Warwick BC80 hiss – any suggestions?

[Aloe]

Hi,

I bought a BC80. When I was testing it in the store, it was noiseless, but when I brought it home, there is notable white noise.

I see it wherever there is no instrument cable plugged in and that’s weird. Even more weird is that if I plug in headphones, I still hear the hiss in the muted loudspeaker. All controls on amp (volume, eq, aux in) do nothing with the hiss — it stays there, nor louder, nor quieter.

Any suggestions for troubleshooting this? Is this power line related or this may be some RF interference? If I plug into my TC BG250 in same outlet and same place there is no hiss.

 

[ole Jason]

Sounds like a power issue. Can you try it in a different building?

 

[Aloe]

Sounds like a power issue. Can you try it in a different building?

not easily. nor I don't have any 220v UPS/other outlets.

thanks for the suggestion, it may be the way to diagnose something.

 

[Thomas Cordery]

I just bought a BC80 and have a different, though similar, noise issue. Did you ever get a resolution to yours, Aloe?

You said you hear white noise that is unaffected by any of the controls or even by plugging into the headphone jack. That tells us the noise is in the power amp stage, as connecting headphones cuts out the preamp and eq entirely from the output. And incidentally, it does not sound like a mains issue problem. Hiss is thermal noise arising in the audio electronics. It would be highly unusual for broadband, higher audio frequency audio noise to get through decent power supply filtering in a noticeable way unless perhaps it's at a very high level.

Mine has a hum with a characteristic, unmusical odd harmonic. Very unpleasant, like a whiny two year old. Mine is similarly unnaffected by the controls, so is definitely after the preamp and effects loop. Probably not noticeable at a club gig with paying customers rattling cutlery and chatting away, but irritating for practicing at home at low levels.

Very disappointing given how Warwick makes such a point of the low noise of their circuits. I'm hoping this is a fault that can be resolved and not a feature.

 

[Aloe]

I just bought a BC80 and have a different, though similar, noise issue. Did you ever get a resolution to yours, Aloe?

nope, eventually considered that this doesn't bother me. a plugged in mic in my room makes more white noise than BC80 did to me.

I sent this amp to official Warwick service center here, the guys disassembled the amp and left open and powered on for a week. they said, they listened to all components, but everything was dead silent. got it back, got same whine likely somewhere in power amp section.

I still suspect that this was power-related. I spoke to local Warwick dealer guys (many of staff there play bass) and they said that from their experience BC combos are sensitive to grounding. one guy had a similar sounding problem to mine on a BC150 at his home (not reproducible in shop) and the solution was to duct tape the ground on the outlet. he said that after this it became dead quiet. if that was not power-related, this sounded like a noisy condenser or something like this.

odd harmonic issue sounds as broken amp for me though, mine was just white noise.

 

[Aloe]

p.s. frankly I don't remember if I heard the same whine in my latest home, but I think no.
I sold it in person and I recall that not me, nor the buyer heard it.

I really forgot to check this after moving, so hard to remember it 100% correct, but I believe a different power source indeed made improvement.

 

[Thomas Cordery]

p.s. frankly I don't remember if I heard the same whine in my latest home, but I think no.
I sold it in person and I recall that not me, nor the buyer heard it.

I really forgot to check this after moving, so hard to remember it 100% correct, but I believe a different power source indeed made improvement.

Okay thanks Aloe.

It won't be a grounding problem; in North America only the BC150 has a grounded power chord. BC80 and below are double insulated and only connect to live and neutral. And I've had nothing else connected that have introduce a ground loop.

The low level hum I'm getting sounds like our 60 cycle mains plus harmonics. If it was just hiss at that level it would be much less annoying. You may be right about a power supply condenser.J