Hey all, first post in the forum! New to Axe-FX II, please help with power amp!

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Smags1268

Member
Hey everyone,

My Axe-FX II is finally on the way, and I can't wait to learn about this amazing machine even further on these forums... I have a Crown XLS 1000 and Marshall 1960 Lead Cab, and I was planning to use a speakon cable to run that cabinet at 4 ohms mono. Is this a suitable setting ?
 
Smags1268 said:
...i was more concerned about wattage, I know I should be fine running at 4 ohms out of the crown amp into the 4 ohm mono jack for the cabinet, but in general, i was a little confused about solid state power amps and guitar cabs with impedance, as i always ran heads right into cabs
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You amp is rated at 350 watts/channel at 4 ohms, which is close to your cab's power rating. You're not likely to damage your cab by playing your guitar through it, at any level.
 
However, if you run the full 350 watts through a jack plug, they may overheat and melt. you should be fine at reasonable volume levels, but pushing the amp up full may cause issues. Speakons are much better for high power levels, though you would need to convert you cab to take a speakon socket. Running a cable with speakon one end and jack the other wont help - as your still pushing the power through a jack plug.

Its a reasonably easy mod though, I did it on my cab. I got a second jack plate, and routed it for speakon then fitted the plate. That was If I want to put it back stock I just change the plate.

You "may" have no issues running the crown full - but you may not.
 
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I wouldn't worry about running the amp full up. The signal's crest factor will pretty much assure that you don't average more than half power, even when driving the power amp into limiting.
 
Smags1268 said:
Hey everyone,

My Axe-FX II is finally on the way, and I can't wait to learn about this amazing machine even further on these forums... I have a Crown XLS 1000 and Marshall 1960 Lead Cab, and I was planning to use a speakon cable to run that cabinet at 4 ohms mono. Is this a suitable setting ?
Click to expand...

Welcome to the forum...:p I ran an older Crown amp (Class A/B) for a wile before it became part of a monitoring system I put together, never had a problem running with 1/4" speaker cable.

Things to know, the the down side to running any power amp wide open as it will allow all the power to be available to your speaker cab. If your going to run it in this fashion just remember to turn the Amp on last and off first. This way you lessen the possibility of damage to your speaker from any stray signal or at the very least an extremely loud pop from your cab.

One other thing here, you weren't very clear on is how you were going to be running the amp. When you say your going run it mono do you mean mono bridged or mono single sided? There is a huge difference in power between the two @ 4 Ohms... 350 Vrs 1100 watts.
 
Sixstring said:
Welcome to the forum...:p I ran an older Crown amp (Class A/B) for a wile before it became part of a monitoring system I put together, never had a problem running with 1/4" speaker cable.

Things to know, the the down side to running any power amp wide open as it will allow all the power to be available to your speaker cab. If your going to run it in this fashion just remember to turn the Amp on last and off first. This way you lessen the possibility of damage to your speaker from any stray signal or at the very least an extremely loud pop from your cab.

One other thing here, you weren't very clear on is how you were going to be running the amp. When you say your going run it mono do you mean mono bridged or mono single sided? There is a huge difference in power between the two @ 4 Ohms... 350 Vrs 1100 watts.
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The RMS on my cabinet is 300w at 4 ohms in mono so I would be running it single sided. one thing I have not considered is backlined cabinets at shows. There is no 16 ohm rating on the amp. It seems like my cab will be fine, but I want to make sure I have a pretty accurate understanding of Bridged/unbridged ohm breakdowns in relation to guitar cabs.
 
Don't sweat the impedance ("ohmage") with a solid-state amp. The manufacturer will specify a minimum speaker impedence. As long as the cab impedence doesn't drop below that, you're safe.
 
Smags1268 said:
one thing I have not considered is backlined cabinets at shows. There is no 16 ohm rating on the amp. It seems like my cab will be fine, but I want to make sure I have a pretty accurate understanding of Bridged/unbridged ohm breakdowns in relation to guitar cabs.
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When you run a 16 Ohm load the total wattage will be less then what it would be running at 8 not quite half, but in the ball park. The other thing to consider is head room. Whenever you cut or use less wattage the head room of the amp will be equally less as well. Meaning the amp will clip sooner at the volume you want to use. Head room at volume is important which is why the rule of thumb when using a SS amp when running a guitar cab is 3-5 times the tube head counterpart your used to using.

When a SS amp clips it is not musical at all, very harsh sounding. The other down side to this is it can destroy your speakers pretty quick so to see the Clip lights turn red when your cranked up is not good. Running in Bridged mode can help this issue but it can create another one and that's heat. Your cab is rated at 300 Watts and that relates to how much heat dissipation the voice coils can handle continuously, I doubt your cab will ever see that if you play at regular gig volumes but if you ever go for "Hey check out how loud my rig can get" then you need to be aware of this.
 
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