Contact B&K directly and ask for Jerry in Technical support. From what i can remember, they don't recommend doing this with any of their earlier amps. Sean
"Running the channels in parallel to the same voice coil requires massive circuit re-working, much more than the simple circuit required for bridging."
Huh? One simply parallels the 2 inputs and the 2 outputs. No circuitry required, as there is for bridging, wherein one channel runs an inverted signal and then half of each channel's signal is combined at the output. B&K even has this parallel method in their manuals.
Jeffrey: I've never tried doing anything like that nor would i ever recommend such a configuration. I can think of a million different reasons why i wouldn't want to try anything like that, especially given the quality control on this type of product.
If there is any type of difference in output levels due to a channel imbalance in the amp, one channel will see the other channel as a load. The end result could be quite disastrous and very costly let alone a step down in signal purity. This is why i said that one would have to re-work the circuit internally if they wanted to do it both safely and properly.
How old is this info and is it still being included in their latest amplifier manuals? Sean
I have several B&K power amps. I tried to find reference to this parallel configuration in the manuals and can't.
The manual of a Parasound HCA1000 I previously owned recommended "Single Stereo" configuration, citing that it's cleaner than bridged mode. This is simply using only one channel of each stereo amp. This allows all of the power supply output to be dedicate to a single channel. The HCA1000 has built in bridging mode with the flip of a switch. The power rating for the HCA1000 is 110 wpc both channels driven; 185 wpc "single stereo"; and 300 wpc bridged mono.
I imagine some more technically skilled folks than I can confirm this, but I assume this single stereo mode may also work with other amps too, though I wonder if dual mono amps like my Reference 4420 gain the same PS benfits.
Bdgregory: I've owned several different B&K amps and never seen that info either. Then again, these were all older amps and B&K was never much on owner's manuals per se, hence my questions to Jeffrey.
As to running one channel of an amp, this is an old trick that i first saw back in the late 1970's. The first company that i knew to recommend such a thing was Quad. So many of their dealers had found this approach to work better with their 405 series amps that Quad actually came out with a monoblock version of the amp.
While this is nothing to brag about, the fact of the matter is that an amp that drastically improves in terms of output power and / or electrical performance from taking such an approach is simply an under-designed amp. That is, the power supply of the amp is current limited. By removing the current demands of one channel from the power supply, the remaining channel can now function at closer to peak performance.
As to "dual mono" amps improving from this, the answer would be yes and no. It all depends on how stiff the power supply for each channel really is. That is, one can have a separate feed for each channel, but if each feed is still too small, you're still starving the amp. Disconnecting one channel won't solve this so much as stiffening the power supply would.
By "stiffening" the supply, i'm talking about upgrading the transformer to something with a measurably greater amount of current capacity and / or adding increased amounts of power supply reserve via a larger bank or quantity of total filter capacitance. Such an approach increases dynamics and allows a more transparent presentation, even during the most difficult passages. It is not uncommon to find that amps that can drive very difficult loads with the greatest of ease tend to have very high current capacity and large reserves of it available on demand. The only way to get this is to have a big transformer and a lot of capacitance, hence the greater size and cost. Sean