how do you tell what a good amp is from numbers

[simpsonbuck 10+ year member]

Most of the specs are garbage. Slew rate only needs to be adequate. Never seen an amp where it wasn't. With s/n, higher is better, but without a standard (which there isn't) it's pretty meaningless. Some give the s/n at full power where the signal is the highest which gives you an artificially high number. A more telling number is max gain and s/n compared to one watt output which actually tells you how bad the noise is. Damping factor only needs to be sufficient which is pretty much into the double digits. THD below 1% is generally accepted as below audibility with music. The last thing that matters is frequency response. This is the one where just a spec doesn't tell you much. A simple +/- spec doesn't tell you a whole lot without actually seeing where the peaks and dips are. A smaller tolerance is better here because if the deviation from flat is small enough, it isn't going to be audible. Slightly higher devs with a peak in the lower octaves and a slight roll off on top is what characterizes what most people call a "warm" sounding amp as an example.
Once the basic specs are adequate, power is really all that matters.

Your brain holds a wealth of knowledge.

 

[snb778 5,000+ posts]

Did you not read the thread about how the specs on paper don't really mean much besides power ratings? Brand integrity is far more important than the numbers on paper as long as the amp fits into your power requirements.
Hour meter? It must be that alphasonik amp.

correct

i know on paper doesnt mean much, but there are some important stats like the THD and others

 

[DNick454 10+ year member]

so what would you guys say about these ratings, not knowing what brand it is. I really really want it, but don't know if its a solid amp.... subs don't have the best rep, but its in great condition, and only 170 bucks!
4-Channel High Current Power Amplifier

RMS Power Rating:

160 watts x 4 chan. @ 4 ohms

290 watts x 4 chan. @ 2 ohms

490 watts x 4 chan. @ 1 ohm

500 watts x 2 chan. @ 4 ohms bridged

825 watts x 2 chan. @ 2 ohms bridged

960 watts x 2 chan. @ 1 ohm bridged

Hour Meter

Remote Mount Digital Voltmeter Included

Bass Remote Included

Clear Acrylic ANL Fuse Holder and 80 Amp Fuse Included

Heavy Duty Heat Sink

Beveled Clear Acrylic Protective Cover

1 Pair RCA Outputs

Tiffany-Style Input and Output RCA Jacks

High Speed Switching Power Supply

Double-Sided Glass Epoxy Circuit Board

Variable Low-Pass Filter: 50 - 250 Hz

Variable High-Pass Filter: 50 - 250 Hz

Variable Subsonic Filter: 15 - 60 Hz

Variable Bass Boost @ 45 Hz: 0 - 18 dB

Input Sensitivity: 200 mV - 8 V

Input Impedance: 10,000 ohms

4-Way Protection Circuitry: Thermal, Short-Circuit, Overload, and DC Offset

On-Board Hook Up Terminals

Frequency Response: 5 Hz - 50 kHz

Dimensions: 19-3/4" L x 9" W x 2-5/8" H

1-year Sonic Electronix warranty

That's impossible. If it's 4 channel and it is 1 ohm stable at 4 channels, then theres no way it would be stable at 1 ohm bridged to two channels, because the amp is then seeing 0.5 ohm load per channel. So either you've got a weird amp, or you copied those stats down incorrectly (or the person who is selling it to you made those stats up)

 

[snb778 5,000+ posts]

http://www.sonicelectronix.com/item_4640_Alphasonik+PMA640HCA.html

 

[DNick454 10+ year member]

Hmmm, weird I'm a bit confused on the stat sheet for the ratings per ohms and bridged or unbridged.

 

[Immacomputer 10+ year member]

correct
i know on paper doesnt mean much, but there are some important stats like the THD and others

I guess you didn't read the thread then...