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

Which power amp?

  • Total voters
    92
#82
xgabriele said:
Ok, lets talk about "feel" then. When I A/B amps, I do my best to try to get the approximately the same volume level. Or, in other words, I'll turn both channels of each side of the power amp to max, and control my volume from my preamp. When A/B'ing, I touch nothing but the cable, swapping from amp to amp. Not touching the volume, why does one feel like it has more punch and headroom than the other?
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Hang on, haven't you contradicted yourself? If you want to get the two amps to produce the same gain you need to adjust the gain controls so the amps produce the same gain. Putting both amps at max gain is a surefire way to miss out on amps with lower max gain.

Alex
 
#83
alexclaber said:
Hang on, haven't you contradicted yourself? If you want to get the two amps to produce the same gain you need to adjust the gain controls so the amps produce the same gain. Putting both amps at max gain is a surefire way to miss out on amps with lower max gain.

Alex
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Ok, I see what you mean. But then I guess I have to ask, if an amp has a lower max gain than the CA-9, it won't "sound" as good, right?
 
#86
xgabriele said:
Does it seem the common idea that more gain sounds better than less gain?
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Absolutely. If you have two identical amps the louder one will sound better, even if the gain difference is very minimal, like 0.5dB. Consider that similar power power amps can vary by as much as 5dB in total gain and you see why the more sensitive amp tends to be the popular choice for tone.

Alex
 
#88
xgabriele said:
Ok, this makes sense to me. Is it possible to match gains from say, the PLX2502, to the CA-9? Does it seem the common idea that more gain sounds better than less gain?
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Well, more gain is louder for a given input signal level.

And if you look at the equal-loudness article I linked to earlier, you can see that louder = better perceived bass response.

The CA series amps have enough gain at maximum that even an iPod or personal CD player can drive them to full power. That's necessary for weak input signals.

Too much gain in the power amp stage can have drawbacks. For optimum signal-to-noise ratio in a system, you would want a fair amount of gain up front, to amplify the source signal up to a reasonable line level. Then you'd want to maintain that level so that it's substanitally above the noise floor of the device that it's passing through. And finally, in the power amp you would want only enough gain to get the sound level that you need. This gain structure approach minimizes the buzz and hiss that you would otherwise hear in between songs or during quiet parts if you had a low signal level through the system and then a huge boost in the power amp.

Strong input signal + relatively low amp gain = loud.
Weak input signal + relatively high amp gain = loud + noise.

When a manufacturer chooses a gain "philosophy" for a power amp design, it's essentially a compromise between designing for handling the input signal levels that the amp is likely to face on the one hand and controlling noise on the other.

The main reason for gain controls on power amps and most other pieces of gear is so you can make stuff work with other stuff.
 
#89
tombowlus said:
So, when all other factors being equal (same instrument, preamp, and cab), how would you explain the situation where the 'less loud' amp sounds better?
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Does it really sound better or does your brain just want to think it does? A lot of hi-fi snake oil sells on that basis.

Irregardless I don't believe the sonic difference between quality power amps is likely to be significant enough to be clearly audible once all other factors are figured in.

Alex
 
#92
alexclaber said:
Does it really sound better or does your brain just want to think it does? A lot of hi-fi snake oil sells on that basis.

Irregardless I don't believe the sonic difference between quality power amps is likely to be significant enough to be clearly audible once all other factors are figured in.

Alex
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It just might.

Louder doesn't sound better, it sounds louder. I often turn down an amp because it is too loud in the mix, and that often makes it sound better.

What is the % difference in low end "appearance" due to F-M curves with a <2db difference in output with a signal that is already very loud? I'd guess nearly none, but would love to see the math.

Many, many people have tried both and determined there is a sonic difference, despite a desire for the lighter amp to come out on top for obvious reasons!

And many people can't hear a difference or swear there can't be one.

Search and ye shall find hundreds or thousands of posts on this topic ( I especially like the one with the bench test data showing poor low end response on a PLX ;) ).
 
#93
alexclaber said:
Does it really sound better or does your brain just want to think it does? A lot of hi-fi snake oil sells on that basis.

Irregardless I don't believe the sonic difference between quality power amps is likely to be significant enough to be clearly audible once all other factors are figured in.

Alex
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+1

If there were differences in sound quality among good power amps, the differences would show up in double blind tests instead of just sighted tests or casual comparisons.
 
#98
Horny Toad said:
So if there are no differences in sound quality, I wonder why anybody would choose a 50lb. amp over a 20lb. amp?
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There's that, and where are those who believe lightweight amps sound better? As Tom B. said above, the heavier amp isn't necessarily the more powerful one.

I'm looking forward to my Stewart 2.1/Crest CA9 comparisons. I want them to sound identical because I DON'T want to haul a 50 pound amp.
 
#99
Horny Toad said:
So if there are no differences in sound quality, I wonder why anybody would choose a 50lb. amp over a 20lb. amp?
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Two products could have no actual sound quality differences between them, yet the purchasers of one or the other (or both) believe that there are.

Why do some people choose $500 cables instead of $15 ones?

Or even why did some people buy green Magic Markers to color the edges of their CDs?

There's all kinds f stuff in marketing, myths, peer pressure, stuff like that …
 

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