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Noise from instrument input normal, or resolvable?
Old 16th September 2018
Gear Head

Noise from instrument input normal, or resolvable?


I'm having some problems with hum and wondering whether this is just normal for amping guitars or whether there are problems I can resolve.

I have a usb soundcard which caused some interference, so I moved this to a new usb port which has made a lot of difference. I no longer get whirring hard drive noises.

However, when I plug into the "instrument level" input with my guitar and put a VST amp modeler like Amplitube on there, I can still here some high pitched sound. Is this normal? My gain is on 9db.

Is the real test to just attach the instrument and put the gain up to 20db without any VST amp, to see whether I can hear any sound? It seems pretty quiet to me, however, when I hook up to a VST amp, I can hear some hiss/noise.

I'm wondering whether I need a DI box on these instrument level inputs, or are they basically DI anyway?

I'm plugging guitars into my sound interface which has 2 mic inputs and 2 instrument inputs, so I have the choice of using a DI box to go into the mic inputs or just go directly into the "instrument level" inputs without a DI.

I do still hear some noise and humming, would a DI box get rid of this? (I am using balanced cables). Will the humming always be there?
Old 16th September 2018
Gear Guru

Noise issues can be difficult to track down. Be as systematic as possible. Only change one thing at a time, put it back before trying the next thing. Keep good notes.

When hearing the noise, try twisting and turning with the guitar in your hand, does the sound get louder and softer as if your guitar was an "antenna?" If so, this would suggest that the amp sim is simply, well, amplifying the low-level noise inherent in the signal. Just like many real amps would.

Try a different guitar, too. Some people may need to have work done on their guitar to fully fix hums. On the other hand, I have been in locations where there is some ambient RF in the space, that won't go away and shows up on every guitar.

A DI may help, especially if it has a ground lift switch. Also check your environment for potential RF sources. Light dimmers are a notorious culprit. Motors sometimes as well.

I no longer get whirring hard drive noises
Theoretically these should be shielded from such interference.
Maybe a longer USB cable could allow you to get the interface even farther away from the computer?
Old 18th September 2018
Gear Head

Hi Joeq,

Thanks so much for your response. This has really helped me work through these issues to determine what is normal and not. I believe the amp is just increasing some normal hissing noise from feedback so everything is ok

I got a couple of di boxes just in case so will experiment with these. If it weren't for your response I would have bought a whole lot more that I didn't need.

Cheers, will report back here with my findings once I figure everything out.

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