Amp crackle sound... Help!

anewstatic

Member
Messages
72
Hey gang,

Quick question about a problem I just started having with my amp... I changed the 12AX7 tubes in my head to a few 12AY7's I bought online. One of them is new, and the other two were used but it good condition.

When I play low notes, I hear a crackling sound coming from my amp... Sometimes it does it at idle, too. I tried two different speaker cables to connect my head to my cab to make sure that wasn't the issue. I even plugged straight in with two different cables and it still did it.

When I unplug the speaker cable, and plug it back in, the problem stops for a little while and then happens again. My head has an 8 and 16 ohm out and the problem happens on both outputs (don't worry, my speaker is 16 ohms so I'm not hurting anything trying both outputs).

I've never experienced tube failure before, but is that what this could be? I'm really hoping so!
 

WaltC

Member
Messages
2,129
have you tried swapping back in the old tubes (which I assume didn't have this new problem)? Or even removing the new (to you) tubes and re-inserting them to make sure you have a good socket connection and don't have corrosion in the way?

worth trying ...
 

anewstatic

Member
Messages
72
have you tried swapping back in the old tubes (which I assume didn't have this new problem)? Or even removing the new (to you) tubes and re-inserting them to make sure you have a good socket connection and don't have corrosion in the way?

worth trying ...
Oooh. I tapped one of the pre-amp tubes with the amp on and it went crazy. Gotta be a bad tubey.
 

Koop

Member
Messages
320
When I unplug the speaker cable, and plug it back in, the problem stops for a little while and then happens again. My head has an 8 and 16 ohm out and the problem happens on both outputs (don't worry, my speaker is 16 ohms so I'm not hurting anything trying both outputs).

QUOTE]


I'm probably stating the obvious, but I hope you're not unplugging the speaker cable with the amp turned on.
 

soundguruman

Member
Messages
140
Don't unplug the speaker from the amp while it's on. This can melt the output transformer. Don't do that! :eeks
Crackles? It is pretty common for something like this to need the circuit board re-soldered. Probably a bad solder connection.
If you change the tubes and it still crackles, then re-solder the board.
 

KindaFuzzy

Member
Messages
816
I had a 12au7 do that the other night, but clean your tube pins and sockets with a little deoxit just to be sure.
 

johann

Member
Messages
2,753
I was going to post a similar thread, my Carvin vintage 33 began doing the same yesterday o a gig, how can I check if it is a tube or a bad solder, and how do I clean the socket and pins???

Thanks guys.
 

cap47

Member
Messages
2,273
Spray Deoxit in sockets and on the pins and work the tube in and out. Make sure it is not the lubricated contact cleaner. Allow 10 minutes for fumes to dissipate before turning on. Flammable fumes!
 

johann

Member
Messages
2,753
Thanks Cap47, I'm in Mexico, and there's no Deoxit, what shoul I look for on a spray cleaner for that???

Thanks again
 

VaughnC

Silver Supporting Member
Messages
17,836
Don't unplug the speaker from the amp while it's on. This can melt the output transformer. Don't do that! :eeks
A properly designed tube amp should have shorting type speaker jacks which will prevent any (flyback) damage to the output transformer...so unplugging the amp end of a speaker cable, even when amp is on, should do no damage. However, unplugging the speaker end of a speaker cable will present an open circuit to the amp which could damage the output transformer with flyback if a signal is applied to input of the amp.
 




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