Axiom Home Page Forums General Discussion Advice from Axiom Owners Help! I think I need more power.

I pretty much agree. What I did gather from all the amp pictures over on avs is that they are not all designed the same, even if there are clones of some designs.

Dean, I tend to share the view that factory refurbs are more reliable and have lower return rates than brand-new units, although I haven't seen any statistical study on the point. My personal experience with them has been excellent.

The best buy on the 876 at this time appears to be $860 with free shipping from Accessories4less .

Adrian, slew rate is one of the specs(damping factor is another)that the audio consumer doesn't have to worry about comparing between units he's considering for purchase. The reason is that the frequency response of the unit serves as a proxy for necessary slew rate. In order to reproduce 20KHz with a flat response and with low distortion an amplifier has to be able to respond to a signal moving 20,000 times a second quickly. The formula for calculating this at a certain power level is (6.28 x frequency x peak voltage)/1,000,000. For example, for 100 watts into 8ohms a peak voltage of about 40v is required, and the formula becomes (6.28 x 20,000 x 40)/1,000,000= 5.02 volts per microsecond. So, as long as the amplifier can change("slew")at a rate of 5.02 volts per microsecond, the 20KHz signal can be reproduced accurately at 100 watts. Typically, an octave higher response, i.e., 40KHz, is designed, which requires twice the slew rate, 10V/microsec. Since lab tests routinely show flat low distortion response to beyond 20KHz in even modest cost units, this establishes that the slew rate is adequate and not a matter of concern.

Of course, sometimes manufacturer hype(or naive audiophile belief)promotes much higher slew rates than required, with at least an implication that this would somehow make the sound "quicker". This is pure nonsense, and if a frequency was reproduced quicker than the Hz number, the correct term would be distortion. So, any number in the low double digits is fine for typical power levels, and specs showing rates of 50 or more which appear for some units aren't of real significance.

Thanks for the link John. Nice that they have a 1 year warranty.

The 6.28 is 2 Pi, which is the formula to calculate the slew rate of a sine wave. Other functions have higher slopes, and would require a higher slew rate.

I have a QSC GX-5. The inside is a very clean layout, but nothing about it implies made in a German lab or Swiss watch factory. I don't care if it is made in China if held to QSC's tolerances. I'd love a built in the US option, but I'm too cheap for that right now.

As to the competitors you mention, they may well be made in the same line with the same components - I have no idea. But when shopping I found the specs varied a decent amount - power, S/N, THD, etc. I tried a Peavy and it was too noise at idle for me. And the GX is a class-H layout, I did not remember those others using the H layout.

I am a big fan of the H topography as it keeps the heat to an absolute minimum except for high volume use when it switches to the high-current rail.

And note that the QSc GXs have RCA inputs so you don't have to work around the XLR inputs on most pro gear.

That does sound appealing, Charles.

Oh yes, I also forgot, under $400 for endless power. Took the fan out and toned down the laser bright power light and she was good to go. Nice thing about a $400 amp - not afraid to open it up and pull out the noisy fan.

I would never do that to a Krell or Bryston.

$400 is still a little steep for me to muck about on the insides, but I'm cheap.

I hear you - my AVR and speakers are 10 yrs old so I don't like to trash stuff. But when I bought it I knew of the fan noise issue so I went into the purchase knowing a repair might be needed if I mucked up something. It was super easy, just like the inside of a computer, unplug the fan and pull it off the plastic clips. No hassle.