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No input from bass, but guitar is fine

So I just got an FM9 turbo (second hand). I don't think my problem is related to the unit, but I'm just making sure.

So I plugged my guitar into the unit (in1, the instrument one), loaded a preset, and it works as expected. No problems. Tried to bring my bass guitar over, and nothing. No input lights nothing. I changed the battery just in case, and that was not the problem. Fired up my axe fx 3 mk 2, loaded up the patch, used the same cable and plugged into the front end, and my bass plays and processes just fine.

I've done a factory reset, updated firmware to the latest, and reloaded the preset banks. Given that the bass and cable work just fine on the axe fx 3, and the fm9 works with the same cable and my guitar just fine, I'm really confused where the problem might be here.

If it matters, it's a Warwick Thumb BO 6.

Any thoughts?


Presumably you are using the same preset to test both the guitar and bass on the FM9? If not, use the same preset.

There might be an issue with the physical configuration of the cable: i.e. it is "not bent" when plugged into the AFXIII and thus makes contact internally; and "bent" when plugged into the FM9 and then not making contact internally. I've seen more than a few cables that exhibited this behavior. Testing: plug into the AFXIII and start flexing the cable a bit, a few inches at a time.

Of course, it could be something else entirely that isn't coming to mind at the moment.


Power User
Plug your bass into something else and see if it works.

Edit: I see it works on your Axe. So I’m puzzled.
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Fractal Fanatic
My money is on the cable too…. Is it a trs cable? If so it may be incorrectly wired.


Glad you got it sorted out. This reminds me of this sticky post from @FractalAudio


If you are one of those who refuses to read manuals or search for information at least read this:


I used to have this on a sign in my office at my old job. Whenever a salesman or tech would come into my office all panicked I would point to the sign.

One day a sales technician came into my office and said "The System 5000 down at NOAA has failed. You gotta fly down there and fix it". I pointed to the sign. He says "No, they checked all the cables and connectors and they're sure something failed. They're getting telemetry errors". I pointed to the sign again.

A couple hours he comes back all sheepish and says "Uh, yeah, turns out someone ran over the deck cable with a forklift and didn't tell anyone. They replaced the cable and it's working fine now".


Power User
Curious why you're not using a standard TS instrument cable?
This. Input 1 is unbalanced/mono according to the manual so it's not all that surprising a TRS cable might not work properly.

On the other hand the AxeFX III manual says the same thing and it was working with that so wth do I know 😂

So you swapped to a different TRS cable and that's working? And why does your bass require a TRS cable? Do you use a TRS cable for guitar as well?
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