HT, WHAT'S BETTER 2 CHANNEL + 3 OR ONE 5 CH

Depends but then it doesn't really,

5 monoblocks (if its a five channel system) would be the best, but keep in mind that amplifiers like the Bryston 9BST have five monoblocks in one box. soooo

Anthem amplifiers have two power supplies, 1 power supply handles two channels the other handles the other three...all in one box.

Design of the amplifer is a little detail one should look into. Short speaker cables good thing, appropriate electricity important....but what can your budget both in time and money allow?

Speaker Loading and room size also play into the equation, because the demand on the amplifier will also determine heat dissapation requirements and the power supply stress levels during playback. As units that share 1 common power supply under more stressful conditions will get crosstalk etc. and other small but cumulative issues spreading through other channels through the power supply that may slightly degrade the performance.

Hope everyone feels that was a summary of the important non specific parts of their post till now.

I've built my multichannel-audio/video system around a 2-channel system. I use tubed monoamps (ASL Hurricanes in triode) for the L- and R-front speakers and a 7-channel Outlaw 770 for everything else. That 'everything' includes 2 channels for the dipole-woofered Eminent Technology 12 centerchannel, 2 channels for the bass modules of the Eminent Tech. 8s, and 2 channels for the surrounds. Works quite well. Previously I used a Proceed BPA-3 poweramp (125WPC times 3) for the fronts and a B&K 125.5 for the other channels.

Either way, the front-channel speakercables were and still are quite short, and the 2-channel system sounds great. If I had to start over, I think I'd do it the same way, ie monos for the 2-channel system and another Outlaw multichannel amp for everything else.
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Five monoblocks are less likely to cause you a hernia.

In theory all things being equal, 5 monoblocs would be best, then 3 and 2 channels, and then 5 channels.

Just having 5 individual power cords and power supplie/transformers would make the monoblocs the best.

This is assuming that all electronics are equal, and the efficiency advantage of 5 blocs over a single chassis would and could be realized.

Even heat dissipation would be better, with larger radiating surface areas and more metal.

In my HT set up, I had a 2 channel and a 3 channel amp set up before. I ran of out space on my rack so I sold both and bought a 5 channel amp. I did not realized how much better the 2&3 were vs. the 5 alone. My amps were all from Cary and put out the same 200w/channel, so I guess that should answer your question.
Nick

I have no argument with Markphd's statements but let me give you another take.

Since all the amps, regardless of how they are configured, are limited by the AC signal, you can optimize using separate amps only with dedicated AC lines for each.

Now, if you look at a multichannel power amp, regardless of the number of channels, you can have each channel with its own PS, in which case Markphd's arguments for separate amps applies here as long as the power cord is up to the task.

OTOH, if there's one really beefy PS for all the N-amps, it can supply much more to active channels when there's less demand from others. In other words, since there's rarely instantaneous and simultaneous power demand from all channels, the needy ones get help from what the others don't need.

Kal (who thinks it really makes no difference in general)

In theory, it should not make a difference. However, in practice, it may make a difference. The more channels you have in one box, the greater the possibility that there may be electrical interference between the channels. One box also increases the possibility that the power supply is insufficient in size for all of the channels at once. It also increases the possibility that with one plug in one wall outlet, the circuit may not be able to provide enough current for all of the channels. It becomes a question of the design of the particular unit, and your house's electrical circuitry. With isolation of channels, a sufficiently large power supply, and sufficient wall current, then a single amp would be okay. Otherwise, it might be better to have multiple amps plugged into differrnt circuits. So the answer to your question will depend upon the particluar amp(s) being considered, what speakers they are driving and what it's all going to be plugged into.

It should also be noted that it is important to keep speaker cables short. All other things being equal, it's better to have long interconnects and short speaker cables than the other way around. With this logic, it would be better to have the three channel amp driving the front and centre speakers since the amp could be close to all three. Then sit the 2 channel amp somewhere in the back where it could be closer to the surrounds.