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All this is related to the one smart thing atmasphere said about phase shift down into the audio band, but it was on another thread and the direct opposite to what he's trying to sell you here.Actually I'm saying the same thing here as well. But the above statement is in regards to amps lacking feedback. I am **also** saying that amps with **enough** feedback (plus 35dB) can have 0 phase shift in the audio band even without that bandwidth.atmasphere
this would only be true if there was a difference in phase-shift between the left and right channels:@roberttdid Absolutely correct. But that difference has to come from the signal, and the amp has to otherwise not mess with it. When we are talking about amps that have no feedback (which can be an SET or a class D amp) minor differences between the two channels can result in slightly different bandwidths and so a difference in phase shift between the two channels. To avoid this both channels have to have enough bandwidth that this is off the table.
I guess I’m doomed to not understanding this. I thought a phase shift like that shown in the plot where it dips is a negative shift which means a lag in the signal.No a negative "-phase angle" is what’s with the speaker bass loading, totally different, the dotted line ("-phase angle") in this Tannoy speaker review
This is "phase shift" on this Class-D https://ibb.co/jfd6tqy (no - negative wording at all) Like a sub woofer being 180 degrees out of phase to the mains, easily heard when it back in phase
And no you wouldn’t hear it if the whole audio band were 70 degrees out of phase from bass 20hz to highest 20khz. But only the upper/mids and highs are 70 degrees out of phase to the mids lower mids and bass, and this is what many listeners object to when the hear Class-D, coincidence? I think not. And why many say Class-D’s make great bass amps, agree on that.
The only fix is to raise the switching frequency 3 x higher, then the output filter and the 70 degrees of phase shift go up accordingly 3 x higher to around 80-100khz then. It as simple as the that.
As atmasphere correctly said on another amp thread
Bruno Putzey on phase shift in his purifi module.
The way I understand it if the phase shift is different between the two channels in a stereo amp then one signal would be slightly behind the other which would sound like distortion?
@atmasphere Is saying "to avoid this both channels have to have enough bandwidth that this is off the table."
Or I am still lost??
- 713 posts total