Need technical explanation

Wow. Both excellent replies. Thanks very much. I thought discreet must have meant separate power amps but wasn't sure. So a 7.1 A-V receiver (for example) then has 7 separate and distinct amplifiers.

Kirkus, you must be a graduate electrical engineer or audio engineer. Fantastic explanation. To me, distortion is of the utmost importance since I listen at at an average of 90 dB's and it's distortion that damages hearing more than background noise (my best guess on that). So "current feedback amps" would be the better choice but probably a very subtle difference.

Can I ask you another question? Do the internal amps inside these A-V receviers get physically larger the more watts RMS they produce and output? For example, a 110 x 7 watt into 8 ohms receiver would have physically larger amps inside the unit than say a 90. Is that correct? Many thanks again to you both.

Well actually, the "number of separate amplifiers" is simply the same as the number of channels . . . in the same sense that all "stereo" power amplifiers have two channels. Most of the time these days I'd expect a "7.1" receiver to have seven channels of amplification, one for each of the surround-sound speaker outputs. Usually when there's a "speaker B" or "area B" outputs, this doesn't include extra amplifiers to run them . . . they just tack on a switching relay and a couple more binding posts so you can easily hook up more speakers to the same amplifier. Usually also there isn't an amplifier for the ".1" output (subwoofer or LFE channel), because most people hook this up to a powered sub.

When they say "discrete", they're referring to the individual parts that make up each amplifier. Most semiconductor manufacturers offer a smattering of "amps on a chip", that are the audio-engineering equivalent of a cake mix - most of the parts are ready to go in a pre-done package. By saying that it's an "all-discrete" amplifier, Marantz is basically bragging that they made all seven cakes (amplifiers) from scratch, rather than using a mix.

And all else being equal, yes, the amplifier parts for a higher-output receiver are physically larger. However, all else is rarely equal . . . and humans have an infinate capacity for cutting corners.

And again, no one can say whether a current-feedback topology is better or worse in your case. An automotive analogy would be a V-6 engine versus a straight-six . . . much ink has been spilled on the subject, but what it really comes down to is who built each engine, and how good of a job they did on thousands of little details. But if Marantz is proud of their current-feedback architecture, and they feel that it differentiates them from their competition, it's a perfectly legitimate thing to put in their advertising literature.

Current-feedback......well, not sure what Marantz means. In the world of op-amps and engineers, the exact meaning of current-feedback isn't something that everyone agrees upon. Some use it to describe the type of feedback loop, and a though explanation is beyond the scope of this forum.

Some refer to it as a type of op-amp, that has one of its inputs a low-impedance, as the terms used to ascribe its characteristics is not a voltage gain, but a transresistance.

Yeah, I know......what does that mean to the average consumer.

Precisely nothing. My bet is that someone on the marketing department thought up something that they thought sounded cool enough to differentiate them from the competition.

In order to know which, if any of those they mean, one would have to look over the schematic.

In either case, it is not something that would automatically lead one to believe that any amp using such technology is better than any other kind.

What most of us call "current-feedback" is the latter. Yes, it is used when the designer needs to keep BW high, regardless of gain. The drawback is that the resistors in the feedback loop need to be very low resistance. Which in turns means you have to use a non-inductive resistor, that can dissipate several watts. Amps made this way are usually few. Rowland made one......late 90s.