Good find, Hal, as the review makes clear that the design of the M6si draws significantly on the design of the M5si, and the relevant specs that are provided for both are not greatly different.
The total gain of its line-level and power amplifier sections can be calculated from the specified 270 mv sensitivity for a 150 watt output (presumably into 8 ohms) as being about 42 db. That is somewhat highish, but not unreasonably so, and given also the 91.3 db/2.83 volts/1m sensitivity of your speakers as measured in the Stereophile review (which corresponds to about 88 db/1 watt/1m in the mid-bass and lower mid-range regions where speaker impedance is around 4 ohms) seems consistent with the lowish volume control settings you are using. Especially if you are using digital sources, that typically have higher output levels than an analog phono stage would.
Possible indications of too much gain are overloading of circuitry that precedes the volume control in the signal path, which would manifest itself as obvious distortion, and depending on the design of the volume control mechanism the possibilities of excessively coarse resolution of volume adjustments that may occur at low settings, introduction of channel imbalances that would not be present at higher settings, and some degree of sonic degradation. But you would almost certainly have already perceived these kinds of things if they were occurring to any significant degree.
As far as power and low impedance drive capability are concerned, I note the following in the M5si review:
So while the design falls significantly short of doubling its continuous power capability into 4 ohms relative to 8 ohms, and the considerably higher capability into 2 ohms appears to be limited to intermittent dynamic demands, it seems to me that the compromises that were introduced into the design in the interests of keeping the cost at the desired level were chosen judiciously and intelligently. Especially in the context of an application such as yours where the speakers have a combination of reasonably good sensitivity and the ability to handle copious amounts of power.
Best regards,
-- Al
The total gain of its line-level and power amplifier sections can be calculated from the specified 270 mv sensitivity for a 150 watt output (presumably into 8 ohms) as being about 42 db. That is somewhat highish, but not unreasonably so, and given also the 91.3 db/2.83 volts/1m sensitivity of your speakers as measured in the Stereophile review (which corresponds to about 88 db/1 watt/1m in the mid-bass and lower mid-range regions where speaker impedance is around 4 ohms) seems consistent with the lowish volume control settings you are using. Especially if you are using digital sources, that typically have higher output levels than an analog phono stage would.
Possible indications of too much gain are overloading of circuitry that precedes the volume control in the signal path, which would manifest itself as obvious distortion, and depending on the design of the volume control mechanism the possibilities of excessively coarse resolution of volume adjustments that may occur at low settings, introduction of channel imbalances that would not be present at higher settings, and some degree of sonic degradation. But you would almost certainly have already perceived these kinds of things if they were occurring to any significant degree.
As far as power and low impedance drive capability are concerned, I note the following in the M5si review:
Rated at 150W/8ohm, the latest in Musical Fidelity’s ’super integrated’ amplifiers achieves 2x165W/8ohm and 2x265W/4ohm with 200W, 355W and 545W possible under dynamic conditions into 8, 4 and 2ohm loads, respectively.... While its output into the lowest 1 ohm loads is protected at 275W or 16.6A ... the M5si still looks capable of grappling with any likely partnering loudspeaker.And I note that for a 2 ohm load the 16.6 amp figure corresponds very closely to the 545 watt maximum dynamic (non-continuous) power capability that is indicated.
So while the design falls significantly short of doubling its continuous power capability into 4 ohms relative to 8 ohms, and the considerably higher capability into 2 ohms appears to be limited to intermittent dynamic demands, it seems to me that the compromises that were introduced into the design in the interests of keeping the cost at the desired level were chosen judiciously and intelligently. Especially in the context of an application such as yours where the speakers have a combination of reasonably good sensitivity and the ability to handle copious amounts of power.
Best regards,
-- Al