Amp Noise

bluesky636

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One of my amps has started making a soft crackling noise. The noise sounds like a combination of static and rustling leaves.

The amp in question is a Weber 5F1 Champ clone that I built about 5 years ago. It is modified with a 5F2A tone stack replacing the low level input jack. Speaker is a Weber 8" alnico.

Troubleshooting to date is as follows:

1. Replaced the 12AX7, 6V6GT, and 5Y3 tubes with new ones. No real change in the noise but the original 6V6GT apparently was on the way out as the new tube (JJ 6V6S) sounds louder and better.

2. Checked all mechanical and soldered grounds, all are good.

3. Touched up a few suspicious looking solder joints and replaced the wire to ground from the 12AX7 cathode resistor and bypass cap.

4. Tubes are not microphonic. Tapping on the solder joints between the input jack and the grid input of the 12AX7 with a wooden chop stick creates some noise but I think that is to be expected.

5. Cleaned volume and tone pot with Deoxit.

6. Noise seems to be in the 12AX7 stage as it goes away when the tube is pulled or volume turned down.

7. Tube sockets all cleaned.

8. Noise seems to increase as amp warms up.

All this has resulted in a noticeable decrease in the noise but it is still present. It is not hiss.

Any other suggestions or thoughts?
 

judson

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had a similar issue with a 15 watt tube amp...drove me nuts

finally unplugged it from the power strip and made sure it was directly into the wall plug with nothing else....

one other time it was the guitar cord i was using was bad.

sometimes the simple things work...check those out, other than that , i have not a clue :dunno:
 

efstop

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My Class 5 snapped and crackled even with the volume off. It was a power tube in my case. Totally silent now until I want it to be not quiet.
 

Duane_the_tub

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My Champ suddenly developed a hiss, and it was because I was playing it with my cell phone in my pocket. Others have talked about interference from ceiling fans and other elements of their surroundings. It's not always the amp.
 

Big John

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Measure all the screen & plate resistors. Got a hunch.
 

judson

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My Champ suddenly developed a hiss, and it was because I was playing it with my cell phone in my pocket. Others have talked about interference from ceiling fans and other elements of their surroundings. It's not always the amp.
when i had my issue it drove me nuts for weeks.. so after swaping tubes and cleaning and other suggestion i tried all the simple ideas and thats what worked.......been fine ever since :fingersx:
 

redking

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I had this happen to me once - I thought it was interference from my garage furnace running (I happened to be set up in the garage at the time). It would run and this "rustling leaves" noise would come through my amp, and then it would stop running (was on a thermostat) and the noise would dissipate shortly thereafter. I have never been able to recreate this with the same amp plugged into other locations in the house.
 

bluesky636

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I decided to replace both plate resistors and the cathode resistor/bypass cap on the 12AX7.That seems to have done the trick. After a total of about an hour playing and just sitting idling there is just a barely audible hiss. I'm satisfied.
 


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