BillFitzmaurice.info

I recently acquired a Crown 460CSL on Craigslist for around $125.00.

This thing is really... odd.

Here's how my rig used to be:

Bass pre-amp (Presonus Studio Channel) -> line mixer ->amp
I had it wired so that the mixer presented a dual-mono signal to the amp and ran each Jack-10 to its own channel. At a couple of indoor gigs it was just ludicrously over-powered. No problem, I'd rather have too little power than too much.

I wanted to simplify things so I pulled the mixer and threw everything into a 4-space rack (it was originally in an 8-space). I omitted the mixer and a couple of other non-essential boxes and ran the output of the pre-amp straight into the line-1 input on the Crown.

Last Saturday I had an outdoor gig. Totally free-field. No walls, no ceiling, so I was prepared to have to push the rig a lot harder to get a usable amount of power out of it. To my dismay it was completely anemic. Per the diagram on the back I plugged the banana jacks across the red terminals and then ran a jumper between the cabs. I checked for polarity and they were properly in phase. It was so bad I had to pretty much stay off the E-string to keep from clipping the amp. Cone travel didn't seem excessive so I really doubt that it was cone slap I was hearing. I ended up switching basses in the second set to an active with a lot more midrange and totally dialed the 100-hz out of the mix at my preamp.

Yesterday I was looking at the owner's manual and this thing is really strange.
Here's the full manual:
http://www.crownaudio.com/pdf/legacy/125168.pdf

This is the excerpt that is confusing me. It's on page 11:

Stereo mode (both channels driven):
240 watts into 4 ohms.
200 watts into 8 ohms.
Bridge-Mono mode:
455 watts into 8 ohms.
395 watts into 16 ohms.
Parallel-Mono mode:
455 watts into 2 ohms.
400 watts into 4 ohms.

Wait... This amp can only go down to 8 ohms bridged? Ok, I guess it is 13 years old. But wait... Parallel Mono? In that mode it'll go down to 2 Ohms. What the hell? If you look at the diagram on page 7, you have to run a jumper between the red posts and then connect your plugs to the channel 1 output.
If I understand this correctly... and I don't doubt that I'm not... parallel mono is pretty much the same as bridging minus the phase inversion between channels, right? Why the strict impedance requirements when bridging?

So, here are my questions:
Were the problems I was having due to being free-field? I was expecting 6db or so of loss from a lack of boundary loading, should I have expected 9 or more?
The rated 455 watts is perplexing. They don't indicate what that means... Does Crown rate by max, RMS, program or something else? Assuming that the 6 or so ohm load of a pair of 2512 jacks would pull the full power out of this amp, is this approaching the max power of the Jacks, did I perhaps damage something early on?
Is there something else I'm not thinking of? Unfortunately, this amp has one light for power. It has no other means to communicate with me. I also did not have my trusty Fluke so I couldn't measure A/C voltage or anything. The first set was pure misery. It's hard to give a good performance when you're pissed at your rig and having to mentally re-write every bass line and sing at the same time.

Sorry for the super-long over-detailed post. Anyone have thoughts or suggestions?

Without actual voltage readings at the amp outputs, my guess would be the lack of boundries. Were the cabs by your feet, by chance?

Pole-mounted. The bottom of the bottom cab was at about 4 feet.

kynetx wrote:Were the problems I was having due to being free-field? I was expecting 6db or so of loss from a lack of boundary loading, should I have expected 9 or more?

You bet, DJPhatman's on to something. Boundaries greater than 2.5 feet away with respect to cancellations...IIRC

The amp is a pretty close match for the cabs with the hat tip to the Jacks in rating. You wouldn't be getting any more power by direct virtue of the amp to the cabs running the latter setup as opposed to the earlier (same amp and same number of cabs) , however, the output voltage of your pre-amp might not necessarily have been the same lunch as the mixer that you removed. The manual spells out all their definitions of ratings in the power matrix charts and footnotes. Electrical setup is in section 2, which I think you have a good handle on. Time to get out the multimeter.

If I understand you correctly you were running the amp into a 4 ohm load with the amp bridged? Maybe the amp was in the ODEP protect mode cause it didn't like it. Split the output of your preamp into both channels - 1 jack on each channel - stereo mode.

Yeah, you guys are awesome. Those are good directions for me to look. My instinct is telling me that it was more than just a loss of boundaries. I've had better luck in a free-field environment with 350 watts into a traditional 1x15 and 2x10 stack. The voltage difference isn't much, but I don't think a traditional setup like that is as efficient.

You hadn't mentioned that when in Bridge or Parallel mono that you had indeed turned the channel 2 input fully down. If not this will cause the amp to distort and go into protect way early.

The good news is the Crown will live to do that again if that's the way you ran it! CSL is basically a Power base amp.

FWIW Parallel mono at 4 ohms is basically the same as running dual channel at 8 ohms except you actually get the full doubling of output power unlike running 4 ohms per side and it allows you to run down to 2 ohms as well.

Ron K wrote:You hadn't mentioned that when in Bridge or Parallel mono that you had indeed turned the channel 2 input fully down. If not this will cause the amp to distort and go into protect way early.

Holy crap, I didn't. It was probably pointing at 10. I'm gonna throw the rig together and do some testing tonight.


Again... You guys are awesome.

Ok, so I spent some time in the garage trying to mess around without pissing off the wife...

I only have one cab on hand, the other is at the practice space. I dialed down the gain to channel two and managed 22 volts at 50 and 100 hz. Seems like that should be enough. I wish I was on a big chunk of property, it sucks testing things in a residential area.

I would think you should be seeing close to 40 Volts at full power before clipping. There may be a problem with that Amp. Even with 100Hz. you should get 40 volts into an 8 ohm load before ODEP kicks in.

If you head on over to Crowns website you can download the full repair manual with all the testing procedures and correct test equipment needed to fully repair your old Crown.They're not that hard at all with basic understanding of using simple test equipment and following simple procedures.You must read the manual completely especially the WARNINGS and Cautions lest thee likes high voltage through the skin!

Take it to a qualified Crown repair facility and they should be able to fix her up in short order for a decent price if you don't want to attempt the repair yourself. What I usually do is test in my shop and then decide whether or not I want to ship for repair depending on what I find.Usually fried output can are the culprit but not from abuse but from age. Remember these are quite old and depending on the duty cycle they saw it wouldn't surprise me if they were ready for a complete driver and output can replacement.

Interesting stuff Ron. Thanks. I stopped at 22 volts because I ran out of source voltage. I was using a test tone generator on my phone and the output starts to get ugly when run at 100%. This weekend I'll be making some cleaner test tones on my computer and running it off those and maybe a mixer to get closer to a .775 volt input. I'll see if I can get her to stretch to 50 volts. 3 more dB shouldn't get me into much more trouble with the wife, right?

I pored over the manual last night and learned quite a bit. For starters, this amp can be run on mains power down to 108V (10% variance with 120VAC), and that might have been another factor in all the fail. We had to run everything (Peavey IPR1600, processing gear, a 50W guitar head, a couple of fans and my rig) and while it didn't trip the breaker the voltage might have sagged enough to cause a problem.

never operate potentially-self-frying hardware without proper reading of the documentation

(lol, been waiting forever to use that emoticon)
just kidding, not trying to be an a-h#ole here; but yours seems to be a great (and expensive) amp, she deserves the reading.

EDIT: This data is golden, I'm learning a lot from it! suscribing

kynetx wrote:Pole-mounted. The bottom of the bottom cab was at about 4 feet.

Between having them elevated and being outdoors they were pretty much in free-space, that's 12dB less low end output than indoors on the floor against the wall. That's the equivalent of one versus four cabs. Even with the cabs on the ground the lack of walls outdoors means you need at least twice the cab count as indoors for the same levels.