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QSC PLX v. Crest Audio CA Series

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Folmeister

Folmeister

Knowledge is Good - Emile Faber
May 7, 2003
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Tomball, Texas
home.netcom.com
#1
For the time being, I am divesting myself of tube amps and going back to solid state for a while. I own two PLXs, but have been informed, and inferred through searching, that Crest CA series has better low-end response. I will be using my Demeter HBP-1. True or false?
 
#3
Very True, the CA is thick sound and very clear. Crest also has the LT series which is a light weight amp weighing 30 Lbs and and very solid as well. The Pro 200 series Crest amps are THE amps in the Crest line, the 7200 is the most popular in that series.

Also you might check out the Lab Gruppen amps.



Best of luck,
 
#4
Brian Barrett said:
Very True, the CA is thick sound and very clear. Crest also has the LT series which is a light weight amp weighing 30 Lbs and and very solid as well. The Pro 200 series Crest amps are THE amps in the Crest line, the 7200 is the most popular in that series.

Also you might check out the Lab Gruppen amps.

Best of luck,
Click to expand...

...and Brian is a great guy to deal with if you decide to go with Crest!
 
#6
This has been a subject that has had a bit of debate, and QSC's Bob Lee has stated if both brands of amps' gains were matched, there would be no audible differences in either brand.

From my experiences I've owned QSC's USA and PLX-Series amps. I now own a Crest CA-9. Not to start a flame-war, but the Crest has worked much better for me in terms of volume, and headroom. I'm not an amp tech or electronics expert, but from a performance standpoint, the CA-9 has been a much better match for my Read Purity preamp. Maybe it's the preamp or my speakers, I don't know why.

For some reason my Read Purity preamp didn't push my PLX2402 enough. I think this has something to do with input sensitivity; the Crest CA-9's is .775 volts, the PLX2402's is 1.7 volts. I wasn't getting adequate volume and it was clipping frequently. possibly my Purity doesn't produce enough voltage for the QSC's input section.

The QSC PLX 2402 had some nice features I miss that the Crest doesn't offer: Speakon outputs, selectable filters and clip limiter, etc., and it weighs 21 lbs compared to the CA-9's 47 lbs. So, if your preamp's output matches up with the QSC's input section, I think you'd be in business.

I notice there's many happy QSC amp users on this forum. Hopefully they'll share their knowledge on how to get the most out of one and what brands of preamps work well with them.

-Art
Please read below.
 
#7
Folmeister said:
For the time being, I am divesting myself of tube amps and going back to solid state for a while. I own two PLXs, but have been informed, and inferred through searching, that Crest CA series has better low-end response. I will be using my Demeter HBP-1. True or false?
Click to expand...

BTW, I just bought a Demeter HBP-1; it's output matches up perfectly with my CA-9. But I wouldn't give up on those two PLX's. I'm interested to hear how the HBP-1 works with your PLX amps. Please keep everyone informed.

Thanks,
- Art
 
#10
This input sensitivity variable is making a rational comparison of power amps confusing,apparently. Suppose one power amp has an input sensitivity of .5 volts and the other one is 2.0 volts. Guess what? The first one is going to sound fuller, ballsier, thicker, and just plain better. :eek:

Edit. Dang it! I forgot the smiley faces again. Of course the first one will sound better. Unless the signal is boosted more for the second amp, it may not put out. When comparing power amps, a weak input signal will certainly make the sound less ballsy, weaker and thin sounding. ;) :hmm: :) :crying: ;)
 
#11
Joe Beets said:
This input sensitivity variable is making a rational comparison of power amps confusing,apparently. Suppose one power amp has an input sensitivity of .5 volts and the other one is 2.0 volts. Guess what? The first one is going to sound fuller, ballsier, thicker, and just plain better. :eek:
Click to expand...

Sort of, but not necessarily.

If they have similar power ratings, then the difference in input sensitivity specs would indeed mean that they have very different maximum gain settings, with the first amp being 12 dB louder than the other (both set at maximum gain). The point at which the output clipped, though, would be the same.

If they both had the same gain, though, then the difference in input sensitivities would intrinsically mean that they have different power ratings, because maximum power, gain, and input sensitivity are all mathematically interrelated so if one term changes, at least one other has to change also. So if they have the same gain--say, 40×--then the first amp would have a power rating of 50 watts into 8 ohms, while the other has a power rating of 800 watts into 8 ohms. At maximum gain and at levels lower than 50 watts, both amps would sound equally loud, but the lower-power one would clip at a much lower level if you started bringing up the signal. You would get to a point where the sound from the first amp is all hash but the second one is still clean.

At any rate, the usual cause of one amp sounding louder, fuller, more ballsy, etc., than another is simply listening to it at a louder sound level.
 
#12
Arthur U. Poon said:
BTW, I just bought a Demeter HBP-1; it's output matches up perfectly with my CA-9. But I wouldn't give up on those two PLX's. I'm interested to hear how the HBP-1 works with your PLX amps. Please keep everyone informed.

Thanks,
- Art
Click to expand...

I used a Dem VTBP with a PLX 2402 and if it has similar output level as the HBP then it should be able to easily drive the amp to full output.
 
#14
On the input sensitivity issue, the Lab Gruppen is very flexabile on this issue. It has dip switch's on the back of the unit that allows for adjusting the input level;
20db, 23db, 26db, 29db, 32db, 35db, 38db, 41db.

Also as someone mentioned the Lab Gruppen also is setup with Speakons as is the Crest LT series and Pro 200 series.
 
#15
Bob Lee (QSC) said:
Demeter preamps that I'm aware of have very high output voltage capability, comparable to good pro mixers and processors. They should be capable of driving any power amp satisfactorily.
Click to expand...

So, Bob:

1. Thanks for contributing!

2. What can you do for those devices that don't have enough output to drive an amp like a PLX? I know there is a factory mod, but what would one do with out that? Is there a transformer or gain-thingee that could do the job?
 
#16
#17
My QSC PLX is light weight and sounds great! I really dig the 30hz filter too, pretects the speakers and sounds tighter.

I'm sure those Crests are great amps, but even if there is a sound diffence, unless you A/B you'll be more than happy with the QSC, and your back won't hurt when you get home.
 
#18
pickles said:
I'm sure those Crests are great amps, but even if there is a sound diffence, unless you A/B you'll be more than happy with the QSC, and your back won't hurt when you get home.
Click to expand...

Ignorance is bliss, eh? :) That's kind of the way I always felt too, because I loved my PLX for its great sound and its weight. But then I've recently had a chance to try out other amps, and a Crown MT-1200 has totally outperformed the PLX in a room I've played regularly for many years. Was it louder? I dunno, but the low end sure seemed fuller and tighter to me, and the headroom was greater. Just more SLAM, period. :cool: The first night I used it, the drummer commented that he thought my sound was great that night (and he didn't know anything had changed).

And if it was louder, then it makes me wonder what use power ratings are since the PLX is double the power of the Crown. Anyhow, if I have time this weekend, I plan on doing a little controlled shootout with the PLX and the Crown. Wish I had a Crest to throw into the mix, too!

In a way, I wish I had never tried the Crown... at double the weight of the PLX, I had to break it out into a separate rack, and it's extra work carrying it and hooking it up. I'm hoping my shootout proves the QSC is just as good as the Crown, actually, and I can go back to lightweight bliss! :smug:
 
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