follow the noise.

[robertod]

I have monoblocks, when i turn on my system, there is a crackle noise coming out of the left speaker. I upgraded some caps and resistors about 8 months ago and everything worked no crackle).
I removed the monoblock from system and check solder.  I noticed one connection was loose on a resistor. I re soldered the resistor, turned on system noise gone, so I thought.
Next day turned on system a slight crackle noise out of speaker again. (sounds Muffled).  I checked all solder joints they looked good. (re soldered a few that looked suspicious) crackle noise still there.
Today I moved monoblocks, Left one to the right and right to the left.  The noise followed the monoblock.

What else should I check for?  Thanks for your help and recommendations.

[Paul Birkeland]

Swap the tubes.  Also keep in mind that any solder joint in the amp could cause a noise like this, not necessarily what is associated with the recent mods.

[robertod]

Thanks for the reply.  I will swap tubes once system cools down.

[robertod]

I could only swap tubes from one mono block to the other.  There was no crackle noise out of right or left speakers.  I'm wondering if the tubes were not seated correctly.
 
The 2A3's are 2 years old.
The 5y3's are 2+ years old.
The 6sn7's are 2+ years old.

[Paul Birkeland]

It could just be a little pin oxidation.

[robertod]

PB, thanks for your replay. Time to clean pins.  The tubes should be good for awhile or should I consider replacing the rectifier tube.
Last night all good no crackle and music sounds good.
Thanks again.

[robertod]

Could a tube or tubes cause the crackle noise?

[Paul Birkeland]

If the crackling noise is related to a specific tube, then the noise will follow that tube if you swap it to the other channel.

[robertod]

okay thanks, I will do that this evening.

[robertod]

moved the tubes to the right monoblock and noise followed.

[Paul Birkeland]

If you move them one at a time, you may be able determine which one is crackling.

[robertod]

I moved one and no noise.  It is the 5y3(rectifier).  I'm glad it was just the one tube.