Axiom Home Page Forums General Discussion Stereo Anyone need a new amp with some umph!!!!

Check this puppy out at Steve's Music Store in Toronto

http://www.stevesmusic.com/index.php?main_page=product_info&manufacturers_id=186&products_id=1782

I know it's not a conventional HT amplifier, and it isn't pretty, but for 700 bucks you get 760 watts per channel into 4 ohms, and some pretty good circuit protection to boot. Talk about headroom. Style and noisy fans would probably limit this to an audio closet for most.

And if you get two, and bridge them, well how does 2150 WPC RMS into 4 ohms sound???

Your thoughts?

pn

Seems like we'd need to know THD, damping factor, slew rate, and all that engineering gobbledegook to have an informed opinion.

Still, Zimm's experience with pro-audio amps does give me pause.

Frequency Response: 10 Hz - 25 kHz; +0, -1 dB at 1 watt
T.H.D. 2 x 4 ohms: <0.2% @ 675 W per channel from 20 Hz to 20 kHz
Slew Rate: 17V/µs
Damping Factor (8 ohms): > 400:1 @ 20 Hz - 400 Hz

Are those respectable spec's for this price range?

pn

Distortion is a little high, most solid state amps these days are less than 0.1%, many in the 0.025% range. Slew rate is a little slow, even for a single-ended amp, where good ones hang around 25 volts per microsecond.

Unless you really need that much power, smaller amps generally have better ratings. But can a person really hear the difference between 0.2 and 0.02% THD? Does your listening material have many high amplitude square waves that you need a slew rate of 50V/µs for accurate playback?

I didn't list it, but the cross-talk was surprisingly high on this amp: -60 dB. That may actually be audible in some cases.

Most pro amps are in this price range, at about $300/channel. You can probably do better if you look around. Just to give you an idea, Outlaw's excellent 7-channel amp is $2149, but only delivers 300W into 7 x 4Ω.

Peavy, Qsc, Crown, Behringer, a number of the pro amps have been tried by a few around here with great success, as Chris noted the cross talk and THD does seem to be higher on some of the pro amps which may or may not be noticeable. Also have to watch for XLR only inputs for many pro amps as well.

Peavy is a well known name, at least to musicians, and not a fly by night company. I am just curious if they can design and manufacture a power amp this powerful for that price. And I do understand it could use some refining, whether that refinement will be audible or not is an interesting conversation. I can only imagine what the profit margins are on some of the more exotic no-pro home audio power amp companies.

I am not advocating that anyone needs 700 plus wpc in their living room. However, it is a fraction of the cost of some of the more exotic amps and has more than double and even triple the power.

pn

Yes, I think so.

Paul, it wouldn't sound any different than 215 watts(or 21.5 watts)if they weren't actually used.

Find out here.

I do love a good amp thread.

You guys are great.

But it sure would look cool!

Rick,


Now, THAT'S funny!

I got down to 24 db. Whatever that means in terms of percent THD.

I got down to -30dB before I couldn't tell.

Here a page which converts between distortion attenuation (what the test measures), and % THD: http://www.sengpielaudio.com/calculator-thd.htm

-30dB is 3% THD!

And to go back to my example. 0.2% THD is -54dB, while 0.02% is -74dB.

Good to know.

Let's not forget that the THD is also at max output, lower volume levels would have much less THD, this leads to the idea of having extra horsepower available being a good thing in that the THD you hear(or don't hear) would most likely be non-existent at most listening levels with higher powered amps.

And Tom, it is still working great. So good in fact, I had to stop myself from buying another one just "because" when Guitar Center was advertising a 70% off sale over Labor Day ($400 - 70% = CHEAP). The fan noise fix may discourage some, but for the price the fear should be minimal. And to my surprise, it only makes detectable heat when the high current rails kick in, which is very seldom. (ala, FredK's comment about only never really needed the whole 800 watts.)

But when it's time to really enjoy the music, it gets hot, but sounds great. None of the sonic limits of my Denon AVR (which i can still find via A/B switching when I use the center ch signal from the AVR - certain sounds have a harshness that stands out (to me anyway!).

As for stats, I found the Peavey amp I tried had noticeable hiss, and a related (I think) higher THD and SN Ratio. So don't assume all pro amps are the same. Try them first.

Thanks Rick, cool site now I just need to know what the different tests represent. I ask because my scores varied quite a bit depending on the test. For example on the “octave” test I hit -45dB four out of four times but in the others I varied anywhere from a little above to slightly below the mean. Is any one of those tests more representative of “real” music?

I did the test with both my Axiom M80s and Sennheiser HD600s and got results that were mostly dead on with a few exceptions where they were within +-3dB of each other.

Dean, as explained there when the name of the test is clicked, those test tones mask distortion less than real music does(i.e., a lower percentage of distortion is audible than on real music), but the "terz" tests mask to a greater extent than do the "octave" tests.

Thanks John, I read that in the pop-ups but what I don’t understands is the difference between the “octave,” “octave L,” “octave BI” etc… Maybe I missed it but I thought there was a generic pop-up for each the “octave” and “terz.“ I am much better able to hear the distortion on both the basic “octave” and “terz” tests than the tests which follow each of them and was wondering why.

An additional question I haven’t tried looking up yet is how distortion combines. Can you just add the distortion from each component in a system to get a reasonable idea of the total distortion in the system or is it more complex than that?

Yeah, Dean; it's more complex. Distortion in different components can add or subtract to/from each other depending on the phase relationships of the distortions. For example, negative amplifier feedback intentionally takes distortion sampled from the amplifier output, reverses it in polarity or phase, and adds it to the input("pre-distorting" it)so that the two distortions tend to cancel each other, making for a cleaner amplifier. In other situations these phase relationships are a matter of chance and can either increase or decrease the overall net distortion.