2. amps-preamps
  3. 123836-4181

Is a stereo amp, when bridged to mono, by definition differential?

I've been reading about amps and the seemingly endless choices that designers make, and found myself wondering this, but haven't been able to find the answer. It would seem, if I'm correctly understanding the definition of differential, also called push-pull, that bridging the two sides of a stereo amplifier would, by necessity, be creating exactly this topology. Unless I'm missing something, of course, which may well be the case.

Thanks to those who understand such things much better than I for any clarification.

Also, those who'd rush to weigh in about the likely sonic benefits -- or detriments -- of such arrangements needn't bother, as that's not what I'm wondering about.

Thanks.

-- Howard

hodu

Showing 2 responses by hodu

hodu OP
239 posts
 
Thank you both for your responses -- they are much appreciated.

-- Howard

hodu OP
239 posts
 
Here's why I posed this question in the first place. I was reading (in 6moons) a review of the McCormack DNA-500 and read the following from designer Steve McCormack:

"In the context of its power rating, how I can achieve this size and weight factor while still delivering this type of power is because unlike previous DNA designs, the DNA-500 is a fully differential/balanced amplifier from input to output," McCormack explains. "Speaker drive is thus differential or push-pull as well. We combine two complete amplifier sections per channel, each of which is driven from an input phase-splitter. (The incoming signal is split into a pair of opposite-polarity waveforms, each of which drives one section of the amplifier pair.) In most conventional amplifiers, the speaker is connected to a single positive output and ground. In the DNA-500, the speaker is connected across a pair of positive outputs of opposite polarity, thus driving the speaker in push-pull mode. This arrangement delivers a degree of speaker control that is not possible otherwise.

"Having experimented extensively with this design approach over the years, it has come to be my favorite method for producing high-performance amplifiers. It creates what is often referred to as a bridged amp. There are four independent amplifier channels, two per side, each channel pair in bridged/balanced configuration to double the voltage over a conventional amplifier. An ordinary 100-watt stereo amplifier in bridged mode will net you a 400-watt amplifier if the power supply can process the current. That's the principle of how the DNA-500 works.

"Many audiophiles feel that such a bridged-style amplifier design is a bad approach. Their prejudice is based on past experiences with stereo amplifiers that were switchable into bridged mono. These amps often had poorly designed input phase splitters and were not optimized to handle the reduced load impedance in bridged mode. The result was often compromised audible performance, instability, overheating, blown fuses and more than a few damaged amplifiers. It's no wonder that bridged amps have acquired such a bad reputation. However, the DNA-500 demonstrates that this need not be the case."

This all got me to thinking, and wondering. As I'm nobody's electrical engineer (or any other type of engineer, for that matter), I may well have been confused by some of the terminology, perhaps conflating this with that and the other thing. 

Thanks to all for your thoughtful and considered responses.

-- Howard
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