Weird issue with FM3 Crackling/Noise

[Miihkali]

Came across with weirdly loud noise connecting Fm3 from Output 1 to RME Babyface - even if the output on FM3 is all the way down to 0 (actually the output volume doesn’t affect the noise at all). Not sure if this a fault or byproduct of the digital signal flow. So, if the input gain on the Babyface is around 42-46 I start to hear crackling. Cranking the gain further, it abruptly becomes noise at 48dB. If I go below 42 dB, I hear nothing even if I crank the output gain on my RME. I’m thinking maybe the crackling is just the lowest bits near the noise floor crossing some border like noise gate, but not sure if this actually makes sense.

If I turn FM3 off, the noise is gone, so it’s not just the RME, but changing the gain definitely makes a difference? If I switch the output/input from line level to instrument level on either device or put on a pad, the ”crackle floor” rises, but the issue remains when cranking the gain.

I can still work as I don’t actually have to use any gain on the RME when recording like this. Just wanted to make sure there won’t be any unpleasant surprises with the unit blowing up or worse - that the audio quality is less than optimal!

 

[sprint]

even if the output on FM3 is all the way down to 0

Are u referring to the physical output knob on FM3? If your preset is clipping output1 (front panel out1 meter hitting red typically resulting in crackling noise), turning the physical out1 knob down won't help.

 

[Rumbletone]

Are you running out1 into line level inputs (not mic level) on the RME? Is your DAW set to get clock from the RME? Is Out1 set to -10dB or +4dB in the FM3’s settings?

 

[Miihkali]

Are u referring to the physical output knob on FM3? If your preset is clipping output1 (front panel out1 meter hitting red typically resulting in crackling noise), turning the physical out1 knob down won't help.

Nope. Crackling occurs on RME input with no signal going in or out FM3.

 

[Miihkali]

Are you running out1 into line level inputs (not mic level) on the RME? Is your DAW set to get clock from the RME? Is Out1 set to -10dB or +4dB in the FM3’s settings?

Yes, line level.

This occurs before opening the DAW (Reaper) and changing clock source on RME settings has no effect.

I tried both levels like I said and the difference is that with lower output level, the problem remains, but only occurs when I turn the gain up on the RME.

 

[Rumbletone]

Yes, line level.

This occurs before opening the DAW (Reaper) and changing clock source on RME settings has no effect.

I tried both levels like I said and the difference is that with lower output level, the problem remains, but only occurs when I turn the gain up on the RME.

Thanks - this is helpful in eliminating potential noise sources.

Does the noise change if you engage the ground lift on the FM3?

Is the noise present if you use output 2 into the RME? Is it present in the headphone output of the FM3?

Is the noise present if you plug output1 into a different device (not the RME)?

 

[Miihkali]

Thanks - this is helpful in eliminating potential noise sources.

Does the noise change if you engage the ground lift on the FM3?

Is the noise present if you use output 2 into the RME? Is it present in the headphone output of the FM3?

Is the noise present if you plug output1 into a different device (not the RME)?

Ground lift makes no difference. Output 2 is the same. Headphone jack gives similar thing, but at lower level, so you get the crackle at 35db. I tried a Scarlett 2i2 and I got similar noise plus some extra hiss, but that's probably just the Focusrite preamps... So I guess RME isn't the problem, but still the preamp gain is affecting the cause very dramatically, which is something I've never encountered before.

What I did notice is that while the cracklin starts at 42dB gain at line level (on the RME), the correspondent number on instrument level is 60dB. Why that is interesting, is that that's 6dB more than the level difference between line and instrument levels (12dB). Not sure if it'll help to crack the problem, though...

Another new observation was that the amount of interference doesn't come gradually, but in steps. So 42-44dB light random crackles, 45-47dB crackle and noise, 48-50 more noise than crackle, and it get worse every 3 dB's...

 

[pauly]

It’s not a sample rate issue is it?

 

[Miihkali]

It’s not a sample rate issue is it?

I don't think so, both devices are running at 48k. And never heard of gain dependent sample rate issues anyway...

 

[scottburrow]

I had to put an Ebtech hum eliminator between my FM3 and the audio interface. It solved my issue. I originally had the Ebtech going out of the Audio interface into the powered speakers that didn't work. I had to go right out of the FM3 and it worked. Mine was more of a weird whine.

 

[Miihkali]

I had to put an Ebtech hum eliminator between my FM3 and the audio interface. It solved my issue. I originally had the Ebtech going out of the Audio interface into the powered speakers that didn't work. I had to go right out of the FM3 and it worked. Mine was more of a weird whine.

Thanks, but I don't think it's a hum or anything to do with grounding. I tried running the fm3 from a separate output of the Furman Power conditioner from which my recording setup is getting its juice as well and it had no effect on the noise.

 

[Rumbletone]

Ground lift makes no difference. Output 2 is the same. Headphone jack gives similar thing, but at lower level, so you get the crackle at 35db. I tried a Scarlett 2i2 and I got similar noise plus some extra hiss, but that's probably just the Focusrite preamps... So I guess RME isn't the problem, but still the preamp gain is affecting the cause very dramatically, which is something I've never encountered before.

What I did notice is that while the cracklin starts at 42dB gain at line level (on the RME), the correspondent number on instrument level is 60dB. Why that is interesting, is that that's 6dB more than the level difference between line and instrument levels (12dB). Not sure if it'll help to crack the problem, though...

Another new observation was that the amount of interference doesn't come gradually, but in steps. So 42-44dB light random crackles, 45-47dB crackle and noise, 48-50 more noise than crackle, and it get worse every 3 dB's...

For the headphone output test, is that with headphones plugged directly into the FM3, and no other outputs connected to anything and with no inputs connected (analog or digital)? If not, then I recommend trying that. If so, then yes it sounds like it's clearly the FM3 by itself that is making the noise, and if it does it on all presets (i.e., it's not something in the preset itself generating the noise) it would seem to be originating in the output section. That said, is it the same with a blank preset loaded (not even an output block)?

Also, can you try the digital out on the FM3 - for example, SPDIF output, with the downstream devices set to clock from the FM3 - with all the analog connections unplugged? That would help isolate the issue to pre- or post- converters.