2 stereo amps in a mono-block config = 2 x power?

Now, now - the crime wasn't that bad!! Bose is the audiophile death penalty.

Dan, there's lots of misinformation here and some good advice from John. But allow me to again* explain paralleling and bridging amplifier channels.

Connecting the stereo amp's positive binding posts together and the negative terminals** together and driving the 2 channels with the same signal is called paralleling. The now-single-channel amp has the combined power, in your case 180 Watts, and it's TWICE as capable of driving low-impedance loads. For instance, a SS amp that's rated at 90WPC into 8 Ohms will be able to drive 180 Watts into 4 Ohms. AFAIK, ANY stereo amp, tubed or SS, that doesn't prohibit combining the common terminals can do this.

Bridging involves driving the 2 channels with opposite-polarity signals and using only the positive terminals for driving the speaker. The result is FOUR times the power because the powersupply Voltage is combined (doubled), and that quadruples the output power. HOWEVER, each channel is now driving HALF the apparent load, so many stereo amps do not have the current capacity to quadruple rated power. Only if an amp can double each channel's power into half the load will it quadruple total power. IOW, if a SS amp that's rated at 100WPC into 8 Ohms can deliver 200WPC into 4 Ohms, it's capable of delivering 400 Watts into 8 Ohms.

So bridging is NOT a good idea for driving power-hungry, low-impedance speakers such as Maggies or, even worse, Apogees, but would work well driving 8-Ohm (or higher) systems.

Dan, if the poweramp available to you is indeed identical to the PA section of your integrated amp, buying one and paralleling their channels might be an economical way to buy more power. But you might find a, say, 200WPC amp, used, for as little money. Look around; you're in the right place at AudiogoN.

* Seems I've written this a half-dozen times already.
** This can NOT be done with amps such as the Spectral DMA-100 that prohibit the joining of the negative terminals.

Bridging is one thing, but paralleling is another.

You certainly won't get an increase in power by paralleling since the voltage applied to the load will be the same (assuming each output stage has infinite internal impedance), and power is voltage squared divided by load impedance. Bridging works because it effectively places the two channels in series (an oversimplification, I know)and doubles the voltage across the load (which in theory yields 4X the power).

Real amplifiers don't have infinite internal impedance.

If you parallel the two channels as Jeffreybehr suggests, then the load impedance that each channel sees is the speaker impedance in parallel with the impedance of the output stage of the other channel.

Most transistor amps have very low output impedances (inversly proportional to the damping factor), usually well below 1 ohm. Thus the load each channel sees will also be below 1 ohm, since the effective parallel impedance will be less than the smaller of the two loads in parallel (the other channel and the speaker).

Most amps will activate protection circuitry, blow fuses, or worst case smoke in this scenario.

It's just basic Ohms law.

Nad integrated amps used to be able to run as a mono amp.I used a 7100 receiver in mono for a centre channel amp to match the greater power of a couple of nad 2100 power amps in a home Theatre.
If I were you I would look for a better power amp and forget what the dealer said because unless you can run the integrated in true mono you will not get double power out of just one channel.I would take my business elsewhere if told this from a dealer.

Ghost, I know you're wrong but I don't know enough about it to argue your psuedo-science. Paralleling works. SOMETIMES bridging works, as in now having enough power whereas one didn't before.
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