This is a general questioning about internal power distribution within an AVR and because I own A own a cinema 60 I'm asking here. I am not trying to make any changes in my system. I am only looking to have a general understanding of the control and flow of power of these types of AVR's, regardless of the manufacturer.
Basically, I am using the AVR as a processor. Because I am using an external amp none of the current four channels driven nor the active sub are pulling power from the AVR. The Cinema 60 is rated at 125W at 8ohms. (their marketing says into "ALL" channels. In a Q&A they clarified it is not simultaneously with all channels driven). When going through the original set up menus, it requests that you indicate large or small speakers when assigning FL and FR. (I am assuming that is for the purposes of allocating power and or room correction.)
As a general rule, does the circuitry manage and limit the amount of allocated power to specific channels even if the internal AVR computer is told they are not being used?
Because in my situation I am using the pre-outs, does that leave the full 125W of power to drive the remaining channels, if added later?
Again, I fully understand that I will never be short of power in my current set up and I don't need to worry.
The power supplies don't work that way ... they can provide a certain voltage/current, and that is supplied to all the amplified channels on a shared power line....
Think of it as a fat water pipe, with pipes then going from it to a series of taps (speaker outputs).
If you turn on the first tap (front L/R) to maximum, there may not be enough water coming down the main feeder pipe (from the power supply) to be able to run the other taps at the level of output you want.
If you run the taps at a more constrained level, you may find that all the taps can have your desired output to each tap...
Having said that - the front channels L/C/R typically require a lot of water (in this analogy), whereas the surround and height channels, typically require only a relative "trickle" - and being a dynamic environment, the demand on your "water supply" is highly variable....
Your transformer acts as the connection to the mains (Grid), and you have an additional water tank after your transformer, which can respond "instantly" to demands for more water from the taps... but once it is empty, then the amount of water supplied to the taps is limited by the transformer.
large and small speaker settings relate not to power, but to the crossover settings / bass - small speakers have limited bass, and therefore are set to crossover at your crossover setting frequency (most commonly 80Hz - but adjustable on most AVR's) - Large speakers are "full range" - so in theory, cover some or all of the subwoofer frequencies... typically they can go down to 30Hz, some can go down lower.
The relationship between large/small and power is highly variable, but, the bass frequencies are often the major power hog in the system, so in my previous analogy - the bass requires a LOT of water... hence setting speakers to Small will provide more reserves for the speakers, but it then has to be balanced with appropriate powered subs to fill in the frequencies the speakers aren't covering (and as the subs have their own power supplies - that load has been removed from the speakers and amps/AVR's).
A key thing most people miss, is that unless you are talking about huge spaces and very high SPL's, the actual power requirements are much much lower than most people think... issues more commonly relate to current rather than power, and low impedances in the speakers (which then require high current, and may cause instability in the amps, as the feedback loops used to control distortion are often unstable into very low impedance loads, causing them to generate distortion rather than eliminate it!)
As an example - in my large open living space (lounge, dining, kitchen, cathedral ceiling) with inefficient speakers (86db/wm) - my measured typical listening level is under 75db (at MLP) - and typically remains under 4W (!) @ 8ohm (8W@4ohm, 16W@2ohm)... during maximal peaks, I have never seen my setup cross the 16W@8ohm threshold (32W@4ohm, 64W@2ohm).
However, my AVR was unable to provide optimal sound quality into my main speakers, probably due to the 1.6ohm minimum impedance... Feeding the main front L&R speakers with an external power amp, freed up enough current from the power supply, for everything to settle down and sound the way it should.
On previous AVR's I have owned (which had much, much larger and heavier transformers, and claimed to have "high current capabilities" ) - this was not an issue.
I run all the surround and height channels (5.1.4 setup) from the AVR directly - and even though it is a weeny 10kg AVR (weight usually will tell you how big the power supply is, unless it is a switching PSU) - with the external power amps driving the front L/C/R speakers, the entire setup gets the "atlas treatment"!
So yeah I would not hesitate to recommend running the surrounds and heights from the AVR, while running the Fronts off an external amp - just make sure the external amp has enough current for the impedance of the speakers...
