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In Reply to: Sunfire Reference amp posted by schlagelk on September 28, 2004 at 13:04:29:
how much power it delivers at clipping as impedances are reduced. That's because this drives both the power supply and output stage into saturation simultaneously, resulting in a far more representative view of how "sturdy" the amp actually is. At the same time, it also tests the amp as it would see an actual loudspeaker load i.e. varying in impedance as frequency changes. If the amp is "sturdy" and of an SS design, the power output at clipping should keep doubling ( or very nearly double ) as impedance is halved.If one were to check most amps in this manner, i'm quite certain that most "big brute" amps would actually become known as "not quite as sturdy as we thought" amps. That's because most amps don't even come remotely close to "doubling down" at clipping, hence their "RMS" ratings at higher impedances are actually relatively conservative.
This is a common "trick" i.e. de-rating the RMS power at 8 ohms so that the manufacturer can claim that it "doubles down" at the RMS rating into 4 ohms. Manufacturers caught on to the "doubling down" being thought of as a good thing, so they adjusted their ratings to cater to audiophiles and the marketing hype surrounding this rating. Like i said though, the real test is what the amp does at clipping, NOT what the manufacturer rates the amp at in terms of an RMS value.
According to a third party test bench review published in April of 1995, the standard Sunfire amp actually does "double down" ( or very nearly so ) as impedances are halved. While the amp is factory rated at 300 wpc RMS @ 8 ohms, 600 wpc RMS @ 4 ohms and 1200 wpc RMS @ 2 ohms, the measured power of the amp in the review actually produced 387 wpc @ 8 ohms, 768 wpc @ 4 ohms and 1460 wpc @ 2 ohms when driven into clipping. As one can see, the amp doesn't quite "double down" as impedances are halved, but it comes impressively close.
After reviewing those figures, i don't think that anybody could say that this amp is a "gutless wonder" by any means. This is especially true since it EASILY surpasses the surprisingly high power levels that it's rated for at every impedance level tested. After all, how many amps do you know of that are actually rated at 2 ohms??? Now take that a step further. How many of the amps that you can think of that are rated for operation at 2 ohms are rated to "double down" from their 4 ohm power rating? Now take that yet another step further. Try to think of an amp that surpasses it's "doubled down" factory rated power at 2 ohms by over 20%. My guess is that you've got more fingers on one hand than there are other amps that achieve this level of performance. This type of performance is called a "voltage source" and most amps could only dream of this type of performance.
For sake of clarity, the amp that Lou S. tried with his Acoustats was an early production standard Sunfire, not the Sunfire Signature. I know this as it was one of my amps that i lent him to check out. Given that the standard Sunfire is rated at 300 / 600 wpc ( and EASILY does that ) and the Signature is rated at 600 / 1200 wpc, there's just a bit of difference in the voltage and current capacity of the amps.
As a side note, either of the above amps will suck a 15 amp and even a 20 amp breaker dry. That is, if your standing on the throttle and / or driving low impedance loads. Given that the amps are VERY voltage sensitive ( they run very high rail voltages ), any type of voltage sag that the amp encounters from a less than adequate AC system will be quite detrimental to their performance. As such, if you want one of these amps to operate at peak potential and really see what they are capable of, one must have at least 10 gauge wiring from their breaker box and a fresh circuit breaker or fuse. A standard 15 amp breaker with 14 gauge wiring will not provide one with the type of power that this amp needs to provide the results that it is capable of.
With all of that in mind, Sunfire has both improved the sonics and increased the size of the power supply on Sunfire amps since that review was published almost 10 years ago. As such, the amp is not only capable of higher output levels and better performance, but the limitations of the amplifiers' performance will rest solely on the quantity and quality of the AC power that you can feed it.
If there was one sonic attribute of this amp that i would have to pick out, it is that the presentation remains very cohesive regardless of the dynamic power demands placed upon the amp. That is, IF you can supply it with enough AC : ) Sean
>PS... I don't know much about the newer "Symphonic Reference" models, but i would assume that they share common design parameters and build quality to that of their more powerful brethren mentioned above. While i have NO doubt that the Sunfire will provide both more steady state and dynamic power than the Stratos would, the real thing that matters here is whether or not you like the sonics of the amp. Being able to drive a speaker and have it sound enjoyable are two different things.
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- The true test of an amp is.... - Sean 22:11:17 10/01/04 (0)
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