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Ampeg Bass Head "windy" backgroud noise

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paulp8246

Sep 25, 2010
8
0
#1
I have an Ampeg B2R bass head that is frustrating me. I will be playing through it fine, but after some time (About 10 minutes) it will make a strange "windy" type of sound. It is intermittent, not constant...comes and goes. I talked to some people and they said that it could just be dusty connections. I tried blowing it out to no avail. Tried taking it apart to see any obvious wire issues (I am not proficient with this stuff). Saw no issues, blew out the inside, still making the noise. Any other ideas?

Thanks in advance, ABP.
 
#10
paulp8246 said:
Hmm...not quite sure what you mean. There is no mic involved. Not sure what big caps are either.
Click to expand...

Like a recording of wind. Rather than what you hear when it is windy, because that doesn't have much sound itself.

Amps all have capacitors inside, to smooth the power supply at high demand (loud and bassy) moments, when they are on the way out, they make noise, I'd guess it isn't unique to valve amps.
 
#12
renniw said:
If I remember correctly, my B2R had an internal fan that made some noise at full speed. (assuming the sound don't come out of your speaker)
Click to expand...

Yeah, I was thinking of this as well. I have an SVT-350, which is basically a B2R in a classic SVT cab. The fan on that thing, though not "noisy", can get to be noticeable at times. Would want to replace it one of these days if I have the time, or mount something to isolate the noise. You sure it's not this sound coming from the amp?
 
#13
That sort of noise has many possible causes...

Bad capacitors, sure....

A little more likely a semiconductor of some type which is on its way out..... They can develop problems with 'flicker noise" which can be very much like what you describe.

EXTREMELY hard to find....... Intermittent problems stink to begin with, because you have to have the unit operating and be ready at a moment's notice to go look at it when you see/hear the problem. Then just as you get close, it quits messing up for a day and you get to wait.

The "good news" is that with time it probably will get more consistent and findable.

I am not too "on board" with dusty connections..... it almost always is a "leaky" capacitor or a semiconductor.

One often forgotten is the protection diodes on inputs and outputs..... usually one to the + preamp power supply, and one to the -. They protect against static electricity "zaps".... but if the input one becomes leaky, it gets amplified a lot. And if they HAVE been zapped in the past, they could eventually get leaky from that.
 
#14
"Flicker noise" is a very good term for what I'm experiencing. I wish I knew about electronics so I could try to look at the semiconductors. I don't think I would even know what to look for. By the way, it is getting worse...much worse. The other day at practice I just had to shut it off it was getting so loud.
 
#15
Find out what controls affect the noise. The source is "before" the first control that affects the sound, usually (some feedback type controls can fool you). Or it is "after" all the controls, if none affect the noise.

That information will be very helpful to the technician.

Faced with that, I would be very tempted to replace all the semiconductors that were before that first control, if there were a reasonable number of them. It might be cheaper than having definite proof of the cause and fix.

Another good way for the tech to find it is to use "freeze mist".... comes in a can and cools the part it is sprayed on. Usually when the noise is heard, it will stop when the bad part is sprayed (but not always)..... Good for solid state components... no help at all with tubes ;)
 
#16
Thanks for the tips. None of the knobs effect the windy sound. I assume that that means that it is "after the controls." I am thoroughly stumped. I think I need to take this into a professional. Atleast you have given me some significant information to pass on. Thanks Jerrold.
 

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