![]() ![]() I think some of the subsequent comments on the post were kind of going towards this idea. This quote was taken from an Absolute Sound review of the AHB2. Both approaches are valid, so you pays your money and takes your pick according to your needs, desires, and wallet. The price there is increased distortion, but the argument goes that because the music is so loud, and the duration so brief, the extra distortion goes essentially unnoticed. ![]() But there are other amplifiers with less tightly regulated power supplies that allow for much greater power output on instantaneous peaks (this is a design feature on the NAD amps). This is salutary because it keeps the amp within its noise and distortion specifications vis-à-vis its power output. ''That said, there is one aspect of the design that must be emphasized: The power supply is very strictly regulated, the 100 watts of continuous power generating only about 110 watts on instantaneous peaks. Is it possible the amp considers the short sharp transient signals as noise and ignores them? Or is it simply a question of available headroom? Or limits to rate of change rate? I think I understand the inbuilt protections in the AHB2 but they don't seem to explain the behaviour observed. This is puzzling actually because at no point did a single light flicker on the AHB2. ![]() Before this threshold is reached, the high-current warning lights will flash, but this is not an indication that current is being limited, it is just a warning that you are near the shut-down threshold." Until this shutdown threshold is reached, there is no limit to the output current delivered by the AHB2. The output current of the AHB2 is only limited by an overload protection system that measures the output current and then shuts the amplifier down is an unsafe load (or short circuit) is causing excessive output current. In contrast, the AHB2 output stage is drawing current from tightly regulated power supply rails and there is no current limiting circuit in series with the output stage. The third issue is that the Accuphase may have output current limitations that are contributing additional distortions. The Accuphase cannot damp the drivers as quickly. A second issue is that the damping factor is much higher in the AHB2. The effect of this is that Accuphase delivers frequencies near 20 Hz slightly late (due to the low-frequency phase response errors which are a direct result 5 Hz lower limit of the Accuphase amplifier). The Accuphase response is -3 dB at 5 Hz while the AHB2 extends all the way down to 0.1 Hz (-3 dB). "In measuring the AHB2 and attempting to confirm its specified (very) high signal/noise ratio, JA observed nonlinearities in his testing equipment that "haven't affected the measured performance of other amplifiers I've tested, but they were detectable with the AHB2's very low intrinsic distortion and noise." His conclusion: "an extraordinary amplifier.There are several important differences between these two amplifiers that can change the way the low frequencies are reproduced. "An extraordinary amplifier"- John Atkinson, Stereophile ![]() Burdick, the engineer whose work formed the basis for its design, Benchmark's AHB2 makes use of THX Corporation's Achromatic Audio Amplifier (AAA) technology, in which a low-power feed-forward amplifier drives a low-bias class-AB output section." "In his listening tests KR discovered "much more apparent low-level detail in already-familiar recordings"-a characteristic he credited to the Benchmark's evident noiselessness-and a tonal balance that "sounded more 'right' than any of. ![]()
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