Dual rec hissing and crackling

[TheJayGibbs]

Hello!
This is my first time to this board and im happy to be here.

Anyway, not to long ago I had a mesa stiletto ace combo. I loved the thing but then joined a band that was heavyer sounding and then needed a heavyer sounding amp. I look around and found a guy saleing his Dual rec. I emailed him and we traded.

The other day I took it apart and cleaned the inside. You know clean around the tubes, get the dust off and what not. Anyway I notice when cleaning the amp, it still had the original preamp tubes still in them. Even tho he told me that he retubed it. My fault for not checking. At this point the amp sounded fine but just to make sure I checked the preamp tubes.

Took one out at a time, it looked ok so I put them back in. After all of that I tuned it on and started to play a bit. Soon after I started to hear hissing and cracklying comeing from the amp. To the point ibhad to stop because it was so bad. Its doing it in all the channels too.

Should I replce all the preamp tubes? Btw the power tubes are new.

 

[deeman]

How old is the amp? Preamp tubes can last for a while but if the amp is new to you its probably a good idea to replace them. Is the cable good? Perhaps you messed up the input or some other circuitry while cleaning it?

 

[domct203]

Hello!
This is my first time to this board and im happy to be here.

Anyway, not to long ago I had a mesa stiletto ace combo. I loved the thing but then joined a band that was heavyer sounding and then needed a heavyer sounding amp. I look around and found a guy saleing his Dual rec. I emailed him and we traded.

The other day I took it apart and cleaned the inside. You know clean around the tubes, get the dust off and what not. Anyway I notice when cleaning the amp, it still had the original preamp tubes still in them. Even tho he told me that he retubed it. My fault for not checking. At this point the amp sounded fine but just to make sure I checked the preamp tubes.

Took one out at a time, it looked ok so I put them back in. After all of that I tuned it on and started to play a bit. Soon after I started to hear hissing and cracklying comeing from the amp. To the point ibhad to stop because it was so bad. Its doing it in all the channels too.

Should I replce all the preamp tubes? Btw the power tubes are new.

Welcome to The Board!

Are you sure you didn't mix up the positions of the preamp tubes? A well-worn PI tube moved into an early gain stage could cause this type of thing.

Does the crackling stop if you HARD-BYPASS the FX Loop? If so replace V4.

If not, use V4 to swap with the other positions until you find the bad tube (stay in HARD-BYPASS). If the noises are very loud and it effects all the channels I would guess it is V1.

The Preamp tube positions (V1, V2 etc) and their functions are shown in the back of the amp's manual.

Make sure it is not a bad cable or other connection!

Dom

 

[TheJayGibbs]

The amp is 5 years old. I figure since the preamp tubes are the original ones that came in the amp I would just replace all of the them.

No I put all of the tubes back in the same place.

When I HARD-BYPASS the FX Loop it doesn't hiss or crackle but I use the Solo so I would need to take it off the HARD-BYPASS.

Do you think I should just change all of the preamp tubes so I don't have to worry about it down the road? And if I do should I change out the 5u4 tubes as well? There will be JJ tubes in the amp besides those two.

Thanks for all the help guys. You all are awesome!

 

[domct203]

If the noises stop when you HARD-BYPASS the FX Loop, most likely your problem is the FX Loop driver stage, V4. When the FX Loop is in HARD-BYPASS, that entire part of the circuit is bypassed, including the V4 preamp tube.

If I was in your shoes, being a used amp and all, I would change all the tubes, but keep the ones I now know are good as spares. Going through the hassle of troubleshooting has (possibly) identified the bad 12AX7 for you, as well as educated you a bit.

If you deciede to use non-Mesa branded powertubes be sure you get a set that is selected to run at Mesa's bias spec's.

BTW- Throw some (properly rated) spare fuses in with those spare tubes, you'll thank yourself later :wink:

Dom