi-driver speaker and crossover will do, but it's significant. This is something the Technics SE-A1 compensates for in the input.

Erik,
Buried on page 5 of the NC400 spec sheet is the figure relating to output coil inductance. Typically, 10uH. This equates to an output impedance of 1.25 Ohms at 20kHz and SIGNIFICANT phase shift within the audio band.

Page 8, graph 9.1 is particularly telling. -0.5dB @ 20kHz is nothing to write home about. It also suggests serious phase shift problems well down into the audible spectrum.

I remember seeing more info somewhere about this,but I did'nt save it.

This is related to the nc400 only but I did'nt stress about it too much I just continue to enjoy them.I do like my 600 m's more than the 400, but I'm using my nc400 right now.

I hope this points u in the right direction,I way spend some time later looking for more info.
Kenny.

Hi Kdude,

That output coil is perfectly in line with the output coil in many SS amps.

Based on my simulations, this ends up being no more than about 10 degrees of phase shift at the top end. Far better than ICEPower. :)

Best,

E

George,
I have looked at at the Technics,very interesting,now we need other designers too go in that direction and evolve.

They can’t yet, as that technology needs to be taken up by the major semiconductor manufacturers Motorloa, Sanken, Fairchild, Toshiba ect.
Then the small Class-d manufacturers will be able to get them as well at a decent price.

Remember the guy http://epc-co.com/epc/Applications/ClassDAudio.aspx  that invented these special Gallium Nitride transistors that Technics use in that amp, also invented the Mosfet years back, and look where that ended up, every big manufacturer makes them now.

So hopefully it won’t be long, then all other Class’s of amps will become defunct, and there’ll just be Class-D.

Cheers George

+1 kdude66  This equates to an output impedance of 1.25 Ohms at 20kHz and SIGNIFICANT phase shift within the audio band. 

Just what I’ve been saying all along, would be great if you can post a link to this.
This is why it important to increase the switching frequency by hopefully x5, which then takes the filter up higher by the same amount, away from the audio band. And why the above transistor development (in my last post) is so needed to get it up there.

Cheers George