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

[Tony G]

If you were to do a true blind test you could not tell the difference.

Have you done a true blind test? I understand the theory behind it, but I am well aware that in many things that theory doesn't always match up with "real world" results.

I just want someone to convince me.

 

[seamonkey]

I just want someone to convince me.

What you said in your previous post. If you think you hear a difference, a little EQ will make them EQual to your ears.

 

[Horny Toad]

Have you done a true blind test? I understand the theory behind it, but I am well aware that in many things that theory doesn't always match up with "real world" results.

I just want someone to convince me.

If someone were able to convince you, then you did your own A/B test and heard an obvious difference, would you ignore what you heard?

 

[Tony G]

That's okay. But not everyone has the money and time to just try one of everything and hope that the settings just happen to be right for at least one of them. Many of us have to learn what does what so we can get it dialed in.

Bob, I pose a question to you. Why is it that I seem to prefer the "tone" I get when I use a preamp into a high powered power amp (doesn't matter which poweramp, just in general) over say a normal 500-600 watt head? I used to use an Epifani Quest II preamp into a Crown XLS602 power amp. That thing kicked major thump, but it was too heavy, and I downsized to just a UL502. However, I've come to miss that serious girth and thump that I used to pound out, have since used the CA-9 with my UL502's preamp out, and have had very similar and likable results. Is it simply that having "more power" is giving me a fuller, more balanced tone? If not, please help me understand. Or anyone for that matter, not just Bob.

 

[tombowlus]

But I guess the only way that is going to happen is if I just get these amps and A/B them myself on the gig.

That would be my suggestion as the best real world solution as to how these amps work (not necessarily how they measure) in an actual gig environment. Actually, trying them on a variety of gigs - with a variety of 'house power' options - would be even more valuable.

Of course, this is all heavily IME/IMHO, and YMMV. But I really love playing with a wide variety of great gear and I am on an endless quest for what works the best for me.

And FWIW, I gigged for years with a PLX 3002 as my main amp, then logged many gigs on a Stewart World 2.1. As it stands, my PA rack is loaded with CA9's, and when I use a SS amp live, it is a CA9 98% of the time. Regardless of the 'why', they just work the best for me and my rigs invariably sound better (to my brain, at least ) when I use them.

Tom.

 

[Tony G]

If someone were able to convince you, then you did your own A/B test and heard an obvious difference, would you ignore what you heard?

I'm not sure. I'm so impressionable....

 

[tombowlus]

I don't have the time or ego for a blog.

Neither do I...

And hey, aren't you at work, anyway? You shouldn't have free time for a blog!

 

[Tony G]

What you said in your previous post. If you think you hear a difference, a little EQ will make them EQual to your ears.

Well, I'm not sure how satisfactory that is to me. I use my UL502 almost always with the EQ flat. I can plug the preamp out of my UL502 into a CA-9, and seemingly it seems to balance out the sound, no eq at all. If I try a different power amp, but have to eq to get a tone I like, than I'm not sure that is what I want....

 

[Horny Toad]

Regardless of the 'why', they just work the best for me and my rigs invariably sound better (to my brain, at least ) when I use them.

Tom.

Amen.

 

[tombowlus]

Playing "Bob's advocate" here , the common factor is that people use the same preamp with the same settings for both amps. Since the power amps have different sensitivities, the preamp output has to be adjusted in order to get "equal" results.

Not true in my case, at least.

 

[tombowlus]

That's okay. But not everyone has the money and time to just try one of everything and hope that the settings just happen to be right for at least one of them. Many of us have to learn what does what so we can get it dialed in.

Good point. Which is why I tend to recommend products that do not require tremendous amounts of 'dialing in' or preamp modifications to work their best.

 

[tombowlus]

This makes the most sense to me out of anything in this thread. So if I understand it correctly, it doesn't matter what power amp I use. I may have to adust the preamp output a bit up or down, but effectively once the output volume on the preamp has been dialed in correctly, the power amp shouldn't matter?

That is the theory. However, at least IME, actual usage in a gig environment has led me to the conclusions I have stated herein.

Perhaps the typical bass preamp just isn't up to driving certain amps with the type of input they'd prefer to see?

Tom.

 

[Bob Lee (QSC)]

Bob, I pose a question to you. Why is it that I seem to prefer the "tone" I get when I use a preamp into a high powered power amp (doesn't matter which poweramp, just in general) over say a normal 500-600 watt head? I used to use an Epifani Quest II preamp into a Crown XLS602 power amp. That thing kicked major thump, but it was too heavy, and I downsized to just a UL502. However, I've come to miss that serious girth and thump that I used to pound out, have since used the CA-9 with my UL502's preamp out, and have had very similar and likable results. Is it simply that having "more power" is giving me a fuller, more balanced tone? If not, please help me understand. Or anyone for that matter, not just Bob.

It could be "more power," if you mean the amount of power that the amp is actually putting out, not just what it's capable of.

A 500-watt amp that is putting 100 watts into your loudspeaker will tend to have deeper, fuller bass (the equal-loudness thing again) than a 650-watt amp putting out 40 watts into the same loudspeaker.

If you match their output levels, though, you'll find the tone indistinguishable among good power amps below their clipping points. The way to match the output levels using the same preamp or other source is to match the gains of the amps being compared, so that X volts in = Y volts out on both. You could boost or cut the preamp or source signal level instead, but that makes it extremely difficult to do an accurate comparison.

It's not my goal to sell you an amp, but to help you understand how they work so you can get the sound you want in a reasoned way, not a haphazard one.

 

[Bob Lee (QSC)]

Good point. Which is why I tend to recommend products that do not require tremendous amounts of 'dialing in' or preamp modifications to work their best.

If you know how the gear works, the "dialing in" part becomes a lot easier. And it's almost always easier than swapping gear in and out of a rack, especially if it's gear that won't address what you seek to correct. Compared to swapping an amp, turning preamp and/or amp gain up or down is extremely easy and inexpensive.

 

[Tony G]

It could be "more power," if you mean the amount of power that the amp is actually putting out, not just what it's capable of.

A 500-watt amp that is putting 100 watts into your loudspeaker will tend to have deeper, fuller bass (the equal-loudness thing again) than a 650-watt amp putting out 40 watts into the same loudspeaker.

If you match their output levels, though, you'll find the tone indistinguishable among good power amps below their clipping points. The way to match the output levels using the same preamp or other source is to match the gains of the amps being compared, so that X volts in = Y volts out on both. You could boost or cut the preamp or source signal level instead, but that makes it extremely difficult to do an accurate comparison.

It's not my goal to sell you an amp, but to help you understand how they work so you can get the sound you want in a reasoned way, not a haphazard one.

Ok, but I'm specifically talking about gig volume levels. Just for example, my UL502 is rated 600 watts at 4 ohms. My CA-9 bridged is rated something like 2000watts at 4 ohms. Now, when using just the UL502, I've never clipped the power amp, and it certainly gets loud enough when playing with my very loud band to cut through well, but since adding the CA-9, it seems to cut through with a fuller sound, filling out whatever holes might have been left from the UL502's output alone.

I guess what I'm saying is, if the UL502 is rated at 600watts at 4 ohms and is loud enough, and could go louder if I needed too, that it would never actually hit the 600watt rating? If that is so, when using the CA-9 rated at 2000 watts, if my volume is approximately the same, am I only using about 1/4 of the CA-9's capability? I mean if the volume is the same, and the UL502 is rated only at 600 watts, and I plug the CA-9 in and bring it to the same volume, I'm only using less than 600 of the available 2000 watts? Or does the CA-9 go higher into the "watts" range than the UL502 at the same volume yeilding what I percieve to be a more balanced tone?

 

[tombowlus]

If you know how the gear works, the "dialing in" part becomes a lot easier. And it's almost always easier than swapping gear in and out of a rack, especially if it's gear that won't address what you seek to correct. Compared to swapping an amp, turning preamp and/or amp gain up or down is extremely easy and inexpensive.

True. But when turning the pre up or down does not yield the desired results (or where you have to drive a preamp into clipping to get the required output for the amp's input), it's easier to just start off with an amp that functions well and sounds great within the usable range of your preamp.

 

[Bob Lee (QSC)]

That is the theory. However, at least IME, actual usage in a gig environment has led me to the conclusions I have stated herein.

Perhaps the typical bass preamp just isn't up to driving certain amps with the type of input they'd prefer to see?

Tom.

What is the typical bass preamp? A lot of them today have pro-audio-type output sections capable of maximum output levels of +22 dBu or even more. Such an output can drive any power amp on the planet, even the ones with the high input sensitivity like the Crest 8001, 9001 and 10001, the PowerLight 6.0 and 9.0, et al.

There are some that can only put out about 1 volt, though I don't know why they design them that way. With something like that, unless you boost the signal somewhat you're stuck with power amps that have very low input sensitivities.

 

[Bob Lee (QSC)]

Ok, but I'm specifically talking about gig volume levels. Just for example, my UL502 is rated 600 watts at 4 ohms. My CA-9 bridged is rated something like 2000watts at 4 ohms. Now, when using just the UL502, I've never clipped the power amp, and it certainly gets loud enough when playing with my very loud band to cut through well, but since adding the CA-9, it seems cut through with a fuller sound, filling out whatever holes might have been left from the UL502's output alone.

I guess what I'm saying is, if the UL502 is rated at 600watts at 4 ohms and is loud enough, and could go louder if I needed too, that it would never actually hit the 600watt rating? If that is so, when using the CA-9 rated at 2000 watts, if my volume is approximately the same, am I only using about 1/4 of the CA-9's capability? I mean if the volume is the same, and the UL502 is rated only at 600 watts, and I plug the CA-9 in and bring it to the same volume, I'm only using less than 600 of the available 2000 watts? Or does the CA-9 go higher into the "watts" range than the UL502 at the same volume yeilding what I percieve to be a more balanced tone?

I'm not familiar with the UL502, so I don't know whether it's made for accuracy or has some custom response tailored into it. But if it's designed like a pro power amp, with flat response, low distortion, et al, then matching it up volume-wise with the CA9 or any other amp, for that matter, will also match it up tone-wise.

 

[Bob Lee (QSC)]

True. But when turning the pre up or down does not yield the desired results (or where you have to drive a preamp into clipping to get the required output for the amp's input), it's easier to just start off with an amp that functions well and sounds great within the usable range of your preamp.

If you run out of preamp headroom before you get the desired results, then yes, you need higher gain in the amp. If the amp's maximum gain still isn't high enough, then you need to either boost the signal in between the preamp and the amp or use an amp with higher gain. High gain is the CA9's advantage in this respect.

 

[tombowlus]

What is the typical bass preamp?

My experience (including use with the CA9, PLX 3002 and World 2.1) has been limited to the following preamps (and perhaps one or two that I am missing):

Aguilar DB 659
Aguilar DB 680
Alembic F-1X
AMP SL-1
Ashdown EVO II RPM-1
Bergantino line driver (prototype)
Demeter HBP-1
Demeter VTBP-201s
EBS MicroBass II
Eden Navigator
Epifani Quest II
Fender TBP-1
Kern IP-777
PreSonus Eureka
Read Purity
Stewart UDP-1a

With each of these preamps, I could not dial in the level of performance on the PLX 3002 or World 2.1 that I was getting out of the CA9. I was able to get usable tone and volume out of all three, for sure, but across a variety of volume levels, a variety of gigs, and a variety of associated equipment, I (and my bandmates) consistently preferred the results obtained when the CA9 was involved.

FWIW, I have no axe to grind with any company, nor do I have any affiliation with Crest (or Peavey). While I don't mind heavy weight gear, of course I'd rather lug lightweight gear. And, if anyone searches the archives, I was a strong proponent of the PLX 3002 for some time. All I know is that my best got better when I stepped up to the CA9.

Tom.