4CM Noise

M

marshall2553

Power User
I have both an FX8 and an AX8. I primarily use the AX8 with amp modeling into a power amp and cab but I'd like to use it with the 4CM and my real amps occasionally. The FX8 is silent with my amps but the AX8 has a persistent, loud hiss that is really annoying. I mainly want to know whether this is normal or if something is wrong with my AX8. I know the FX8 is optimized for use with the 4CM and has a lower noise floor, but the AX8 noisier than I expected.

I am using Humbuster cables with the blue/TS sides going into the front of the amp and into the amp loop return. The amp, alone and with the FX8 in 4CM, is dead quiet even with the noise gate disabled. The AX8 and amp are plugged into the same outlet. I have Out 1 and Out 2 maxed to reach unity gain. The noise is a background hiss, not ground loop hum. It occurs with all blocks bypassed (except for the FXL block). I can kill the hiss by putting a gate block after the FXL block but I have to use fairly drastic settings to do it and the hiss is still very audible when playing. Other than the hiss the AX8 works well in 4CM.
 
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Set your Input Pad/Boost as high as your guitar can handle (0dB) for the lowest input noise floor. You can also try the +12dB Out 2 Boost/Pad, which lowers your noise floor going into the amp. See page 82 of the manual.

I'm curious to see if those adjustments will make the situation better, or if the noise floor really is that different between the two units.
 
4CM is a demanding task. Whatever gain you have dialed in on your amp, that's how much you reduce your signal-to-noise ratio. The AX8 was designed primarily as a stand-alone amps-and-effects box. The FX8 was designed to play with live amps, so it was equipped with extra-low-noise analog hardware to optimize the 4CM experience. That's part of the reason it was introduced at essentially the same price as the AX8, even though it doesn't have amp modeling. Those premium op-amps are expensive.

As @philipacamaniac said, mess with Boost/Pad to minimize the noise.
 
philipacamaniac said:
Set your Input Pad/Boost as high as your guitar can handle (0dB) for the lowest input noise floor. You can also try the +12dB Out 2 Boost/Pad, which lowers your noise floor going into the amp. See page 82 of the manual.

I'm curious to see if those adjustments will make the situation better, or if the noise floor really is that different between the two units.
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The input pad doesn't really seem to affect the hiss but setting the Output 2 boost to +12dB definitely reduced it. I'll need to wait until tomorrow when I can play louder to see how much. Thanks!

A lot of times I see noobs ask questions and think that guy just needs to RTFM, this time it's me that needs to RTFM.
 
Rex said:
This noise issue can't be fixed with a Hum Eliminator, Humbuster cables, or anything designed to break a ground loop, because hum isn't the problem.
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Maybe....but I also used the Hum Eliminator with the AX8 and a Tubemeister36 Head connected in 4CM, and it reduced all of the unwanted noise (hum, hiss, strange high pitch noises....).
 
Supermatzi said:
Maybe....but I also used the Hum Eliminator with the AX8 and a Tubemeister36 Head connected in 4CM, and it reduced all of the unwanted noise (hum, hiss, strange high pitch noises....).
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It must be attenuating your signal somehow.
 
Supermatzi said:
The ebtech hum eliminator can really be a lifesaver in some situations.
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Yes, it can. As long as there's a ground loop that's giving you problems. It won't help interference or hiss.

The OP reported hiss. Though I've seen people report all kinds of things as hiss, when they weren't actually hiss.
 
I just had a chance to play at volume this morning and @philipacamaniac 's suggestion about the changing the Output 2 pad worked perfectly. I should have checked the manual. There's still just a little more noise than the FX8 but it's perfectly usable. As for the Hum Eliminator, this is definitely not ground loop hum so I don't think it would help.
 
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