Questions For Interview With Bruno Putzeys & Lars Risbo About Purifi Audio

[maty]

A year ago I opened a thread in the diyaudio forums asking about the phase shift in class D technology and its influence on the sound and I still do not know the answer.

 

In class A and AB technology, this shift is less than 6 degrees at 20 kHz, which almost nobody specifies. But in class D it is much higher!  There is a new module, IcePower 1200AS2 that reaches up to 70 degrees!!!

Phase shift in class D amplifiers. How it affects the sound?

 

Specially with acoustic instruments and "natural" voices (without autotune, vade retro satana).

I take the opportunity to raise the issue directly, thank you very much from Spain.

[maty]

Second question.

 

Yesterday I read a very interesting article wrote by Bob Katz a year ago.

 

https://www.innerfidelity.com/content/katzs-corner-episode-25-adventures-distortion

 

Quote

In today's investigation I aim to get a handle on how to use distortion to improve the sound quality of our playback gear. Yes, I said "improve", because we're going to redistribute the harmonic emphasis of our signal chain. Not all amplifiers with ultra-low distortion sound harsh or small: Notable among good sounding (or at least sonically neutral) low-distortion amplifiers is the Hypex Class D amplifier, invented by Bruno Putseyz. His recent model, the Hypex NCore, has near zero harmonic distortion and is audibly close to the proverbial straight wire with gain.

 

No distortion sounds better than a little bit of bad distortion, but moderate, well-distributed distortion sounds better, too!. I believe there's a middle amount where distortion can sound deadly. Why? Because in that middle area, where the overall distortion measures somewhat low, but not close enough to zero, the presence of some higher harmonics can psychoacoustically predominate over the important lower ones. In other words, the distribution of the distortion is the key to sonic differences.

 

What do you think about predominant H2 and other decreasing monotonous harmonics? To enjoy the music at home.

 

[IMG, link] http://maty.galeon.com/WP-imagenes/hum/xrk971-Alpha-20-2.87vrms-8ohms-FFT.png

 

[maty]

57 minutes ago, mocenigo said:

Yes and no. Class D amps have a phase rotation that is a linear function of the frequency. This is just a delay. So in fact this is often much better than irregular phase rotations as in A and AB amps. Luckily, the rotation of the latter are much more contained.

 

NCore also has much smaller rotations than ICEpower and, it seems, ICEEdge - I expect the same for Eigentakt

 

Still, it would be VERY INTERESTING to hear Putzeys take on the matter.

 

 Roberto

 

 

Bambino, hai un regalo per posta.

 

Sag mir was du denkst.