Setting levels between Axe-Fx and Power Amp

shantustarsun

shantustarsun

Member
I'm a new user running an Axe-Fx into a 2000 watt Carvin power amp and an Atomic Passive Wedge.

Does anyone have any suggestions on setting the levels?

Do I run the Axe output 1 level high and adjust the power amp output to the desired volume, or do I run the power amp high and adjust the Axe level? (My power amp does not have a level meter, just an input and clip LED).

Thanks for any suggestions, this is my first time with this type of system and I want to make sure I'm setting things properly. BTW, this forum has been a huge help with choosing the right system and getting everything working right!
 
Normally you leave the power amp all the way up and use the level control, but if you're using a 2,000W amp, you may want to attenuate it some so you don't accidentally blow the wedge.
 
Thanks for the reply!

The amp is rated at 425W at per channel at 8 ohms. I figured based on Jay Mitchell's post "a power amplifier with a rating of twice the speaker's rating is safe to use" I'd be ok.

I haven't pushed the amp past half power at this point.
 
shantustarsun said:
Thanks for the reply!

The amp is rated at 425W at per channel at 8 ohms. I figured based on Jay Mitchell's post "a power amplifier with a rating of twice the speaker's rating is safe to use" I'd be ok.

I haven't pushed the amp past half power at this point.
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Probably a safe place to set it...
 
For maxing out the gain, you would set the output level so that the input to the amp clips at the same signal level that causes the output of the Axe-Fx to clip. However, when you've got excess gain, as you likely do here, I would set the amp level lower in order to lower the noise floor.
 
shantustarsun said:
I haven't pushed the amp past half power at this point.
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Unless you've been monitoring the amp's output with a 'scope, there is no way for you to know this. The level controls on a power amplifier do not limit the maximum power the amp can produce. I've had to repeat this fact many times, but it is extremely important. If you reduce the level control on your power amp, then increase the output level of the device feeding it by the same amount, you have changed nothing, at least until you reach the (extreme) point at which you begin driving the amp's input stage into clipping before its output stage.
 
LMO said:
For maxing out the gain, you would set the output level so that the input to the amp clips at the same signal level that causes the output of the Axe-Fx to clip.
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That does not max out gain, it optimizes gain structure, which has the beneficial effect of maximizing signal/noise.

However, when you've got excess gain, as you likely do here, I would set the amp level lower in order to lower the noise floor.
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If you synchronize clip points (and therefore maximize S/N) with the Axe-Fx driving a pro power amp, you will always find that you must substantially reduce amp levels below their maximum settings.
 
If you synchronize clip points (and therefore maximize S/N) with the Axe-Fx driving a pro power amp, you will always find that you must substantially reduce amp levels below their maximum settings.[/quote]
If you don't you'll get the ultimate punch. At least from one of your band mates.
 
DieSchmalle said:
If you don't you'll get the ultimate punch. At least from one of your band mates.
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You're missing the point: synchronizing clip points does not reduce the maximum volume at which you can play. It simply makes the best use of the available gain to maximize S/N. After reducing the amp level control to align clip points, it is still possible to drive the amp to its maximum power output.
 
Thanks for the replies and forgive my ignorance. Coming from a tube amp set up, I'm trying to learn the in's and out's of powering speakers.

I just want to make sure I'm not doing anything to risk damaging my awesome new Atomic wedge (very nice cab by the way!).
 
From the technical side of things I applaud you for want to learn the differences coming form the tube amp side of things. A lot of times it's just boils down to common sense.
 
Thanks for the reply.

I have been planing on getting a new amp (just to save on weight, the old Carvin is around 34lbs).

Would I be better off (safer) picking up a Carvin DCM1000L (200 watts at 8 ohms) or an ART SLA-2 (200 watts at 8 ohms)?
 
Jase2677 said:
Turn your power amp up like 85% of the way. That way if the thing has issues running all the way up you'll avoid them. Then use your Axe-FX output knob as the volume control where you would start at off and creep your level up to where you want it. The FAS has a pretty high output, so seriously, start low and work your way up.
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As you say, the Axe-Fx has a pretty high output, so it's likely you are better off setting the power amp attenuator to a lower level. As a first guess, 50% is probably more reasonable than 85%.

If your power amp has a clip indicator, here's one way to set things up:
1. Record a track of yourself playing, and make a loop out of it.
2. Pipe the loop into the appropriate input (probably 1L rear) and select your favorite preset.
3. Set the input level properly (red light just flickering).
4. Increase the output level until the clipping light turns on, then back off the level just enough to keep it off.
5. Insert earplugs.
6. Turn up the power amp until the clip indicator lights, then back off until it stays off.

From that point on, you can leave the power amp input level (attenuator) alone, and control your level with the Axe-Fx Out1/Out2 controls.
 
LMO said:
4. Increase the output level until the clipping light turns on,
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The Axe-Fx output level pot will not light the "output clip" indicator. The output level control is in the analog portion of the output circuitry, and the clip indicator detects digital clipping, which can occur with the output level control set to zero.
 
Jay Mitchell said:
LMO said:
4. Increase the output level until the clipping light turns on,
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The Axe-Fx output level pot will not light the "output clip" indicator. The output level control is in the analog portion of the output circuitry, and the clip indicator detects digital clipping, which can occur with the output level control set to zero.
Click to expand...

So would it be best just to set the output level control (analog) to unity gain?
 
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