from blog of Paul McGowan of PS Audio:
My friend and fellow audio designer Jeff Rowland came by to say hi the other day. Jeff’s always a welcome guest as he and I manage to nearly always be on parallel paths when it comes to product designs. I found Jeff and friend Tim Jerome in our listening room playing music on the new amp we’re working on developing. I’ve written before that this new amplifier is a stunning breakthrough in audio reproduction and to date I haven’t heard anything close.
The amp technology I am referring to is, as many of you guessed, based on the new Hypex class D technology and sure to form Jeff had independently made the same decision and was on a parallel path to building his own version.
Stuck in the middle | PS Audio
meanwhile it looks like Theta postponed the launch of their Hypex-based amp. so it looks like we found one of the mysterious names to use NCOREs.
My friend and fellow audio designer Jeff Rowland came by to say hi the other day. Jeff’s always a welcome guest as he and I manage to nearly always be on parallel paths when it comes to product designs. I found Jeff and friend Tim Jerome in our listening room playing music on the new amp we’re working on developing. I’ve written before that this new amplifier is a stunning breakthrough in audio reproduction and to date I haven’t heard anything close.
The amp technology I am referring to is, as many of you guessed, based on the new Hypex class D technology and sure to form Jeff had independently made the same decision and was on a parallel path to building his own version.
Stuck in the middle | PS Audio
meanwhile it looks like Theta postponed the launch of their Hypex-based amp. so it looks like we found one of the mysterious names to use NCOREs.
guys the conversation on the PS Audio DAC is off topic. I'm going to split it off into a separate thread. moved to here --> http://www.diyaudio.com/forums/digital-line-level/220061-dacs-use-ncore-amps.html
Maybe he does, but i couldn't find it at the links.
I am asking something extremely simple. Hook a scope to the output, set sweep to free running oscillator frequency range (500kHz?) and get a reading of the amplitude.
You described your phono preamp getting upset if you power up your Class D amp. I did not fully understand what You ment by "even when it is not used" part. Did You meen that even if your amp (the Class D one) is not connected to any equipment (sources or speakers) powering up messes with your phono preamp?
Exactly that. There is a subtle change in phono pre noise and a not so subtle collapse of sounstage, change in tonality, reduction in microdynamics...
Wouldn't that imply that PSU of the class D amp is generating noise into your mains network which your sensitive (presumably with high gain) phono preamp picks up?
I am really out my areas of expertise, but how would that be visible in the output of amp if the PSU is generating noise back to mains network? And to make sure, I am not trying to imply anything, I just don't understand
It is certainly possible to test for this by running the pre on batteries. Common sense though would indicate against the PS being the culprit. Class D gets power from a linear PS utilising EI transformers. It doesn't appear likely that the mains supply gets significantly more polluted than it already is. Arm wiring on the tt, otoh is not screened or twisted over a significant length and can very well act as an aerial.
And then, there is also the question of magnitude. Several volts @500kHz in the speaker cable... And this is why i am curious about the Hypex.
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Well, I still haven't managed to get my nc400's back onto my lab bench - too many other projects. But from the measurements shown in that thread on audiocircle it seems that the output noise is less than 0.1 μW (THD+N, dominated by noise at the low end, is around 0.1 % at 100 μW). That would be 0.6 μV into 4 ohm...
Excellent Idea!
I really don't see how this figure is relevant. Output noise is certainly not measured at 500kHz...
My apologies - I thought output noise was what you were interested in. You are right in that those noise measurements only look at nose up to 20 kHz.
Great! Thanks! So 0,6 V peak-to-peak. I assume that is with open outputs? Wonder how it would look with a normal load...
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