FM3 Noise Spectra Problem?

mechenix

New Member
First post here woo! I got my FM3 in February and it's awesome, but was curious about the noise I'm seeing in the spectra and if it was normal.

The patch I'm using for my test is Input (gate off) -> filter (flat w/ 20 dB boost) -> output.

The first measurement I have FM3 -> usb (no cable attached). Looks good to me, I don't know what the reference voltage is but still looks low and flat.
noise_no_cable.png

Now I add my TS cable so TS cable -> FM3 -> usb and get this. Which shows the 60 Hz and harmonics. Obviously, the cable acts like an antenna and so it has to be either EMI or poor isolation in the unit itself? As expected putting the free end of the TS cable near a power cord boosts the 60 Hz and the harmonics, I feel like

noise_cable.png

If I switch my interface to my zoom uac and swap the TS cable cable -> zoom -> usb I get this. I didn't set the noise floor to the same level but you can see the peak of that 60 Hz isn't nearly as high relative to the background regardless.
noise_uac.png

Any ideas?
 
Maybe I’m not reading this right, but you’re taking these measurements with the one end of the TS cable open? Nothing connected/terminated? Yes, the FM3 is potentially and very likely producing way more EMI/RFI than the Zoom interface. I will admit that when I’m close to my laptop, FM3 and interface and using higher gain settings with single coils the EMI/RFI can get extreme. All it takes is positioning away from the sources to get it to settle down.

I’m a nut case when it comes to eliminating any noise so it was a little off putting at first. One other thing is since I got the FM3 I’m having to play in another room than my home studio that I spent a good bit of time isolating noise sources and proper cable routing, grounding and shielding.

Edit for context and critical minds…
When I say “One other thing is since I got the FM3 I’m having to play in another room” I don’t mean because of the FM3. It’s due to being temporarily kicked out of my music room for other domestic reasons.😉 Relatively speaking there’s nothing out of the ordinary with the FM3.
 
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Maybe I’m not reading this right, but you’re taking these measurements with the one end of the TS cable open? Nothing connected/terminated?
Yep, it's mostly for experimentation. I get the computer/cpu noise when I hook up the guitar but that is sorted by just turning and moving back a bit. I have a measurement with the guitar attached as well here. 8 string kiesel aries with lithium p/u
noise_guitar.png
The pickups basically color the noise and pickup a bit more, the 60 Hz is still there.

If I cup my hand around the other end of the TS, not touching, just shielding the 60 Hz disappears. I doubt my hand is giving that much more isolation but it's interesting.
 
Yep, it's mostly for experimentation. I get the computer/cpu noise when I hook up the guitar but that is sorted by just turning and moving back a bit. I have a measurement with the guitar attached as well here. 8 string kiesel aries with lithium p/u
View attachment 101966
The pickups basically color the noise and pickup a bit more, the 60 Hz is still there.

If I cup my hand around the other end of the TS, not touching, just shielding the 60 Hz disappears. I doubt my hand is giving that much more isolation but it's interesting.
I use to do electronic testing with high end equipment so this whole thing opens up a can of worms in my head that I have not ever bothered to sus out. One thing to remember is the PSU is internal (60 Hz AC in close proximity) for the FM3 while possibly the Zoom is USB bus powered or using a wall wart and delivering DC.

Edit:
Oh one other thing. Those measurements are rather far down in the floor. Not trying to be contrary. Just bringing up some things to think about. My whole life at one time was making things FCC and every other certification compliant plus meeting high performance specs. So as I mentioned I can go on forever about this stuff.😉
 
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I use to do electronic testing with high end equipment so this whole thing opens up a can of worms in my head that I have not ever bothered to sus out. One thing to remember is the PSU is internal (60 Hz AC in close proximity) for the FM3 while possibly the Zoom is USB bus powered or using a wall wart and delivering DC.

Edit:
Oh one other thing. Those measurements are rather far down in the floor. Not trying to be contrary. Just bringing up some things to think about. My whole life at one time was making things FCC and every other certification compliant plus meeting high performance specs. So as I mentioned I can go on forever about this stuff.😉
Yea, certainly they're not too bad. I was just curious if it was expected. Yep, the zoom is usb powered, and the proximity of the PSU to the input is probably the culprit here. My background is in signal processing so I also like to dig into this stuff :)
 
Yea, certainly they're not too bad. I was just curious if it was expected. Yep, the zoom is usb powered, and the proximity of the PSU to the input is probably the culprit here. My background is in signal processing so I also like to dig into this stuff :)
Yes then you understand. I’m semi retired, but did R&D for high speed data transmission cabling and interconnects. Mostly for server backbones.
 
Am I misunderstanding this? Seems to me that the FM3 is accurately displaying what I think it should for this scenario. I would expect to see a 60hz fundamental and the proper harmonics in all their glory. I don't see this properly at all in the Zoom setup. I would seriously be questioning the later.
 
Am I misunderstanding this? Seems to me that the FM3 is accurately displaying what I think it should for this scenario. I would expect to see a 60hz fundamental and the proper harmonics in all their glory. I don't see this properly at all in the Zoom setup. I would seriously be questioning the later.
Ideally, there is just white noise if there's no signal being input. This is basically the 60 Hz leaking into the input because we can't get enough isolation. It's not a huge deal because it should be additive and it's not too strong.
 
Ideally, there is just white noise if there's no signal being input. This is basically the 60 Hz leaking into the input because we can't get enough isolation. It's not a huge deal because it should be additive and it's not too strong.
Well, with a cable plugged in there's actually some signal being input, and that's the EMI the cable is picking up since it is "floating" being unconnected on the other end.

Plug it in your guitar and turn the guitar volume all the way down, do you still see 60Hz hum and ripple?
 
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A good tube amp with a guitar cable not plugged into the guitar should amplify any emi around, you hear monitors, motors, long wave radio signals and whatever. That's is just how tube amps are. And when a model is perfect it must do exactly the same.

Now, when you don't have a tube amp to compare you don't know what the target is.
 
Ideally, there is just white noise if there's no signal being input. This is basically the 60 Hz leaking into the input because we can't get enough isolation. It's not a huge deal because it should be additive and it's not too strong.
No, you've created an antenna. You're sampling the EMI in your environment. Plug the other end into something.
 
Ideally, there is just white noise if there's no signal being input. This is basically the 60 Hz leaking into the input because we can't get enough isolation. It's not a huge deal because it should be additive and it's not too strong.

I don't understand much about this stuff, but is anything concerning you about the actual real life use of the FM3? Are you asking for something to be fixed? I am not trying to be argumentative, but if the the FM3 does what it does without issues I don't understand what your point is?
 
It’s pretty clear that, with one end unplugged, the cable is working as an antenna and FM3 is being used merely as a tool to measure the “environment” EMI.

The point that OP is raising in this experiment is that the “environment” has more EMI when FM3 is on than with the zoom, which means fm3 is leaking more EMI to the environment than the zoom.

While it’s an interesting experiement, the problem here is we can’t conclude anything whether is too much EMI leaking or not as the measurement is not calibrated to any standard.

We can ask for a usb powered version of FM3 though 😂😂😂
 
This thread is amusing.
Actually this thread is blown way out of proportion by the worst combination of ego centric complexes. That would be the combination of Musician (not just musician, but electric guitarist) mostly male and Techno Weenie. Ask any mature woman with any life experience with a musician. She’ll let you know that we can be real assholes. Of course most will never admit it!!!😉

Edit:
It was or should have been put to rest about 8 posts ago.
Not to include @FractalAudio (reasonable and to the point)
 
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It’s pretty clear that, with one end unplugged, the cable is working as an antenna and FM3 is being used merely as a tool to measure the “environment” EMI.

The point that OP is raising in this experiment is that the “environment” has more EMI when FM3 is on than with the zoom, which means fm3 is leaking more EMI to the environment than the zoom.

While it’s an interesting experiement, the problem here is we can’t conclude anything whether is too much EMI leaking or not as the measurement is not calibrated to any standard.

We can ask for a usb powered version of FM3 though 😂😂😂
There's no such thing as "leaking" EMI.

The reason the "measurement" shows more 60 cycle with the FM3 is because the FM3 is grounded to the mains whereas the Zoom is not (because it's powered by a wall wart).

The entire exercise is fundamentally flawed and the measurements have zero meaning or value. You NEVER, EVER use a cable where one end is floating. You will get hum, especially when the equipment is grounded to the mains.
 
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