Originally Posted by knappster007
I've been reading as much as I can to understand how multi-channel power amps allocate power to different channels, but have not been able to find an answer to the question that I have.
I just got a new Yamaha RX-A820 with the following specifications:
- 100W/ch rated output power (2 channel driven, 8ohms)
- 160W/ch maximum effective power (JEITA, 1kHz, 10% THD, 8ohms)
- 140W/ch dynamic power (IHF, 8 ohms)
- 400W/500VA Power Consumption (total unit)
This unit is currently driving a pair of Paradigm Studio 100 v4 (L/R) and a pair of Paradigm ADP (rear effects). The center channel is off of the pre-amp out and is powered (Paradigm Active CC).
My questions are these: How is power allocated between the seven channels? Does activating the bi-amp setting in the receiver allocate more power to my L/R speakers? Is power allocated with each channel as a separate lane or is power allocated dynamically to each channel as needed by the demands of the passage being played?
I do understand the minor benefit of passive bi-amping with the Studio 100's crossover still being utilized (I also have a pair of Paradigm Studio Active 40s which are actively bi-amped as my office system). My question gets to the matter of the allocation of power to my L/R speakers.
Any advice of clarification from those more technically knowledgeable is appreciated.
The amps are what they are. In most cases modern QVRs us identical power amps. That means each of the 7 outputs is served by its own power amp section. You'll never get anything more from the amps than what they have to give, individually.
In many if not most AVRs, compromises in the power supply dictate that the amp cannot make nearly as much power all at once to 7 channels as to 2. Whether that ever becomes an issue in real life depends.
The line level signal that feeds the input sections of each power amp is almost a pure voltage source, as the input impedance of the power amps is very high. What that means it that, in effect, connecting an internal Y connection between 2 separate amp modules to allow biamping changes nothing about the input to the power amps. Each effectively sees the same input that a single one would see. Each of two power amps now can supply the 2 sections of your speaker. If power were equally distributed between the tweeter and woofers, you'd have a theoretical 3 dB increase in available power. But as I understand it, with typical crossovers in the 2KHz range the treble portion of the signal will not be more thatn 30% of the total signal, so any actual power increase is much much less, maybe on the order of a decibel at best.
To the extent that the 2 added power amps were unused before activating biamping, there is a theoretical possiblity that the extra drain on the power supply could limit total power, further decreasing any power gains from biamping.