Are these noises from my Warwick Gnome i Pro amp normal?

[jjeff]

I recently purchased an used Warwick Gnome i Pro off reverb and noticed a few sounds that concern me. Aside from these noises, every thing is sounding great.

Does anyone know if these sounds are normal and I shouldn't worry about them? Or is this unit defective and I should return my the amp?

• High pitch hiss during operation (sound example on YouTube)
  • Gets worse when I increase gain/volume
  • Gets worse when I increase the treble EQ control
  • Present whether I plug something into the amp input or not
  • Present whether I mute my bass (with tuner pedal) or turn my bass volume knob all the way off
  • Present for outlets on different circuit breakers (both straight into outlet or into surge protector)
  • Present for all instrument cables I own
• "Zipper"/"buzz" noise when powering off (sound example on YouTube)
  • Present whether I plug something into the amp input or not
  • Present even when I turn gain/volume to zero before powering off
  • Present for outlets on different circuit breakers (both straight into outlet or into surge protector)

Equipment involved:

• Warwick Gnome i Pro
• Ampeg SVT-210AV
• Pro Co S12 Speaker Cable
• Ibanez BTB-675
• Polytune 3 mini (for seeing if muting input helps)

Sadly I don't have another speaker cable or a different amp/cabinet I can try to narrow things down further.

 

[Aloe]

well, all amplification and treble boost circuits do have some floor noise, when you're maxing out volume, gain or treble, you should expect some. the question is: how loud is the noise compared to the signal. if like 70dB below or more, nothing to worry about.

the zipper sounds to me like a stopping fan. if yes, it should be there as well if you disconnect the cab. if the button click is acoustic (not through the speaker), it's pretty quiet as well.

 

[eniac]

The second (power-down) noise doesn't worry me all that much. The first noise (high-frequency hash) worries me a lot. I'd return the amp.

 

[basss]

Both are normal. Diming thing treble will cause hiss on a lot (not all) of amps. The noise at shut down is something I've seen in other amps as well. I have a Gnome ipro (actually 2 of them) and they had the same noises. It's a bright amp overall and I'd never need to turn up the treble that much. I had a GK that was noisier, neither ever bothered me, at home I didn't turn it up enough to hear the noise and on a gig any noise is easily covered.

 

[jjeff]

well, all amplification and treble boost circuits do have some floor noise, when you're maxing out volume, gain or treble, you should expect some. the question is: how loud is the noise compared to the signal. if like 70dB below or more, nothing to worry about.

the zipper sounds to me like a stopping fan. if yes, it should be there as well if you disconnect the cab. if the button click is acoustic (not through the speaker), it's pretty quiet as well.

I don't have super good ways of measuring the signal vs noise, but using an app called Spectroid on my Android phone, my signal when playing with gain/volume/treble at 12 o'clock was at about -20db and the background noise was at -90db or so. Sounds like that's probably a reasonable level of signal vs noise then

I tried unplugging the cab before turning it off and it wasn't the fan noise. It is an acoustic noise coming out of the cab only when it's plugged in to the amp when I turn the amp off.

Appreciate the input everyone!