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RE: "differential bridged output " balanced or not?

Posted by Charles Hansen (M) on September 10, 2017 at 22:01:06

In Reply to: RE: "differential bridged output " balanced or not? posted by Ugly on September 10, 2017 at 13:41:13:

> > Are you saying there is a Marantz with some "differential bridged output" n-core configuration, and it hits current limit too early? < <

I have no idea of what is inside of the N-Core modules inside the Marantz. I highly doubt that each stage of the signal path, from the input jack through the volume control to the output stage is actually connected in such a way as to achieve all of the audible performance benefits of true balanced circuitry. Without seeing a detailed schematic diagram, my educated guess (based on a complete understanding of linear amplifiers and only a limited understanding of switching amplifiers - especially "proprietary" ones) would be that they are offering just *one* of the many possible benefits of true balanced circuitry - the ability to swing twice the voltage and therefore deliver four times the power - but only into a relatively high impedance load.

The formula for power into *resistive* load is P = I^2 * R.

We know from the review in Hi-Fi News that the current limiting kicks in at 13 amps peak, equal to 9.2 amps RMS when using a sine wave. Therefore the power of that amp will be current limited to:

84 watts into a 1 ohm load
168 watts into a 2 ohm load
336 watts into a 4 ohm load, and
672 watts into an 8 ohm load

(assuming that voltage clipping doesn't kick in first).

Definitely an unusual design, in that it will deliver gobs of power into a load that is quite a bit higher than the minimum of most modern loudspeakers. And the more difficult the load, apparently the less power the unit will deliver - typically more characteristic of tube-type amplifiers rather than solid-state amplifiers.

Again, it is virtually impossible to predict how this will translate into actual sound quality with a given pair of speaker is a specific listening room played at unpredictable levels. But it would not be my first choice for (say) the 1 ohm Apogee ribbon speakers of decades ago, and may possibly also run into problems with less exotic speakers. As always, the best way to tell is to connect in to the intended system in the intended listening room and playing the type of music you enjoy at the levels that you prefer. Anything else just becomes a guessing game.

Hope this helps,
Charles Hansen

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