Bias Amp w/External Cabinet: Amplifier "Hiss"



  • I'm wondering if anyone is experiencing a pronounced his from the original Bias grid 600 watt amp? This happens when plugged into an external cab without any guitar being plugged in and doesn't appear to be "amp" driven. It's just a pronounced hiss when the amp is turned on.

    I was told to do a factory reset but that doesn't seem to have any effect on i.

    Anyone else experiencing this?

    • rob c


  • ... hiss like this? https://youtu.be/H3NKdA8UiwA
    That's the Bias rack of our bassist.



  • @rob-cheplicki
    I have the head and don't have any issues.

    Can you answer these questions for me -
    Is there a guitar cable plugged in without a guitar attached to it?
    If you switch to a clean amp model is there a hiss?
    If you lower your volume knob is there a hiss?
    If you turn the "utility" Noise Gate knob up is there a hiss?



  • @danbieranowski The hiss appears even when no cable is connected. It is independent from the chosen amp, the master volume and from the noise-gate. Unfortunately there is a unforced temporary loss of volume too so it might be a hardware problem with the output stage. We will contact the support for further investigations and RMA.



  • Unfortunately there is a unforced temporary loss of volume too so it might be a hardware problem with the output stage. We will contact the support for further investigations and RMA.

    Does anyone have an idea how to investigate the theoretical offered output/volume of the BIAS Head/Rack?

    We recognise a completely different output-volume on a 212/8 Ohm guitar cab to a 410/8 Ohm bass cab. Though, it could be a matter of the add of compression on the 212, too :/



  • Sounded like normal power amp signal noise from amplification.



  • @sascha-ballweg Are you referring to the "master volume" of the amp model, or the actual "output" knob on the amp?

    What if you turn the output volume down or up, does the hiss increase/decrease?



  • @danbieranowski the actual "output" knob on the amp. If we turn up the output volume the hiss keeps unchanged.
    But over all it is not recognizable in a rehearsal environment and the Yamaha DXR12 activ-monitor of our singer does a similar hiss in standby. So it might be okay, but it is a bit anoying when playing at home at a low volume.



  • @sascha-ballweg That's very interesting. The only thing I can think of is either just standard amp noise, or possibly "dirty power"... the circuit it is plugged into is introducing noise.



  • @danbieranowski we had tried different circuits in different locations so it should be standard amp noise (similar to our Yamaha DXR12). But thank you anyway!



  • Sorry for the delayed response, I never received notice that my question had been answered.

    It is a pronounced and for me, unacceptably loud hiss.

    From danbieranowski:
    Can you answer these questions for me -
    Is there a guitar cable plugged in without a guitar attached to it?

    • No

    If you switch to a clean amp model is there a hiss?

    • Yes. Switching to any amp from the amp makes absolutely no difference.

    If you lower your volume knob is there a hiss?

    • Yes

    If you turn the "utility" Noise Gate knob up is there a hiss?

    • Yes No amount of knob turning for the gate, volumes, switches, etc effects the hiss one way or the other.

    I have a Mesa 1x12 Thiele and Bogner 2x12 guitar cabs as well as a 2x10 Avatar bass cab and it makes no difference what type of cab I plug it into.

    I did get a response from Bias Tech Support to do a hard reset of the amp and no change whatsoever. It's extremely frustrating.

    Rob



  • And Sascha yes, it is exactly like your amp is demonstrating - except mine is the head version not the rack.

    Rob


  • Moderator

    @rob-cheplicki have you tried using the noise gate feature?(custom-knob on the device) I'd suggest you to set it to around 7~8'oclock position to dissipate the hiss.



  • @felix The noise gate feature works well for the models, its the hiss that is produced when the amp is turned on that I find problematic. It has nothing to do with the models.

    I've had a Boss Katana 50 amp modeler and when you turn that on it's completely silent, so this is obviously a power amp issue.

    • rob


  • @rob-cheplicki It's odd because it seems unit-specific. My head does not produce any hiss like that. I'm curious if there is a unit issue, or a dirty power issue.



  • @danbieranowski Was there a fix for the hiss? I'm having the same hiss noise. I've used many other processors and never had anything but dead silence unless I was using high gain amp models. Tried the reset and and im using a furman rack mout power conditioner so its not noise from power.



  • @danyaglowski I had the hiss issue and after some back and forth via the support desk it was deemed my Bias head needed a replacement part. Mine's currently still in for repair so I'm not sure what exactly the issue is but if you email/ contact PG support they'll be able to see whether you need a replacement/ repair to be conducted. They were really good with helping me so I wouldn't worry too much