Negative Feedback a deal killer?

Aljordan,

In my post I expressed NO JUDGMENT of the sound of H2O and other amplifiers which use B&O ICE Module whatsoever. I knew in moment I will do it people like you will attack me and I like to be attacked exactly the same as next guy. If you still feel offended then my sincere apologies - we really talked about differences in designs and their effect on even/odd order of ditortions as well as capability to drive difficult loads.

"...they sound different from other ICE module amps"

Here, I must take issue this this statement. Firstly, if linear power supplies used are BEEFY then most certianly this amplifier will have better dynamic range then all others based on tiny switching power supplies (again - huge exception is Jeff Rowland). So here I agree with you but in regard of the dynamic range only.

Secondly, if your amplifier is reasonably neutral and B&O modules certainly are then any change (say in PS wire or input capacitor) will produce somewhat different texture, so obviosuly each of them will sound slightly different but their main sonic signature is determined by their input/output stage...which are identical or nearly indentical (with some mods) in all of them.

Cheers

"better dynamic range then all others based on tiny switching power supplies (again - huge exception is Jeff Rowland)"

Not only that most (if not all) of Rowland Icepower amps use SMPS supplies but he uses them as well in Capri preamp and new generation of class AB amps. Rowland amps like 102, 201, 501 use standard B&O modules with built in SMPS.

Magfan, to answer your question, in a power amplifier of conventional design (not class D IOW) the problem you face if you use local feedback as opposed to global is the issue of gain. IOW if the stage that the feedback is around does not have a lot of gain, it may not help you all that much. Where this really plays a role is in the output section, wherein if the amplifier is to conform to the ideals of the Voltage Paradigm (IOW, be a voltage source), there is rarely enough gain in the output section for said local feedback to do the job.

I did say rarely: the Ayre amplifier is able to be a voltage source without any feedback.

Anyway, you encounter many of the same problems with local feedback as you do with global, but overall I would say they are less pronounced, as (in theory) a single stage is going have a shorter propagation delay than an entire amplifier. This will tend to push the time domain issues to manifest at a higher frequency. That does have its good and bad side, so again a lot depends on the actual design!

How I see all this is very simple: as long as the amplifier fails to add **any** distortion to the 5th, 7th and 9th harmonics, then it all should be good. It will be even better if the lower ordered harmonic distortions fail to appear as well, although this is far less important.

Dob,

Mentioned Rowland 102, 201, 501 have standard SMPS without anything coming from Rowland. You can buy amplifiers with built in PFC like model 312 or buy additional power supply but most of Rowland Icepower amps have only standard B&O modules with integrated SMPS.

Please check power amp listed in my system before you make another silly personal remark involving elephants.