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Crest CA-9 vs. QSC PLX2502 (PLX2 Series)

Which power amp?

  • Total voters
    92
#122
Hmmm....The pic of the Stewart is a blurry, and the QSC pic is a little blurry as well. Since the pic of the CA-9 is nice and clear, I can only assume that translates into nice clear tone as well. :D
 
#123
xgabriele said:
Hmmm....The pic of the Stewart is a blurry, and the QSC pic is a little blurry as well. Since the pic of the CA-9 is nice and clear, I can only assume that translates into nice clear tone as well. :D
Click to expand...

Well, in all fairness to QSC and Stewart, the hi-res pic from QSC was larger than the Crest hi-res pic, so I downsized it. That caused some fuzziness. The Stewart pic was smaller, so I upsized it, which always looks bad. So they all started off crystal clear until I monkeyed with them. :D
 
#125
The bottom line is that a power amp is not a tone stage, but a voltage gain stage. Even though they're called "power amps," they're actually voltage amplifiers, but with additional current capacity to drive low load impedances. The output signal voltage is a multiple of the input signal voltage, and that multiplying factor is called "gain."

Amp designers at reputable companies have consistently been getting highly accurate performance out of power amps for a pretty long time now. That's the state of the art. You can believe otherwise if you like.

Just like you can drive a car without knowing how it works, you can play bass without knowing how the power amp or other parts of a bass rig work. You can even decide to consciously reject knowledge about how they work and still play bass (I'm not too keen on people who try to induce others to reject knowledge, though; I think that's wrong). But not knowing that sort of thing will tend to make it harder to get the sound and performance you want. If you don't have the tone you want, sure, you can replace the power amp instead of learning how to dial it in, just as sure as if your bass is out of tune you can replace the pickups instead of learning how to tune the strings. The effectiveness is going to be hit-and-miss, though. But if you want to get your sound with a minimum of expense and hassle, learn at least the basics of how the stuff works.
 
#126
#127
Bob Lee (QSC) said:
The bottom line is that a power amp is not a tone stage, but a voltage gain stage. Even though they're called "power amps," they're actually voltage amplifiers, but with additional current capacity to drive low load impedances. The output signal voltage is a multiple of the input signal voltage, and that multiplying factor is called "gain."
Click to expand...

Then why do people bother bench testing them? They're all the same, right?
 
#133
tombowlus said:
I thought the bottom line was to use what sounds/works the best for you. :hiding:
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Yup. That's the other bottom line.

Knowing how to get to what sounds/works best for you will help you ge there quicker and in a less hit-or-miss way. That's where knowing the bottom line of "a power amp is not a tone stage, but a voltage gain stage" will help you.
 
#134
Bob Lee (QSC) said:
So do I, as the data does not indicate reduced low end response. I encourage everyone to read all they can about power amps.
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Last time you said that either the amp or test was flawed. I thought that meant you agreed that the test showed poor low end performance?

Could you please explain exactly how the conclusions I stated in that post are wrong?

You've made the same statements over and over again, but I've never seen you back them up with real technical proof. My questions on technical matters are ignored in favor of repetition of the same "stance". The only bench test results I know of (linked to above) show that the PLX is not able to push as much low end power before distortion as the conventional amps in the test (if that isn't what it shows -- then what DOES it show?). Can you provide 3rd party bench tests that show the output of the PLX and CA to be identical? Please, just pony up some evidence and put this to bed once and for all.

If you can prove it to me technically, I'll buy a PLX.
 
#135
pickles said:
Last time you said that either the amp or test was flawed. I thought that meant you agreed that the test showed poor low end performance?

Could you please explain exactly how the conclusions I stated in that post are wrong?

You've made the same statements over and over again, but I've never seen you back them up with real technical proof. My questions on technical matters are ignored in favor of repetition of the same "stance". The only bench test results I know of (linked to above) show that the PLX is not able to push as much low end power before distortion as the conventional amps in the test (if that isn't what it shows -- then what DOES it show?). Can you provide 3rd party bench tests that show the output of the PLX and CA to be identical? Please, just pony up some evidence and put this to bed once and for all.

If you can prove it to me technically, I'll buy a PLX.
Click to expand...

Better yet, why don't you contact the guy who did the bench test that you're touting? He was there, I was there, and you weren't.

How about a double blind listening test proof?
 
#137
pickles said:
Can you provide 3rd party bench tests that show the output of the PLX and CA to be identical? Please, just pony up some evidence and put this to bed once and for all.
Click to expand...

I can, assuming I can actually find my test results. :cool:

The PLX 1804 and the CA9 weren't quite identical, but any differences were tiny. Both met specs easily in any case. While I'm looking, please read through this thread: http://www.talkbass.com/forum/showthread.php?t=307748

If I can't find the results, I will be perfectly happy to do the test over again. That would require borrowing the CA9 from Arbitrary again, which is a bit of a hassle, but I'll do it.
 
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#139
pickles said:
I'd really like to learn the technical details and see scientific evidence.

Books, links, anything?

And if you were there, can't you just set me strait? Teach us something instead of telling us something.
Click to expand...

Good on you for now wanting technical knowledge. I've been trying to teach all through this thread and in others.

Contact Bink about the bench tests. He's the one who borrowed the Audio Precision set, loaded the test procedures, and ran them on the dozens of different power amps.
 

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